岛1odule
10
Piping and Tubing
Systems for Industrial and
Commercial Applications
The requirements for gas installations vary between requirements
for single family dwellings and for commercial and industrial applications. This learning module details four areas where significant
requirements for the installation, operation and testing of large piping and tubing systems should be understood by the gas technician.
At the end of this module you will be able t。：
Describe c。de requirements and approved joining
methods
•
Describe welding safety, certification and procedures
Identify utility and
n。n-utility
piping and tubing
symb。Is
•
Explain piping layout, drawings and
•
Size high pressure piping and tubing systems
•
Explain
purging 。perati。ns 。n
large piping systems
·s
1i
-
Gas Technician 2 Training - Module 10
@ Canadian Standards As就比iation
Ken Bales, Manager, Gas Information Products, CSA, wishes to acknowledge the following individuals
who contributed as members of a Review Panel during the development of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology (BCIT) is
acknowledged for its work in the technical development and editing of the original edition.
Contributors and members of the Review Panel
John Cotter
Bill Davies
Eric Grigg
Warren Hayes
Darrel Hilman
Ken Kell
W. John Lampey
Lorne Lowry
Jim Noseworthy
Gary Prentice
Nick Reggi
Rick Rogozinski
Ron Royal
John Semeniuk
Allen Sidock
John Simmons
David Stainrod
Terry Waters
iv
Ganado「e College
Union Gas Limited
Canadore College
Superior P「opane Inc.
Southern Alberta Institute of Technology
Centra Gas Manitoba
Alberta Advanced Education & Caree 「 Development
Algonquin College
Durham College
Environmental Energy Consultants
Humber College
Union Gas
Fanshawe College
Northern Alberta Institute of Technology
Cambrian College
Loyalist College
D.J. Stainrod & Associates Ltd.
Enbridge Consumers Gas
Gas Technician 2 Training - Module 10
。 Canadian Standards Association
Module 10
Table of Contents
Unit 1
Code requirements and approved
joining methods
Code requirements for industrial and commercial
piping
applicati。ns
.......................….................... 3
Appr。ved j。ining meth。ds
...….......................... 15
Assignment 1 ....…················…··············…......... 19
Unit 2
Welding safety, certification and
procedures
Comm。n
Safety
hazards ..............................…….......... 23
precauti。ns
Certification
................…........….............. 29
requirements 国................................ 33
Preparation for welding ..................................... 35
Testing ..............………....................................... 43
Assignment 2 ..............……·················…............ 45
Unit 3
Utility and non-utility piping
Utility piping and tubing ..............……….............. 49
Non-utility piping and tubing .............................. 51
ldentificati。n
and tracing ................................... 53
Assignment 3 ..........................….........…........... 55
Gas Technician 2 Training- Module 10
© Canadian Standards Association
v
Unit 4
Piping layout, drawings and symbols
Blueprints and specifications ..........………… ….. 59
E
Valves. ……..…………………………………········…… .67
Assignment 4 ...........….........…··················…….. 73
Unit 5
Size high-pressure piping and tubing
Use 。f tables. …………………………······················ 77
General sizing procedure
........…······················
79
High-pressure sizing pr。cedure ........................ 83
Assignment 5-1 -
Unit 6
5-6 ........................….......... 93
Purging operations on large piping
systems
Review Code requirements .......................….. 111
Safety reasons for purging ........…·······…........ 113
Types of purging. ….......….........………….......... 115
Assignment 6 ....................................…........... 117
vi
Gas Technician 2 Training - Module 10
© Canadian Standards Association
Unit 1
Code requirements and
approved joining methods
Purpose
The installation of gas piping and tubing is a basic part of a gas technician ’ s
duties. The student must be aware of the code requirements concerning
approved types of piping and tubing, as well as applicable joining methods.
Pipe sizes, locations and pressures are all factors that must be considered
before a piping or tubing system is installed.
Learning
I . Describe the Code requirements for industrial and commercial
applications.
o均ectives
2. Describe the joining methods that may be used.
Gas Technician 2 Training - Module 10
© Canadian Standards Association
Topics
1. Cod.~
re9uirements for industrial and c。mmercial piping
applications .............................................................….............. 3
Allowable pressures ..........…………………................………...... 3
Pressure testing requirements ........…··… …·…,............……………··…4
Underground piping ......……........………………....………..........……... 8
Identification of gas piping . .... .. ......... . ........………回……. .. .. ..... . ............ 11
Shut-off valves ..........……·········…….............,....·-………………........... 11
Commercial cooking ap酬1ances .......…………......……··…·-…······ ... 13
a
2.
Approved joining methods .......……........…................…........... 15
General requirements of piping, tubing and connectors ................……..... 15
Piping material and R忧ings ….......………………………………………....... 15
Joints and connections in large” size piping ..............…….........…................. 16
Iron and galvanized steel piping ........………….......“…….........….......…..... 17
Other types of piping and tubing. ……………….......,…………·……….......... 17
Assignment
2
1 …...............…·······….......….......…··….......…·········….. 19
Gas Technician 2 Training- Module 10
。 Canadian Standa『ds Association
TOPIC
I
Code γequiγementsfor
industrial and commeγcial
piping applicαlions
As a gas technician you must familiarize yourself with how Canadian Gas
Code requirements for piping in commercial and industrial applications
differ from requirements governing single-family dwellings. Note the
following areas of significant di证erence between residential and
commercial buildings and the applicable Code sections relating to the
following:
•
allowable pressures
•
pressure testmg reqmrements
•
underground piping requirements
•
identification
•
shut-off valves
•
commercial cooking appliances.
Review also Module 8 of the Gas Technician 3 training.
Allowable
pressures
The most significant of the Gas Code variations is contained in Clause 5 .1
Gas System Pressure. Gas pressures in supply mains (natural gas) and 丘。m
storage containers (propane) are generally higher than the safe operating
pressures of connected appliances. So gas pressures must be controlled to
fall within an appropriate range, depending on the operating characteristics
of installed appliances.
Table 5 .1 from the B 149 .1 Code shows the maximum allowable gas
pressures in buildings for natural gas and propane. Gas press田e regulators
are the only practical means of meeting these requirements in most
installations.
Gas Technician 2 Training- Module 10
Canadian Standards Association
©
3
CODE REQUIREMENTS AND APPROVED JOINING METHbDs
UNIT 1
Table 5.1
Pressure inside buildings
(See Clause 5.1.1.)
Maximum oressure, psia (kPal
than central boiler or Central boiler or
mechanical room
mechanical room
。ther
Tvoe of buildina
!
One- and two-family dwellings and row housing
Hotels and motels
!
Residential, other than one- and two-family dwellings and row
housing
!
Care or detention and assembly buildings
Commercial buildings
Industrial buildings
Central heating plants
2 (14)
5 (35)
20 (140)
5 (35)
20 (140)
5 (35)
20 (140)
5 (35)
20 (140)
20 (140)
66 (450)
20 (140)
20 (140 ）汁
66 (450) Natural gas
20 (140) Propane
66 (450) Natural gas
20 (140) Propane
Natural gas
Propane
!
Building under construction using p「opane
I
(construction heater aoolicationl
i
25 (175) Prooane
25 (175) Prooane
’ 20psig l 飞 40 kPa) may be used in boiler or mechanical r也oms located on the roof of commercial buildings for propane .
t66 psig (450 kPa) may be us电~d in boiler or mechanical rooms located on the roof of commer℃ial buildings for natural gas.
Pressure
testing
requiremen始
After a gas piping sy旨tern has been installed, it must be pressure tested in
accordance with the requireme盹 of the applicable codes and 吨u ions.
All piping and comppnents that will be concealed must be inspected and
tested be扣re being cpncealed. Te蚓ng should be performed at two specifi c
times:
First pressure test:
before any appliances are installed
Second pressure test：础er appliances are installed.
Visual inspe9tion
During installation 们i阿 and 毗
visually inspect pipitjg and tubing for cuts, abrasions, and other defects 由at
may cause leaking or failure of the system when under pressure.
Remember that all piping and components that
will be concealed must be
inspected and tested before being concealed.
4
Gas Technician 2 Training - Module 10
。 Canadian Standards As叙>eiation
CODE REQUIREMENTS AND APPROVED JOINING METHODS
UNIT 1
First pressure test: before appliances installed
The first system test is performed after the piping system is installed and
before any appliances are connected to it. Refer to the Code for this test.
Any components of the system that have a pressure rating below the test
pressure must be isolated or removed from the system before testing to
prevent them from being damaged.
Procedure
1.
2.
3.
4.
Isolate the piping system that is to be tested.
Cap or plug all open ends.
Insert a pressure gauge at one end of the system
Pressurize the system with air or inert gas (nitrogen or carbon dioxide)
to the specified test pressure. Refer to Figure 1-1.
(Table 1-2 shows the pressure test requirements for gas piping and
tubing systems. )
The pressure is measured with a pressure gauge calibrated in 14 kPa
(2 psig) increments or less, or 2% of the full-scale reading of the gauge,
whichever is greater.
Note that the Code requires that the pressure and duration of the test be in
accordance with Table 6.3 (see next page).
~l~：o
Optional air compressor
or hand pump
High
pressure
hose
valve
Figure 1-1 Pressure test before appliance installation
Gas Technician 2 Training - Module 10
Standards Association
。 Canadian
5
CODE REQUIREMENTS AND APPROVED JOINING METHbDS
UNIT1
T圳e 6.3
Pressure te~t requirements
(See Clauses p.22.1 and 6.22.2.)
U咱th of pi畔。rtubing,
ft (m)
I
200 (60) or les$
蓝白i
15 (100)
All sizes
More than 2001(60)
15 (100)
60
All sizes
200 (60) or
50 (340)
60
All sizes
Mo叫an 2叫0)
50 (340)
180
All sizes
All lengths
I
I
1
All welded pipe
All sizes
All lengths
i
I
I
i
I
tim叫e
AMU’
E
a---on
『
…
Test pressure, psig
sn
Diameter of
pipe or tubing
All sizes
M
－ M一句
Working pressure,
psig (kPa)
Up to and including 2
(14)
υp to and including 2
(14)
Over 2 (14) b川 not
mo 陀 than 33 (230)
Over 2 (14) but not
more than 33 (230)
Over 33 (230)*
1.5
maximum operating
pressure
The greater of
50 psig (340 kPa)
or 1.5 times
the maximum
ooeratino oressure
180
180
甲ropane maximum operating pressure is defined as
I
(a) 2回 psi (1725 kPa) for piping and tubing opera.垣ng at qontainer pressure;
(b) 350 psi (2400 kPa) when connected to the outlet of a /pump or compressor; or
(c) 375 psi (2570 kPa) minimum or these世ing of the hydrpstatic relief valve in piping that 臼n contain liquid propane,
that can be isolated by valves, and that requires hydrosta~ic relief valves as specified in Clause 5.4.1 of this Standard or
Cla叫.6.1 of CAN/CSA-8149.2.
I
Notes:
问 These test pressures and test durations are minimu川剧uirements.
Circumstances 臼n require test pressures and test dul1明ions in excess of those shown in the Table.
(2) All wrapped and/or factory-coated piping systems of ~II sizes and lengths shall be tested at a minimum
pressure of 100 psig (700 kPa) in accordance with th母 time duration in the Table.
Leak detect；，。n
6
Gas Technician 2 Training - Module 10
©Canadian S恼ndards Association
CODE REQUIREMENTS AND APPROVED JOINING METHODS
UNIT 1
Suspected
leak point
内
Figure 1-2 Soap test
Checking for shut-off valve seepage
A gas meter valve may sometimes seep gas if its sealing grease becomes
dry and hardened. If the valve passes gas in this way, the system test will
not be accurate and results will be invalid. For this reason, b写fore the
second pressure test is p町formed, the gas meter valve should be checked
for seepage using the following procedure.
1. When the system is brought to a static pressure condition, release a
small amount of the contained gas pressure by quickly removing then
replacing the manometer or pressure gauge tubing.
2. This action opens the service regulator and allows the system to be
tested back to the gas meter shutoff valve.
3. If the gas pressure increases slowly to static pressure, the meter valve is
seeping gas and should be se凹iced be岛re testing proceeds.
Second pressure test: after appliances installed
After appliances are installed, the system should be checked visually to
ensure there are no openings in the system 仕om which gas could escape.
The manometer or pressure gauge used for this test must be calibrated in
one inch w.c. (250 Pa) increments or less. Since the procedures for both
natural gas and propane are covered in detail in Module 8, please refer to
that module for more detailed information.
Gas Technician 2 Training- Module 10
Standards Association
© Canadian
7
CODE REQUIREMENTS AND APPROVED
Underground
piping
JOI 阳GM仨TH仰s
UNIT1
Clause 6.15 of the Gas Code identifies requirements for installing
underground piping ~ystem~.
Installation d~pth~ and location
Clause 6.15.4 gives hiinimum depths for underground piping locations:
15 inches (400 mm) generally
24 inches (600 mm) under a commercial driveway or parking lot,
except when the piping or tubing rises above ground at the point of
supply to either ~ buildirg or an outdoor appliance.
Figure 1-3 shows mibimurtj depths and location of rise prior to piping
entering the buildi咯｜
*Mini 『ilium
24 inches
ntim). under a
commerc1al driveway
(600
Figure 1-3 Required piping depths for underground piping
An exception to the above minimum depths is where physical damage may
occur to piping 企om comm~rcial operations (such as farming). In this case,
'
'
underground piping [will
require
additional depth of cover, appropriate t。
由eop制ion involvfd.
:
Note also C/a；脚 6飞5.8：唱pi；吨 en阳ing a building shαII rise α1bove
grαde before en町， unless otherwise permitted by the authorii纱 having
jurisdiction.
In such exceptions (Figure 1-4):
a watertight seal, must qe provided where the piping passes through an
outside wall bel~w gra<Je
piping or 灿ir盯部sin~ 也rough concrete or maso町 walls must be
sleeved, coated <i>r doutjle-wrapped (if one layer is wrapped in one
direction, say clci>ckwise, the second layer is wrapped in the opposite
direction, counterclockwise)
8
Gas Technician 2 Training- Module 10
© Canadian Standards Association
UNIT 1
CODE REQUIREMENTS AND APPROVED JOINING METHODS
piping may not pass under a footing or building wall because of
building settlement which can cause crushing or rupture of the pipe.
Shut-o仔
valve
Figure 1-4 Underground piping entering building below grade
Supports for piping
Clause 6.8.3 of the Code states that above-ground piping must be installed
with individual supports of su证icient strength and quality (Figure 1 －匀， and
be spaced according to Table 6.2 of the CSA Bl49.l Code.
Table 6.2
Spacing of supports for piping
(See Clauses 6.8.3 and 6.26.1.)
旦旦呈
1/2 or
less - horizontal
3/4 - 1 - horizontal
1-1/4 一 2-1/2 - horizontal
3 - 4 - horizontal
5 - 8 - horizontal
10 or larger - horizontal
All sizes-ve此1cal
Tubing - all sizes - vertical and horizontal
Gas Technician 2 Training- Module 10
© Canadian Standards Association
Maximum soacina of suooorts ft （町、｝
6 (2)
8 (2.5)
10 (3)
15 (5)
20 (6)
25 (8)
Every floor but not more than
125%
of horizontal
6也
9
CODE REQUIREMENTS AND APPROVED JOINING METHODS
~igure
。ther
UNIT 1
1-5 Supports for piping
installation requirements
Note the following additional requirements for underground piping:
•
Trenches for piping must be properly graded to avoid any sagging in
the pipes or tubes.
Back fill material must be 丘ee of sharp object, large stones or other
material that may damage the piping.
Buried plastic piping must be accompanied by a tracer wire or equivalent.
Figure 1-6 shows requirements for venting when the piping or tubing is
covered with paving, or the paving extends 25 ft (8 m) or more 仕om the
building:
•
A vent pipe inspection point must be installed.
•
A sleeve in the pavement should be provided to permit 仕eemovement
of piping.η1is sleeve can also serve as a vent pipe inspection point.
－
e·ω···
uvnvdue
Figure 1-6 Venting of underground piping under pavement
10
Gas Technician 2 Training- Module 10
© Canadian Standards Association
CODE REQUIREMENTS AND APPROVED JOINING METHODS
UNIT 1
Identification
of gas piping
In all industrial and commercial buildings, gas piping must be clearly
distinguished from other types of pipes and tubes. The Code in Clause
6.17 provides three options for identifying gas pjpes:
painting the entire gas piping system yellow (this is an international
ruling)
providing the piping with yellow bands at no more than 2。我（6 rn)
intervals
marking or labelling the piping system with the words ” GAS”。r
“ PROPANE” in yellow labels or markings at 20 ft (6 m) intervals.
Clause 6.17.4 requires that piping entering a building having more than one
gas meter must be clearly identified, showing the number of the room,
apartment or area of the building each meter serves.
Shut-off
valves
Clause 6.18 of the Code describes manual valve requirements for large
piping installations:
•
to enable servicing
to provide large buildings that have multiple gas outlets with a clearly
identified shut-off valve in an accessible location.
In large installations the shut-off valve must be ball, eccentric or lubricated
plug type, with piping larger than NPS 1 and tubing 1 inch (25.4 mm)
outside diameter or larger.
Location of valves
A ”readily accessible" manual shut-off valve for each appliance must be
installed:
in either the drop or riser as close as possible to the valve train of a
commercial and industrial type appliance
in the horizontal piping between the drop or riser and the appliance
valve train and may be the same size as the appliance connection when
located within 2 ft (60 cm) of the appliance.
These requirements may be waived when a ” readily accessible single
manual shut-off valve is installed for commercial cooking appliances
mani岛lded in line" (Clause 6.18.3).
Gas Technician 2 Training- Module 10
© Canadian Standards As曲ciation
11
CODE REQUIREMENTS AND APPROVED JOINING METHODS
UNIT 1
Piping that extends between 队,vo buildings must have a shut ff valve at the
point of exit from the first buildings and one at the point of entry to the
adjoining building (Figure 1-7)..
口
Minimum
15inches
(400 mm)*
口
*Minimum 24 inches
(600 mm) under a
commercial driveway
Figure 1-7 Location of shut-off valves when piping
extends between two buildings
When multiple outlets are installed in a classroom, laboratory or similar
room or area, they must be controlled by a clearly marked master shut-off
valve in a readily accessible location within the room.
Shut-off valve controlling several piping
systems
Clause 6.18.5 requires that shut-off valves that control more than one
piping system be:
readily accessible for operation at all times
•
provided with an installed handle
•
provide protection from damage
clearly marked with an enameled metal, substantial fibre or other
permanent tag, for easy identification of the piping system.
12
Gas Technician 2 Training - Module 10
。 Canadian Standards Association
CODE REQUIREMENTS ANO APPROVED JOINING METHODS
UNIT 1
Commercial
cooking
appliances
The Gas Codes stipulate that commerciαl cooking app/i,αnces certified for
use 叭th casters or othenvise subject to movement for cleaning， αnd other
large gas utilization equipment thαt mαy be moved, shall be connected by α
certified connector complying to Standard CAN/CSA-6.16,“Connectors
for Movαble Gas Appliances. "
When a metal connector is used with a commercial cooking appliance
installed on wheels or rollers, a noncombustible restraining device shall be
provided to protect the connector, and the installation shall be in
accordance with Clause 7 .31.4.
Refer to Figure 1-8.
A noncombustible, fixed
means for maintaining a
minumum 6 inch clearance
between combustible
materials and the sides and
rear of the appliance
Note:
Moveable commercial cooking
appliances by must be connected
by a certified connector for
this application
When a metal connector is
used on a commercial
appliance installed on wheels
or rollers, a restraining device
acceptable to the autho时ty
having jurisdiction must be
provided
Figure 1-8 Commercial cooking appliance installation
Gas Technician 2 Training - Module 1O
© Canadian Standards Association
13
TOPIC
2
Appγoved joining
methods
The information in this topic reviews the different types of piping and
tubing systems used for gas, associated valves and fittings, and describes
approved joining methods for gas piping and tubing.
The Gas Code requires that joints in steel piping be threaded, flanged or
welded. However Clause 6.15.2 specifies that underground piping systems
be joined or connected by welding or approved mechanical compression
fittings. This means 也at for the large underground piping described in this
learning unit, for all practical purposes welding is the acceptable method.
The Boilers and Pressure Vessels Act, certification requirements and
procedures related to welding are dealt with in more detail in Unit 2.
General
requirements
of piping,
tubing and
connectors
Pi pin~
material and
fittings
Section 6 of the Gas Code details requirements for piping material and
It also outlines the proper connecting methods and the many piping
practices you must follow.
自ttings.
Table 1-4, on the following page, lists the types Of pipe and tubing, the
fittings used with them, and the approved methods for making connections.
For a good general review of this material, look through the table and
review the articles in the Code pertaining to each.
Gas T民hnician 2 Training- Module 10
© Canadian Standa『ds Association
15
CODE REQUIREMENTS AND APPROVED JOINING METHODS
UNIT 1
Table 1-1 Pipe or tubing, fittings and their connections
Type of pipe 。r tubing
Iron and galvanized iron
pipe
Type of fittings
malleable iron
Type of connections
threaded
steel -
welded (but not
recommended for galvanized
iron pipe}
compression
flanged
mechanical
connector with forged nut
ring ，何 ange
Polyethylene
pipe to pipe
butt fusion
saddle
saddle fusion
compression
not ball sleeve
LK
卜
not ball sleeve
single 45° flare
o
compression
币ared
俨、－
single 45。相are
-
B
flared
LM
-o-VE
叮－ nu
C<
GZ
mWFaw C GMUHnv
- nU
-nM
- -e 4-41nU
am
slip-on
copper to copper
B·
Joints and
connections
in large国size
piping
hot iron socket fusi。n
同川川”’
Steel tube
hub to hub
臼－mw
Copper tube
& bolts
The following requirements in Clause 6.9 of the Gas Code
apply to joints and connections in large-size piping
(NPS 2 1/2 and over).
•
Piping ofNPS 2 1/2 and over must have welded pipe joints.
•
Welding of gas piping must be performed in accordance with a
procedure and by an operator registered under the applicable Provincial
or Territorial legislation.
•
The acceptance criteria for any welds shall be as specified in CSA
Standard Z662, Oil and Gas P伊eline 砂·stems.
Gasket materials are required to be of neoprene or a similar material
that resists any action of gas. Natural rubber is not acceptable.
Lubricants used in valves or controls have to be approved for gas use
and able to withstand the service conditions to which 也eymaybe
subjected (when used in accordance with the manufacturer's
recommendations).
16
Gas Technician 2 Training - Module 1O
。 Canadian Standards Association
CODE REQUIREMENTS AND APPROVED JOINING METHODS
UNIT 1
Iron and
galvanized
steel piping
Steel gas piping must conform to ASTM specification A53 or A I 06 as
described in Natural Gas Instαllation Code, Clause 6.2.1.
Black pipe is most commonly used for gas with pipe fittings of steel or
malleable iron.
Pipe sizes
Black pipe used for gas systems is sized by the Nominal Pipe Size (NPS).
For any nominal size of pipe, the outside diameter (OD) remains the same
and the inside diameter (ID) changes as the wall thickness increases.
Nominal size is a designation used for the pu叩ose of general identification.
Pipe is threaded on the outside only, therefore, the OD must remain
constant.
Types of ends
The ends of gas piping and tubing may be finished in the following ways,
depending on the application:
•
plain
bevelled
threaded.
Wall thickness
Steel pipe used for gas systems is Schedule 40 or Schedule 80. Schedule
refers to the wall thickness of the pipe. Schedule 40 pipe is standard and
Schedule 80 is extra heavy. Schedule 40 and Schedule 80 pipe have the
same outside diameter (OD).
Markings and labels
Piping used for gas systems must be marked and labeled as described in
Natural Gas Installation Code, Clause 6.17.
Other types
of piping and
tubing
Refer to Module 8 of the Gas Technician 3 training material which
describes Canadian installation codes and regulations covering the use of
copper, stainless steel, aluminum and polyethylene piping and tubing.
Gas Technician 2 Training - Module 10
©Canadian S恒ndards Association
17
UNIT 1
CODE REQUIREMENTS AND APPROVED JOINING METHODS
Assignment 1
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
State a Code practice during installation of piping and tubing that will ensure the system stays
leak-free for years to come.
2.
Describe the first pressure test of the system, before appliances are connected.
3.
When and where would you perform a soap test?
4.
What must be done to piping or tubing passing through concrete?
5.
May a sleeve installed in pavement to
pipe inspection point?
6.
List three methods of identifying gas piping inside a commercial or industrial building.
allow 企ee
movement of the pipe also serve as a vent
a)
b)
Gas Technician 2 Training - Module 10
© Canadian Standards Association
19
CODE REQUIREMENTS AND APPROVED JOINING METHODS
UNIT 1
7.
How would you recognize a manual shut-off valve as being approved for installation in a
natural gas or propane system?
8.
How must multiple outlets that are installed in a laboratory (school or other), be protected from
leaking gas into the area accidentally?
9.
Joints in steel piping used in gas systems shall be:
10. List all approved gasket material for gas systems and why natural rubber is not approved.
20
Gas T自如nician 2 Training - Module 10 ·
。 Canadian Standards Assα湖tion
Unit 2
Welding safety, certification
and procedures
Purpose
A gas technician is not required to hold any type of welding certification,
however a thorough knowledge of the requirements for welded gas piping
is important. This, along with an understanding of welding procedures and
welding related hazards, is vital to a safe and secure installation.
Learning
objectives
1. Describe some of the common welding hazards.
2. Describe the safety preacuations that need to be taken.
3. Describe the certification requirements.
4. Describe the preparation that is required for welding testing.
Gas Technician 2 Training- Module 10
© Canadian standa『ds Association
21
Topics
1.
c。『nm。n
hazards ................................................................... 23
Physical hazards ........….........………….......…........…................………...... 23
Chemical hazards ..….........................…········· ........…............................... 25
Environmental hazards ...........… ……..........................…..............…............27
2
2. Safety precautions ........................................”··”......”…........ 29
Protective clothing .......................................................................................29
Fire prevention .................................................................…..........................29
Oxy-acetylene equipment ............................……...........................................30
3.
4.
Certificati。” requirements
Preparati。n
.........….........…............................ 33
for welding ............................”…........................ 35
Measuring pipe and fi位ings .....…....................…······················ •••••••••••••••.•.. 35
Marking the cutting line .................“............................….........…·········…...38
Cutting pipe and tubing .........................………........................…..................39
Pipe and 币抗ing alignment ..............................….................………................40
Joint assembly .‘················…...............…........……….......................…...........41
Tacking ........….........………….........….........…...........…........….......................42
5. Testing ........................….......…............................................... 43
Radiographic testing .....................................................................................43
Liquid (dye) penetrant examination ............................................................. .43
Assignment 2 ”..............”··”......................................................… 45
22
Gas Technician 2 Training - Module 10
© Canadian Standards Assc回ation
TOPIC]
hαzards
Common
As a gas technician you are not required to hold a welding ticket. However,
since you will be working alongside a welder for all welding operations,
you must be aware of a number of hazards and safety issues related to
welding.
Major welding hazards to welders, or gas technicians working in their
vicinity, may be divided into three general categories:
Physical:
Chemical
Environmental
Physical
hazards
•
various types of radiation
•
visible light
•
noise
•
electrical energy
•
flammable and combustible products
•
welding 且rmes
•
dust
•
extremes of temperature
•
poor ventilation
•
biological hazards
and toxic gases
Ionizing radiation
X-rays and gamma rays produce ionizing radiation during the welding
process. These rays are emitted 企om equipment used to gauge 由e density
and thickness of pipes and to check welds. They are invisible forms of
ionizing radiation and can be extremely damaging to unprotected parts of
the body. Welding chambers must be completely shielded to confine x-rays
and protect 由e welder.
Gas Technician 2 Training - Module 10
© Canadian Standards Association
23
\l\ELDING SAFETY, CERTIFICATION AND PROCEDURES
UNIT2
Non-ionizing radiation
Ultraviolet, infrared and visible light radiation are also produced by certain
welding processes. Ultra-violet radiation is produced from the arc or from a
reflection off bright objects like white clothing or shiny metal. If eyes are
not adequately protected, 'it produces arc eye, a burnt and blistered
condition of the eyeballs. Eyes become watery and painful in the period up
to 24 hours after exposure and the condition can last up to five days. It is
usually reversible, but repeated exposure can result in scar tissue and
impaired vision.
Ultraviolet rays may also cause skin bum and blistering in extreme
cases.
In仕ared and visible light radiation can cause eye damage and, after
prolonged exposure, chronic conjunctivitis.
Fire, flying hot metal sparks, etc.
η1e high temperatures involved in welding produce hot metal and sparks
which can quickly cause fire, particularly when working in combustible
surroundings. For a time after work has been carried out around
combustible materials, there can be a risk of fire. Stay around for at least 30
minutes after welding in such environments, and keep fire extinguishers at
hand.
Flying metal particles, sparks and slag are hazardous to eyes, skin and
readily combustible clothing material.
Plastic butane lighters should never be carried in your clothing or
elsewhere around welding operations or welders. If the casing on the
lighter were to come into con阳ct with hot slag it would melt and explode
causing damage 由at could be fatal.
Noise
Substantial hearing loss has been observed in welders as a result of the high
noise levels 仕om sources such as grinding, machining, polishing,
hammering and slag removal.
24
Gas Technician 2 Tr画ining - Module 10
©Canadian S恒ndards Association
叭.ELDING
UNIT 2
Chemical
hazards
SAFETY, CERTIFICATION AND PROCEDURES
Pure oxygen
The combination of pure oxygen (0纱， when combined with other
materials, is a potential combustion danger. Materials that bum in air bum
much more readily when exposed to 02. Other materials which may not
bum in air become combustible in 02. Either oil or grease, not normally
thought of as highly flammable, can cause explosion when brought into
contact with pure oxygen.
Oxygen cylinders are pressurized containers. You should never a忧empt to
repair a faulty cylinder.
Acetylene
Acetylene gas (C2 H2) used in welding work is a colourless unstable
compound. However, even veηF small quantities of acetylene produce a
pungent odour which is quite noticeable. Since any mixture of oxygen and
acetylene is regarded as explosive, ensure you take immediate precautions
if you smell acetylene.
Thete口n “四1stable” means
that the material is likely to break down
(decompose) or undergo a physical change without much provocation or
cause. The point at which this happens is called its critical point.
The critical point of.free αcetylene (acetylene which is the only occupant of
the volume) is 28 psi (193 kPa) pressure at 70。F (21 。C). At this point,
acetylene breaks down into carbon and hydrogen and results in an
explosion 仕om the hydrogen gas. If the temperature is increased, the
pressure at which acetylene becomes critical is lowered. To allow for any
temperature fluctuations in the work area，企ee acetylene is not stored or
used at pressures over 15 psi (103 kPa).
Other physical properties of acetylene are:
Explosive Limits:
Temperatures:
Ignition
Burning
Lower
Upper
763-824。F
4770。F
(406-440。C)
(2632。C)
2.50% Acetylene
97.5% Air
81 % Acetylene
19% Air
Gas Technician 2 币raining - Module 10
© Canadian Standards Association
25
VIELDING SAFETY, CERTIFICATION AND PROCEDURES
UNIT2
Storage of cylinders
Cylinders must be stored where they will not be knocked over or damaged
by falling objects, passing vehicles, or persons. They should not come into
contact with salt, corrosive chemicals or fumes. Whether they are 岛II or
emp守， cylinders should always be secured upright to a stationary object,
such as a wall ot portable cart to keep them from falling down. Figure 2-1
shows safe storage conditions for acetylene containers. Empty containers
are chained to one wall and 创l containers are separated and chained to the
opposite wall.
。
。
。
H
。 O
。
。
。
。
。
000 。
00
‘
。
Empty
:o.
旦iii> I
Figure 2-1 Storage of full and empty cylinders
26
Gas Technician 2 Training - Module 10
。 Canadian Standards Association
V\ELDING SAFETY, CERTIFICATION AND PROCEDURES
UNIT2
Figure 2-2 shows a portable oxy-acetylene outfit where the acetylene and
oxygen containers are separately chained to a cart in an upright position.
The cylinder cart is designed to roll easily when tilted back on its wheels,
yet be stable and secure when it is stationary.
Protective
cylinder cap
Oxygen
Portable
cylinder cart
Figure 2-2
Safety chain
Po『table
storage unit
Other chemical hazards
Other chemical hazards to be aware of include risks of fire 企om
:flammable/combustible products, toxic gases and fumes, and dust which
may become :flammable.
Environmen钮i
hazards
Inadequate ventilation of welding shops or confined work areas produces
dangerously toxic, combustible or inflammable conditions
Extremes of temperature during welding can cause excessive, sometimes
life-threatening effects:
•
Extreme heat causes muscle cramps, dehydration, sudden collapse and
unconsciousness.
Extreme cold leads to fatigi后， irregular breathing, lowered blood
pressure, confusion and loss of consciousness.
Gas Technician 2 Training- Module 10
© Canadian Standards Association
27
V'.ELDING SAFETY, CERTIFICATION AND PROCEDURES
UNIT2
Welding helmet
Optional
respirator
\\
Steel tpe boots
Figure 2-3 Protective clothing for welding operations
28
Gas I忌chnician 2 Training - Module 10
© Canadian Standards Assoc阳ti on
TOPIC 2
Sαifety pγecαutions
Proper safety precautions to be observed wherever welding work is being
carried out include: appropriate protective clothing, radiation protection,
fire prevention, appropriate oxy-acetylene safety measures, and working in
a well-ventilated environment.
Protective
clothing
Heavy clothing fabric that sheds sparks is recommended for wear around
welding operations. Leather is best, but heavy denim is adequate and more
practical. Wear clothing that is free of grease and oil and that covers all
exposed skin. Refer to Figure 2-3 opposite.
•
Wear adequate eye and face protection against visible light rays, ultraviolet light rays, in企ared rays, heat rays, and flying metal particles,
sparks and slag. Gas technicians working with welders should wear
flash goggles.
In special circumstances you may have to wear a respirator or mask.
•
Wear gauntlet typ巳 gloves .
.•
Cover and protect head and hair by wearing a cap or other protective
headgear.
•
Protect your feet with steel-toed boots.
Wear cu旺less pants and make sure there are no tears, frays or hanging
pieces of light fabric or jewelry attached to your clothing. Ensure yo山
shirt pockets have flaps.
Fire
prevention
Strictly follow all fire prevention orders at the work-site. The high
temperatures involved in welding can quickly cause extreme danger of fire
and explosion in combustible surroundings and when flammable
equipment and materials are in use. (See the following section for specific
precautions when working with oxy-acetylene equipment.)
Keep fire extinguishers close to hand and ready for use. Stay around areas
where welding has been carried out for 30 minutes after the work has been
completed.
Gas Technician 2 Training- Module 10
© Canadian Standards As回ciation
29
队正LDING
SAFETY, CERTIFICATION AND PROCEDURES
Oxy-acetylene
equipment
UNIT2
Oxygen cylinders are protected from extreme pressure caused by heat by
means of a fusible metal rupture disk that controls the slow escape of gas.
Figure 2-4 shows the components on an oxy-acetylene outfit, including its
safety features.
Adjusting
screw
Acetvlene
regu ator
/!
Oxygen
hose
All oxy en fittings
- right-hand thread
Adjusting /
screw
/
Oxygen
cylinder
All acetylene
青ttings
- left-hand thread
RFCV
Acetylene
cylinder
Torch
Note the following:
• All the oxygen connections have
时ght-hand threads
• Cylinder valves must be fully open
while in use
• Ti。 ensure that the two gases
cannot mix in the hose, reverse 伺ow
check valves (RFCV) are attached
to each end of the hose
• The cylinder has no fixed
Acetylene _,...,,..,,
hose
draw-o仔 limit
Fusible plugs
Figure 2-4
30
Comp。nents
of an oxy-acetylene outfit
Gas Technician 2 Training 『 Module 10
©canadian S恒ndards A部ociation
w.三LDING
UNIT2
SAFETY, CERTIFICATION AND PROCEDURES
Rules for working with oxy-acetylene
equipment
Follow these rules when working with oxygen and acetylene.
•
•
Never use oxygen:
-
as a compressed air substitute
-
to start or run internal combustion engines
’
to blow out pipe or tubing lines
帽
to
-
for ventilation
”
to dust off clothing or work areas.
create pressure
Keep oxy-acetylene equipment away from oil or grease. Never oil
regulators or torch parts.
If a cylinder appears to be leaking or faulty, it must be removed to the
outside, left in the open, tagged to indicate its fault, and the supplier
notified. Never attempt to repair it yourself.
Acetylene cylinders are required by Codes to have at least one fusible
plug on each end of the cylinder. The plug, with a melting point of
212°F (100。C) is designed to melt out in case of fire. This allows for a
slow, controlled escape of gas and avoidance of explosion. Note the
following rules 岛r ace可lene cylinders:
To prevent acetone 企om being drawn off, use the cylinder in a
vertical position.
Store cylinders in a cool area.
Never transfer acetylene from one cylinder to another.
Do not attempt to interchange equipment 仕om one gas type to
another.
If your cylinder has a key-type acetylene valve, open 江 only
1 112 turns. The hand-wheel type should be opened fully.
If you smell acetylene, immediately extinguish all open flames and
ventilate the room or work area，问fore you turn on a light switch 扩
possible.
Test for leaks using a soap test (never test near an open卢ame).
Welding shops are required to have a minimum of four air changes per
hour. Ensure 也at good ventilation is provided at all times around
welding operations.
Gas Technician 2 Training- Module 10
© Canadian Standards Association
31
TOPIC
3
Certification γequirements
Welders are required to meet the standards set out in provincial Boilers and
Pressure Vessels Acts. Testing of welders for qualification in Canada is
conducted by or through the governing provincial Boiler and Pressure
Vessel Safety Branch (BPVB). The BPVB may issue a red seal of approval
for interprovincial certification of welders. Before performing any work
requiring welded pipe, contact the provincial gas safety branch for specific
certification requirements in your province.
The following general rules relate to qualification:
•
No welding operator shall weld except under an approved procedure.
•
The chief inspector shall issue an identification card to eve可 welding
operator who passes a qualification test.
•
Every identification card shall indicate the employer for whom the
welding operator is qualified to weld or that he or she is self-employed
or that he or she desires to be employed and the class or position of
welding that he or she is qualified to do.
•
A welding operator may be required at any time to pass such further
qualification tests as the chief inspector may require, at which time his
or her identification card shall be cancelled, and, on passing such
further tests, a new identification card shall be issued to him or her.
•
In 也is
section,”employer” includes a trade association of persons or
companies whose business includes welding.
Gas Technician 2 Training - Module 10
© Canadian Standards Association
33
TOPIC4
Pγepαγαtionfoγ welding
Shielded metal arc welding is the process normally used for welding steel
gas piping. However, the welding procedures used for this process fall
beyond the scope of this learning unit, and would not be part of a gas
technician ‘s normal duties. The layout of welded piping systems is the gas
technician ’s responsibility and may include such tasks as measuring,
marking, cutting, joint preparation and assembly. The following sections
give an overview of typical layout procedures.
Measuring
pipe and
fittings
Before any welding operation is started, the gas technician selects pipe
sizes and related fittings and connectors, measures pipe lengths and marks
locations of joints and connectors.
Piping drawings represent each pipe by a single line drawn along the centre
of the pipe, with the fittings represented by the meeting of lines. Dimension
lines are drawn parallel to the length in question, with arrows in opposite
directions pointing toward the boundaries of the measurement.
Figure 2-5 shows a segment of a piping system with the dimensions
7 7/8 inches (200 mm) end-to-centre of pipe. This does not mean that the
pipe must be cut exactly 7 7/8 inches long, since you must allow for
fittings.
A7
ε
ε
8
f唱
的
。
§
c:
∞
俨‘
B －卢卢－－－·~」 h
Figure 2-5 Piping drawing showing a segment of a piping system
Gas Technician 2 Training- Module 10
Association
。 Canadian Standa『'ds
35
队ELDING
SAFETY, CERTIFICATION AND PROCEDURES
UNIT 2
Pipe length is measured along centre lines. Where two centre lines cross, a
centre point (Figure 2-6) is located in a fitting. In Figure 2-5, the dimension
7 7/8 inches (200 mm) refers to the total distance between centre point A
and point B.
＼丁！（
EEgigsh
4川
This is known as an end-to-centre measurement. The tee in Figure 2-6 will
make up part of the 7 7/8 inches (200 mm); a 1/8 inch (3 mm) root gap and
a length of pipe will make up the rest
｜↓－
Figure 2-6 Centre point of a fitting
To find the coηect length to cut the pipe, you have to measure the fitting.
Measure the distance between.the centre point and the point where the pipe
will end. Subtract this fitting allowance from the dimension shown on the
drawing. This dimension-minus-fitting allowance is the correct length to
cut the pipe.
As shown in Figure 2-6, length A is deducted 仕om the overall end-tocentre measurement to arrive at 也e length of pipe needed.
Common weld fittings
Examples of common butt weld fittings are shown in Figure 2-7. To
calculate the fitting allowances for weld fittings, you have two options:
1. You could make field measurements.
2. You would refer to a table such as Table 2-1 which shows various
dimensions for butt weld fittings s趾1ilar to those illustrated in Figure 27. Table 2斗 is shown in Imperial units of measurement, since these are
the most widely used measurements for pipe and fitting dimensions.
36
Gas Technician 2 Training - Module 10
© Canadian Standards Association
队i£LDING
UNIT2
90°Long radius elbow
SAFETY, CERTIFICATION AND PROCEDURES
45°elbow
Concentric reducer
出
Straight tee
Figure 2-7 Common
weld 负忧ings
Table 2-'1 Sample table of dimensions for butt weld
90。 long
radius
elbows
45。 elbows
and dimensions
n创 ngs
Tees and
crosses
Reducing
couplings
c。 N/ECC
Nominal pipe
size (inches)
一－一”’A－一一一
一一一－B－一一一
一一－C一一一
1/2
1.50
。蝇 62
1.00
3/4
1.12
0.44
1.12
1.50
1.50
。‘88
1.50
2.00
1 1/4
1.88
1.00
1.88
2.00
1 1/2
2.25
1.12
2.25
2.50
2
3.00
1.38
2.50
3.00
2 1/2
3.75
1.75
3.00
3.50
3
4.50
2.00
3.38
3.50
31/2
5.25
2.25
3.75
4.00
4
6.00
2.50
4.12
4.00
5
7.50
3.12
4.88
5.00
6
9.00
3.75
5.62
5.50
8
12.00
5.00
7.00
6.00
10
15.00
6.25
8.50
7.00
12
18.00
7.50
10.00
8.00
Gas Technician 2 Training - Module 10
© Canadian Standards Association
·…’一－0－一…一一
37
V\ELDING SAFETY, CERTIFICATION AND PROCEDURES
Marking the
cu忧ing line
UNIT2
For a square cut, the cutting line may be accurately marked using a
wraparound and a piece of soapstone. A wraparound is a strip of leather
belting or other strong, flexible material approximately 4 inches (100 mm)
wide.
The wraparound should be long enough to go around the pipe at least
1 112 times. The edges must be perfectly straight.
Use the following procedure to mark a straight line around the pipe:
1. Place one edge of the wraparound against the point at which the pipe is
to be cut.
2. Circle the pipe with the wraparound and line up the edges accurately as
shown in Figure 2-8.
3. Use the wraparound edge as a guide to draw a line around the pipe with
a piece of soapstone.
Pipe
Mark cutting line here
Figure 2-8 Using a wraparound to mark cu忧ing line
38
Gas Tee才mician 2 Training - Module 10
。 Canadian Standards As就沁iation
叭.ELDING
UNIT2
Cutting pipe
and tubing
SAFETY, CERTIFICATION AND PROCEDURES
Gas technicians use a variety of methods to cut pipe and tubing. Pipe
cutters are frequently used on small pipes and may also be used on larger
piping. On piping being prepared for welding, the pipe end must be
bevelled to accommodate the welding procedure. This is generally done in
one of the following ways:
A pipe cutting and bevelling machine is used (Figure 2-9).
•
The end can be cut using a pipe cu扰er or cut-off saw, then beveled to
suit, using a side grinder (Figure 2-10).
Cutting
torch
Figure 2-9 Pipe cutting and bevelling machine
Figure 2-10 Angle side grinder
An oxy-acetylene torch is often used to cut large diameter pipe. The piping
is bevel cut with the torch by hand, or by placing the torch in a machine
出at is angled to suit the bevel. The end is then further prepared with a side
grinde立
Gas Technician 2 Training- Module 10
© Canadian Standards Association
39
w.三LDING
SAFETY, CERTIFICATION AND PROCEDURES
UNIT2
剖
pum 咱
pn
dm
em
a3m
nt
.
n
AT
--
To avoid weld failure and system malfunction, the gas technician must
ensure the pipe fitting and alignment is correct before any tacking or
welding of fittings, valves or pipe. Fitting and alignment work must
include:
•
preparation of pipe ends
assembling and gapping joints
alignment of pipe and fittings to other parts of the piping
tacking.
To prepare pressure pipe for butt welding or matching of fittings, you V”
bevel the ends to an angle of approximately 37 1/2 degrees. Note that the
bevel does not come to a sharp point, but has a flat portion of
approximately 1116一 1/8 inch (1.ι3.2 mm). This is called a land or root
face.
The land helps in preventing the sharp edges of the bevel 仕om burning off
during welding (Figure 2-11 ). Note that welded pipe fittings and pipe
lengths come supplied with standard bevelled ends which only require
cleaning.
37
1/2。
L「…川
Figure 2-” Bevel preparation
40
Gas Technician 2 Training - Module 10
© Canadian Standards Association
V\£LDING SAFETY, CERTIFICATION AND PROCEDURES
UNIT2
Joint
assembly
Before tacking, it is important to assemble and gap together the pipe and
fittings. The gap (or root) opening between the two ends is evenly spaced at
1/16一 1/8 inch (1.6-3.2 mm). Besides maintaining the gap between the
bevelled ends, the inside and the outside surfaces of the joint must match
evenly without high or low spots.
Clamps are often used to maintain the correct gap and high-low alignment.
On smaller pipe and fitting sizes, proper alignment is maintained using an
angle iron. Figure 2-12 shows three methods of maintaining pipe and
fitting alignment.
Hand clamp
Flange and pipe clamp
Figure 2-12 Joint alignment methods
Gas
T~nician
。 Canadian
2 T1『aining-Module 10
Standards Association
41
υNIT2
V\ELDING SAFETY, CERTIFICATION AND PROCEDURES
Tacking
Tack welds are made in aligned and gapped pipe and fittings to hold the
piping in place during complete welding operations. A common method is
to make four tack welds evenly spaced around each joint. The tack weld
should be three times the thickness of the pipe wall.
Sometimes a spacer wire is used, in which case the wire must be removed
after the first tack is welded. Make the second tack
180 degrees opposite the first tack. The third and fourth tacks are made at
90 degree angles to the first and second tacks.
When making the third tack, adjust the gap until the openings are
equalized. If one side of the root opening is slightly wider, place the third
tack weld at that point, since any shrinkage in the third tack weld will even
out the root opening space.
The fourth tack weld is at 180 degrees 仕om the third tack. Figure 2-13
shows the orientation and order in which the tacks should be made al<?ng
由e circumference of the pipe.
Tack #3
Tack ＃丁
9广
Tack #2
Tack #4
Figure 2-13 Four tack welds
42
Gas 丁丽chnician 2 Training- Module 10
© Canadian standards Association
TOPIC
5
Testing
Pressure testing of welded pipe to Code requirements is carried out using
normal pressure testing methods with air or an inert gas. Other nondestructive testing that may be required includes radiographic testing and
liquid dye testing.
Radiographic
testing
Liquid (dye)
penetrant
examination
Radiographic (X” ray) testing may be conducted upon a customer ’ s request,
or according to job specifications. Radiographic testing must adhere to
Section 5, Article 2 of the American Society of 岛1echanical Engineers
(AS孔伍） Boilers and Pressure Vessels Code. When the testing is
completed, the radiograph must be submitted to the inspector for
acceptance.
Section 5, Article 6, of the Boilers and Pressure Vessels Code sets out
requirements for liquid (dye) penetrant examination of welded piping. The
part being tested is allowed to dry and a “ developer” is applied. The
penetrant shows through the developer if any faults are present.
The dyes in the penetrant are visible under white light (colour contrast), or
under ultra蝴violet light.
Gas Technician 2 Training- Module 10
© Canadian Standards A馅。αation
43
叭.tLDING
υNIT2
SAFETY, CERTIFICATION AND PROCEDURES
Assignment 2
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
The three general categories of major welding hazards to workers in the vicinity of welding
operat10ns are:
a)
、、‘
J，
b
2.
State the adverse health effects from exposure to welding X-ray equipment.
3.
List the adverse effects from ultraviolet radiation produced by arc welding.
4.
After welding is completed in an area where combustible material is present, how long should
a “ fire watch" be maintained?
5.
List the 可pes of personal protective equipment that must be worn when working with or
around a welder.
Gas Technician 2 Training- Module 10
© Canadian Standards Association
45
w.二 LDING
SAFETY, CERTIFICATION AND PROCEDURES
UNIT2
6.
List two important safety precautions to be observed when working with an oxygen cylinder.
7.
Is acetylene
8.
孔'hat
9.
What type of gloves should be worn around welding operations?
aveηstable
gas that is easily compressed to high pressures?
should be done if welding is taking place in a confined area?
10. Should oxygen and acetylene regulators be oiled regularly?
11. How many air changes per hour are required in a welding shop?
12. With what are oxygen and acetylene cylinders fitted to minimize the possibility of explosion in
case of fire?
13. To what angle should pipe be bevelled if it is to be welded?
14. When the pipe and fittings are set up for welding, how wide is the root gap?
46
Gas Technician 2 Training 一 Module 10
。 Canadian Standards Association
Unit 3
Utility and non-utility piping
Purpose
A gas technician must be prepared to install various types of pipe and tubing, as well as recognize many other types. Piping can caηy substances
other than gas, and the type of piping is not always an indicator of what is
inside. A basic understanding of how piping is identified on drawings, and
on the worksi旬， is important to ensure installation and repairs are done
safely and efficiently.
Learning
1. Describe utility piping.
o均ectives
2. Describe non-utility piping.
3. Distinguish gas piping 仕om other types of piping.
Gas Technician 2 Training- Module 10
© Canadian Standards Association
47
Topics
1. Utility piping and tubing .........…........…..............................… 49
Underground piping …………－·．．．．，．．．．．．．．．．．．．．．．··－……·町，... ····· .49
Underground tubing ................…··”………..……··…………... .. . ..... 50
2. N。n-utility piping and tubing .........................….................… 51
3. Identification and tracing ........................................... ~ .......… 53
Type of pipe, colour coding and marking ......……········…........................... 53
Blueprint identification .........……国…………................ .. .. ..... .””’...... 54
Tracing ..............………..……… ……….
..….............................. 54
2
Assignment 3 ..........…..................................................…............. 55
48
Gas Technician 2 Training - Module 10
© Canadian Standards Association
TOPIC
1
Utility piping αnd tubing
Piping and tubing in existing buildings or underground pipe lines are not
always clearly identified. As a gas technician, you may have to work on or
isolate an area of piping or tubing and be sure of how to determine which
piping or tubing conveys what. This is not always easily done, but there are
certain steps you can take to ensure that the contents of a sealed line can be
clearly identified.
Underground
piping
Piping is run underground to caηy a variety of things from one place to
another, such as electricity, water, sewage and gas.
The location and identification of underground piping is important
whenever work is being done 出at might affect or come in contact with
underground lines. All utility lines are blueprinted by the relevant utility
when first installed and the plan drawings are updated whenever there have
been changes to existing systems. The utility will supply a drawing of area
piping whenever it is required, for digging, new construction, etc.
Gas service lines normally run in a straight line 企om the distribution line at
the street to the gas meter.
Underground gas piping will be either wrapped steel pipe or polyethylene
plastic pipe.
•
Wrapped steel is coated with polyethylene and coloured either blue or
yellow.
Polyethylene plastic gas piping is available in various colours: yellow
or orange is normally used by the utility.
When polyethylene plastic pipe is used underground, a minimum 16-gauge
copper wire is taped along the piping 岛r tracing purposes using a metal
detector or radio signals.
Gas Technician 2 Training - Module 1O
© Canadian Standards Association
49
UTIL门Y
AND
NON 句 UTILITY
Underground
tubing
PIPING
UNIT3
Underground utility piping is generally either steel or polyethylene
plastic-however, copper tubing is approved for underground use. So,
while it may not be common, there will be areas of the country where you
will encounter underground utility gas tubing.
Normally, gas tubing that is installed underground must meet the Gas Code
requirements. This means that the tubing will be either type K copper or
type Lor G polyethylene or PVC coated. However, gas utilities are
governed by the requirements of the CSA Z662 Oil and Gas Pipeline
Systems standard. This may involve requirements that are somewhat
different to those to which you are accustomed as a gas technician.
Whenever you are dealing with underground utility p伊ing, you should
contact the utility in the area for proper locations and identification.
50
Gas Technician 2 Training - Module 10
© Canadian Standards Association
TOPIC
2
MM
t,
7
W4P.mi ng on,d
4 ’ι
4 ’ι
NOn
g
ULU n
Most, but not all, non-utility gas piping and tubing is run above ground.
The piping downstream of a gas utility meter is usually the responsibility
of the property or building owner. In most instances the piping runs from
the meter into the building and remains in the building.
There are situations where gas piping is run underground downstream of
the gas meter, for example:
com~lexes that have more than one building requiring gas but the gas is
distributed from one central meter.
single family dwellings that have a detached building for a pool heater
or other gas appliance.
Gas Technician 2 Training- Module 10
。 Canadian Standa『ds Association
51
TOPIC
3
Identificαtion
and tγαcing
Whether you are dealing with utility or non-utility piping or tubing, it is not
always clear or easy to identi命 at particular locations underground which
are gas lines and which are not.
Underground gas piping downstream of the gas meter will be one of three
types: polyethylene coated steel pipe, polyethylene plastic pipe, or copper
tubing, either coated or non-coated. Knowing this will help you identify
underground piping but will not always ensure correct identification. Water
lines are also installed underground using copper and plastic. Identification
of above-ground piping is easier but not always obvious.
The following are the typical indicators of the contents of sealed lines.
type of pipe and its colour coding and marking
•
blueprints
tracmg.
Type of pipe,
colour coding
and marking
There 盯e separate criteria for identification of underground and aboveground gas piping and tubing.
Underground gas piping and tubing
•
Steel will have either blue or yellow plastic coating.
Polyethylene pipe may be yellow or orange; pipe will have markings
indicating it is approved for gas, and a tracer wire should be found with
the piping.
•
Cop~er tubing type Lor G will have a yellow polyethylene or PVC
coating. Copper tubing type K approved 岛r use uncoated will have
markings stamped on the side.
Underground piping and tubing, other than gas
Common water lines are copper, plastic, galvanized steel, cast iron, and
ductile iron.
Common sewer lines are plastic and cast iron.
Electrical and telephone conduits are metallic and non metallic.
Gas Technician 2 T1『aining - Module 1o
Standards A路。ciation
。 Canadian
53
UTILITY AND NON-UTILITY PIPING
UNIT3
Above-ground piping and tubing
Gas lines above ground will be either steel or copper, identified by yellow
paint, yellow banding, or labelling (natural gas copper tubing). The B149.1
Gas Code specifies the colour coding of piping and tubing as follows:
a) the entire piping or tubing system shall be painted yellow;
b) the piping or tubing system shall be provided yellow banding; or
c) the piping or tubing system shall be labelled or marked “gas”。r
“ propane” utilizing yellow labels or markings respectively. When
identified in accordance with (b) or （吟， the identification shall be
no more than 20 feet (6 m) intervals. However, tubing installed in a
residential occupancy shall be identified at no more than 6 ft (2 m)
intervals.
Other above-ground piping, such as water piping, drainage piping,
sprinkler lines etc, may or may not be identified by marking or
colour-coding.
Sometimes water lines and heating pipes are insulated to maintain
temperature or to eliminate condensation. The insulation may be
colour-coded and the tubing marked for identification and to show
direction of flow.
Blueprint
identification
Piping in commercial and industrial establishments is generally installed
according to the blueprints provided, and mechanical and plumbing
drawings will show all the various piping arrangements. These drawings,
along with the specifications, will indicate the types, sizes and location of
installed piping.
Whenever blueprints are used to locate and identi命 piping，由efinal
drawings must be used. These are called “ As Built" drawings meaning 由at
也e piping arrangement on the original blueprint may have been changed
and the drawing revised to show any changes. 咀ie drawing will indicate
也e system, as it was built.
Blueprints and drawings are covered in more detail in Unit 4.
Tracing
In some situations the easiest and s町·est way to identify what a sealed pipe
is carrying is to trace 让 back to its source. Obviously you will need to look
at and follow the entire line to ensure proper identification.
54
Gas Technician 2 T1『aining - Module 10
。 Canadian Standards Association
UTILITY AND NON UTILITY PIPING
UNIT 3
Assignment 3
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
What size is the tracer wire (a) on underground gas piping? (b) What material is it made of?
a)
..
、、
b,,/
2.
Who is responsible for piping downstream of the meter?
3.
Coatings on underground steel pipe are made of (a) what material; and (b) in which colours?
a)
..
、
hu
/
4.
What are two methods to identify above-ground gas piping?
a)
b)
5.η1e
6.
final drawings on a job are called:
The surest way to
identi命 contents
Gas Technician 2 T1『·aining - Module 1O
© Canadian Standards Association
of a sealed pipe is to:
55
Unit4
Piping layout, drawings and
symbols
Purpose
Before installing any equipment, the gas technician must have a plan. The
plan must take into consideration things like how, what, where and when.
The plan can be ve可 simple, such as setting up a small gas barbecue, or
very complex, such as for heating a large office building. In many cases the
basic plan will be supplied through blueprints and specifications.
Documents such as these, and a knowledge of how to read and apply them,
will ensure that the piping layout and installation goes ahead with a
minimum of problems.
Learning
objectives
1. Explain blueprints and specifications.
2. Describe valves.
Gas Technician 2 Training - Module 10
© Canadian Standards A鹅。ciation
57
Topics
1. Blueprints and specifications ..................................….......… 59
Blueprints ....町，.... . . . .............…….....,……….................... 59
Specifications. …......…….,...............-………..………··…………”..... 60
Interpreting instructions and symbols ...…··…，......…………...............国........... 61
Manufacturers' installation data . .... . . ... . ..... . .. .. . . . .. .....…·… …·········. 64
E
2. Valves ..........................…·….......…····························’··········….67
Manual ．．．……········…．．．．，．．．．．．，．．．．．町……..…··….......…·………... 67
Automatic ..........坦……………………………. ······· .……·-…................ 70
Manual/ Automatic .........……·········…................,… …............... 71
E
Assignment 4 ............................................................................… 73
58
Gas Technician 2 Training - Module 10
© Canadian Standards Association
TOPIC 1
Blueprints and specifications
The installation of gas piping is a regular part of the gas technician ’ s duties.
How and where the piping is installed depends on the type of building, the
type of piping and piping equipment, and the location of the piping.
Answering these questions begins with blueprints and specifications.
Blueprints
On small buildings or installations found in single family dwellings, the
gas technician can work from a blueprint or set of house plans. These
would not normally show water or gas piping. However, the location of
fixtures and equipment (such as water heaters and furnaces) for water or
gas would be shown. Then the piping would be installed, at the discretion
of the gas technician. The technician does this in accordance with all
applicable codes and bylaws.
Many gas technicians make an isometric drawing of the planned
installation which can be used as a takeoff sheet for estimating and
ordering of materials. This could include a drawing that can be submitted
for approval to the local authority, if required.
On larger installations, the technician works from a complete set of
blueprints. This set includes architectural, structural, electrical and
mechanical drawings and so on, as required. The gas piping and equipment
is found on mechanical drawings, and located and identified on the plan
drawing. There may also be detailed and isometric drawings of the layout
of specific equipment and components.
The piping shown on 由e plan is normally a rough location of where piping
is to be installed, but there are many factors to be considered before you
can begin installation. As a gas technician, you must be aware that you are
only one of many trades involved in the building process. Before installing
any piping, check other piping or equipment located h 也e same area, such
as plumbing, duct work, light fixtures, etc., since all installations must be
coordinated with the other trades. It is vital to problem－仕ee installation that
you have a full set of prints showing both the structure and all 由e
requirements of other trades.
Gas Technician 2 Training - Module 10
©Canadian S惚ndards Association
59
PIPING LAYOUT, ORAWNGS AND SYMBOLS
UNIT4
Piping may be located in ceilings, crawl spaces, pipe chases, rooftops,
floors, underground, or in open areas. Wherever the location, the piping
must meet Code requirements, as well as requirements of the building
itself. Figure 4-1 shows a typical piping diagram for a building containing
two gas appliances.
1 1/4"
（阮iler
G
]
G
3/4"
口时阳
Scale 1/8”= 1 ＇。”
Figure 4-1 Piping d阳wing of a building containing two gas appliances
Specifications
A specification normally accompanies the construction prints, and can vary
considerably in length depending on the size and complexity of the project.
On smaller jobs，由e specifications-or “ specs” -may consist simply
of a list of materials written on 由e same page as the drawings.
On large projects, the specifications are printed in book or manual
form. Often spanning several hundred pages，也ey cover every aspect of
the job from 也e initial bidding process to the final payment.
60
Modu悔 10
。 Canadian S恒nda『ds Association
Gas Technician 2 Training -
PIPING LAYOUT, DRAWN GS AND SYMBOLS
UNIT 4
Precedence of specifications
The specification is an integral part of the contract documents and is
generally considered to be the most important document after the actual
written agreement. For example, if there is any disagreement between the
specification and a drawing, the information in the specification is usually
taken to be correct. The reason for this is that, since the specifications are
usually prepared last, they reflect final decisions. Written instructions also
ca汀y more weight in a court of law. However, if a discrepancy is found, it
should be reported to the architect and the correct information confirmed in
wntmg.
Interpreting
instructions
and symbols
Blueprints and specifications provide the gas technician with instructions
for the installation of gas piping and equipment. To read and interpret the
drawings, you must be aware of how the various pipe lines are identified on
the drawings, as well as the symbols for related fittings and valves. Figure
4-2 is an example of how figures show line identification and fitting
symbols.
Temperature and
pressure relief valve
2汁M iI-2 ·2.
；一寸《
1
占
i
u
.
》国 R
00←十C叫r#5
Heater
咀m
DM阳
2 1/2飞＋
----I'•
s阴II into FD.+'
／创
·-
Figure 4-2 Sample pipe 币忧ing drawing
Gas Technician 2 Training- Module 10
standards Association
。 Canadian
61
PIPING LAYOUT, DRAWINGS AND SYMBOLS
UNIT 4
Symbols
Symbols are the shorthand signs used on drawings. Most are recognizable
internationally, but some countries still have different symbols. Accredited
organizations are 也e International Standards Organization (ISO), Canadian
Standards Association (CSA) and the American National Standards
Institute (ANSI). These three organizations publish tables of symbols for
welding, piping, surface texture, and electrical elements, all of which you
will use as a gas technician.
The Canadian Gas Association lists all of the symbols you will use as a gas
technician in the Indus的J Glossary to its Natural Gas Manual. Figure 4-3
shows the most common piping symbols.
Double line
Single line
Na阿ie
Left
Front
90°Elbow
空
45。 El切w
Right
Left
气
~
~
~
i
尘
~
Tee
蛋
任
§
Wye
运
~
(3
重
意
自
Cross
歪
tfi
§
~
口
Cap
Plug
Reducing
coupling
Front
E与
企
~
自
口
Il
9
~
也
E一
b
Right
•
-t::iFigure 4-3 Common piping symbols
62
Gas T职::hnician 2 Training- Module 10
©Canadian S恼ndards Association
PIPING LAYOUT, ORA叭ANGS AND SYMBOLS
UNIT 4
Figure 4-4 is a plan drawing of a recommended valve train for a lowburner with an input of over 400α附 Btu/h to 10αmα泊 Btu/h. Each
component is identified by a symbol. The key to these symbols is shown in
Figure 4-5.
press旧e
2
甘卜扣－飞
＼、一
Figure 4-4 Drawing of a valve train showing symbols for various components
S泸nbol Interpretation
Symbο陆
-{><}-
T
Pressure test point
I
Uni
nnec
2IPil。
医三三旦 3
I Pilot pressure regulator low pre目ure
世ω
Gas input 响。w ratio valve automatic
if modulating
1
I Symb。i In怡rpre恼ti。n
~：~n1＝~~~~；.：：~~~· slow-opening input control！括电 41 阳 automatic control 削 safety shut-off valve
Main burner automatic, safety shut-o胃 valve
Main burner gas pressure 陪gulator
(low pressure)
Pilot supply take-o何
S归tem 啕ulator
Figure 4-5 Key to symbols used in Figure 4-4
Gas Technician 2 Training- ~odule
© Canadian Standards Association
10
I
Symb由
们一蜘一们
Main burner test firing valve manually
。perated low p如essur警
：内；
63
PIPING LAYOUT, DRAlllllNGS AND SYMBOLS
UNIT4
Plans for piping installations also contain special lines to distinguish the
various types of pipes. Figure 4-6 shows an orthographic view of some
common piping line symbols and what they represent.
Acid
Acid waste
Cold water
Compressed air -A －…－－一－
A-
Hot wate「
Fire line
-F 一一一－ F 一
Hot water
return
Gas line
-G 一－ G 一
Vacuum
- V - V-
Figure 4-6 Various piping line symbols
Manufacturers'
ins＇坦nation
da钮
Manufacturers provide certified installation and service manuals with their
appliances. Although the literatµre varies from company to company, and
from product to product, all necessary information for the installation and
basic maintenance of the appliance will be included in the manual. It is up
to you to find it!
The following exce甲ts from manufacturer ’s manuals will show you 由e
various ways installation information can be presented. Again, it is up to
you to read the complete manual and study the charts and diagrams before
you start so 也at you can begin to locate the tools, hardware, wiring, and
piping needed for a trouble-free installation.
Model number
Manufacturers often publish one 回t of instructions for many different
models of the s缸ne series of appliances. Table 4-1 shows a typical example
of the different vent and combustion pipe details for six different models of
由e same appliance.
64
Gas Technician 2 Training - Modu梅 10
©Canad恼n Standards Associa回on
PIPING LAYOUT,
UNIT 4
ORA叭ANGS
Table 4斗 Example of air and venting information for various
Model number
Combus
Combustion
Vent pipe
。r series
tion air
air pipe
pipe
terminal
2 in diameter
2in
2in
Model 40 ME
90。 elbow
diameter
diameter
20甲50 负
20-50 ft
Model 50 ME
Model 40/50 ME
Model 70 ME
Model 80 ME
3in
diameter
20-60 ft.
3 in diameter
90。 elbow
3in
diameter
20-60 佼
ANO SYMBOLS
models
Vent
terminal
2in
diameter
45°
elbow
3in
diameter
90。
elbow
Model 70/80 ME
Tools and hardware
Manufacturers will often indicate the tools and hardware required for the
installation as shown by the following excerpts:
Level each unit by acijusting levelling bolts or legs. Use a spirit level
and level unit four ways.
Use a Robertshaw test instrument with special disc 沙pe thermocouple, or
reliable "su旷ace ” type thermometer.
They may also indicate when hardware is supplied, for example:
Secure in place with 阳10 hex nuts supplied.
Gas Technician 2 Training 四 Module 10
© Canadian Standards A岱ociation
65
PIPING LAYOUT,
ORA叭~NGS
AND SYMBOLS
UNIT4
Wiring and piping
Most manuals come with wiring and piping diagrams which are o白en
accompani•~d by schedules (Table 4-2) and keys {Table 4-3).
了able 4-2 Example of gas orifice schedule
Gas pilot orifice schedule
Natural gas
J(R) 15A-10, J(R) 30A-10(12), JSOA-15-flame Std. #44
rod
J(R) 15A-10, J(R) 30A-10(12) Scanner
Std. #36
JSOA-15 Scanner
Std. #36
LP gas
N/A
Std. #44
白d.#44
Table 4-3 Example of wiring diagram key
Description
Key
Component
A67
Receiver-infrared
83
Motor-blower
GV1
Valv
R32
Potentiometer
S1
了hermostat-room
S10
Control-fan
S66
Switch-wall
TC1
Thermopile
Y1
Generator-piezo
• gas-millivolt
Replacement parts
The manuals sometimes specify details on the replacement parts, as shown
in the following excerpt:
Replac,ement wire must be type
wire or equivalent.
66
“T” （63 。F or35 。C temperαture
rise)
Gas Technicia『1 2 Training - Modu怡 10
© Canadian Standards Association
TOPIC 2
Valves
Gas piping is installed to supply gas to gas-fired equipment and the gas
flow is controlled by valves. Of the many types of valves used on gas
systems, some are operated manually, some automatically, and some are
both manual and automatic. As a gas technician, you must be able to
recognize valves as symbols on drawings and to physically identify them
on a piping system. All valves used on natural gas and propane systems
must be certified.
Since valves are discussed in detail elsewhere in the learning materials, this
topic confines itself to identifying the various types of manual and
automatic valves, for gas and some for water or steam systems.
Manual
A typical manual valve found on gas systems is a 1I4-turn valve which will
open or close with a quarter-tum of the handle. This ensures that the valve
can be opened or closed rapidly. Typical locations for manual valves are at
the utili勾r gas meter and the drop to the gas appliance. On large-input valve
trains, the most downstream valve is also a manual valve, identified as the
卢ring valve.
Some manual valves (the Code requires the firing valve to be one) have a
handle attached. Others, like the valves found at the gas meter, do not have
an attached handle. Figure 4-7 is a handled ball-type valve approved for
both indoor or outdoor use.
/
Lever Y. turned to open
ball valve
Lever in
off position
Flow
Closed
。pen
Figure 4-7 Cross-section 。f a manual ball-type valve
Gas Technician 2 Training- Module 10
Canadian standards Association
©
67
PIPING LAYOUT,
ORA叭nNGS
AND SYMBOLS
UNIT4
Some valv{:s are designed to be lubricated, and can maintain lubricant
between tht~ bearing surfaces. The lapped bearing surfaces are lubricated
and the lubricant level mamtained without having to remove 也e valve. The
construction of such valves also allows for the lubricant to be reservoired
and distributed evenly over the entire lapped bearing surfaces of the valve
when the p:lug is rotated.
Gate valves
As the name implies, a gate valve has a gate that moves up or down to open
or close the: valve (Figure 4-8). Because of excessive vibration and wear
created in partially closed gates, these valves are not intended for throttling
or flow regulation, but 盯e designed to operate fully open or fully closed.
咀iey are typically used on water and steam installations, never on gas
systems.
Wheel
Yoke
Gland
Stuffing
box
Stem
Body seat
rings
Figure 4-8 Gate valve
68
Gas Technician 2 Training - Module 10
。 Canadian Standards Association
PIPING LAYOUT, DRAVVINGSAND SYMBOLS
UNIT4
Globe valves
Unlike gate valves, globe valves are used in applications with 仕equent
operation or throttling of flow. The design of the globe valve keeps seat
erosion to a minimum (Figure 4-9). They are generally used in steam or
water applications, never on gas systems.
Handwheel
Disk
Figure 4-9
GI。be
valve
Jointing methods for manual valves
Manual gas valves are incorporated into the piping system in different
ways. In most cases, the size of the valve dictates 由e jointing method used.
η1e I缸ger valves are usually flanged in place; the mid-range sizes are
threaded; and the smaller sizes, when used with copper tubing, are
connected using flare fittings.
Gas Technician 2 Training - Module 1O
©Canadian S阳dardsAsso曲tion
69
PIPING LAYOUT,
ORA队ANGS
AND SYMBOLS
UNIT4
Automatic
Automatic valves typically control the supply of gas to the burner. Most are
electrically operated to:
control the firing of the burner (on/off modulation)
act as safety shut-off valves (ssov) which open on a call for heat and
close when the call has ended or when an unsafe condition (such as
flame failure) is sensed.
Solenoid valve
The solenoid gas valve function is to open or energize when the controller
calls for th(: burner to “ ignite” and close or de-energize when the heat
demand has been satisfied. Refer to Figure 4-10.
Figure 4-10
70
s。lenoid
valve
Gas Technician 2 Tr百ining - Module 10
。 Canadian Standards Association
PIPING LAYOUT, DRAVIANGS AND SYMBOLS
UNIT4
Manual/
Automatic
An example of a valve that operates both manually and automatically is 也e
latch valve shown in Figure 4-11. This type of valve is opened manually,
but only when specific conditions such as proof of air flow are met. When
the condition is lost, the valve automatically closes.
Figure 4－”
Manually 。pened,
automatically closing latch valve
Manual reset shut ·off valves shut off the supply of gas to the combustion
system when any interlocking limit device 姐 the control circuit opens. If
the power unit in the shut-off valve is de-energized, the valve closes and
由e handle disengages 齿。m the internal components to prevent the valve
from re-opening. The valve handle cannot be re-engaged with the internal
components until the condition causing the open switch 扭曲e control
circuit is corrected.
Gas Technician 2 Training - Module 10
@ Canadian Standards As叙沁iation
71
PIPING LAYOUT, DRAVIANGS AND SYMBOLS
UNIT 4
Assignment 4
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
If there is a discrepancy between the specifications and the drawings:
a) which one is taken to be correct? b) State the reasons for your answer.
a)
b)
2.η1e
manufacturer's installation and service manual is supplied with every appliance. How
much of it should you read?
3.
Do the installation and service manuals supplied by the manufacturer always speci行 details of
replacement parts?
4.
The two ways that manual valves are joined to 由e gas piping sys臼ms are:
a)
b)
5.
What two functions do automatic valves perform?
a)
b)
6.
Describe the 如nction of a solenoid valve.
)
Gas Technician 2 Training - Modu阳
Canadian Standards Association
@
10
73
Unit 5
Size high-pressure piping and
tubing
Purpose
To ensure 由at gas equipment will operate to design specifications, it must
receive the correct amount of gas. One of the main factors governing gas
flow is pipe size. The gas technician must be aware of the procedure used
to determine the coηect pipe size. An organized and methodical approach
to sizing will result in the coηect size being determined.
Learning
objectives
1. Explain the use of sizing tables.
2. Describe the general sizing procedure.
3. Describe the high-pressure sizing procedure.
、）
Gas Technician 2 Training - Module 10
。 Canad阳n Standards Assc.比骗咀on
75
Topics
1. Use of tables. …······································································· 77
Pressure drop …..............……… …….........................…......... 77
Copper tube .................…..………........…………….. ..…··”…......... 78
Natural gas vs. propane gas ........…........………..........………............. 78
u
2. General sizing procedure ...................................................... 79
Pr。cedural steps E ….........……·－．．．．，．．，．．．．．．．．．．．．．·町……………………·… 79
Proof of procedure ......................、........... ········ .........……........... 81
3. High-pressure sizing procedure ........................................... 83
Summary of procedure ........….......…..........…········ ...........…............. 83
Natural Gas Example 1 (Imperial) ........…································…….........…85
Natural Gas Example 2 (metric) .........…………. .
. ......………国…········….. 88
Propane Example 3 (Imperial) .................…......…………….................. 90
Assignment 5-1 -
5-6 ................................….......…........…........ 93
APPENDIX A TO UNIT 5 .......阻….................................…............. 105
Pipe sizing and proving work sheet
76
Gas Technician 2 Training - Module 10
© Canadian Standards As铅ciation
TOPIC
1
Use of tables
This topic describes how factors that influence gas flow must be taken into
account before you can s饵rt to size gas piping systems using Code tables.
The factors include:
•
maximum pressure drop in different piping systems
•
different measurements for copper tubing
•
differences between natural gas and propane.
Each table has a number of rows called Code zones. These zones
correspond to 由e different Ieng由s of the piping systems.
刀ie gas pipe sizing tables in the Code have been calculated to give the
thousands of British Thermal Units per hour that will pass through the
different sizes of pipe. The tables record the exact pressure loss allowed
according to the pressure and length of the system.
Calculations for low-pressure and 2 psi gas systems include a 20%
for a reasonable number of fittings.
allowan~e
Sizing higher pres.sure systems must include proof that the measured
of the system plus the equivalent length of the fittings do not
exceed the Code zone length upon which the piping system was sized.
len剧i
Pressure drop
ηie
amount of gas that flows 也rough a pipe increases:
as the pipe diameter increases
as the pressure drop across the length of the pipe increases
as 出e
length of the pipe decreases
as the density of the g部 decreases.
Gas is usually only supplied at distinct press田es (7 inch w.c., 2 psi, 5 psi,
10 psi and 20 psi). The maximum press町e drop across 由e len钊i ofa
piping system is a distinct 缸nount 岛r each system pressure.
As a result, the pipe sizing tables in Annex A and Annex B of the B 149.1
Code include separate tables for each system press田·e.
Gas Technician 2 Training - Module 10
Standards A翩翩ation
。 Canadian
77
UNIT5
SIZE HIGH-PRESSURE PIPING AND TUBING
Copper tube
Since the inside diameters and inside surface textures of tubing are
different from those of pipe, there is a completely separate set of tables in
the Code for sizing copper tube.
Note that the tables in the Codebook list tubing sizes in outside diameters.
Some tubing found in the field is identified by nominal size (inside
diameters). Therefore, be sure that the outside diameter is used when
referring to the tables.
Natural gas vs.
propane gas
78
The set of tables for natural gas (Annex A) are completely different 企om
the set for propane (Annex B), because of the difference in the densities of
the two gases (0.6 for natural gas and 1.52 for propane).
Gas 丁echnician 2 Training -
Module 10
© Canadian Standards Association
TOPIC
2
General sizing procedure
It is important to be familiar with the general procedure for pipe sizing
before you address specific high帽pressure sizing procedures (described in
Topic 3). Be consistent in following the procedural steps described in this
topic.
Procedural
steps
1. Sketch the
system
When you sketch the system, determine the length of
the pipe sections and label them. Check for system
regulators and do a separate sizing proced田e for the
piping downstream of each regulator.
2. Select a table
To select the
的
coηect
pipe sizing table you must:
Identify the type of gas一由e densi可 determines
the use of natural gas or propane tables.
b) Identify piping material-iron pipe or copper
tubing. Note whether iron pipe will be screwed or
welded.
c) Identify the gas pressure and the coηesponding
pressure drop. Consider the following factors:
•
•
•
•
3. Determine
Code zone
available gas pressure from the utility
job specifications
Code requirements
cost
Determine the appropriate Code zone:
a) For low-pressure and 2 psi systems: These are
found by adding 由e section lengths 台om your
sketch to find the longest measured run (L孔1R).
b) For pressures over 2 psi: Your estimate is based
on the measured run lengths, and on the
equivalent lengths of fittings in the runs.
4. Size pipe
sections
Gas Technician 2 Training 『 Module 10
©Canadian S恒ndardsAssc比iation
Make a list of the pipe sections.
Include labels, thousands of Btu/h, and the pipe size
for each section.
79
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT 5
5. Prove. Code
For pressure over 2 psi only: you must prove that the
zone is correcr length of the equivalent run (LER) is smaller than the
Code zone used to size the pipe.
•
The LER for an appliance is the total measured
length of the piping run to that appliance, plus the
equivalent lengths of all fittings (Table A.16 and
B.12) in that run.
If the LER is larger than the Code zone, you must
increase the Code zone length you have estimated in 3
b) above, and continue until the Code zone is long
enough. If your Code zone estimate is too long on the
first t巧与 prove that a shorter Code zone guess would
be too short, unless this is obvious.
6. Consult Code When you have estimated your Code zone length you
的ble
would go to the relevant Code table and under the lefthand vertical column find the Code zone according to
your estimate.
Read across the table to the right to find the highest
capacity that is closest to your calculation. Then read
straiβt up to the top of the table to ascertain the
appropriate pipe size. (Refer to Figure 5-1 which
reproduces a sample Natural Gas Code table with the
columns and lines highlighted.)
Equivalent lengths of tees are counted only if the flow to the appliance in
question makes a turn at the tee.
The size
ofα tee
is that of its
Iα1rgest
opening. Refer to Figure 5-2.
Figure 5-3 shows a typical completed worksheet for carrying out pipe
sizing. A blank worksheet is contained in the Appendix to this unit.
80
Gas Technician 2 Training - Module 10
。 Canadian Standards Association
SIZE HIGH-PR仨SSURE PIPING AND TUBING
UNIT5
Maximum Capacity in Thousands of Btu/h for
Schedule 40 Pipe, for Pressures of 5 psig
Based on a Pressure Drop of 2.5 psig
~~~~~
吁〈｝
io
部
俨 40
'5Q
嚣。专
1:
11••
Code zone
~L匍i
200
250
300
350
400
450
500
550
600
Pipe size (NPS)
1/2
3/4
2 800
1 924
~：~
1 323
1 172
1 062
977
909
853
806
714
647
595
554
491
445
409
381
357
337
320
306
1 1/4
1 1/2
2
2 1/2
22 643
15 562
33 926
23317
65 338
44907
5 2才 0 10 696
4 617
9 480
4 184
8 589
3 849
7 902
3 581
7 351
3360
6897
3 173
6 515
2 183
5 774
2 548
5 232
"'2344… 4;813
4478
才 158
2 181
1 026
1 933
3 969
1 751
3 596
930
才 611
855
3 308
1 499
3 078
796
747
1406
2 888
1 329
2 728
705
670
1 262
2 591
1 204
2471
639
16 026
14 203
12 869
11 840
11 014
10334
9 762
8 652
7 839
30 864
27 354
24 785
22 802
21 213
19903
18 800
16 662
15 097
104 139
71 574
57 476
49192
43 598
39 503
36 3以i2
33 810
31 722
29 965
26 557
24 063
22"138'.1
20 595
18 253
16 538
15 215
14 155
13 281
才 2 545
11 915
11 367
11 029
7 580
72坦 J注3 徽章自
6 709
5946
5 388
4 957
4 611
4 327
4 087
3 881
3 703
12 921
11452
10 376
9 546
8 881
8 333
7 871
7 475
7 132
Figure 5-1 Sample Code table for sizing large pipe
If a tee changes the
direction of flow in
the line being calculated
an equivalent length must
be added. The largest
opening of the tee is the
size used.
Figure
Proof of
procedure
5~2 丁·ee-fi忧ing
To prove the procedure for any appliance run, you must
the direction of flow.
1.
List valves and all fittings that change
2.
Look up their equivalent lengths 仕om either Table A.16 or B.12 of the
B149.l Code.
3.
Total the fitting equivalent lengths.
4.
To this total, add the length of the measured run to the particular
appliance. The resulting s四n is the LER of the appliance.
Gas Technician 2 Training - Module 10
Standards Association
。 Canadian
81
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
问ing System .£L4t:J.且ιj
Type of Gas
NArufi.tl
h,刷
Type of Pipe
System P陀ssure 二且孟ι
T如，， Pr/!I' γi./fl,-AD;－ρ
Allowable Pressure Drop _.z.二三gG
wι且
Line
Number
Load
MBtu/h
kW
Estimated
Pipe Size
Fittinos
Thread
Weld
Ft
Line#
Fitting
Size/Type
＃。f
Equiv.
Length
Total
3
J',)
1.91,
/
).,;'/
'S. .Jγ
qo•
.2
.2 dι
Lt./.]
~.，，，附ι
/
2.P品
.2 .(Jι
c。n胃rmed
Max.Load
Pipe Size Allowable
A
I tJo 6
马f
马’
/)<IS
8
平古:-2'
骂「＜／
均’
t主咛T
／＇ γ
c
/'1-亏ti
:13·树
司与
/
,
A-c
Fi世 lngs
l ’ ?tJ'
”
/9.,,28
5，乙
/’ '/A•
3
）. ι」
1. 盘4
5.:N
：「” .1'/
~ .，，~
).06
2 、 8ι
1匀班机
).D6
2D也
t＂ γ
f+,.JJ
line#
Measured I Estimated
U嗨协
I
CZ
L回归st
(LER)
I Confirm
I
CZ
Pr。of
Proof
Pr。。f
Figure 5-3 Sample p协e sizing and proving work sheet
82
Gas Tee如nician 2 Training - Module 10
。 Canadian Standards Association
TOPIC
、
3
High-pγ'eSSUγe
、’一
sizing
pγo cedure
Normally, the Gas Code considers any gas above 0.5 psig to be highpressure. However, the pipe” sizing tables are based on the 岛rmulas which
are included in the Codebooks. Two sets of formulas are used:
for pressures up to 1.5 psig
for pressures 1.5 psig and higher.
The tables in the Codebook are derived from these 岛rmulas.
Summary of
procedure
The procedure for sizing a high-pressure piping system is very similar to
the general procedures, as summarized in the following list of calculations
to be made, except as shown for Steps 8 由rough 10:
1. Type of gas
2. Type of pipe
3. System pressure
4. Pressure drop
5. Pipe sizing table
6. Pipe loads
7. Longest measured run
8. Estimate Code zone (based on the measured length of the piping run
and an allowance of equivalent len钊i for 也e fittings).
9. Size pipe, based on the estimated Code zone 齿。m Step 8.
10. Prove Code zone.
（η垃s is a check to see whether you chose the correct Code zone. It is
very important because, since you have estimated the· Code zone, you
must check whether that pipe size will actually c町rythe g部 load. You
do 由is by checking whether the measured Ieng由 added to 也e
equivalent length exceeds the Code zone len酬。
、、甲卢
Gas Technician 2 Training - Mα加幅 10
©Canadian S饵”dards Associa伽n
83
SIZE
HIGH-PR仨SSURE
PIPING AND TUBING
UNIT 5
Systems containing more than one-s阳 ge
A piping system may contain more than one pressure zone. You must
repeat the same procedure for each zone, starting 企om the pressure
regulator that applies to each zone.
Size the lower pressure zones 卢rst!
84
Gas Technician 2 Training- Module 10
© Canadian Standards Association
SIZE HIGH-PRESSURE PIPING AND TUBING
UNITS
The following examples are shown for natural gas and propane.
Natural Gas
Example 1
·(Imperial)
Referring to Figure 5-4 on the following page, go through the following
pipe sizing proced田e.
Typeofg，αs
Type ofpipe
System pressure
Pressure drop
Pipe sizing tαble
Pipe loαds
Natural gas
Iron pipe (screwed fittings)
5 psig
2.5 psig
Table A.5(a) in the B149.1 Code
Pipe A carries a load of 1000 MBtu/h
Pipe B carries a load of 750
Pipe C (A+ B) carries a load of 1750 岛但tu/h
75 + 70 = 145 ft (Pipe “ A ”)
LMR
*Note: I MBtulh
岛1Btu/h
=
1000 Btu/h
Gas Technician 2 Training - Module 10
Cl Canadian Standards Association
85
SIZE HIGH-PRESSURE PIPING AND TυBING
UNITS
65 ft
750 MBtu/h
B
75 ft
c
1000 MBtu/h
Natural gas
iron pipe
threaded fittings
70 ft
A
All。wable pressure
dr1。p 2.5 psig
METER
Figure 5-4 Schematic diagram for sizing high-pressure gas piping system
(lmpe时al measurements)
1. Preliminary analysis (estimating)
Code zone (CZ)
Choose a Code zone equal to, or longer than, the
equivalent length of all pipe runs in the system.
At this point, you do not know the size of the
fittings, so you must estimate their equivalent
length. If you refer to Table A.5（玛丽 the Code,
you can see that the choice of zones is limited to
150 班， 175 班， and 200 ft. Making an allowance
for a reasonable number of fittings, the 175 ft
Code zone is the best choice.
(This allows an extra 30 ft of pipe as an
allowance for the fittings.)
Sizep伊e
On 175 ft Code zone:
Pipe
L。ad (1\儒”／b)
ABC
Prove length of
pipe runs
1000
750
1750
Dia.
Mai:. load (MB徊局｝
3/4 inch
3/4 inch
1 inch
1245
1245
2344
To prove 也e len钊i of pipe runs, add the
measured length of pipe wi白白e equivalent
length of pipe to find the length ofequivalent
run(LER）.白ie LER of any pipe run must not
exceed the Code zone that was used to size the
p1pmg system.
－蝇飞
86
Gas Technician 2 Training - Modu脑 10
C Canadian Standards As回ciation
SIZE HIGH-PRESSURE PIPING AND TUBING
UNITS
2. Proof procedure
I. List all fittings on the run, starting with the longest measured run.
2. Look up their equivalent lengths 丘om Table A.16 in the Code.
Prove Pipe A
3 - I inch threaded 90°@2.62 ft
1 －：－一 l inch threaded T@ 5.24 ft
2 - 314 inch threaded 90° @ 2.06 ft
1 - 314 inch valve @ 2.06 由
7.86 丘
11
-
11
20
。onu － 00
Length (EL)
Measured Length (Mυ
Length ofEquivαlent Run (LER)
-2
－扰
ιHAH
n
Equiv.αlent
nyz ，且 A饨
’－
『一正。
A
Equivalent length
5.24 ft
4.12 ft
2.06 ft
19.28 ft
Prove PipeB
7.86 f王
5.24 ft
2.06 ft
3 - I inch threaded 90° @ 2.62 ft
1 - 1 inch threaded T @ 5 .24 负
1 - 314 inch threaded 90° @ 2.06 ft
1 - 314 inch valve @ 2.06 ft
L坠.fi
l 7.22 ft
Equivalent Length
Equiv.αr/ent
length (EL)
Measured Length (ML)
Length of Equivalent Run (LER)
17.22 ft
丛生豆豆豆
157.22 ft
If both pipe A and pipe B ’s length of equivalent runs are less than the
selected Code zone, the Code zone is within limits. In neither case does the
LER exceed the selected Code zone of 175 ft. Therefore, the 175 ft Code
zone is okay and the pipe is sized correctly.
Note:
If any LER had exceeded the chosen Code zone,
it would indicate the chosen Code zone is too short and the p伊ing would have to be resized, re-analyzed and re-proved on the next longest Code zone.
Gas Technician 2 Training- Module 10
。 Canadian Standards Association
87
SIZE HIGH-PRESSURE PIPING AND TUBING
Natural Gas
Example 2
(metric)
UNIT5
Referring to Figure 5-5, go through the pipe sizing procedure.
Natural gas
Iron pipe (screwed fittings)
34kPa
17 kPa
Table A.5(b) in the B149.J Code
Pipe A carries a load of 293 kW
Type ofgas
Type ofpipe
System pressure
Pressure drop
Pipe sizing tα~ble
Pipe loα＇ds
Pipe B
caηies
a load of 220 kW
Pipe C (A + B) carries a load of 513
22 + 26 = 48 m (Pipe A)
LMR
k孔1
1. Preliminary analysis (estimating)
Code zone (CZ)
CZ chosen is 60 m
Size pipe
On 60 m Code zone:
Prove length of pipe
runs
Pipe
Load(kW)
Dia.
Max. load (kW)
A
293
314 inch
339
B
220
314 inch
339
c
513
1 inch
639
At this point, the pipe has been sized but you do
not know if the le吨位1 of the pipe runs一
including fittings-will exceed the length of the
60 m Code zone. To prove the length of each
pipe run, add the measured length of pipe with
the equivalent length of pipe to find the length of
equivalent run.
Starting with 由e longest measured run, list all
fittings on 由at run. Look up their equivalent
lengths 企om Table A.16(b) in the Bl49.l Code.
88
Gas Technician 2 Training- Module 10
© Canadian Standards Association
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
24 m
34kPa
B
22m
220kW
c
293kW
26m
Natural gas
iron pipe
threaded 白!tings
A
Allowable pressure drop 17 kPa
Figure 5-5 Schematic diagram for sizing high-pressure gas piping system
(metric measurements)
2. Proof procedure
Prove Pipe A
3 - 1 inch threaded 90° @ 0.8 m
1___,,1 inch threaded 'T'@ 1.60 m
2-3局姐ch 出readed 90° elbows @ 0.63 m
1 - 314 inch valve @ 0.63 m
Equivalent length
Equivalent Length (EL)
5.89m
Meα·sured Length (ML)
48.00 m
Length ofEquivalent Run (LER)
53.89 m
、马町－·
2.40m
1.60m
1.26m
0.63m
5.89m
ProvePipeB
3一 1
inch threaded 90° @ 0.8 m
1 一 1 inch 由readed 'T'@ 1.6 m
1-3/4 inch 也readed 90° elbows @ 0.63 m
1 - 3/4 inch valve @ 0.63 m
Equivalent length
Equivalent Length (EL)
5.26m
Meα·sured Length (ML)
46.00m
Length ofEquivalent Run (LE却
51.26 m
2.40m
1.60m
0.63m
0.63m
5.26m
lfbo也 pipe
A's and pipe B ’ s Ieng曲。f equivalent runs are less than the
selected Code zone, the Code zone is within limits. In neither case does the
LER exceed the selected Code zone of 60 m. Therefore，也e 60 m Code
zone is okay and the pipe is s垃.ed correctly.
Gas Technician 2 Training - Module 10
。 Canadian
Standards Ass<犯阳tion
89
SIZE HIGH PRESSURE PIPING AND
Propane
Example 3
(Imperial)
TυBING
UNIT5
Note that Example 3 has two pressure zones identified. We use the normal
low-pressure procedure for sizing the low-pressure zone; and then use the
high-pressure procedure shown in Examples 1 and 2. As there are no
fittings that change direction in Example 3, there is no need for the
preliminary analysis and proof of procedure shown in the previous
examples.
Referring to Figure 5毡，
go
through the following procedure:
Step 1-Calculate low pressure zone
ofg，αs
Type
Propane
Type ofpipe
Copper tubing
System pressure
11 inch w.c.
Allowα·b/e
pressure
1 inch w.c.
drop
Pipe sizing table
Table B.l(a) in the B149.J Code
Pipe loads
Pipe A carries a load of 250 岛ffitu/h
Pipe B carries a load of 35
孔ffitu/h
Pipe C (A+ B) carries a load of 285
LMR
20 + 5 + 5 = 30 ft
Code zone
30 ft
Size
90
eα·ch pipe
岛1Btu/h
Line
Load 份侃侃/h)
Dia.
Max. load (MBtu/h)
A
250
7/8 inch
343
B
35
1/2 inch
68
c
285
7/8 inch
343
Gas Technician 2 Training - Module 10
© Canadian Standards Association
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
Second stage
regulator havi 『19
outlet setting
of 11 inches w.c
First stage
regulator
having outlet
setting of 10 ps19
\
20ft
5贯
c
B
A
5ft
5 ft
Not to scale
Water heater
Furnace
35 MBtu/h
250 MBtu/h
Allowable pressure drop
1 inch w.c.
Allowable pressure drop
5 psig
Figure 5-6 Schematic diagram of a two-stage propane piping system
Step 2…
- Calculate high pressure zone
Type ofgas
Propane
Type ofpipe
Copper tubing
System pressure
10 psig
Allowαrble
pressure
5 psig
drop
Pipe sizing tαble
Pipe
loαds
Table B.4(a) in the Bl49.l Code
Line D= 285
肌ffitu/h
LMR
50 ft
Code zone
50 ft
Size Line D
Load: 285 MBtu/h 3/8 inch
Max.
Load:496 如ffitu/h
Now complete Assignments 5-1-5-6.
Gas Technician 2 Training - Module 10
© Canadian Standards Association
91
UNITS
SIZE HIGH-PRESSURE PIPING AND TUBING
Assignment 5-1
When you have completed the following questions and the exercises that follo问 ask
your instructor for the Answer Keys.
1.
Why are there different sizing tables in the Code for (a) copper tubing and (b) steel pipe?
a)
b)
2.
State the five procedural steps when pipe sizing.
、、－－
Gas Technician 2 Training - Module 10
Standards Associa植on
。 Canadian
93
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT 5
Assignment 5-2
川℃
步
γC
几
－
l飞
A
Natural gas
welded iron pipe
forged tees
1 500 MBtu/h
3 000 MBtu/h
METER
All。wable
pressure drop 2.5 psig
Figure 5-A2
94
Gas Technician 2 Training - Module 10
© Canadian Standards Association
UNITS
SIZE HIGH-PRESSURE PIPING AND TUBING
Assignment 5-2
Size the drawing in Figure 5-A2 (opposite) and show your calculations here.
Gas Technician 2 Training - Module 10
© Canadian Standards Association
95
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
Assignment 5-3
B
A
哦『L
Fr
Ft
。
E
c
白u
..>o
qu
'eFr
D
ti.':>
吃L
METER
Natural gas
welded iron pipe
forged tees
5 psig
Allowable pressure drop 2.5 psig
Figure 5-A3
96
Gas Technician 2 Training - Module 10
© Canadian Standards Association
UNIT 5
SIZE HIGH-PRESSURE PIPING AND TυBING
Assignment 5-3
Size the drawing in Figure 5-A3 (opposite) and show your calculations here.
Gas Technician 2 Training - Module 10
。 Canad阳n S恒ndards A槌ociation
97
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
Assignment 5-4
40 MBtulh
65MBtulh
120 MBtulh
3
坦白。尽
~／
4
co\) 吃1
/
D
飞~
5 psig - 7 inches
4,000 MBtu/h
60
METER
i
Natural gas
iron pipe
threaded fittings
净
A
B
6 000 MBtulh
Figure
98
Allowable pressure drop 2.5 psig
s” A4
Gas Technician 2 Training - Module 10
。 Canadian Standa『ds Association
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
Assignment 5-4
Size the drawing in Figure ιA4 (opposite) and show your calculations here.
Gas Technician 2 Training - Modu胎
@Canadian S恼ndards Association
10
99
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
Assignment 5-5
B
A
气。币、
?.J 仍
/
Z』
τ
AV
6
夕7
G
D
Natural gas
welded iron pipe
forged tees
c
METER
34 kPa
Allowable pressure drop 17 kPa
Figure 5-AS
100
Gas Technician 2 Training - Module 10
。 Canadian Standards A键。ciation
UNIT5
SIZE HIGH-PRESSURE PIPING AND TUBING
Assignment 5-5
Size the drawing in Figure 5-A5 (opposite) and show your calculations here.
Gas Technician 2 Training - Module 10
Standards Association
©Canad幅n
101
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
Assignment 5-6
First stage
regulator
having outlet
setting of 10 psig
Second stage
regulator having
outlet setting
_of 11 inches w.c.
才
35 ft
C
15 ft
sl
10ftl I
A
I
10ft
Not to scale
Water heater
45 MBtu/h
Allowable pressure
drop 5 psig
Furnace
175 MBtu/h
Alrowable pressure
drop 1 inch w.c.
Figure 5-A6
102
Gas Technician 2 Training - Module 10
© Canadian Standards Association
UNITS
SIZE HIGH-PRESSURE PIPING AND TUBING
Assignment 5-6
Size the drawing in Figure 5-A6 (opposite) and show your calculations here.
Gas Technician 2 Training - Module 10
©Ca帽伽n S恒ndards A部ociation
103
SIZE HIGH-PRESSURE PIPING AND TUBING
UNIT5
APPENDIX A TO UNIT 5
Pipe sizing αnd pγoving woγk
sheet
The attached work sheet is described in Topic 2 of this unit.
Gas Technician 2 T1『·aining-Module 10
© Canadian Standards As缸阳ation
105
Piping System
Type of Pipe
Type of Gas
Allowable Pressure Drop
System Pressure
Table
Line
Number
L。ad
MB!u/h
kW
Line#
Proof
Pro。f
Proof
Est’”、ated
c。 nfirmed
Pipe
Size
Pipe
Size
Measured
Length
Max.
L。ad
All 。wable
Estimated
CZ
Fittinas
Thread
Line#
Fitting
Size/Tvoe
Fitting
Allowance
from above
Length
Equivalent Run
(LER)
Weld
v'
＃。f
Fittinas
Longest
(LER)
Ft
Equiv.
lenath
Mtr
Total
Confirm
CZ
Unit 6
Purging operations on large
piping systems
Purpose
The methods used to purge large diameter piping are somewhat different to
those used to purge small diameter piping. This is due to the large air gas
volumes involved, as well as the greater chance of pipe wall rupture if there
is an ignition and explosion. The gas technician must be aware that the use
of inert gases to purge large lines removes the posibility of accidental ignition and explosion.
LO
nd
ze
eb
ng
aj
-
n @s
1. Describe the Code requirements.
2. Explain the safety reasons for purging.
3. Describe the types of purging.
Gas Technician 2 Training- Module 10
Standards Association
。 Canadian
109
Topics
1. Review c。de requirements ................................................. 111
2. Safety reas。ns for purging ..........................….................... 113
Fire and explosion outside pipe .......................…,················……········ .113
Fire and explosion inside pipe ...........................…...…………............... 113
3. Types of purging .................................................................. 115
Two purges in succession ........……........……............回·….....…....... 115
Slug purging .....................…………......… ………·-……….. . .............. 116
a
Assignment 6 .........................................…......................…........刊 7
110
Gas Technician 2 Training - Modu梅 10
。 Canadian Standards Association
TOPIC
1
Review Code requirements
Purging is carried out in the gas industry for two reasons:
to safely introduce fuel gas into a pipeline
to safely remove fuel gas
abandonment and repair.
仕om
a pipeline for the pu甲oses of
The Codes are concerned with purging:
•
of piping and tubing systems and hose after leak testing.
and refer to gas mixtures to be used for purging other than for leak
testing: i.e. “ for the pu叩ose of repair, alteration, or abandonment. ”
The CSA B 149 .1 Code contains specific recommendations for large
piping:
•
If the piping is NPS 4 or larger, and air has been used for testing, it
must be first purged with carbon dioxide, nitrogen or a mixture of
these, and then purged with gas in accordance with Clause 6.23.7.
•
The person doing the purging shall be in direct control of the purging
gas supply during the p田ging operation by means of a valve having an
attached operating handle.
•
The piping for the gas being purged shall either be of a size or be
reduced to a size not larger than NPS 112 for piping up to NPS 4.
If the piping exceeds NPS 4嗅 purging pipe must follow engineering practices.
Gas Technician 2 Training- Module 10
© Canadian Standards Association
111
TOPIC
2
Sαifety γeαsonsfoγ purging
Whenever air and fuel gas are mixed together, there is a very real risk of a
serious explosion. Gas technicians who are ignorant of, or refuse to 岛II ow
proper purging procedures create highly dangerous conditions. Code
regulations require that you purge correctly to prevent the accidental
explosion of a gas-air mixture outside and inside the pipe.
Fire and
explosion
outside pipe
If you mix natural gas and air in a ratio that falls between 4% and 15%, you
produce a combustible mixture. It is therefore important that you not purge
into any confined space, such as a room where the potential 岛r fire and
explosion exist.
Do not:
•
Fire and
explosion
inside pipe
purge a new gas line through the burner system into a
combustion chamber
crack the p伊ing union open and allow an uncontrolled
escape ofgas.
Explosion inside the pipe is a serious hazard, especially when the diameter
of the pipe is 4 inche~ or greater. 刀ie larger pipe walls are not strong
enough to contain the pressure increase as the gas-air mix bums-inside, and
也e pipe bursts, causing serious damage.
Remember 由at there are sources of ignition inside the pipe. Even with a
very little pressure drop, g脑 moves at very high velocities. At high
velocities, iron filings, stones, and other debris inside the pipe 缸e swept
along and create sparks. In 也e case of an inadequately purged pipe，也is
causes any volume of combustible mixture inside 也e pipe to burn, since
the three conditions necessary for ignition一缸el, oxygen and heat-are all
present.
Gas Technician 2 Training -
Mαiule
Cl Canadian Standards Association
10
113
TOPIC
3
Types
ofpuγgin
Purging may be divided into 队.vo broad categories, based on whether the
pipes fall above or below Nominal Pipe Size 4 (NPS 4). Note the difference
between them and ensure you follow the category for all large-size piping.
Review the description of purging of pipes less than NPS 4 in
Module 8.
For larger pipes, two types of purging can be used:
Two purges in
succession
•
two separate purges m success10n
•
slug purging.
For larger pipes, introducing or removing fuel gas into a pipe requires 阳o
separate purges m successwn
•
Introduce 卢el gas
1. Purge air with inert gas on new installations, or after repairs or
alterations.
2. Purge inert gas with fuel gas. This will prevent the formation of
gas-air mixtures.
•
Remove fuel gas
Purge 如el gas with inert gas before you repair or abandon an existing
large system.
Gas Technician 2 Training- Module 10
© Canadian Standards Association
115
PURGING OPERATIONS ON LARGE PIPING SYSTEMS
UNIT6
Slug purging
For very long, large pipes (such as those installed by the gas supply
company), instead of doing two successive purges, you might slug-purge
to flush out all the contents of the pipe. Slug purging reduces the amount of
inert gas you would otherwise have to use.
To slug-purge large pipes:
1. Inject a mass of inert gas, called a slug, into .the pipe.
2. Flush the slug_ gas with the fuel gas.
Example
A common example of the use of slug purging
from a large-diameter piping system.
is 白e
safe removal of air
Ra由er than completely purging the line wi也 nitrogen, it is more
economical to insert a large slug of nitrogen into the piping first and then
turn on 也e fuel gas to force the nitrogen and air through the purge point.
The nitrogen acts as a divider between the air and gas to prevent them from
mixing. Observe the following practices:
Maintain normal purge velocity (200 ft/min in large piping) so that 由e
pipe is scrubbed as the gas moves and prevents the gases from
intermingling as they move.
τhe
slug must have enough volume to prevent 由e formation of fuel
gas-air mixture. The volume of the slug takes into account the diameter
and length of the piping system (found in piping tables).
•
116
Since the slug is slowly destroyed over distance and time and since
longer piping systems require longer purge times, you must be sure that
the slug of inert gas is long enough to compensate.
Gas Technician 2 Training - Module 10
。 Canadian Standards As回ciation
UNITS
PURGING
OP巨RATIONS
ON LARGE PIPING SYSTEMS
Assignment 6
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
With what would you p山ge a pipe sized 4 inches or over, if it has been tested with air?
2.
What can occur when purging is not carried out correctly?
3.
Is it acceptable to purge a new gas line through the burner system into a combustion chamber?
4.
Why is it important to purge the air out oflarger diameter pipes with an inert gas prior to 由e
fuel gas being introduced into the pipe?
5.
What is an alternative to completely purging long, large pipes with nitrogen?
6.
What is normal purge velocity for large pipes?
Gas Technician 2 Training - M创u陆 10
C Canadian Standa『ds A”。ciat阳，
117
Module 12
Controls
Gas-fired appliances are designed, built and installed for various
processes. The supply of gas and the disbursement of the energy
produced must be done safely and efficiently. This is accomplished
with the use of controls and control systems. The types, concepts,
and operations for these controls are numerous ：台om manual to
automatic, electrical to mechanical as well as solid state. This mod“
ule gives an overview of how gas systems are controlled and how
various components are used to start, stop, and sequence the operation in such a way as to ensure the equipment is working correctly.
At the end
Gas Technician 2 Training- Module 12
© Canadian Standards As四ciation
。f this m。dule
you will be able t。：
•
Describe the fundamentals of controls
•
Describe and
•
Service and
•
Describe and select motors
troublesh。。t
con tr。l circuits
troublesho。t c。ntr。Is
··t·l
Ken Bales, Manager, Gas Information Pr<?ducts, CSA, wishes to acknowledge the following individuals
who contributed as members of a Review Panel during the development of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology (BCIT) is
acknowledged for its work in the technical development and editing of the original edition.
Contribut。rs and members of the Review Panel
John Cotter
Bill Davies
Eric Grigg
Warren Hayes
Darrel Hilman
Ken Kell
W. John Lampey
Lorne Lowry
Jim Noseworthy
Gary Prentice
Nick Reggi
Rick Rogozinski
Ron Royal
John Se『neniuk
Allen Sidock
John Simmons
David Stainrod
Terry Waters
iv
Canadore College
Union Gas Limited
Canadore College
Supe时or Propane Inc.
Southern Alberta Institute of Technology
Centra Gas Manitoba
Alberta Advanced Education & Career Development
Algonquin College
Durham College
Environmental Energy Consultants
Humber College
Union Gas
Fanshawe College
Northern Alberta Institute of Technology
Cambrian College
Loyalist College
D.J. Stainrod & Associates Ltd.
Enbridge Consumers Gas
Gas Technician 2 Training - Module 12
。 Canadian Standards Ass<比iation
岛1odule
11
.Basic Electricity
A thorough understanding of basic electricity and its application to
gas system installation, servicing and maintenance is an important
part of a gas technician ’s training.
At the end of this module you will be able to:
•
Understand the function of a building power supply
Rec。gnize
common features of p。wer supplies
Interpret electrical drawings
Gas Technician 2 Training- Module 11
© Canadian Standards Association
•
Use measuring and test instruments
•
Understand the function 。f electrical circuits and
hardware
•
Understand and service millivolt systems
iii
Ken Bales, Manager, Gas Information Products, CSA, wishes to acknowledge the following individuals
who contributed as members of a Review Panel during the development of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology (BCIT) is
acknowledged for its work in the technical development and editing of the original edition.
Contributors and members 。f the Review Panel
John Cotter
Bill Davies
Eric Grigg
Warren Hayes
Darrel Hilman
Ken Kell
W. John Lampey
Lorne Lowry
Jim Noseworthy
Gary Prentice
Nick Reggi
Rick Rogozinski
Ron Royal
John Semeniuk
Allen Sidock
John Simmons
。avid Stainrod
Terry Waters
iv
Canadore College
Union Gas Limited
Canadore College
Superior Propane Inc.
Southern Alberta Institute of Technology
Centra Gas Manitoba
Alberta Advanced Education & Career Development
Algonquin College
Durham College
Environmental Energy Consultants
Humber College
Union Gas
Fanshawe College
Northern Alberta Institute of Technology
Cambrian College
Loyalist College
D.J. Stainrod & Associates Ltd.
Enbridge Consumers Gas
Gas Technician 2 Training - Module 11
© Canadian Standards Assoαation
岛1odule
11
Table of Contents
Unit 1
Power supply
Amperage service ........….........…........................ 3
Gr。und
fault circuit interrupters (GFCI) ........….... 9
Electrical bonding to gas pipe ........…................ 13
Single-phase and three-phase. …...................... 15
Types and ratings of fuses and breaker-s .......... 19
Types and
gauges 。f wires ............................... 29
Assignment 1 .................................................... 47
Unit 2
Interpret electrical drawings
Types of dr~wings .........................…................. 51
Standard electrical
symb。ls .............................. 55
Wiring diagrams ................................................ 57
Assignment 2 .................................................... 63
Unit 3
Measuring and test instruments
Types and applications
。f measuring
and test instruments .................... 67
Operation and
c。nnection
of measuring and test
instruments ........…················“.............…........... 73
Assignment 3 .............................… ··········~·········83
Gas Technician 2 Training - Modu幅
© Canadian Standards As配>Cialion
11
v
Unit 4
Circuits and hardware
Electrical panels and transformers .......……······ 87
Electrical hardware ...............…········……··········· 91
Assignment 4 ......…···········圄··············……......... 109
Unit 5
Millivolt systems
Generation 。f small-value DC voltages ．．．．．．．匾，. 113
Testing control circuits ...…·········………............. 119
Millivolt thermostats ..................…......…......…. 135
Assignment 5 ...........................…···················· 137
vi
Gas Technician 2 Training - Module 11
© Canadian Standards A臼∞阳tion
Unit 1
Power supply
Purpose
Most gas appliances are designed with some electrical components to aid
in the operation of the appliance. It is important for the gas technician to
understand how power is supplied and accessed, as well as the various
methods and devices used to ensure that the electricity is distributed safely.
LO
eb
nge
aj
nd
re
-
ws
1. Describe amperage service.
2. Describe ground fault circuit interrupters (GFCI).
3. Describe electrical bonding to gas piping.
4. Explain single-phase and three-phase.
5. Describe the types and ratings of fuses and breakers.
6. Describe the types and gauges of wire.
Gas Technician 2 Training 『 Module 11
© Canadian Standards Association
Topics
1. Amperage service ........….................…......................…............ 3
Electrical service rating ..........…..................…….......….........…·曹....... 3
Calculating electrical current draw ..……..…….................................…….... 5
Electrical distribution system ......…….........……·...,.....…...…··‘.. 5
2.
Gr。und fault circuit interrupters (GFCI) ............….................. 9
GFCI applications ...…........‘........…..................................……….................... 10
3. Electrical bonding to gas pipe ..............................…............. 13
Bonding and grounding ...............…………..............且…........…··……................ 13
4. Single-phase and three-phase ...............................…............ 15
Single-phase, three-wire system .....................………·······……….......…......... 15
Three-phase, three- and four-wire systems. ….............................................. 17
5. Types and ratings of fuses and breakers ............................ 19
Purpose of fuses and breakers .....圄…………..........….......……......…...….......... 19
Fuses ．．．．凰．．．．．．….................……………························….................................. 21
Renewable fuse links. … ……………...…..........……….......................24
Circuit breakers ...监.................……………........……·衡.........................….......... 24
Circuit breaker installation ...........…............….................…........................27
u
6. Types and gauges of wires ................................................… 29
c。nductors
.................….........….........………··········……………………..... 29
Properties of conductors ..........…...............................……··············……........ 30
Wire conductors .........………·························… …................…........…............ 33
Conductor size (gauge) ........…………………… ………………………………...... 33
Conduct。r ampac1ty ................…………………….................................. 35
Conductor insulation ..............…·..............,…............................... 35
Conductor appli但tions ..........………..........................……·······……....... 38
2
a
Assignment 1 ............…….......…….......….........................….......... 47
2
Gas Technician 2 Training - Module 11
© Canadian Standards Association
TOPIC
1
Amperage service
The electrical supply to a building is carried through wire conductors from
a transformer located on a utility pole or in an underground vault. The
conductors (supply lines) connect to the building at a meter base installed
on the exterior of the building or in a utility room.ηie local power supply
authority is responsible for the installation, maintenance and servicing of
supply conductors up to 也e meter base of the customer ’ s building. The
components of a typical electrical service are shown in Figure 1-1 on the
next page. Underground supply lines enter the meter base through a
protective conduit, eliminating the requirement for a service mast and its
related hardware.
Electrical
service rating
」
The electrical service supplied to a building is measured in amps
(amperes), the unit of measurement for electrical current. The amperage
rating of a service is the maximum total current draw of all electrical
appliances in the building.
The minimum requirement in most new residential construction is
100 amp service. However, many older homes have 60 amp services, and
homes heated by electricity require a 200 amp service.
As more appliances are added, the electrical service may need to be
upgraded to a higher amperage rating. This often requires a ne吼 larger
capacity distribution panel and may require installation of larger capacity
supply lines by the power supply au由ority.
Gas T假如nician 2 Training - Module
©Canad泪n S姐ndards Association
11
3
PO叭R三R
SUPPLY
UNIT 1
Service entrance cap
(weather head)
Hydro supply
lines
入
--Mast
support
Kilowatt-hour 一一＋
meter
Meter
h’』
base 一一／
LB 而忧ing
(cover and gasket）一→
Grade level
oue
－
dueg
hug
ndH
unn
o’’
FLKUKUZH
忧
-
(a)
m
o
-
(b)
Figure 1-1 Components of an overhead elect时臼l service (a) and an underground service (b)
4
Gas Technician 2 Training - Module 11
© Canadian Standards Association
PO叭ER SUPPLY
UNIT 1
Calculating
electrical
current draw
Section 8 of the Canadian Electrical Code (CEC), Part I covers the
calculation of the total current draw for single-family residences to
determine the size of service required. Before calculating the size of
service required, the total building 町ea in m2, based on the interior
dimensions of the building, must be determined as follows:
100% of the total main floor area, plus
•
75% of the total basement area, plus
100% of any liveable area on upper floors, including finished attics.
The CE Code, Part I Rule 8-200(1), is used to calculate the total electrical
load in watts (W) as summarized in Table 1-1 on 由e next page. The
following 岛rmula is then used to determine the required amperage rating
of the service:
amps=wa忧S÷volts
Most residential lighting and appliances operate on 120 volts, while larger
appliances such as ranges, dryers and heaters require 240 volts. Therefore,.
120 V and 240 V loads must be calculated separately when determining the
amperage rating of a service.
Electrical
distribution
system
A residential electrical distribution system consists of:
•
an electric meter
•
a main switch or breaker
•
a distribution panel
•
fuses or circuit breakers
•
wire conductors.
Gas Te由nician 2 Training- Module 11
C Canadian Standards As踊ciation
5
PO队.ER
SUPPLY
UNIT 1
Electric meter
The supply wires to a building first pass 也rough an electric meter, which
records the amount of electrical energy in kilowatt-hours consumed over a
certain period of time.
Main switch
The main switch is used to shut off the supply of electricity to the building.
Some systems have a main switch or circuit breaker separate from the
distribution panel. In this type of system, the main switch is located after
由e meter and is us凶lly mounted 硝acent to the distribution panel. It
contains a pair of 岛ses or a circuit breaker sized according to the
maximum capacity rating of the service (60 A, 100 A, 200 A, etc.)
Table 1-1 Summary of CE Code, Part I Rule 8-200(1)
Basic load
The basic load is all lighting and small appliance
loads up to and including 1500 W in total.
Range load
Electric cooking range.
Other loads
Hot water heater,
elect对c
clothes dryer, etc.
Heating load
The heating load includes all fixed elect叫c space
heating units with thermostatic controls.
Air-c。『1ditioning load
Swimming pool heater load
This load includes electric heaters for swimming
pools, hot tubs, and spas.
6
Allow 5000 W for the first 90 m2 of living ar，阁， plus
an additional 1000 W for every 90 m2 or p副
thereof in ex臼ss of 90 m2
Allow 6000 W for each electric co。king range rated
at 12 kW 。r less, plus 40% of the po此ion of the
rating that exceeds 12 kW.
If an electric cooking range has been included in
the calculation, all other loads rated higher than
1500 Ware factored in at 25% of their individual
ratings.
Allow 100悦 up to 10 kW, plus 75% of the p。此ion
that exceeds 10 kW.
Allow 100% if a heating load is not included,
。therwi蹈， factor in 100% of both air-cond投ioning
and heating loads.
Allow 100% of the total ratings.
Gas Technician 2 Training - Module 11
© Canadian Standards A部ociation
PO'队.ERSυPPLY
UNIT 1
Distribution panel
The distribution panel contains fuses or circuit breakers that connect the
120 V and 240 V electrical supply to the various loads and protect them
from overc田rent and short circuits.
Combination panels contain the main switch or circuit breaker and the
fuses and circuit breakers for the connected loads. A typical combination
panel is shown in Figure 1-2.
To meter panel
「＿＿／...一一飞
Bonding
jumper.
Grounding
bushing
Main disconnect
怡
S
On~O青
breaker
L
11
广12
’’
hm
阴阳
nuoea
nHJNe
1却与ott[I]on5j
:
工工士1
！刀 W
•
Ground wire
(bare}
Gr1。und
bus
To ground
system
Figure 1-2
Gas Technician 2 Training- Module 11
© Canadian Standards As:四ciation
c。mbination
panel
7
POVl.ER SUPPLY
UNIT 1
Fuses and circuit breakers
Fuses and circuit breakers are sized according to the loads of the individual
branch circuits they protect. 120 V branch circuits are limited to a
maximum number of receptacles and fixtures to avoid overloading. Some
120 V appliances, such as refrigerators and freezers require separate
circuits and breakers.
Individual heating circuits are limited to a maximum wa忧age rating and
have separate fuses or breakers. Electric ranges, dryer, and hot water
heaters are on separate circuits, protected by high-amperage fuses or
breakers.
Wire conductors
Individual branch circuits are sized according to the size of wire used in the
circuit-as more circuits are added, the total current increases.
Most residential lighting and receptacle circuits and other 120 V circuits
are supplied by 14-2 AWG (14 gauge, 2-wire, plus bond) conductors.
Heating circuits, including most hot water heaters, generally use 12-2
AWG conductors, while ranges and dryers require much heavier gauge
conductors.
8
Gas Technician 2 Training - Module 11
。 Canadian Standa时s Association
TOPIC
2
Gγoundfault ciγcu it
inteγγupteγ~
(GFCI)
When electrical appliances and equipment are used under wet conditions or
when they are old or worn, a potential shock hazard exists. A GFCI is a
specially designed receptacle or distribution panel circuit breaker used to
protect users of electrical appliances and equipment from electric shock
(see Figure 1-3).
Reset
switch
GFCI circuit breaker
GFCI duplex receptacle
Figure 1-3 GFCI receptacle and panel circuit breaker
A GFCI does not protect a circuit or electrical device 丘om current
overload-that is the pu叩ose of the circuit breaker. It will not protect 仕om
electric shock if a person touches both conductors of the GFCI-protected
circuit, or a live conductor from another circuit.
Gas
2 Training - Module 11
Standards Association
Technic凋n
。 Canadian
9
PO~RSUPPLY
GFCI
applications
UNIT 1
GFCI devices are used to protect receptacles near sinks, swimming pools,
hot tubs, and other potentially hazardous locations. Most electrical codes
now require GFCI protection in specific locations, for example:
•
bathrooms
•
pool and spa areas
•
outdoor receptacles.
How a GFCI works
The GFCI continually senses the flow of current in the circuit to which it is
connected. If a ground fault or other condition causes some of the current
to pass to ground the GFCI trips almost instantly, stopping the flow of
current. 古ie GFCI will trip when it senses a change in c町rent flow as small
as 5 milliamps.ηie trippmg action occurs quickly enough to prevent
serious or fatal electrical shock.
A GFCI receptacle has an internal circuit breaker 由at can be reset by
means of a red pushbu忱。n when the ground fault is corrected. A GFCI
distribution panel breaker must be reset at the panel.
GFCI panel circuit breaker
A GFCI panel circuit breaker is a thermal-magnetic device. It contains a
solid-state, ground-fault sensmg circuit 出at can detect ground currents as
small as 5 mA (see Figure 1-4).
The sensing circuit is composed of:
10
•
a current transformer·monitor (CT)
•
a solid-state amplifier
•
a shunt trip coil.
Gas Technician 2 Training - Module 11
© Canadian Standards Assoc幅画on
PO叭IERSUPPLY
UNIT 1
Two wires from the 120 V load pass through the current transformer
monitor section of the breaker. Under normal conditions, current flow
through the two wires is equal, and no current flows in the secondary
transformer winding of the monitor. If a ground fault occurs, or some
C田rent flows to ground, current flow through the monitor is reduced. The
supply current then exceeds the current flow through the monitor. When
也is condition occurs, the unbalanced current is amplified and fed to the
shunt trip coil, which opens the breaker to shut off current flow.
Solid
state
amplifier
120 V line
source
120V
load
Load
current
飞F
Ground fault
(leakage current)
Unintentional
ground path
hazardous
to humans
Figure 1-4 GFCI circuit breaker wiring diagram
Gas Technician 2 Training- Module 11
。 Canadian S恒ndards A蛤∞泊lion
11
TOPIC
3
Electrical bonding to gαs pipe
The gas piping system in a building can create fire and shock hazards
throughout the building if it is not properly bonded to ground. This can
occur m two ways:
the piping system can become a path for current flow if it faults to the
electrical wiring
the piping system can become a grounding electrode, with a different
voltage-to-ground than the electrical grounding system.
Bonding and
grounding
Bonding can be defined as: permanently joining all non-current-carrying
metal parts to ensure electrical continuity and establish a low-impedance
path having the capacity to safely conduct any cuηent likely to be imposed
on 1t.
Bonding and grounding:
•
protect persons from electric shock hazards
•
protect prope此y from damage caused by short circuits and lightning
•
open fuses and circuit breakers when short circuits occur.
Interior gas piping systems are electrical bonded to ground at the electrical
panel to prevent possible hazards. Bonding the gas piping system to ground
prevents arcing (sparking) due to electrical potential difference between the
piping and ground, reducing the risk of accidental ignition.
Gas Technician 2 T1『aining - Module 11
© Canadian Standards Association
13
PO\l\IER SUPPLY
UNIT 1
Electrical Code requirements
The CE Code Part I requires gas piping systems to be bonded to ground.
The gas piping should be bonded to the building ’s electrical system
grounding conductor by a No. 6 AWG or larger copper bonding conductor
(see Figure 1-5). The bonding conductor should be attached to the gas
piping as near as possible to the electrical panel, and where the gas piping
enters the building. To maintain the electrical continuity of the interior
metal gas piping where it is interrupted by insulating bushings or devices, a
bonding jumper wire must be installed to bridge the connections.
#6 AWG
Bonding
conductor
To electrical
system
grounding
,/ conductor
Metal (cold)
/water pipe
Insulated coupling
bridged” by bonding
jumper conductor
“
'To electrical system
grounding conductor
Metal gas pipe b。nded t。 electrical system
grounding c。nductor via metal water pipe
Gas pipe
Metal gas pipe bonded t。 electrical
system grounding conduct。r via
” bridge” bonding jumper
Figure 1-5 Gas piping bonding conductor installation
14
Gas Technician 2 Training - Module 11
。 Canadian Standards Association
TOPIC4
Single-phαse αnd three-phαse
Single-phase, three-wire systems are generally used to service only small
load applications such as residences, small stores and commercial units,
and schools. Industrial and large commercial applications require 也ree­
phase, three-wire or 岛ur.:.wire systems.
Single回phase,
three-wire
system
乱.fost residential appliances operate on single-phase voltage, supplied by a
transformer with primary and secondary windings. The transformer is
located upstream of the distribution panel, on a utility pole or in an
underground vault. The primary-side voltage varies, depending on 也e
available system voltage. The secondary winding is a fixed 240 volts.
A single-phase, three唰wire system has a white or grey neutral wire and two
black line wires (sometimes called hot wires). Both line wires are protected
by overcurrent devices for safety reasons. The overcurrent device is a main
circuit breaker or a pair of fuses 也at protect 也e line wires and transfer
power to the two distribution panel hot bus bars. The neutral wire is
grounded at the trans岛rmer and at the electrical panel of the building it
services.
A wire connected to the midpoint of the secondary 240 V winding divides
it to provide two voltages (120 V and 240 V) on a three-wire system (see
Figure 1-6). The incoming voltage is divided into branch circuits at the
electrical panel.
也e
120 V supplies small appliances such as televisions, toasters, and
microwave ovens
the 240 V supplies larger appliances such as elec位ic ranges, clothes
dryers, and electric heaters.
Gas Technician 2 Training - Module 11
@Canadian S幅ndards Association
15
PO叭/ER
SUPPLY
UNIT 1
Uti~~o rm er
tra
Service
box
w
W、
Identified conductor
- - Ground neutral
regardless of voltage
G~
Single phase
”
3wire
(a)
Uti~~o rm er
Service
tra
~ c←一』－－－－－一
w
主－ G
Three phase - 4 wire
star connection
Identified conductor
Ground ）~~：r~i1~~
~~eutral
ss
voltage
Service
box
Utility
transformer
If phase voltage
is 150 V or less
ground one conductor,
otherwise provide
ground fault detection
Three phase - 3 wire
delta connection
Ground fault
detector
(b)
* If the supply authority does not ground the wye-connected secondary, and if the consumer does
not require the neutral, the service can be treated as if it were from a delta-connected transformer.
Figure 1-6 Single-phase, three-wire (a) and three-phase, three- and four-wire (b) cbnnection schematics
16
Gas Technician 2 T1『aining-M创ule 11
© Canadian standards A豁出ia苗。n
PO叭t'ERSUPPLY
UNIT 1
Three-phase,
three- and
four-wire
systems
Three-phase, three- and four-wire systems are used for industrial and
commercial applications. The four wire system has three hot line wires and
a ground wire. A neutral may also be included at times.
The voltage sine waves of each of the three lines are 120。 out of phase with
each other. This allows for higher motor starting torque and lower
amperage (current draw) than is possible with a single-phase supply. Four
commonly supplied voltages are:
120/208 v
•
240/416 v
•
347/600 v
•
600 v.
The wires of a three-phase, four-wire system are colour-coded as follows:
•
Neutral (when present}--white or natural grey
•
Phase A (phase wire A}--red
•
Phase B (phase wire B}--black
•
Phase C (phase wire C}--blue.
The neutral wire (the identified circuit conductor) must be the same colour
throughout the whole length of the circuit it services, for conductor sizes up
to No. 2 AWG Identified circuit conductors larger than No. 2 AWG must
be identified at both ends with white tape, unless the conductor is white.
Gas Technician 2
T1『ai『1ing 甲 Module
© Canadian Standards Association
11
17
TOPIC
5
Types and γα:tings offuses and
bn α： keγs
Purpose of
fuses and
breakers
The 如se
and the circuit breaker are the two most commonly used devices
for the protection of electrical systems. The pu叩ose of a protective device
is to open the electrical circuit, stopping current flow, before damage can
be done to the conductors and equipment connected to the circuit. Fuses are
one-time-use only devices, and must be replaced when they blow. Circuit
breakers can be reset if they trip.
There are several kinds of fuses and breakers, and within each type there
缸e many variations, classes, and ratings. However, all the devices serve the
same purpose: they protect conductors and insulation 企om excess 创nounts
of heat produced by overload and overcurrent conditions.
All fuses and breakers are sized to protect the circuit conductors, not the
appliances connected to the circuit. Fuses and breakers must not be
oversized.
Time-delay fuses or slow-blow fuses should be used to protect circuits
where intermittent momentarily high loads will be encountered, such as
motor and air conditioning circuits.
The CE Code, Part I specifies maximum ampacity values
breaker, and other protective devices.
Gas Technician 2 Training - Module 11
C Canadian Standards Association
for 如ses,
19
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Overload
An overload is a moderate increase in cuηent beyond the rated current
value. A circuit becomes overloaded when the equipment connected to it
draws more current than that for which the circuit is designed or rated. The
heat produced by an overload 。在en causes electrical insulation
deterioration and failure. During an overload, the protective device must
open before damage occurs.
Overload current values may range as high as six times normal
value. Typical causes of overload include:
cuηent
•
too much equipment connected to a circuit (the octopus effect)
•
using equipment with insufficient capacity for the work to be done
•
worn-out or seized motor bearings
•
excessive mechanical load.
。vercurrent
An overcurrent may range from six times to many hundreds of times the
normal rated currents and, unlike an overload, it happens ve可 quickly. Two
s1tuat10ns can cause an overcurrent:
•
a current surge when a motor starts up
•
a short circuit.
When an electric motor starts up, it momentarily draws a current much
greater than its normal full-load current. The overcurrent caused by this
inrush cuηent surge lasts a very short time, but the protective device must
be capable of withstanding it.
Within a few thousandths of a second, the overcurrent caused by a short
circuit can increase to hundreds of times larger than the normal operating
current.
Short circuit
Typical causes of a short circuit are:
•
failure of a conductor ’s insulation, causing the conductor to touch a
metal casing and create a line-to-ground short
a foreign
o均ect
line-t。”line
20
making accidental contact with a conductor, causing a
short.
Gas Technician 2 Training - Module 11
。 Canadian Standards Association
POW::RSυPPLY
UNIT 1
A short-circuit current is different from an overload, because it flows
outside its normal path.η1e thermal and magnetic arcing associated with
short circuits can cause extensive damage.
Fuses
Fuses are simple current” limiting devices 由at protect circuit conductors. A
fuse consists of an insulated tube containing a strip of heat-sensitive metal
that has a lower melting point than copper or aluminum. The metal strip
(link) will heat up before the circuit conductors qo when excessive current
passes through the conductors. The heat generated by the excess c町rent
melts the link, automatically opening the circuit before the conductors are
overheated and damaged. A short circuit will cause the fuse element to
melt in just a 企action of a second.
There are two general categories of fuses:
•
plug fuses
cartridge fuses.
Plug fuses
Plug fuses are also known as screw-base or Edison-base fuses. Figure 1-7
shows two basic types of plug 如ses:
•
Type P-for standard, non-time delay applications
•
Type D-for time delay applications.
Figure 1-7 Type P and Type D plug fuses
、、－
GasTectmic加1
2 Training - Module 11
© Canadian Standards As驳回ation
21
PO叭.£R
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UNIT1
Canadian Electrical Code plug fuse
requirements
Rule 14-208(1) states that the maximum rating of any plug fuse is 30
A. Commonly available ratings are 15 A, 20 A, 25 A and 30 A. Plug
fuses with lower ratings are available for special applications (1A,2 A,
3 A, 5 A, 6 A, 8 A, and 10 A).
Rule 14-202 states 由at a plug fuse shall not be used in a circuit with
more than 125 V between conductors, except where the circuit is
supplied from a system with a grounded neutral and there is no
conductor operating at more than 150 V to ground.
•
Rule 14-204 states that plug fuses with different ratings must not be
interchangeable. Where an alteration or addition is made to an existing
fusible panelboard, all the plug fuses in the panelboard shall comply
with CE Code, Part I Rule 14-204.
Rule 14-204 can be complied with by using a Type C plug fuse with the
correct rejection washer.
Type Cfuses
Type C fuses can be used to upgrade an existing system that uses ordinary
fuses in standard base 如seholders. Type C fuses have cylindrical
extensions holding the bottom contact. The extensions va可 in diameter
according to the ampere rating of the 如se and will only fit into a
corresponding size hole in the rejection washer.
0 to 15A.
Fuse
and rejection washer
colour code blue
Figure 唱，8
22
EZ
0 to 20 A. Fuse
and reiection washer
colour code red
E冒
言
E
Before a Type C plug 在ise can be inserted into the panelboard, a properly
sized rejection washer must be placed in the 臼se holder (see Figure 1-8).
The thickness of the washer and the diameter of the hole prevent fuses with
di直erent ratings 企om making contact. The rejection washer is identified by
colour: blue for 15 A or less, red for 20 A or less, and green for 30 A or
less.
to 30 A. Fuse
colour code green
(no rejection washer)
0
Type C fuses and rejection washers
Gas Technician 2 Training - Module 11
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POVIERSUPPLY
UNIT 1
Cartridge fuses
There are three basic types of cartridge 如se:
•
ferrule-contact
•
knife
•
bolt-on.
Standard fuses and high-rupturing capacity fuses are manufactured in all
three designs.
Standard fuses (Code fuses)
The term Code加e came into use at a time when this w邵阳 only type of
卸se required by the Electrical Code.ηie construction of ferrule-contact and
knifeblade 如es currently in use is similar, however, the knife-type islarger
由m 也e ferrule-contact fuse and has blades on both ends (see Figure 1-9).
Many large cartridge fuses are filled with arc-quenching powder (Figure 110). A short circuit often causes the fuse link to burst into flame. This fireextinguishing powder quenches an arc and prevents it 企om bursting
through the tubing of the fuse.
Ferrule contact
(Available up to 60 A)
Figure 1-9
Ferrule-c。ntact
Knife blade
(Available up to 600 A)
and knife• blade cartridge 仙ses
Arc翩quenching
material
Figure 1-10 Fuse with arc-quenching powder
、、』町，
Gas Technician 2 Training- Module 11
© Canadian Standards Association
23
PO叭JER
UNIT 1
SUPPLY
Renewable
fuse links -
A one-time-use fuse must be thrown away when its fuse link opens or
melts. A fuse with a renewable fuse Ii他 can be reused indefinitely.
When replacing a fuse link, it is important that it have the proper current
rating. The fuse must not be spiked. Spiking means installing a larger link,
or more than one link in the fuse, than is necessary. All fuses with
renewable links are of the non-time delay type.
Circuit
breakers
Circuit breakers, like fuses, protect electrical conductors and equipment
the effects of overload and overcurrent. The type of circuit breaker
shown in Figure 1-11 is used in low-voltage distribution systems under 750
V. It is often used to protect lighting and motor circuits.
仕om
When a circuit breaker trips to open a circuit, it can be reset by hand
without replacing any parts.
Reset
switch
GFCI circuit breaker
Figure t 斗 1 Circuit breaker
24
Gas Technician 2 Training - Module 11
© Canadian Standards Association
PO队ER SUPPLY
UNIT 1
Circuit breaker components
There are different types of circuit breakers, but all have the same major
components:
•
f云ame,
•
operating mechanism
•
trip elements
•
contacts
•
terminal connection.
or case
Circuit breaker operation
A quick-make, quick-break type handle is used to turn the breaker on and
off. This means that the speed at which the contacts snap open or closed is
independent of how fast the handle is moved.
The breaker is trip-free, which means it c缸mot be prevented from tripping
by holding the handle in the ON position. When the breaker trips, the
handle moves midway between the ON and OFF positions. To reset the
breaker, the handle must be moved from the centre position to OFF, then
back to ON.
T11伊 element
The trip element triggers the operating mechanism under prolonged
overload or excessive current conditions, causing the circuit to open. The
trip element may be a thermal or a magnetic type, Many circuit breakers
have both 可pes of trip elements.
Thermal element
The heat-sensitive thermal element is a b技netal strip composed of two
different metals. Each metal has a different rate of thermal expansion. Heat
仕om excessive current or overload will cause one of the metals to expand
and bend.at a faster rate 由m 也e second.ηiis deflection action bends the
bime姐l strip into contact wi由出e trip bar, which moves to open the circuit.
Magnetic element
This short-circuit and ground-fault protection element is an electromagnetic device wired in series with the load. When a short circuit occurs,
也e 岛ult current passing through the circuit causes 由e electromagnet to
at位act an armature mounted on 由e trip bar. This action opens the contacts.
Gas Technician 2 T1『aining 『 Module 11
C Canadian standards Association
25
POWER SUPPLY
UNIT 1
Types of circuit breakers
Mou/dee在case
breaker
The components of a moulded-case circuit breaker are mounted inside a
frame of insulating material, usually plastic. Each type of moulded case is
identified on the frame by the manufacturer ’s letters. This identification
· refers to the characteristics of the breaker, including:
maximum allowable voltage and current
inteηupting
•
capacity
physical dimensions.
Each manufacturer has their own identification system, as each of their
products has unique characteristics.
Magnetic-only breaker
The Canadian Standards Association refers to 出is breaker as an
instantaneous tr伊 circuit interrupter. It looks like a standard thermalmagnetic breaker, except that it has no thermal trip element. This breaker
normally has an adjustable trip element on the 企ont.
The trip elements are interchangeable within the limits of frame size. The
magnetic-only circuit breaker provides short-circuit protection, but no
protection 仕om overload. It is used where overload protection is provided
by some other means.
High-interrupting-capacity breaker
In many low-voltage distribution systems, the available short-circuit
cu口ent often exceeds the interrupting capacity of standard breakers.ηiis
situation requires a special high-interrupting-capacity (HIC) breaker. The
HIC breaker is similar to, and the same size as, the standard thermalmagnetic breaker, except 由at it provides a higher interrupting capacity.
Some breakers have an interrupting capacity of75 000 A or higher. A
current-limiting device may also be integrally installed in a breaker to
provide very high interrupting capacity.
26
Gas Technician 2 Training - Module 11
。 Canadian Standards Association
PO叭.£RSυPPLY
UNIT 1
Circuit
breaker
installation
Proper installation of circuit breakers in the distribution panel is required to
achieve proper branch circuit voltages. Circuit breakers have different
types of terminals, depending on the manufacturer. The make of
distribution panel will determine 由e type of breaker that must be used.
Some breakers simply snap into place in the distribution panel, while
others are installed with a screw-type fastener. The fastener arrangement is
such 由at it is impossible to insert the breaker in the distribution panel in
the wrong orientation. However, it is possible to place the breaker
incorrectly across the bus bars of the panel.η1is will result in 也e incorrect
voltage being applied to the branch circuit that the breaker is servicing.
The coηect method of single币。le and double-pole circuit breaker
installation is shown in Figure 1-12.
Gas Technician 2 T1刚刚ng - Module 11
@Canadian Standards Assc.沁陆曾on
27
POI/VER SUPPLY
UNIT 1
To meter panel
「一人一「
Bonding
jumper
Grounding
bushing
Main disconnect
on[J二 Off
Single
pole
breaker
breaker
L11 「---i:2
如OffII]州 i
Ground wire
(bare)
Ground bus
了。 ground
system
Figure 1-12 Circuit breaker installation
28
Gas Technician 2 Training- Module 11
© Canadian Standa『ds A撼。c阳tion
TOPIC
6
Types αnd gαuges
of wires
Conductors
A conductor is a material that allows electrical current to flow through it
with relative ease. The best conductor is one that will caηy the greatest
amount of current with the lowest rise in temperature. The selection of a
conductor for specific purposes is based on the following factors:
Gas 丁丽chnician
•
Cost-gold and silver are excellent conductors, but very expensive.
•
Weight-aluminum does not conduct as well as copper, but is used in
many applications because it is 30% lighter than copper.
•
Oxidation--aluminum oxidizes faster than copper, but this is offset by
aluminum ’s lower cost.
•
Ductili。」the
•
Malleabilit) the ability of a material to be formed in 也in sheets. Thin
conductive foil is used in some resistors and other electronic
components.
•
Ultimate strengtι一the amount of mechanical stress a material can
withstand before breaking. Aluminum does not have sufficient ultimate
strength to support its own weight when strung over long distances.
•
Oxide resistance-when the surface of a conductor oxidizes, the oxide
can negatively affect connections and terminations.
•
Contact resistance-the resistance per area of contact between two
conductors at a given pressure varies with the conductor material.
•
Conductance一－the
ability of a material to be drawn into wire form. The
finer the wire, the more ductility the material must have.
~
opposite of resistance. A good conductor has high
conductance and low resistance.
2 Training - Module 11
© Canadian Standards Association
29
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SUPPLY
υNIT
Properties of
conductors
1
Different conductors have different properties. Copper is the standard
against which other conducting materials are compared. Table 1-2
compares the properties of several common conductors. In the table,
copper has been assigned an arbitrary value of 100 for comparison
pu叩oses only.
Table 1-2 Conductor properties
c。 nductance
Resistance
per 1000 f目。
Oxidation
Oxide
resistance
Ductility and
malleability
Ultimate
strength
Copper
very good
Aluminum
fair
Silver
excellent
Gold
good
Steel
poor
10.4
17.0
9.6
14.4
75.0
slow
high
fast
very high
sl。w
very slow
very slow
perfect
very fast
very high
very good
poor
good
excellent
poor
100
72
100
100
30
163
120
92
217
139
100
700
90
190
100
50
9600
640 000
(Q
叭/eight
Insulation per
185
88
721
v。lume
Contact
resistance
Cost by weight
30
4
Gas Technician 2 Training - Module 11
© Canadian Standards Association
POVVER SUPPLY
UNIT 1
Gold and silver
Gold and silver are very expensive and rarely used in wire fonηas
conductors. However, they are used in thin layers on electronic contacts
and in other similar applications due to their:
.
A剧
ω
ω
墨
L
J
.1
旷
口b
’n..
沁
a
口b
..
αm
slow rate of oxidation
& &’.-‘’
h.‘. nhmJ
.1Vvu
．即饥
•
Copper
Copper, an excellent conductor, is used extensively in wire form and in
electronic circuits. It solders easily and provides secure electrical
connections. Copper is easily worked and more resistant to oxidation than
steel or aluminum, but it is more expensive.
Aluminum
Aluminum is lighter than copper, but less conductive. An aluminum
conductor must be slightly larger in diameter than a copper conductor of
the same current-carrying capacity. Aluminum has three major
disadvantages when used as an electrical conductor:
•
it oxidizes rapidly
•
it is subject to electrolysis
•
it is prone to cold flow.
Oxidation
Aluminum oxide acts as an insulator and reduces current flow through the
conductor. Brush-on antioxidant chemicals can be applied to aluminum
conductors to reduce oxidation.
Electrolysis
Electrolysis is the chemical breakdown of two metals in contact reacting
with one another. Moisture and current flow accelerate electrolysis. The
effects of electrolysis can be reduced by using approved termination
devices and splice connectors.
、、』卢
Gas Technician 2 T1『aining - Module 11
Standards As回ciation
© Canadian
31
PO队i£R
UNIT 1
SUPPLY
Cold flow
Cold flow causes loose connections. An aluminum conductor secured by a
terminal screw will gradually lose its resistance to the pressure of the screw
and cold flow away from the po坦t of contact. The resulting reduction 坦
contact press田e produces a loose connection. The increased resistance to
current flow at the loose connection will cause overheating, damaging the
connection and the surrounding insulation.
Steel
Steel is stronger and cheaper than the other conductors, and is used in the
following applications:
32
•
as a supporting core for aluminum and copper conductors used
outdoors
•
conducting rails for electric railway and subway systems
•
as a conductor when metal conduit and receptacle boxes are used to
complete a grounding circuit
•
as ground rods in place of metal water-supply piping.
Gas Technician 2 Training - M创ule 刊
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Wire
conductors
Wire is the most common form of electrical conductor. Most electrical
wiring is copper or aluminum, solid or stranded in form.
Solid wire conductors
Solid copper wire is usually formed by drawing a soft copper rod through a
series of doughnut-shaped metal blocks called dies. Each successive die
has a smaller diameter hole than the previous one. As the copper rod passes
through the dies, it is reduced in diameter and becomes longer.
Stranded·…wire conductors
A stranded-wire conductor consists of a group of wires .. The wires are
twisted or braided toge由er, often around a central core. A stranded wire
acts as a single conductor, with nearly the same current-carrying capacity
as a single solid wire of the same gauge.
Stranded-wire conductors are usually No. 8 AWG and larger. The wires
making up a stranded conductor are normally all the same size. The size of
the wires depends on the flexibility required-the smaller the diameter of
the wire strands, the more flexible the conductor.
Conductor
size (gauge)
Wire conductors are sized according to the American Wire Gauge (AWG)
standard. Sizes range from No. 44 AWG to No. 4/0 AWG (0000), as shown
in Table 1-3.ηie smaller the AWG number, the greater the diameter and
cross-sectional area of the conductor.
Gas Technician 2 Training-Module 11
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©
33
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UNIT 1
Table 1-3 AWG wire conductor sizes
AWG
No.
0000
000
00
。
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
丁8
19
20
Dia.**
Area*
AWG
Dia.**
Area*
810
38
39
40
28.5
25.4
22.6
20.1
17.9
15.9
14.2
12.6
11.3
10.0
8.93
7.95
7.08
6.31
5.62
5.00
4.45
3.96
3.53
3.15
42
2.50
6.3
44
1.97
3.9
N。．
460
410
365
325
289
258
229
204
182
162
144
128
114
102
91
81
72
64
57
51
45.3
40.3
35.9
32.0
211 600
167 800
133 100
105 500
83690
66370
52640
41 740
33100
26250
20 820
16 510
13 090
10 380
8 234
6530
5178
4107
3 257
2 583
2 048
1624
1 288
1 022
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
642
510
404
320
254
202
160
126.7
100.5
79.7
63.2
50.1
39.8
31.5
25.0
19.8
15.7
12.5
9.9
**Diameter is in mils
* Area is in circular mils
34
Gas Technician 2 Training - Modu幅刊
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POVVER SUPPLY
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Conductor
am pa city
Ampacity is the 创nount of current、a conductor is rated to safely handle.
The larger the AWG number of a conductor, the greater the electrical
resistance per unit length. The resistance of a conductor increases with
temperature and, as resistance increases, the voltage drop increases. This
means that long wiring runs may require the use oflarger-gauge conductors
in order to maintain required circuit voltage values and remain within
ampacity limits.
The ampacity rating of wire conductor cables is specified in the CE Code,
Part I. Some typical values are shown in Table 1-4. Ampaciy rating
depends on the type of cable, it ’s insulation, and the maximum temperature
to which the cable will be exposed.
Conductor
insulation
Conductor insulation is used to prevent the undesirable flow of electric
current such as grounds faults and short circuits, and to protect -against
electric shock. Common conductor insulating materials include rubber
compounds, and pol~inylchloride (PVC) and polyethylene plastic. In
order to perform satisfactorily, conductor insulation must:
•
have a voltage rating suitable for the intended application
•
have a tempera阳re rating suitable for the intended application
be appropriate for the environment in which it is to be used
•
be protected against possible mechanical damage
Conductors are sized to carry different maximum currents，岛r exampls:
No.12 AWG-15 A maximum 如se size
•
No.12 AWG - 20 A maximum fuse size
No.12 AWG-30 A maximum fuse size
If a circuit is 臼sedhigher 由an allowed, the conductor can overheat and
start a fire.
Gas Technician 2 Training - Module
Standards As!捕ciation
。 Canadian
”
35
POV飞~R
SUPPLY
UNIT 1
Table 1-4 Allowable ampacities for not more than 3 copper conductors in raceway or cable, based on
ambient temperature of 30。 C ( see note 2 )
60。c
AWG
size
**
TypeTW
75°C **
Types
RW75,
TW75
Allowable ampacity *
刊 0。 C**
85-90。 c **
Types
R90,RV四0,
See
Note 1
125。c
**
See
Note 1
200。 c
**
See
Note 1
T90 Nylon
Paper
Mineral
insulated
cable 'I**
15
15
15
30
30
30
20
20
35
40
20
40
45
30
30
50
55
30
45
40
45
60
65
70
65
65
80
55
85
95
85
85
105
115
70
120
120
100
105
130
145
80
3
115
120
135
100
145
165
2
160
130
140
170
190
1
110
150
155
190
200
225
。
125
175
215
185
230
250
145
00
245
200
210
265
285
165
000
275
340
230
235
310
195
0000
* The ampacity of aluminum-sheathed cable is based on the type of insulation used 。n the copper
conductors且 Consult the CEC for correction factors to be used where there are more than 3 conductors in
a 臼 ble or raceway.
** Maximum allowable conductor temperatures for 1, 2，。r 3 conductors run in a raceway, or 2 or 3
conduct。rs run in a cable.
*** These ratings are based on the use 。f 90。C insulation on the emerging conductors and for sealing.
Note 1 These ampacities are only applicable under special circumstances where the use of insulated
conductors having this temperature rating are acceptable.
Note 2 Consult the CEC for correcti。n fact。rs to be used to determine values over 30。C Type R90 silicone
wire may be used in ambient temperatures up to 65°C without applying the correction factors for ambient
temperatures above 30°C, provided the temperature of the conductor at the terminations does not exceed
14
12
10
8
6
4
90。 c.
36
Gas Technician 2 Training - Module 11
。 Canadian Standards Association
PO＼八~RSUPPLY
UNIT 1
Voltage rating
Electrical conductor insulation subjected to excessive voltage may break
down and lose its insulating ability. The ability of a conductor ’ s insulation
to resist breakdown due to voltage stress is its dielectric strength. A
conductor ’s voltage rating is printed on the insulation.
Temperature rating
If an electrical conductor is used in an application where it is exposed to
excessive heat:
its insulation may melt or bum, leaving the wire conductors bare
•
the life expectancy of the insulation may be greatly reduced.
Stove wire, for example, has a high翩temperat田。resistant fibre wrapping
over top of its rubber or thermoplastic insulation to protect it 企om the heat
of the appliance it services. A conductor ’s temperature rating is printed on
its outer surface.
Environmental considerations
An electrical conductor used in harmful environments must have insulation
that will protect it adequately under those conditions. For example，也e
presence of moisture can reduce an insulation ’s dielectric streng白， and
corrosive vapo田s can damage or destroy insulating materials.
NMD (non-metallic dry) cable must only be used in moisture-free
applications, while NMW (non-metallic wet) can be used in damp
locations. Unsheathed conductors run outdoors must be enclosed in liquidtight conduit.
Mechanical protection
The insulation of elec创cal conductors used in applications where 也ey are
exposed to possible physical damage must provide adequate protection.
Some conductors have an outer layer of flexible metallic sheathing to
protect the conductor and Its insulation from damage.
For example, in order to prevent damage to conductors in locations where
steel joists and s阳ds 缸e used as 企aming members, only armoured cable
(BX) must be used.
、、』’－
Gas Technician 2 Training-Module 11
©Canadian S恒ndardsAs四ciation
37
UNIT 1
POV\IER SUPPLY
Conductor
applications
Section 4 of the CE Code, Part I provides general rules and reference tables
governing the installation and use of electrical conductors for lighting,
appliances, and power supply circuits. It is important to become familiar
with the various types of conductors in common use, in order to properly
interpret Canadian Electrical Code rules for their use.
Different conductors are used for different applications. Three common
applications encountered by the gas technician are:
power circuit wmng
•
fixture wiring
low-voltage control circuits.
Power circuit wiring
Power circuit wiring is the electrical distribution conductors and cabling
for residential, commercial, and industrial buildings. A building ’s electrical
distribution system consists of: .
•
the service equipment
•
the branch circuits.
Service equipment
The service equipment, which uses the largest conductors, is the main
power source for all other circuit wiring in the building. Service equipment
conductors usually require special mechanical protection, in accordance
with Section 6 of.the CE Code, and any local bulletins.
Branch
circui：阳
Branch circuits supply power to receptacle outlets, lighting, heater units,
由yers, ranges, and motorized equipment. Depending on the application
and CE Code, Part I requirements, branch circuits use a variety of
conductor types, including:
38
•
non-metallic sheath cable
•
armoured cable
•
mineral-insulated cable
•
thermoplastic and rubber-coated cable
•
conductors in conduit.
Gas Technician 2 Training - Module 11
© Canadian Standards As翻沁ialion
PO队l:RSUPPLY
UNIT 1
Fixture wiring
Fixture wire is a special type of wire approved for use within electrical
equipment such as lighting fixtures. It is usually a stranded, flexible
conductor with high-temperature rated insulation. This wire, also known as
equ伊nent wire, is used to connect internal fixtures to branch circuit
conductors.
Low-voltage control circuits
The CE Code, Part I defines low voltage circuits as those operating from 31
V to 750 V, inclusive. Some motor control circuits operate at 600 V.
Conductors used for these types of applications must be rated accordingly.
Extra-low voltage circuits operate at 30 V or less. Residential thermostat,
gas valve, and zone valve control circuits fall into this category. These
circuits generally use cable, No. 16 AWG, or smaller.
Conductor colour codes
The wires of electrical conductors must be marked for easy identification,
so 由ey can be correctly connected in circuits. There are two methods used
to mark wires (see Figure 1-13):
、－一
•
the insulation of each wire is a different colour
the insulation of each conductor may have an attached label marker (
larger cables have a coloured 由ip).
White or natural grey is used only for insulated, neutral conductors
Green is used only for ground conductors
Red, black, and blue are used to identi命 live or hot conductors.
Gas Te伪nician 2 Training - Modu陆 11
@Canadian S甜苦dardsAssc:犯iation
39
UNIT 1
PO队IERSUPPLY
Non-metallic sheathed cable (NMSC and NMD)
Non-metallic sheathed cable usually has PVC or polyethylene plastic
insulation which also serves as the outer covering of the cable. This type of
cable is most commonly used for wiring branch circuits. The following
cautions must be taken into consideration when using NMSC and N孔。
cable:
the non-metallic covering of electric cables can bum, and may transmit
fire when ignited
burning non-metallic coverings may emit highly toxic gases that
generate dense smoke
acidic gas emissions may corrode metals in the vicinity of the cables.
Yellow
High side
or
hot wire
Blue
Red
Black
Neutral
Ground mg
White or
grey
－一 natural
Bare or
一－ green
Five
Four
Three
Two
conductor conduct。r conductor conductor
cable
cable
cable
cable
Figure 1-13 Insulation colour codes
40
Gas Technician 2 Training 。 Canadian
Module 11
Standards Association
PO叭.£RSUPPLY
UNIT 1
Armoured cable (AC)
Armoured cable, also called BX, has a flexible outer metal sheath to
protect the insulated conductors. BX is commonly used in residential,
commercial, and industrial applications where wiring may be exposed to
mechanical damage. CEC Part I Rules 12-600 to 12-618 cover the
specifications for installation of armoured cable. Different types of BX
cable are used, depending on the application:
Type AC is used only in dry locations
号pe A CL, which has an additional lead covering, is used where
moisture resistance is required
号pe ACWUhas a thermoplastic outer covering, and is used in wet
locations and for underground installations
TECK is a special type of armoured cable for use in exposed wiring
locations and for adverse service conditions (see Figure 1-14). It is
manufactured in single and multi-conductor form, with voltage ratings
of 600 V, 1 kV, or 5 kV.
PVC inner
jacket
PVC
Grounding
conductor
armour
Figure 1-14
Gas Technician 2 Training- Module 11
© Canadian Standards Association
Binder
Fillers
Copper
conductors
TECK9。但ble
41
POV\£R SUPPLY
UNIT 1
Aluminum-sheathed cable (ASC)
This type of cable has a seamless aluminum protective sheath with either a
smooth or corrugated finish. The corrugated type, shown in Figure 1-15, is
called Co吃flex. A PVC outer covering allows ASC cable to be used in
adverse conditions. Aluminum-sheathed cables are commonly used in
industrial applications requiring voltages of 600 V to 5000 V.
CE Code, Part I Table Dl specifies ASC voltage ratings. CE Code, Part I
Rules 12-700 to 12-716 cover the specifications for installation of
aluminum-sheathed cable.
Insulation
PVC outer
jacket
Aluminum
sheath
Figure 1-15 Corflex ASC
Mineral 回insulated
cable (MIC)
Mineral-insulated cable has a magnesium oxide filler between its
uninsulated internal conductors and outer metallic sheath, making it fireresistant (see Figure 1-16). The outer sheath is usually copper tubing. This
type of cable, often referred to as Pyroten矶 is able to withstand severe
physical abuse without failing.
岛日
cable is used in applications where conductors may be exposed to
mechanical damage, moisture, or high temperatures. Special termination
kits are required for connecting 阳 cable because of its uninsulated
conductors. Standard MI cable is certified for circuits up to 600 V. L~币哑，
a light-weight cable, is used for circuits up to 300 V.
CE Code, Part I Rules 12-700 to 12-716 cover the specifications for
installation of mineral-insulated 。但） cable as well as for ASC.
42
Gas Techniαan 2 Training - Module 11
© Canadian Standards Association
PO队正RSUPPLY
UNIT 1
Flexible cord and cable
Flexible cords and cables are not generally allowed to be used for
permanent wiring installations. They are used to connect appliances and
equipment that have attachment plugs.
Three common types of flexible cord and cable include:
•
heater cords
•
general-se凹ice
•
power-supply cables.
cords
Heater cord
Heater cord is used to connect portable electric heating units to outlet
receptacles. It is available with two, three, or four conductors and is usually
insulated with rubber and asbestos and has a cotton-braid or
polychloroprene outer jacket. Maximum voltage rating is 300 V. Conductor
sizes range from No. 18 to No. 14 AWG
m
Copper
tube
Magnesium oxide
insulation
Copper
conductors
Figure 1-16 Mineral-insulated cable (A)
Gas Technician 2 Training - Module 11
Canadian Standards Association
©
43
UNIT1
POWER SUPPLY
General-service cord
General service cord (also called cabtire) is used to connect portable
appliances and equipment that is subject to hard usage. This type of cord
consists of rubber-insulated conductors twisted together and enclosed in a
high-grade rubber outer jacket. General service cord is available with two,
世rree, or four conductors. Conductor sizes range from No. 18 to No. IO
AWG Common types of service cord include:
SJ-rated at 300 V (see Figure 1-17)
•
S-rated at 600 V
•
SJOW-300 V for outdoor use
•
SOW-600 V for outdoor use.
CE Code, Part I Table 11 and Rule 4-0 I 0 speci马r allowable uses of various
types of flexible cord and cable. Ampacity ratings for these types of
conductors are indicated in CEC Table 12.
Rubber
jacket
Figure 1-17 Type SJ general 臼rvice cord
44
Gas Technician 2 Training - Module 11
© Canadian Standards Associatiα1
PO\f\IERSUPPLY
UNIT 1
Power-supply cables
Power-supply cable is similar in construction to general service cord (see
Figure 1-18). It is used for connecting equipment drawing higher currents
at up to 600 V. It is available with two, three, or fo町 conductors, and in
sizes from No. 8 to No. 2 AWG
Figure 1-18 Power-supply cable
Gas Technician 2 Training- Module 11
©Canadian S恒ndards Association
45
POV\i£RSUPPL Y
UNIT 1
Assignment 1
When you have completed the following questions, ask your instructor for the
Answer Key.
I.
The electrical service supplied to a building is measured in what units?
2.
An electrical distribution system consists of:
3.
认That device would protect users of electrical equipment 企om shock hazards in damp
conditions?
4.
Once a GFCI receptacle is tripped, can it be reset without going to the distribution panel?
5.
"Permanently joining all non-current-carrying metal parts to ensure electrical
partial definition of:
6.
What size conductor is required to bond gas piping systems to the building ’s electrical system
grounding conductor?
7.ηie
8.
continui旷 is
a
two most co虹rmon devices for the protection of electrical systems are:
Maximum ampacity values for overcurrent protection devices would be specified where?
Gas T叙如『1ician 2 Training- Module 11
© Canadian Standards Association
47
POV\11三R
9.
SUPPLY
Two situations that cause
UNIT1
overcu付ent
are:
10. An electrical overload occurs very quickly. True or False?
11. What advantage does a circuit breaker have over a 岛se?
12. What is the most common form of electrical conductor?
13. The two basic types of wire conductors are:
14. The maximum current rating of a #10 AWG conductor is less than that ofa #14 AWG
conductor. True or False?
15. Where the possibility of physical damage to a conductor exists, what must be done?
16. Electrical distribution, in a building, consists of:
17. Low-voltage circuits operate at what voltage?
18. What type of armoured cable should be used for installations subject to adverse se凹ice
conditions?
48
Gas Technic』an 2 Training - Module 11
© Canadian Standards Association
Unit2
Interpret electrical drawings
Purpose
Just as piping drawings provide the gas technician with a layout of the piping system, similarly electrical drawings provide the gas technician with
the layout of the electrical system. Having a working knowledge of the various types of electrical drawings and electrical symbols is important. This
will enable the gas technician to understand the entire operation of the gas
equipment.
Learning
1. Identify different types of electrical drawings.
。同ectives
2. Describe the standard electrical symbols.
3. Explain wiring diagrams.
Gas Technician 2 Training - Module 11
© Canadian Standards Association
49
Topics
1. Types of drawings ...............................….............…················ 51
Pictorial diagrams ...........…………·……--…….......…….....……...... 51
Ladder and schematic diagrams. ………...............……..........…................ 52
Connection diagrams ........….......………….........….......町............. 53
2. Standard electrical symbols ..…............................................ 55
Electrical symbols ..........…........................………曹....................……...... 55
3. Wiring diagrams ..................................…........…······················· 57
Sequence of operation ..…………·町…．．．．．．．．…·················………................. 57
Wiring diagram interpretation ....................……........…........………........ 61
Assignment 2......................................……..............................….. 63
50
Gas Technician 2 Training - Module 11
© Canadian Standards Association
TOPIC 1
Types of dγα~wings
It is important for the gas technician to learn to recognize and interpret the
different types of drawings and diagrams used in the gas industry.
Electrical drawings are generally produced in one of the three following
forms:
•
pictorial diagrams
ladder or schematic diagrams
connection diagrams.
Pictorial
diagrams
Pictorial diagrams are often used in instruction manuals and installation
guides. Figure 2-1 is a pictorial diagram of a circuit connecting several
components. Pictorial diagrams are generally three” dimensional, and
include the following types of information:
•
components are drawn as they would appear in real life
•
components are located relative to their actual position
•
wires and other items are identified by colour, value, or rating.
Motor
Light
Transformer
1/5A
A1
,
UCAWe
仨－
’L
N
Bell
Figure 2-1 Pictorial circuit diagram
Gas Technician 2 Training - Module 11
Canadian Standards 缸”ciation
©
51
INTERPRET ELECTRICAL DRAVIANGS
Ladder and
schematic
diagrams
UNIT2
The purpose of electrical ladder or schematic diagrams is to show how
circuits work and the function of their components. Figure 2-2 is a
schematic diagram of the circuit shown in Figure 2-1. This type of diagram
often shows a logical sequence of events, and has the following
characteristies:
components are represented by standard electrical symbols
components are labelled to indicate such things as their name, type,
value, and part number
components are not shown in their actual location in the circuit
components are connected by single lines indicating their relationship
to each other in the circuit.
N
L1
M
「
Figure 2-2 Schematic circuit diagram
52
Gas Technician 2 Training - Module 11
© Canadian Standards Association
INTERPRET ELECTRICAL DRAVVINGS
UNIT2
Connection
diagrams
Connection, or wiring diagrams are similar to pictorial diagrams, but are
not as detailed. Components are represented in symbol form rather than as
they appear in reality. Figure 2-3 is the connection diagram for the circuit
shown in Figure 2-1.
N
「「／
Figure 2-3
Gas Technician 2 Training - M创ule 11
@ Canadian Standards Association
Connecti。n
diagram
53
TOPIC 2
Standard electrical symbols
」
Standard electrical symbols are used to represent components on drawings
and diagrams. Gas technicians must learn to recognize and interpret these
symbols in order to be able to properly install and service equipment.
Electrical
symbols
The following symbols, commonly found on electrical drawings, will be
encountered by gas technicians (Figure 2-4):
Normally open
Normally closed
Limit switches
h勺里
--=::JW
Pressure and vacuum switches
τε
τ冒
Liquid level switch
γ
了
Temperature actuated switch
γ
?
Flow switch (air, water, etc.)
ιr·
气’
.L
T
丰
Instant opening contacts
Disconnect switch
tH
AC source
Circurt breaker
}}}
Bimetallic strip
俨」4
~
Coll, resistive
甲代八八l'v-
Heater or 陌sistor
任-vvvν-0
Iron core transformer
Ground
Power or control fuse
Wiring terminal
Thermocou阳
Thermopile
J_
击
~·~
.
)
~
Figure 2-4
、－
Gas Technician 2 Training - Module 11
CCanadian Standards A础沁园ion
θ
J工 or 一-.rx..r一
Junction of paths
(conductor or cable)
J__
Solenoid
@
~：；f :n~~＝~ing
Crossover
Elect时臼l
斗←
十
symbols
55
TOPIC
3
Wiring diαgγα1ms
A wiring diagram is a map of an electrical circuit. It shows exactly how and
where wires are connected between devices. It is used for field-wiring a
circuit, and for tracing wires when troubleshooting.
Sequence of
operation
The sequence of operation of a circuit can only be determined from its
schematic diagram. However, the operation of some very simple circuits
can be determined from a wiring diagram only.
Figure 2-5 shows a thermostatically controlled circuit. In this diagram, the
contacts have the same designation as the coils that control their operation.
From the information shown, the sequence of operation when terminals R
and W 缸e closed can be determined.
Manufactur1町s
often provide only pictorial diagrams wi由 equipment.
Sometimes, it is di伍cult to determine a sequence of operation from
pictorial diagrams, so they must be converted to a schematic 岛r
troubleshooting pu甲oses.
、、四W
Gas Technician 2 Trainir咆『 Modu抱 11
CCanad泊n S恼ndards Association
57
INTERPRET ELECTRICAL DRAWINGS
UNIT2
N
CR2
,.. - :
---- -- - - - - - ----- -- - -- - - -.
IV
II
:
CR1
G
Figure 2-5 Thermostatically controlled circuit
58
Gas Technician 2 Training - Module 11
。 Canadian Standards Association
INTERPRET ELECTRICAL DRAVVINGS
UNIT 2
“ At rest” state
All wiring diagrams are drawn in an “ at rest" state. This means that the
circuit ’s main disconnect device is in the open position, and that any
heating or cooling devices connected to the circuit are not operating, or at
rest. In the “ at rest" condition:
•
no devices in the circuit are energized or operating
•
all devices and switches are in their normal positions.
Normal switch positions
A switch drawn in the open position is said to be normally open, and will
not change position until it is switched manually or remotely.
A switch drawn in the closed position is said to be normally closed, and
will not change position until it is switched manually or remotely.
Figure 2-6 is the wiring diagram for a gas-fired 自江nace control circuit. In
this illustration, the circuit is shown “ at rest飞 with all switches in their
normally open or normally closed positions, depending on their function.
For relay contacts,“normal” is the pos此ion WI由 no power on in the circuit.
、、F’
Gas Technician 2 Traini『'IQ-Moduk量
©Canad阳n S恒ndards Associl蜘n
11
59
INTERPRET ELECTRICAL DRA\/VINGS
UNIT2
Gas valve
HZP工
」的υcgωc。
＠2
－国
>
E
＠＠』。
g
哩。
SEE
Turbo blower
MAG
国E
~
国
Red
N
Black
Blue
Capacitor
＠3甲国
主
N。，te: Important. If any 口f
the original wire as supplied
must be replaced, the
replacement wi阻 must be of
the same type and size of its
equivalent.
Figure 2-6 Furnace control circuit
60
Gas Technician 2 Training - Module 11
。Canadian Standards A销。ciation
INTERPRET ELECTRICAL DRAl/IANGS
UNIT2
Wiring
diagram
interpre阳ti on
Correct interpretation of wiring diagrams and sequences of operation
requires an understanding of certain electrical terms, such as:
control device call-up or call-out
•
factory wiring
•
field wiring.
Control device call-up
Control devices include the following:
•
temperature controls
•
pressure controls
•
humidity controls
•
flow controls
•
level controls.
Control devices on a wiring diagram are represented by symbols and
identified or called up by position, type, and action. For example, it would
be incorrect to identify a temperature control as a heating thermostat on a
drawing, unless it is known for s田e 也at that is its function. The proper way
to identify it would be as 飞 normally-open temperature control which
closes on fall. ”
Controls are normally open or normally closed. All controls open or close
in response to an increase (rise) or decrease (fall) in:
temperature
•
press田e
•
humidity
•
fluid flow.
Gas Technician 2 Training- Module 11
CCanadian S恒ndardsAs四cia目on
61
INTERPRETεLECTRICAL
DRAV\llNGS
UNIT2
Factory wiring
Factory wiring is done at the time of manu臼cture. It is permanent, and may
include printed circuits, wiring harness assemblies, and individual cables
and conductors. Factory wiring is usually designated on diagrams by solid
lines.
Field wiring
Field wiring is done by a technician at the time of installation. It usually
includes 由e cabling required for connection to the power supply, and may
include certain modifications or changes to the wiring required for specific
applications or conditions. Field wiring is usually designated on diagrams
by broken lines.
62
GasTechn刷刷 2 Training - Module 11
©Canadian S幅ndards Association
INTERPRεT ELECTRICAL
UNIT2
DRA\/VINGS
Assignment 2
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
轧That
2.
How are components represented on connection diagrams?
3.
Gas technicians should have a 也orough understanding of electrical symbols. True or False?
4.ηie
is the purpose of ladder and schematic diagrams?
sequence of operation of a circuit can be determined 丘。m what kind of drawing?
5.
What type of diagram is most helpful when trying to trace wires?
6.
In which operating position will the switches and other devices in a circuit be shown on a
wiring diagram drawn 扭曲e “at rest” S臼te?
7.
All control valves open and close in response to changes in what conditions?
Gas Technician 2 Training- Module 11
©Canadian S恒ndards Association
63
Unit 3
Measuring and test
instruments
Purpose
A gas technician must be capable of solving problems on a regular basis. In
many cases these problems will be electrical ones. Solving these problems
requires a thorough knowledge of the system and the tools required to
determine where the problems lie.ηiis means 也at the gas technician must
be familiar with the various types of electrical measuring and test devices,
as well as how and where they 缸e applied.
Learning
objectives
1. Describe the types and applications of measuring and test instruments.
2. Describe the operation and connection of measuring and test
mstruments.
Gas Technician 2 Training- Module 11
Standards A撼。ciation
@Canad恼n
65
Topics
1. Types and applications of measuring and test
instruments .................…......................................................... 67
Meter types ....................................................….................................67
Multi meters ..........................….....................................………................... 70
2.
Operati。nand c。nnection of measuring and test
instruments............”..........................................................”… 73
Before you begin ......................................................................................73
UsingaVOM ...........…···························……..................……….........…..........73
Measuring voltage, current and resistance ................…................................ 73
Reading electrical measuring instruments .........….................….................... 75
Testing circuits with a multimeter. ….......……·········…………….....……......... 76
Handling of electri臼I measuring instruments ............................................... 81
Assignment
66
3 ........”................................….................................. 83
Gas Technician 2 Training - Module 11
© Canadian Standards A斟刷刷∞
TOPIC
1
Types α·nd αrpplicαlions
of meαsuring and test
instruments
Electrical measuring and test instruments include various types of meters,
recorders, and analyzers. These instruments may be analogue or digital
type units.
Analogue instruments indicate measured values with a scale and pointer
display. The pointer ’s movement is directly and continuously related to 由e
measured quantity.
Digital instruments interpret the measured quantity electronically in
discrete numerical data (digits). They have a numerical display like a
pocket calculator that is formed by light帽emitting diodes (LEDs) or liquid
crystal displays (LCDs).
Meter types
The three basic electrical meters are the:
•
voltmeter and millivolt meter-for measuring voltage
•
ammeter-for measuring current
•
ohmmeter一－for measuring resistance, polarity and continuity.
More commonly, the functions of each of these individual instruments are
combined into a single, versatile, instrument, called a multimeter: A
multimeter may often be called a VOM (volt-ohm-milliammeter), or by
various manufacturers ’ names, such as AVO.
In addition to the basic meters, technicians may often be required to use
other instruments such as:
•
megohmmeters (meggers}-for measuring insulation resistance
•
capacitor analyzers一for measuring actual capacitance values.
Gas Technician 2 Training- Module 11
©Canadian S恼ndards Association
67
MEASURING AND TEST INSTRUMENTS
UNIT3
Voltmeter
Electrical potential and voltage are measured in volts (V) or millivolts
(mV).
Voltmeters measure the difference in electric potential between two points
in a circuit. They are used mostly in laboratories. In the field a multimeter
ts more common.
An analogue voltmeter operates without a ba忧ery. It draws a very small
current 仕om the circuit being measured. This current drives a pivoted coil
to which the pointer is attached. The reading is indicated on a scale marked
in volts or millivolts.
Millivolt meter
A millivolt meter is used to measure DC millivolts only. It can be set to one
of three ranges ：。一切，。－ 500, or 0 - 1000 mV. Measurements should first
be made with the meter set on the highest scale. Test leads must be
connected with the proper polar坷， otherwise the meter will read in reverse.
Ammeter
Electric cuηent flow is measured in amperes (A), milliamperes (mA), or
microamperes (µA). The word “ ampere” is commonly shortened to “ amp”So, for example, a milliampere would be called a milliamp.
Ammeters measure the current flowing through a circuit. They are used
mostly in laboratories. In the field a multimeter is more common.
An in-line analogue ammeter operates without a ba忧ery. It is inserted into
the circuit so that the full current being measured flows through the
instrument. The c町rent drives a pivoted coil to which the pointer is
attached. The reading is indicated on a scale marked in amperes,
. milliamperes, or microamperes.
68
Gas Technician 2 Training - Module 11
。 Canadian Standards Association
MEASURING AND TEST INSTRUMENTS
UNIT 3
Clamp-on ammeter
Clampoperation to measure current in the circuit. Clamp-on meters are generally
used to measure alternating current or direct current only, but some digital
clamp” on meters will measure AC and DC, as well as voltage and
resistance.
A clamp-on ammeter has the following advantages:
•
it causes minimal circuit loading, because it is not connected in series
with the load
•
it does not require the use of external shunts, as some in-line ammeters
do
•
it is generally more rugged than an in-line ammete卫
Ohmmeter
Electrical resistance is measured in ohms (Q) or kilohms (kO).
An ohmmeter can be used to measure both resistance and continuity in a
circuit. Unlike the ammeter and voltmeter, an ohmmeter ’s scale reads 仕om
right to left. Ohmmeters are used mostly in laboratories. In the field a
multimeter is more common.
An ohmmeter is powered by a small battery that causes cu汀ent flow
through the tested circuit ’s resistance. This current drives a pivoted coil to
which the pointer is attached. Although it is actually current that is being
measured, the scale is marked in ohms.
The ohmmeter scale must be set to zero for each measurement. This action
also tests 由e battery. It is also important to switch off the ohmmeter after
use, to prese凹e 也e battery.
Megohm meter
Amego趾nmeter
is used for measuring the resistance of electrical
insulation of motor and transformer windings, for example. It measures
values in the 20 kilohm to 2000 megohm range.
The component or apparatus being tested is disconnected from the circuit
and the megohmrneter leads connected (one to the frame and one to 由e
windings). The instrument applies a DC voltage to the component, and the
insulation value is read at 30 seconds and again at 1 minute after being
connected. If the insulation is in good condition, the value will increase
Gas Technician 2 Training - Module 11
©Canadian Standards Association
69
MEASURING AND TEST INSTRUMENTS
UNIT3
slowly. The reading taken at 1 minute should be higher than the one taken
at 30 seconds.
Capacitor analyzer
Unlike an ohmmeter, which only indicates if a capacitor has capacitance, a
capacitor analyzer can test actual capacitance. Its principle function is
detection of current leakage that would normally only be obvious during
circuit operation. It can also detect if a capacitor is open or shorted-out.
The capacitor analyzer operates on a 110 V AC or on DC battery power. To
conduct a test, the analyzer is set to the appropriate capacitance range: less
than 0.5 mfd, 0.5 - 25 mfd, or 30 mfd and over. After the selector switch is
set to the desired range, the two test leads are connected across the
capacitor terminals. A test switch is then depressed to operate the analyzer.
An indicator light will flash on, then off, remain on or off, flicker, or glow
steadily, depending on the condition of the capacitor.
Multi meters
的
HO
br
aE
eap3
nYLHH
d
计H
..
M 川
A multimeter is a combination ammeter, voltmeter, and ohmmeter in a
single, compact unit. Its two main advantages over using several singlefunction meters are
吼
什H
The typical multimeter shown in Figure 3-1 has the following features:
a function switch for setting the meter to measure AC, DC, or
resistance
a range switch to select the correct voltage, current, or resistance range
being tested
a zero-ohms adjustment knob to compensate for variations in the
internal battery voltage of the meter
a zero adjustment for the pointer (set with a screwdriver before each
measurement)
•
a reset button to restore the instrument to normal operation if the
internal circuit breaker shuts off due to over-current
jacks for connecting circuit leads.
70
Gas Technician 2 Training - Module 11
© Canadian Standards Association
MEASURING AND TEST INSTRUMENTS
UNIT3
手：先古~~~，
」土Q ；于·！
co
Function
switch
Test lead
connections
：~~ 二仁5~ 二妥协二
Range and
function
selector
switches
Range
switch
(a) Analogue multi 『neter
(b) Digital multimeter
Figure 3-1 Multimeter features
、、自卢
Gas Technician 2 Training- Module 11
© Canadian standa『ds Association
71
TOPIC
2
Opeγαti on αnd connection
of meαsuring α~nd test
instγuments
A gas technician must be able to identi命 various electrical test and
measuring instruments, select the appropriate instrument for the job, and
operate it correctly. This is covered in detail in Unit 7 of 岛1odule 5.
Before you
begin
You must be aware of the following factors:
•
the zero adjustment
•
parallax error
•
instrument placement
•
proper interpolation of readings.
Using a VOM
The use of a VOM is discussed in detail in Unit 7 of Module 5.
Measuring
voltage,
current and
res is阳 nee
Measuring voltage
To measure voltage, a voltmeter must be connected across the two points in
the circuit where the voltage appears. It is connected in parallel.
Gas Technician 2 Training- Module 11
@ Canadian Standards Association
73
MEASURING AND TEST INSTRUMENTS
UNIT3
Measuring current
In-line ammeter
To measure current with an in-line ammeter, the circuit must be broken at
the point where the cuηent is to be measured, and the ammeter inserted in
series.
Figure 3-2 Measuring current with a clamp-on ammeter
Clamp-on ammeter
Unlike the in-line ammeter, a clamp-on ammeter can measure the current in
a conductor without being inserted into the circuit. Current can be
measured quickly and accurately without interrupting circuit operation.
This is particularly useful when checking loads such as electric motors (see
Figure 3-2). Current measurement with a clamp-on ammeter is done as
follows:
1. Open the jaws of the ammeter by squeezing the handle.
2. Close the jaws over the conductor, as shown in Figure 3-2.
3. Ensure that only one conductor is enclosed in the jaws. If the live and
neutral conductors are both enclosed by the jaws, the meter will read
zero.
4. Ensure 也at the jaws of the ammeter are completely closed. If the
contact points of the jaws are dirty or obstructed and do not make good
contact, the reading will be inaccurate.
5. The cuη·ent reading will be indicated on the ammeter display.
74
Gas Technician 2 Training - Module 11
© Canadian Standards Assoαation
MEASURING AND TEST INSTRUMENTS
UNIT3
Measuring resistance
An ohmmeter is used to measure resistance. The ohmmeter is connected
across the unpowered device or circuit. To protect the ohmmeter it is best if
you isolate the devices being tested from the circuit. Using an ohmmeter is
discussed in Unit 7 of Module 5.
Reading
electrical
measuring
instruments
The principles for reading a meter are not much different from those used
to read a common ruler. You should, however, be able to distinguish
between reading the different types of meter.
Reading a voltmeter and an ammeter scale
The scale on a voltmeter and an ammeter use 也e same principle.η1is is
discussed in Unit 7 of Module 5.
Reading an ohmmeter
η1is
is discussed in Unit 7 of Module 5.
.Reading a capacitor analyzer
A capacitor analyzer has an indicator light instead of an analogue scale or
digital display.η1e capacitor being tested causes 由e light to respond in
different ways, depending on the condition of the capacitor. When testing a
motor-starting capacitor.，岛r example:
1. The analyzer is plugged in (for AC operation) or switched on for DC
battery operation.
2. The capacitance selector switch is set to 由e correct range.
3. The test leads are connected across the capacitor terminals.
4. The test switch is d叩1ressed and held down.
5. The indicator light will respond as 岛Hows:
•
if the capacitor is working properly, the light will flash on and then
go off
if the capacitor 扭曲。rted-o时，也e light will remain on
it 也e capacitor is open, the light will not come on
if 由e capacitor is leaking, the light will flicker.
、、屿，，
Gas Technician 2 Training - Module 11
@Canadian S幅ndards Associa阳可
75
MEASURING AND TEST INSTRUMENTS
UNIT3
Reading a multi-range multimeter
This is extensively discussed in Unit 7 of Module 5.
Testing
circuits with a
multimeter
Many service calls are for problems of an electrical nature. To quickly
identi命 the circuits a他cted and accurately troubleshoot the problem
requires the use of a multimeter.
Fan circuit
Figure 3-3 is a diagram of a 120 V fan circuit associated with a forcedwarm-air furnace.η1e operation of the circuit is tested as follows:
Step 1-Check appliance disconnect switch
1. Make s田e 由at the appliance disconnect switch is wired into L1.
2. Ensure that the disconnect switch shuts off the power suppl予
Step 2-Take readings for circuit voltages
1. Set the meter to 由e proper scale for the circuit voltage and take a
reading from 由e L1 connection in the junction box to ground
(Figure 3-3).
2.
Verify 也at
the reading with the disconnect switch closed is 120 volts.
3. Take a reading from由e N connection in the junction box to ground
(Figure 3-3).
4.
76
Veri马r
that the reading between N and ground is 0 volts.
Gas Technician 2 Training-Module 11
@ Canadian Standards Associa苗。n
MEASURING AND TEST INSTRUMENTS
UNIT3
L1
N (L2)
120 v
Figure 3-3 120 V furnace fan circuit
Step 3-0pen disconnect switch, retake readings
These readings should verify 由at the disconnect switch is located on the L1
or hot line and that it shuts off power to the unit.
1. Open the disconnect switch and retake the readings.
2. Verify that the reading between L1 and ground is 0 volts.
3. Verify that the reading between N and ground is also 0 volts.
Gas Technician 2 Training - Module 11
Standards A部ociation
。 Canadian
77
MEASURING AND TEST INSTRUMENTS
UNIT3
Step 4-Retake reading for circuit voltage with disconnect
switch closed
The second reading on this circuit determines the source voltage between
L1 and N (Figure 3-4 and meter A).
1. Set the meter to the proper voltage scale and take a reading between L1
andN.
2. Verify that the meter indicates 120 volts.
L1
N (L2)
120 VAC
120 v
120 v
Figure 3-4 Taking voltage readings on fan circuit
Step 5-一Take readings across fan switch
1. Take a reading across the terminals of the open fan switch.
2. Verify that the reading is 120 volts (Figure 3-4 and
meter B).
3. Verif旨 that the reading across the fan switch is 0 volts when the fan
switch closes.
Step 6-Take readings across the motor terminals
1. Take a reading across the motor terminals when the fan switch is open.
2. Veri马r that the reading is 0 volts (Figure 3-4 and meter C).
3. Verify that, when the fan switch closes to energize the motoζthe
reading is 120 volts.
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Gas Technician 2 Training - Module 11
。 Canadian Standards Association
MEASURING AND TEST INSTRUMENTS
UNIT3
Transformer circuit
Figure 3-5 shows the line voltage circuit to the high limit (optional
location) and step-down transformer.
If you take a reading with meter A, it indicates a source voltage of
120 volts.
Meter B indicates a reading of 0 volts if the high limit is closed. If it is
open, it should read 120 volts.
Meter C indicates 24 volts on the secondary side of the transformer, or
slightly higher if there is no load connected.
L1
N (L2)
120 V AC
Junction box
Transfo「mer
Figure 3-5
了aking
voltage readings on transformer circuit
＼」－，
Gas Technician 2 Training - Module 11
Canadian Slanda『ds Association
©
79
UNIT3
MEASURING AND TEST INSTRUMENTS
Figure 3-6 shows the 24 volt control circuit for a forced warm-air 且rrnace.
It consists of a 24 volt power supply, a three-terminal gas valve and a
thermostat.
Meter A indicates the source voltage to be 24 volts. If there were no load
on the transformer, it would read 26 or 27 volts. Once the control circuit is
energized, the voltage at A should return to 24 volts.
Meter B is placed across the terminals of 由e thermostat. Wi由 the
thermostat switch contacts in the open position (no call for heat), the meter
should read 24 volts. Once the thermostat contacts close on a call for heat,
the meter should read 0 volts.
岛~eter
C is placed to read the voltage drop across the coil of the gas valve.
When the thermostat contacts 缸e open and not calling for heat, the meter
should read 0 volts. When the thermostat contacts are closed and calling for
heat, the meter should read 24 volts.
Thermostat
EL
-E
a
Figure 3-6 Taking voltage readings on control circu 忧
80
Gas Technician 2 Training- Module 11
。 Canadian Standards Assoc恼币。n
MEASURING AND TEST INSTRυMEN TS
UNIT3
Handling of
electrical
measunng
instruments
Analogue instruments are more delicate than digital instruments-they
have moving parts that may be damaged if the instrument is mistreated.
Analogue instruments should be treated with greater care than digital
instruments.
•
Do not allow measuring instruments to bounce about in the back of a
vehicle.
•
After using a multimeter, switch function away 企om resistance-setting
(preferably to its “ current” function) to preserve the battery.
•
Store instruments in their cases when they are not in use.
•
Do not allow instruments to get damp, or wet.
•
Do not expose instruments to high temperatures and high humidity.
•
Remove battery if instruments are to be stored for long periods of time.
•
Check the battery compartment from time to time to ensure that no
corrosion is taking place due to leaking batteries.
•
Keep a spare set of batteries for digital instruments.
•
Store test-leads to prevent them 企om being damaged.
\~,,
Gas Technician 2 Training- Module 11
© Canadian Standards Association
81
UNIT3
MEASURING AND TEST INSTRUMENTS
Assignment 3
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
A multimeter incorporates which basic electrical meters?
2.
An ammeter is connected in parallel with the circuit under test. True or False?
3.
A continuity check is actually a measurement of what?
4.
An ohmmeter should always be connected to a live circuit. True or False?
5.
Is it advisable to test a fan circuit with a multimeter?
、）
Gas Technician 2 Training - Module 11
© Canadian Standards Association
83
Unit4
Circuits and hardware
Purpose
Knowing how, and from where, electricity is supplied, will help the gas
technician install and maintain gas equipment. Whether the source is an
electrical panel, junction box or transformer, a basic knowledge of the relevant hardware and circuitry is important.
Learning
objectives
1. Describe electrical panels and transformers.
2. Describe electrical hardware.
3. Explain wiring diagrams.
Gas Technician 2 Training- Module 11
© Canadian
Standa『ds A部ociation
85
Topics
1. Electrical panels and transformers .........................….......... 87
Residential electrical service ....... . .... .. .. . . .......….........….......... 87
Control circuit transformers. ………………………………··………….... 89
2. Electrical hardware .........….................................................... 91
Connection devices .......................……......…………………........…....... 91
Switches, relays and contactors ......……，............，……………－…….....川 93
Boxes ..................…··……........................…......................................... 102
Sockets and plugs ......曹...................................………………….......……… .104
Fasteners ...…………..…·‘…····-……..…………………………..........…...... 107
Conduit ...............................………….........……................................ 107
Assignment 4 ...............…........…................….......................…... 109
86
Gas Technician 2 Training - Module 11
© Canadian Standards Association
TOPIC
1
Electγicαl pα， nels α＇nd
甘ansforme.γs
Residential
electrical
service
The electrical service coming into a residential distribution panel is 240
volts, single-phase, 60 hertz (240/1/60). The service conductors consist of:
•
two hot (live) wires or “ line wires"
a neutral wire
•
a ground wire一-connected to the metal distribution panel.
Branch circuits
The 240 V supply coming into a building is divided into branch circuits at
the distribution panel (see Figure 4-1 ). At the panel:
the 240 V circuits are protected by two-pole breakers
the 120 V circuits are protected by single-pole breakers.
Branch circuits are 240 V or 120 V, depending on the requirements of the
circuit they service. 240 V branch circuits have:
•
two fused lines一-one from each hot wire coming into the panel
•
a ground wire.
120 V branch circuits have:
one fused line--from one of the hot wires coming into the panel
a neutral line from the neutral bar in the panel
a ground wire connected to metal panel box.
All line-voltage circuits must have a continuous ground running 仕om the
main distribution panel to each junction box, receptacle, and appliance.
Gas Technician 2 T1『aining - ~ule 11
© Canadian Standa『ds Association
87
CIRCUITS AND HARDWARE
UNIT4
To meter panel
「一～「
Bonding
jumper
Grounding
bushing
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
／－＼一一一－ 120
v
E二 N
Ground wire
(bare)
Ground bus
To ground
system
Figure 4-1 Distribution panel and schematic, showing branch circuit connections
88
Gas Technician 2 Training - Module 11
。 Canadian Standards Association
CIRCUITS AND HARD\/l/J气RE
UNIT 4
Control circuit
transformers
Many gas appliance control circuits and other electrical devices operate on
lower voltages than 120 V. The voltage for control devices is usually 24
VAC. A 240/24 or 120/24 step-down transformer is required to obtain the
necessary 24 V supply. A typical step-down transformer is shown in
Figure 4-2.
Electromagnetic
field
L1
Secondary
winding
120V
AC
power
source
1
、
1·
‘{ -e
e
、
i
、
、
-
E
，咱－
l
、、
N (L2)
f14
’a,,,,,
’’-,,
,
,
24V
,,
'
户，
·-.,_
I 「on
core
Figure 4-2 Typical step-down transformer (ilnd schematic
A transformer like the one shown in Figure 4-2 consists of:
a core of iron plates
sep缸ated
by insulation
a primary winding
a secondary winding.
The 120 V supply is connected to the primary winding terminals of the
transformer and the appliance control circuit connected to 由e24 V
secondary winding terminals. 白ie 120 V alternating current flow through
the primary winding induces a 24 V current in the secondary winding to
power the appliance control circuit.
、、卢
Gas Technician 2 Training - M创ule 11
Standards Assoc阻lion
。 Canadian
89
UNIT4
CIRCUITS AND HARDWARE
Transformer ratings
Manufacturers always speci命 the voltage rating of a transformer ’s primary
and secondary windings. Secondarγwinding rated voltages are specified
for 且ill-load conditions with the rated primaηvoltage.
•
Operating a transform町’s primaηat higher than rated voltage may
cause 由e transformer to overheat, damaging its insulation.
•
Operating the primary at lower than rated voltage does no harm, but
secondary voltages will be less than rated values.
Current ratings are generally specified for secondary windings only. If the
secondary current rating is not exceeded, the primary cu盯ent capacity
cannot be exceeded.
Transformer ratings are based on the amount of power the secondary
winding can handle. Transformer power ratings can be specified h 阳ro
ways:
•
by the voltampere (VA) rating
•
by the power rating in watts.
The voltampere rating of a transformer is the product of the voltage and
amperage (VA= V x A). A power rating specified in watts is understood to
be the power that a transformer can deliver to a resistive load. The power
rating in wa忧s is the product of the current rating and the voltage rating of
the secondary winding (P = E x I).
Transformers are indicated on electrical diagrams in two ways, as shown in
Figure 4-3.
－
」←
FM
川
p~llEa~
Figure 4-3 Electrical diagram transformer symbols
90
2 Training - Module 11
© Canadian Standards Association
GasTechniαan
TOPIC
2
Electrical hαγdwαγe
In order to properly install and service gas appliances and equipment, gas
technicians must be able to identify and use the following types of
electrical hardware:
•
connection devices
•
switches, relays and contactors
•
boxes
sockets and plugs
Connection
devices
•
fasteners
•
conduit.
The Electrical Code requires that all connections be made only in outlet or
junction boxes. The electrical connections used for the installation of gas
appliances and equipment fall into 机iVO basic groups:
solderless terminals and insulators
soldered connections.
Solderless terminals and insulators
Solderless terminals and insulators include
connectors (see Figure 4-4).
crimp-on”可pe
and insulated
cap句pe
Crimp-on connectors
Crimp-on connectors (Figure 4-4) are used to secure twisted and untwisted
wire joints. This type of connector can be a slip-on metal cap for pig-tail
joints, or a metal sleeve for splicing two straight wires. A special tool is
required to install crimp-on connectors.
、、一
Gas Technician 2 Training - Module 11
Standards Association
© Canadian
91
CIRCυITS
AND HARDVVARE
UNIT4
口
\
／／／／，
cω
/
/\
量
Figure 4-4 Solderless terminals and insulators
Insulated cap connectors
η1ere
are several types of insulated-cap connectors. This type of connector
is used for pig-tail joints of two or more conductors.τbe two most
common insulated-cap connectors are the twist-on type and the screw-on
type (Figure 4-4). Both have plastic insulating caps and are available in
several sizes to accommodate a wide range of conductors. The caps are
coloured or are marked with a number to identify their size and capacity.
The twist-on cap has a coiled wire insert 也at grips the twisted conductors
to ensure good electrical contact. The screw-on cap has a brass insert with a
hold-down screw.η1e twisted conductors are slid into the brass insert and
secured with the hold-down sere吼 before the plastic insulating cap is
screwed in place.
92
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。 Canadian S阳ndards A部ociation
CIRCUITS AND HARD\/'\LA,RE
UNIT 4
Soldered connections
Soldering is probably the best method for joining circuit conductors.
However, it takes longer and requires more equipment than other methods.
Bonding conductors must not be soldered.
Switches,
relays and
contactors
Switches
A switch is a device that opens or closes an electrical circuit. A switch has
two positions: open and closed. Switches are always located in the hot (H)
leg of the circuit, never in the neutral (N) leg.
Electricity cannot flow through a control circuit unless all switches are
closed and the circuit is com~lete. If even one of the switches is open, the
circuit cannot conduct electrical current.
All switches are rated for the amount of current that can flow through them.
Always ensure thαt the switch is rated at or above the circuit current flow
and voltage.
Switches are designated by the number of poles and throws they have.
When a switch is thrown, the pole is moved to another position. A throw is
therefore one position of the pole.
Single pole, single
thr1。w switch
The simplest switch is a single pole, single throw (SPST) switch
(Figure 4-5). This means the switch has one pole and one contact.
、、』卢
Gas Technician 2 Training- Module 11
© Canadian Standards Association
93
CIRCUITS AND HARDWARE
UNIT 4
Pole
,
’‘
•/•
Schematic symbol
Figure 4-5 Single pole, single throw (SPST) switch
Single pole, double throw switch
If another contact is added to a SPST switch, the switch becomes a single
pole, double throw (SPDT) switch
(Figure 4-6). The pole can be thrown to one of two positions; energizing
one of two different circuits or loads.
→乞二
Schematic symbol
Figure 4-6 Single pole, double throw (SPOT) switch
94
Gas Technician 2 Training- Module 11
。 Canadian Standa『ds A岱ociation
CIRCUITS AND HARDV\LA.RE
UNIT4
Double pole, single throw switch
、、白，
Some household appliances require 240 V. In this case, two poles, each
carrying 120 V, are linked mechanically to move togethe旦
This type of switch is called a double pole, single throw (DPST) switch
(Figure 4- 7） .ηie poles are connected to two sep缸ate hot legs called L 1
andL2.η1e poles make and break two independent circuits at 由e same
time. A common use of a double pole, single throw switch is the disconnect
switch on a window air conditioner.
飞
飞
r
、
典
、
、
、
1
0--
L1 －－＜γ寸’。－－－－
L2 --0-扩
Schematic symbol
Figure 4-7 Double pole, single throw (DPST) switch
Double pole, double throw switch
If another throw is added to 也e DPST switch, it becomes a double pole,
double throw (DPDT) switch (Figure 4-8). Now the poles can make contact
m two positions.
→之二
J乞二
Schematic symbol
Figure 牛8
Double pole, double throw (DPDηswitch
」
Gas Technician 2 Training- Module
©Ca晒d恼n S剧由rds Association
11
95
CIRCUITS AND
HARD叭队RE
UNIT4
Switch operation
Switches can be operated by hand or they can be actuated in response to
changes in:
•
temperature
•
fluid movement
•
pressure.
Each of the above conditions creates a force that moves the poles to the
opposite position. In switches designated as normally open, the force
moves the pole to close the circuit. On a switch designated as normally
closed, the 岛rce moves the pole to open the circuit.
Motor-s恼 rting
switches
Elec位ic
motors use various types of starting switches. Two switches in
common use are 由e:
toggle switch
push-button switch.
Toggle s饭rter switch
白ie toggle
motor-starter is a snap-action switch, providing simple on-off
It may consist of one contact (single pole) or two contacts (double
pole). Contacts 缸e operated by a toggle lever on the 仕ont of the starte汇 A
thermal overload device is next to 由e contact assembly. Figure 4-9 shows a
single-pole, manual starting switch.
con位ol.
－圄圃h‘喝、
Figure4”’ Manual motor-starting switch
96
Gas Technician 2 Training - Module 11
C Canadian Standar由 A”。ciation
CIRCUITS AND HARDWARE
UNIT 4
This manual starter may be mounted in a standard switchbox installed on
the wall and covered with a standard switchplate.
The ON and OFF positions are clearly marked on the lever and the switch
is similar in appearance to a standard lighting switch. The main difference
is 由at the motor starting switch has hors叹power-rated contacts, which
means that it can safely interrupt the inrush current or locked-rotor current
of the motor. It also contains overload protection 岛r sensing higher-thannormal currents drawn by the motor.
The starter is connected in series with the supply line and the motor
terminals, so that it can switch cuηent to the motor. If a motor overload
occurs, the following happens:
1. Line current to the motor increases.
2. This causes a small heater element to warm up considerably.
3.ηiis
heating automatically trips the switch contacts, which breaks the
circwt.
4. After a cooling period, the toggle is reset by pulling down the switch
lever and then switching on again.
τbe cοmpact
construction of this manual starter switch allows it to be
installed directly on driven machinery and in tight spaces.
Push-button starter switch
Push-button starters are similar in operating principle to toggle switches,
except that they use two separate buttons to activate contacts. Figure 4-10
is an external view of a push-bu忧on, manual starter h 由e on(START)
pos1t10n.
To switch the motor on, press 由e START button so 由at it moves inward
and stays there. A mechanical interlocking device 岛rces 也e STOP button
outward so that it projects beyond 也e START button. 臼ice activated, these
buttons remain in position until the opposite button is pressed.
To turn the motor off, press the STOP button in so that 也e START button
moves out agam.
、、，，
Gas Te<才inician 2 Training-Module
@Car回国n Standards A揭ociation
11
97
CIRCUITS AND
HARD叭队RE
UNIT 4
Figure 4-10
Push嗣button
starter switch
Movable
A叫r←~ontact 二～J
n
川u
a 南
刊，
‘自‘「 J
川HM 晶’a
SO
gn
oa
Sp时ng
:/Coil
Core
Figure 4-11 A simple relay
98
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CIRCUITS AND HARDV以RE
4
Relays
A relay is a magnetically-operated switch that operates on the solenoid
principle. It can have multiple sets of contacts, which can be open or
closed. A solenoid, which is basically a coil of wire wound around an iron
core, converts electrical energy to linear motion (see Figure 4-11 ).
When current flows through the coil of the solenoid, a magnetic field
develops in the core. The magnetic field, which is stronger than the spring
holding the movable armature away 企om the iron core, attracts the
armature.
In the “ at rest" position, the movable contact connected to the armature is
in contact with one of two stationary contacts. This set of contacts is
normally closed. When the magnetic field pulls the armature towards the
iron core, the armature breaks contact with one stationary contact and
makes contact with the other.
Control relays
Control relays are electrically-operated switches that use electromagnets or
solenoids to open and/or close several different circuits at the same time.
η1e contacts are rated for light duty and usually caηy only ve可 small
amounts of current, as is usually the case for the components of control
.circuits. Control relays are not suited for controlling even single-phase
motors of any size. This is because of the high inductance and low
resistance that cause high-starting cuηents when starting, and high backcurrents when contacts are opened for stopping. The high back-currents
tend to keep c町rent flowing when the contacts are opened, causing arcing
and burning or welding of the contacts.
A control relay is shown in Figure 4-12. The T-bar of the armature is seen
at the bottom in Figure 4-12 (a). The bottom sets of contacts are normally
closed, as shown in detail in Figure 4-12 (b). When the solenoid is
activated, the armat旧e moves upward, opening the bottom contacts and
closng the upper con阳cts. The armature is insulated from the electrical
contacts.
Gas Technician 2 Training - Module 11
。 Canadian Standards Association
99
CIRCUITS AND HARD\/\£1\RE
UNIT4
Normally open
contacts
Solenoid
－γF
arπiature
(b) Detail of the contacts
(a) Relay
Figure 4-12 Control relay
Contactors
The term relay is often used to describe any type of magnetically·叩erated
switch. A relay is actually a control device that contains small auxiliary
contacts designed to operate only low-current loads.
A contactor is very similar to a relay except that a contactor contains largeload contacts designed to control large amount of current. In the heating
and air-conditioning field, contactors are often used to connect power to
resistance heater banks. Contactors may contain auxiliary contacts as well
as load contacts.
Motor starters are basically contactors with the addition of overload relays.
Motor starters generally contain auxiliary contacts as well as load contacts.
The auxiliary contacts are used as part of the control circuit, and the load
contacts are used to connect the motor to the line.
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CIRCUITS AND HARDWARE
UNIT 4
Heavy-duty contactors
Heavy-du句f
contactors are solenoid/armature operators for switching
heavy-duty electrical contacts. They are used to control the large amounts
of current and high voltages required by industrial equipment. Figure. 4-13
shows a contactor that might be used to tum on a three-phase motor on a
large boiler. Note that the insulators which hold the conductive crossbars
are attached to the T-bar armature which closes several sets of contacts at
once. The schematic, Figure 4-14, shows the switch in the 110 volt
solenoid circuit which simultaneously activates the 240 volt three-phase
lines to the motor.
&
。
i nCJvHM hMilt
...,
EL
队主…
Conductive －：：：.二三r;::;/
crossbars
》萤－－－..
Terminals
Figure 4斗 3 Heavy-duty contactor
A
B C
c:
2.
82:
A·2,
: Contacts:
Figure 4-14 Heavy-duty contactor schematic
Gas Technician 2 Training - Module 11
Standards Association
© Canadian
101
CIRCUITS AND
HARD叭队RE
υNIT4
Boxes
Many types and sizes of electrical boxes are available to meet the
requirements of various applications. Variations include different depths,
widths, heights, and capacities, and mounting bracket and cable clamp
aηangements.
CEC Rules 12-3000 to 12-3040 cover the requirements for the use and
installation of electrical boxes and their accessories. The two boxes
commonly used in the installation of gas appliances and equipment are
switch boxes and junction boxes.
Switch boxes
Switch boxes (see Figure 4-15) can be used to support outlet receptacles or
switches. There are two basic types：由e gangable type and the nongangable type. One side of a gangable switch box can be removed to allow
one or more additional boxes to be added or ganged to it. The Electrical
Code requires any gas appliance 也at ts connected to an electrical circuit to
have an electrical disconnect switch.ηie switch, which must be mounted
near 由e appliance in an approved electrical switch box, is used to shut off
electrical power during eme电encies, or when the appliance is being
serviced.
Care must be taken when placing a switch box that will be used for
disconnecting the furnace 企om 由e circuit. The CE Code, Part I requires
也就 the switch for disconnection must be located between the furnace and
the point of entry to the room containing the furnace if the switch is a
branch circuit breaker in the distribution panel board. You must not have to
pass close to 也e furnace to reach the switch, and it must not be placed on
由e furnace itself. The switch must be clearly marked with the circuit it
controls.
Figure 4-15 Switch boxes
102
Gas Technician 2 Training - Module 11
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CIRCUITS AND HARDWARE
4
Junction boxes
The two types of electrical boxes commonly used as junction boxes, are:
•
octagon boxes
•
square boxes.
A junction box is often mounted directly on a gas appliance. In most
installations, the connections between the branch circuit supplying the
appliance and the appliance control system are made in the junction box.
This is done to meet CE Code, Part 1 requirements and to prevent short
circuits and electric shock hazards.
Octagon boxes
Octagon boxes (Figure 牛 16) are usually used to support lighting fixtures
or as junction points for wiring connections.τbey may also be used as
switch or outlet boxes when equipped with special cover plates.
Figure 4-16 Octagon junction box
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© Canadian Standards Association
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CIRCUITS AND HARDVVARE
UNIT 4
Square boxes
Square boxes (Figure 4-17) are used primarily as junction boxes for
surface-run and concealed wiring circuits. Square boxes are available in
two sizes. The 今inch wide box, the most commonly used, can be fitted
with special covers that permit its use for switches, receptacles, and pilot
lights. The 4-11/16 inch square box is generally used for range or dryer
receptacles.
Figure 4-17 Square juncti。n boxes
Sockets and
plugs
Some gas appliances and equipment installations require the use of special
sockets (receptacles) and plugs. Occasionally, a gas appliance may be
supplied with the necessary cable and plug and the gas technician will only
be required to select the appropriate receptacle assembly.
In some cases, it may be necessary for the technician to determine the
equipment requirements and specifications 丘。m the manufactur町、
installation instructions and select the appropriate cable, plug and socket.
104
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CIRCUITS AND HARD叭队RE
4
Figure 4-18 Locking and non-locking plugs and sockets
Speciality plugs and sockets can be locking or non-locking
(see Figure 4-18).
•
A non-locking plug is inserted straight into its socket, relying on
contact 企iction to keep it securely in place. It can be withdrawn by
pulling it straight out of the socket.
•
A locking plug is also inserted straight into its socket, then rotated
clockwise a short distance to lock it into the socket. It cannot be
withdrawn 金om the socket unless it is first rotated counterclockwise.
Each type of plug and socket assembly has different socket and terminal
blade configurations, and voltage and cuηent ratings, based on 由e
intended application (see Figure 4-19).
Gas Technician 2 Training - Module 11
©Canadian S姐ndards Association
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CIRCUITS AND
HARDV以旺
UNIT 4
15 AMPERE 20 AMPERE 30 AMPERE 50 AMPERE 60 AMPERE
RECEPTACLE RECEPTACLE RECEPTACLE RECEPTACLE RECEPTACLE
DESCRIPTION
5
125V
SA
*250V
6
*250V
6A
277V AC
7
~＠ ？③ ？③ ？③
347V AC
24
：③ ~＠ ~＠ ~＠
125/250V
14
:@ ？⑩ i ⑩ ?@ ？⑩
3 豆~250V
15
~＠ ~~ ~~ ~~ ~~
茎
。
z
＝。
~
。
~
主
2
问
主
。
~
叶
豆
2
d、
5 。 ~＠ i ③ ~＠
125V
~I⑩
~~ ~＠ i ③ ~©
~1@
*Forconfi伊rations 6-15R, 6-2侃， 6-20RA, 6-30R, and 6-5侃， Y denotes ident沂ed terminal when used on circuits derived
from 3-phase, 4-wire 416 V circuits.
Note: Except as noted above,
G represents the terminal for bonding to ground;
W represents the identified terminal; and
X. Y, and Z represent the terminals for ungrounded conductors.
Figure 4-19 Non-locking re臼ptacle socket co州gurations
106
Gas 丁echnician
2 Training - Module 11
© Canadian Standards Association
CIRCUITS AND HARD叭队RE
UNIT4
Fasteners
Electrical cable and conduit must be secured to building 丘aming and wall
and ceiling surfaces in accordance with Electrical Code requirements.
Fasteners commonly used for this pu甲ose include various types and sizes
of:
staples
clamps
cleats
•
.
sleeves
•
grommets.
anr
v且
034···
c3
Figure 4-20 shows several different types of fasteners used with electrical
cable and conduit.
口
商制
Figure 4-20
日ectrical
cable and conduit fasteners
Conduit
Electrical conduit is metal tubing used to contain and protect the electrical
conductors of a circuit. The CE Code, Part 1 covers the requirements for
the installation of electrical conduit. There are several basic types of metal
conduit:
rigid steel conduit, with a relatively thick wall
•
EMT, a thin-walled metal conduit
aluminum conduit
•
plastic (PVC) conduit
flexible steel or aluminum conduit.
Gas Technician 2 Training- Module 11
Standards Association
。 Canadian
107
CIRCUITS AND
UNIT 4
HARDV回ARE
Assignment 4
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
How m~ny wires are contained in a service conductor to a residential distribution panel, and
what are they?
2.
Branch circuits start where?
3.
All line voltage circuits have a continuous ground from the distribution panel to where?
4.
How are transformers rated?
5.
All electrical connections shall be made where?
6.
Bonding conductors must be soldered. True or False?
7.
Switches are always located in the hot leg of a circuit. True or False?
8.
Switches must be in what position to conduct electrical current?
、、－卢
Gas Technician 2 Training~ Module 11
© Canadian Standards Association
109
CIRCUITS AND HARD叭队RE
9.
UNIT 4
Switches are operated by hand or by:
10. Despite similarity in outward appearance to those of a light switch, how are the contacts in a
toggle motor starter different?
11. Relays are magnetically operated on which principle?
12. Control relays are best suited for controlling single-phase pumps of any size. True or False?
13. How does a contactor differ 仕om a relay?
14. What is meant by the term “ gangable box”?
15. List some common 也steners used for securing electrical cable and conduit.
110
Gas Technician 2 Training - Module 11
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Unit 5
Millivolt systems
Purpose
Many gas appliances are equipped with components that operate on direct
current millivoltage. This voltage is generated using heat from the gas
flame, and is used to operate minor control and safety circuits. The gas
technician must have a complete knowledge of how this voltage is generated, as well as the amount of voltage that is generated. The gas technician
must also know how this voltage is distributed through the circuit and the
test procedures used to isolate problems when they arise.
Learning
objectives
1. Explain the generation of small-value DC voltages.
2. Explain the procedure used to test control circuits.
3. Describe millivolt thermostats.
Gas Technician 2 Training - Module 11
© Canadian Standards Assc冗iation
111
Topics
1. Generation of small-value DC v。ltages ............................. 113
Thermocouple ,......,…···················…......……… …………...………... 113
Powerpile generat。r. ....................………-…….........……·………..... 115
Pilot flame characteristics ....…··‘,.............. ·········· ····· ..................... 117
a
2. Testing contr。l circuits ...........….........….........................….119
Isolating a millivolt circuit from 24 V and 120 V circuits ....................…....... 119
Connecting and reading a millivoltmeter. .....................................…........... 119
Thermocouple test.. ............................…..……··………........…........... 120
Checking for pilot flame failure ..…………·········……······················· ............. 123
Thermopile test ....................…………………… ……………-…............ 123
E
3. Millivolt thermostats ................……...................................... 135
Self-powered heating control system components ..........................…… .135
Wiring requirements. …………........ ················…………········….........……... 136
Assignment 5 .............…............................................................. 137
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Gas Technicia 『1 2 Training - Module 11
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TOPIC 1
Generαtion
of small-value
DC voltages
Unlike alternating cuηent (AC), direct current flows in one direction only.
Direct current is used to power electronic devices, small appliances, and
automotive electrical systems. DC is often supplied by some form of
battery. However, small DC voltages can be generated by other means,
such as heating a bimetallic device called a thermocouple.
Thermocouple
A simple thermocouple consists of two wires, made of dissimilar
(different) metals, joined together at one end. The end at which they are
joined is called the ho/junction. The·opposite end is the cold junction.
When sufficient heat is applied to the hot junction of a thermocouple, a
small voltage is generated at the cold junction, causing a positive-t。”
negative direct current flow. If the cold junction is heated, cuηent would
flow in the opposite direction (negative-to-positive). The voltage generated
is so small 由at it is measured in millivolts (mV). A millivolt is 111000 of a
volt. Thermocouples generate voltages in the 0 - 30 mV range.
Some thermocouples consist of a wire located in the centre of a small,
circular metal tube. The tube and wire, which are made of dissimilar
(different) metals, are joined at one end to form a hot junction (the opposite
end is the cold junction).
Gas Technician 2 Training- Module 11
© Canadian Standards As部C陆甘on
113
MILLIVOLT SYSTEMS
UNIT 5
Thermocouple application
Thermocouples are used to power combustion safety circuits that have
constant pilots. They are also used on appliances with manual reset
controls. The thermocouple shown in Figure 5-1 is the power supply for the
combustion safety circuit of a gas furnace. The thermocouple assembly is
attached with a threaded male fitting, as shown in Figure 5-1.
When the hot junction is heated by the pilot burner, the thermocouple
generates a voltage to power the electromagnet ill the safety shut-off valve
or safety switch. As long as the pilot remains lit, the shut-off valve will
remain energized and open to allow the flow of gas to the main and pilot
burners. If the pilot light goes out, the thermocouple will cool down, and
the resulting drop in voltage will trip the safety switch to shut off the flow
of gas.
Contact{+)
Insulation
Cold
junctions
Insulation
Control
connection
nut (male)
Figure 5-1 Combustion safety circuit thermocouple
114
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© Canadian Standards Association
MILLIVOLT SYSTEMS
υNITS
In order to meet Gas Code requirements, when a pilot fails (goes out), the
thermocouple must cool down and de-energize the safety shut” off valve or
safety switch within 90 seconds,. For this reason, thermocouples are only
approved for use with gas appliances with inputs up to and including
400 000 Btu/h. However, a single thermocouple may be used to supervise
inputs of 1 000 000 Btu/h with appliances having unrestricted vertical flue
passes, and that use gases lighter than air.
Hot junction
The thermocouple only generates a voltage if the temperature difference
between the hot and cold junctions is at least 400°F (204°C). The greater
the temperature difference, the greater the voltage generated. For this
reason, it is important that the pilot flame heat only the first 0.375 to 0.5
inch (10 mm to 13 mm) of the hot junction-no other part of the
thermocouple should be heated.
Cold junction
The insulated wire leads of the cold junction are enclosed in a copper
sleeve and are connected to the safety switch or safety shut-off valve.
Powerpile
generator
A powerpile, also known as a thermopile, consists of multiple
thermocouples joined together at one end and connected in series to
generate more voltage than a single thermocouple (see Figure 5-2). The
total voltage generated by a thermopile is the sum of the voltages generated
by each thermocouple it contains. Most modern thermopiles consist of 10
to 30 thermocouples connected in series.
Powerpile output ranges from 250 to 750 mV, which allows the powerpile
to power an appliance ’s combustion safety circuit and its control circuit.
Powerpile generators (see Figure 5-3) are used on appliances with
automatic-type controls.
Gas Technician 2 Training - Module 11
© Canadian Standards Association
115
MILLIVOLT SYSTEMS
UNIT5
Powerpile types
Two types of powerpile are shown in Figure 5-3:
coaxial (on the left)
modem (on the right).
A coaxial powe甲ile looks similar to a thermocouple, however, its hot
Junction and contact end are larger. A modem powerpile has two cold
junction leads, that are covered with protective armour. Some have the
same connecting nut as a thermocouple.
Hot junctions
「一→一←→二十」一一二一←←「
Copper
Iron
Cold junctions
Load
Figure 5-2 Powerpile schematic
Hot
junctions
Cold
junctions
Protective
ar『noured
Hot----junctions
coating
Positive
Negative
Thermopile leads
Figure 5-3 Powerpile generators
116
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MILLIVOLT SYSTEMS
UNIT 5
Pilot flame
characteristics
In order for a powerpile to operate properly, the pilot flame must have
certain characteristics. The gas technician can control the conditions that
affect these characteristics by proper maintenance and a司justment of gas
supply system components.
A normal pilot flame has the following characteristics:
it is mostly blue in colour
it bums steadily
it envelops 0.375 to 0.5 inch of the powe叩ile tip.
Undesirable flame characteristics include:
•
hard, sharp
•
noisy,
lif王ing,
pnma巧r
•
by too small a pilot orifice
blowing flame--caused by high gas pressure or excess
air
small, blue flame-一”caused by a small or restricted orifice, low gas
pressure, or a clogged pilot filter.
Gas Technician 2 Training - Module 11
© Canadian Standards A筒。ciation
flame一-caused
117
TOPIC
2
Testing contγol ciγcu its
There are several advantages of operating control circuits on millivoltages:
the control voltage is self-generated-no external power source is
required
the heating system can function even during electrical utility outages
the low-voltage system uses lighter,
less幽expensive
components
it is safer 齿。m an electrical hazard standpoint.
Isolating a
millivolt circuit
from 24 Vand
120 V circuits
Connecting
and reading a
millivoltmeter
In order to install, accurately and safely operate, and test millivolt circuits,
they must be physically isolated from 24 V and 120 V circuits.
Millivolt circuits must not be run with or come in contact with 24 V or
120 V circuits. This is because voltage from the conductors of the higher
potential circuits will induce excessive voltage in the conductors of the
millivolt circuit. An induced excess voltage in the millivolt circuit can
damage components and cause inaccurate test results.
Testing and troubleshooting circuits operating with a millivoltage power
supply requires the use of a millivoltmeter. The power supplies to these
cucmts are:
•
the thermocouple which produces 30 m V
•
the thermopile (also known as the powerpile) which produces up to
750mV.
Gas Technician 2 Training- Module 11
© Canadian
Standa『dsAsl白ciation
119
UNITS
MILLIVOLT SYSTEMS
A thermocouple or thermopile produces DC cuηent flow (in one direction).
When testing DC power supplies, the direction of current flow determines
the direction of needle movement. Be sure to connect the leads of the test
meter correctly as some types of meters are sensitive to polarity. If the
polarity of the meter is reversed, the indicator needle will move backward
and cause damage to the meter.
To avoid damage, connect one lead of the meter to the first test point and
then momentarily touch the second lead to the second test point. This is
called a flash test and verifies that the direction of needle movement is
correct before you connect the second lead. If the needle moves backward,
the polarity is reversed, so reverse the position of the test leads.
Thermocouple
test
A thermocouple has an open circuit output of 30 m V and can only be used
to power a pilotstat device in a combustion safety circuit. A thermocouple
can be tested with:
•
an open-circmt test
•
a closed-circuit test.
Open circuit test
An open-circuit test shows the potential millivoltage that can be produced
by a thermocouple when it is not under load. A high-resistance meter must
be used to perform this test. Most digital meters meet this requirement,
however, only special analogue meters are suitable for this application.
Always ens田e that 由e proper meter is used for this test.
You perform the open circuit test when the thermocouple is not under load;
therefore, before starting the test, disconnect the thermocouple 丘。m the
pilotstat (see Figure 5-4). An open-circu让 test is completed as follows:
1. Select a scale on 也e millivoltmeter suitable for reading a maximum
30mV.
2. Connect one lead of the meter to 也e outer copper conductor of the
thermocouple and the other lead to the end of the inner conductor as
illustrated in Figure 13 (watch polarity of meter). Wi由 a pilot flame
heating 也e hot junction of the thermocouple, it should read
approximately 30 mV.
3. Replace the thermocouple if it is old and produces less than 20 mV.
120
Gas Technician 2 Training - Module 11
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MILLIVOLTSYSTEMS
UNITS
Cold junction
Hot junction
Inner conducto 「
Outer copper
conductor
Figure 5-4 Testing thermocouple open circuit
Closed circuit test
A closed-circuit test shows the millivoltage that can be maintained when
the thermocouple is powering a coil, usually the magnetic coil of a pilotstat
device.
Adapter
Gas valve
Millivolt
meter
Figure 5-5 Testing thermocouple closed circuit
Gas Technician 2 Training - Module 11
© Canadian Standards Association
121
MILLIVOLT SYSTEMS
UNIT5
You perform the closed circuit test when the thermocouple is connected to
the coil in a pilotstat device. This will test the performance of the
thermocouple and show the millivoltage level that can be maintained under
load. At 由e same time, the pilotstat coil can be tested to determine its
condition (see Figure 弘5). A closed circuit test is completed as follows:
1. Disconnect the thermocouple from the pilotstat and install the test
adapter as shown in Figure 5-5.
2. Reconnect the thermocouple to the top of the test adapter and relight
the pilot burner.
3. Connect one test lead to the outer conductor of the thermocouple and
the other test lead to the side terminal on 由e test adaptor (watch
polarity). Since the side terminal of the test adaptor is internally
connected to the inner conductor of the thermocouple, a voltage test
can be performed while the circuit is energized.
4. The meter should read 15 mV if the thermocouple is in good condition.
Notice that this is approximately one-half of the open circuit voltage.
5. The thermocouple can produce a potential of 30 mV when not under
load but can only maintain 15 mV while under load. If the closed
circuit voltage should drop to below 8 mV, replace the thermocouple.
Thermocouple
pilots阳t
coil test
It is easy to test the condition of the pilotstat coil with the test adaptor in
place as shown in Figure 5-5. A small cuη·ent is needed to develop the
magnetic field required to hold the pilotstat valve open. Because the
C田rent flow is so small，让 is easier to measure voltage.
Remember, there is a direct relationship between voltage and current. As
voltage goes down, so does the current flow. In the case of the pilotstat coil,
as the voltage becomes less，也e magnetic field will weaken. At some point,
也e pilotstat will drop out and shut off the flow of gas. 咀ie pilotstat coil is
tested as follows:
1. Connect one lead of the millivol伽ieter to 由e copper conductor and the
other to the terminal on 也e side of the test adaptor (check polari守）．
Under normal operation, the voltage reading is between 10 and 15 m V.
2. Blow out the pilot gas and allow the thermocouple to cool. As it cools,
watch the millivoltmet1町 and notice that the reading is slowly decreasing.
3. The coil of the ~ilotstat should create enough magnetic field to hold 由e
valve. open until the millivoltage drops between 5 and 2 m V.
•
122
If the coil drops out with more 由an5m飞 it is weak and should be
replaced.
Gas Technician 2 Training - Module 11
。 Canadian S姐ndardsAs回C幅画佣
MILLIVOLT SYSTEMS
UNIT5
'lfthe coil holds the valve open with less than 2 mV, the valve is
sticking and should be replaced.η1is drop out of the coil should
take place within 90 seconds from flame failure, to meet the
requirements of the Gas Code.
Checking for
pilot flame
failure
Thermopile
test
Loss of pilot flame is a common service problem 由at you can check with a
millivoltmeter and test adaptor. You should check the thermocouple,
pilotstat coil and dropout time to make sure all problems are identified,
then conduct a open circuit test 臼 discussed previousl予
Most of the problems in millivoltage circuits are caused by increases in
resistance which reduce the current flow to a point where the gas valve
coils do not operate. These resistances are caused by:
•
loose wiring connections
•
corrosion to terminals and connectors
•
poor wire splices
•
excessive wire lengths.
The easiest way to identify where increases in resistance have developed is
to measure 由e millivoltage drop across each component in the electrical
crrcwt.
The key to successful troubleshooting and testing of thermopiles is to know
the normal millivoltage readings to expect across each component of the
circuit and to recognize excessive readings. Excessive millivoltage drops
indicates excessive resistance.
Gas Technician 2 Training - Module 11
CCa阳d幅n Slandai'ds Ass剧ation
123
UNIT5
MILLIVOLT SYSTEMS
Thermopile outputs
Thennopiles used to power millivoltage circuits are available in three
outputs:
250 m V open-circuit voltage outputs 缸e used for simple control
circuits consisting of a switch and a gas valve.
•
500 m V open-circuit voltage outputs have enough electrical press町e to
operate control circuits with a gas valve, limit switch and thermostat
with long wire leads (maximum 30 ft or 9 m).
750 m V open-circuit voltage outputs are always used when it is
necessary to power the control circutt and the combustion safety circuit
in p缸allel.
In explaining the testing procedure for millivoltage control circuits below,
岛r thepu甲oses of this Leaming Task, we have concentrated on the
thermopile with the 500 mV output. Special characteristics of 750 mV
thermopiles are also detailed at the end of the Unit.
124
Gas Technician 2 Training - Modu悔 11
。 Canadian Standa时s Association
MILLIVOLT SYSTEMS
UNITS
Identifying electrical test points
For simplicity, the meter test locations in the series circuit shown in Figure
5-6 have been numbered as follows:
1. The closed output of the thermopile.
2甸
The
drop through the valve coil.
3. The drop through the thermostat and thermostat wire.
4.
Thedrop 伽ough
the thermostat only (including contacts and heat
anticipator). To obtain the drop through the thermostat wire alone,
subtract reading 4 from reading 3.
5. The limit control and its wiring. Usually the limit wire is so short that it
is not worth considering as a loss of its own.
High limit
Pilot
generator
Figure 5-6 Reading voltage with a millivoltmeter
、、、恒，，
Gas Technician 2 Training- Module 11
Standards As四ciation
。 Canadian
125
MILLIVOLT SYSTEMS
UNIT5
All readings are taken in parallel across the components and with the
thermostat calling for heat. A typical reading for Figure 5-6 would be:
Meter position 1, thermopile 。utput
Meter position 2, gas valve coil
Meter position 3, thermostat and wire
Meter position 4, thermostat
Meter position 5, high limit
Total losses (2 + 3 + 5)
253mV
140mV
110 mV
80mV
3mV
253mV
Characteristics of 500 mV thermopiles
Figure 5-7 displays a simple control circuit consisting of a thermostat, limit
switch, gas valve and a 500 m V thermopile. Since there is no pilotstat coil,
由e pilot gas flow is not interrupted when there is a loss of flame.
The voltage of the source distributes itself across the resistive components
that make up the load. The sum of all the voltage drops throughout the
system must equal the output of the source.
Figure 5-7 provides an explanation of the millivoltage readings that should
be expected on a 500 mV circuit.
126
Gas Technician 2 Training - M创ule 11
© Canadian Standards A”。ciation
υNIT
MILLIVOLT SYSTEMS
5
Note: With the 500 mV thermopile not under load, the open circuit output
is 500 m V. Under load, the closed circuit output will drop to approximately
the values noted in Figure 5-7 (185 mV -240 mV).
Thermostat
10 mV or less
without anticipator.
(100 mV or less
with anticipator.)
Pressure or temperature
limit control if used
should be type approved
for millivolt circuits.
10 mV or less.
Higher readings
mean loose wiring
or defective limit
switch.
Thermostat
note: All
readings and
meter checks
with thermostat
turned on and
calling for heat.
Jumper if limit
control not used.
Wiring lo~s 50 mV
or less without
anticipator. (110 mV
or less with anticipator.)
Higher readings mean
poor wire splices.
Figure 5-7
Gas Technician 2 Training - Module 11
© Canadian Standards Association
Typi臼l
PG power load 185 mV
or more without anticipator. (240 mV or more
with anticipator.) Lower
readings mean low pilot
flame due to dirt or
mounting.
voltage readings on a simple millivoltage
contr。l
127
UNITS
MILLIVOLT SYSTEMS
Procedure for testing 500 mV circuits
All readings should be taken with the thermostat calling for heat as
indicated in Figure 5-7. Turn off the gas and clean the thermopile and pilot
burner before starting the test. Then, complete the following steps:
1. To determine the m V output necessary to open the main gas valve,
connect the test leads to position 2 as indicated in Figure 5-6. Light the
pilot burner and watch the meter to determine the valve open (V.O.)
reading. A typical reading would be 60 m V.
2. Allow the thermopile to reach maximum output and record at position
1. A typical output value would be 253 mV. This may take
approximately four minutes.
3. Check the power across the valve coil (position 2). A typical reading
would be 140 m V.
For the valve to open consistently, some sa岛：ty margin is required
above 也e power actually required to open the valve. This margin
should be large enough to ensure a consistent opening, but small
enough to allow 也e longest service out of the thermopile.
If 30 m V is considered a good safety margin，也is example provides
140 - 60 = 80 m V over what 1s required to open the valve. Smee some
valves may require as much as 130 mV to open，也e voltage across 也e
~al ye coil would have to be 160 m V or more. If the valve does not open
by 150 m V, the valv~ coil is faulty and must be replaced.
Note: The readings across the coil can be affected by:
low output from the thermopile
satisfactory output from.the thermopile but a high mV drop in 也e
rest of the system due to 岛ulty splices, excessive length of
thermostat wire, or faulty thermostat or limit switches.
4. Check 由e total wire loss at position 3. ηtis will include 也e wire and
thermostat loss. A typical value would be 112 m V.ηiis reading can be
50 mV or less with no heat anticipator or 110 m V or less with a heat
anttc1pator.
5. Check 也e thermostat loss at position 4. A typical value would be 80
mV. These readings are 8 m V or less with no heat anticipator or 100
m V or less with a heat anticipator.
6. Determine thermostat wire loss by subtracting the reading at position 4
企om 由at at position 3. For example,
112- 80 = 32 mV. lfthe wire loss is over 60 mV, check the visible line
for poor splices which can cause over 100 m V losses.
128
Gas Technician 2 Training - Module 11
0 Canadian Standards A部ociation
MILLIVOLT SYSTEMS
UNIT 5
7. Check the limit losses at position 5. This includes the limit and its wire.
Usually the reading is close to zero (2 m飞 for example).
8. Ensure you have taken the correct readings:
Reading 2 +Reading 3 +Reading 5 =Reading 1. If there is a difference
of more than 15 mV, recheck each reading.
This is a summary of the
readings 台om
VO.
Thermopile output
Valve coil
TH and wire
Thermostat
Limit and wire
Gas Technician 2 Training - Module 11
© Canadian Standards Association
the test procedure
212345
60mV
254mV
140 mV
112 mV
80mV
2mV
129
MILLIVOLT SYSTEMS
UNIT5
Troubleshooting 500 mV control circuits
The following examples use Figure 5-6 to demonstrate common problems
and their solutions.
Example 1
The furnace does not always come on but the gas valve opens when tapped.
The thermostat is equipped with a heat anticipator and the following
readings have been taken.
。ι4E
v.o.
75mV
叮LquA
269mV
77mV
斗 RJV
190mV
30mV
2mV
孔'hat
is the problem and how do you correct it?
Solution:
The above readings indicate that the valve opens at 75 mV, but only
increases to 77 m V at full output. This is too low.
The reading at 3 across the wiring and thermostat is 190 m V which is hi民
Subtracting 30 mV 企om the 190 mV indicates a wire loss of 160 mV. This
must be a result of bad wiring contacts or a poor splice in the wiring. To
correct this, clean the terminals and solder the splice.
130
Gas Technician 2 Training - Module 11
© Canadian Standards A部ocia曲。n
MILLIVOLT SYSTEMS
UNIT 5
Example2
The 如mace will not come on. The thermostat has a heat anticipator and the
following readings have been taken:
叮
44tqLqdda
V.O.
w
寸 E－
BOmV
260mV
75 mV
110mV
70mV
75mV
What is the trouble?
Tip: To obtain the V.O. reading when the power at 2 is too low, jumper the
thermostat terminals. This makes the 110 mV in the thermostat and wire
circuit available to help open the valve. Remove the jumper as soon as you
get the V.O. reading.
Solution:
The problem is that the reading at 2 is 5 mV below that required to open the
gas valve. Examination of the above readings shows that the limit switch
reading at 5 is very high, suggesting a faulty limit. If this is corrected, there
is SU任icent voltage drop across the gas valve at 2.
Note: When the thermostat terminals were jumpered, the 110 m V drop in
the thermostat and wire became zero and the 110 m V was available to the
rest of the system; therefore, the valve opened. You could mistakenly think
the thermostat or wire was at fault.
Gas Technician 2 Training- Module 11
© Canadian Standards Association
131
MILLIVOLT SYSTEMS
UNIT5
Characteristics of 750 mV thermopiles
Use a 750 mV thermopile whenever there is a need to power two circuits
such as a control and combustion safety circuit. Figure 5-8 shows both
types of circuits. The safo可 circuit consists only of a pilotstat coil while the
control circuit consists of a thermostat, limit switch, and gas valve coil.
750mV
pilot generator
Main gas valve
Figure 5-8 Testing millivoltage control systems with combustion 臼fety and
control circuits
ηie
open circuit output of the thermopile is 750 mV; however, when it is
connected to 也e pilotstat，也e millivoltage reading at I is reduced to
approximately 550 mV. When the thermostat contacts on the con位ol circuit
close, the millivoltage reading across 1 is reduced to approximately:
185 mV if the 也ermostat has no heat anticipator, or
•
132
240 m V if the thermostat has a heat anticipator.
Gas T制lnician 2 Training - Module 11
。 canadian Standards A”。ciation
MILLIVOLT SYSTεMS
UNIT 5
These are the same values as found on the control circuit of the 500 mV
systems. The test values 1 to 5 are the same for both the 500 m V and the
750 m V systems. The following readings should be taken with the
thermostat contacts closed:
1. 185 mV without heat anticipator-240 mV or more with heat
ant1cipato卫
2. Minimum 140 mV required for valve operation.
3. 120 mV or less with heat anticipator-50 mV or less without heat
antic1pator.
4. 100 mV or less with heat anticipator-8 mV or less without anticipator.
5. 8 mV or less.
Procedure for testing 750 mV circuits
Testing the operation of the control circuit is 白e same as testing the 500
m V system. The di他rence lies in the testing of the combustion safety coil
or pilotstat The following steps apply:
Step
f一Test
the pilotstat coil
Wi由 the thermostat calling for heat and the test meter leads across 由e
thermopile terminals in position 1, depress the manual reset button on the
pilots臼t and light the pilot.
Step
2·一Observe
the pilot flame
When 由e
millivoltage reading is at 170 m飞 release the manual reset
button on 由e pilots臼t and observe the pilot flame. If the valve does not
hold in and the pilot flame goes out, r1叩lace the coil.
If the pilotstat holds in, blow out the pilot and watch the test meter. If the
coil drops out over 140 mV, replace 也e coil.
For testing of the control circuit readings 1to5, refer to 由e testproced田·es
for the 500 mV control systems.
Gas Technician 2 Training - Module
© Canadian Standards Association
11
133
TOPIC
3
Millivolt thermostαts
Millivoltage thermostats are used with self-powered heating control systems
(see Figure 5-9). The control system power is produced by the heat of the
pilot flame acting on the thermopile (pilot ~enerator）.η1is 守~of
thermostat often has a label indicating that it is only for use with millivolt
systems.
As discussed previously in this Unit, thermopiles produce 250, 500, or 750
mV. 750 mV is about one-half the output of a 1.5 VD-size, dry-cell battery.
The gas technician must always ensure 由at the thermostat for a particular
installation is sized according to the thermopile or power generator used.
The voltage rating for a millivolt thermostat is usually 0 to 1.5 VDC.
η1e
powerpile used must produce sufficient power to:
operate 也e
gas valve
overcome total system electrical resistance, including the heat
anticipator if one is installed in the thermostat.
Self-powered
heating
The components of a typical selιpowered heating control system include:
control system • a pit创 burner
components
• a thermopile, or pilot genera伽
a diaphragm gas valve (which includes a safety shut-off)
•
a limit switch
a millivolt (powerpile) thermostat (which may sometimes include a
heat anticipator)
wire runs for connecting the devices in the sys臼m.
Gas Tee却nician2T1『aining - Module 11
。 Canad脑n S恒ndar匈 A”。cia彻n
135
MILLIVOLT SYSTEMS
UNIT 5
Millivolt
thermostat
Pilot
flame
'·
‘y
＿.，，.，~－；
tTl
f等~｛ t Tp~~~：i~~ator)
Limit
switch
Pilot
burner
Figure 5-9 Self-powered heating control system components
Wiring
requirements
The gas technician must ensure that the correct type and gauge of wiring is
used when installing self-powered control systems.
It is also important not to exceed the maximum recommended length for
wiring runs specified by the manufacturer of the equipment, in order to stay
within system total resistance limits.
The following guidelines are for runs of 2-wire control system cables.
Some manufacturers recommendations may differ, in which case their
recommendations must be followed:
•
runs up to 30 ft (9 m)- use #18 AWG minimum
•
runs up to 50 ft (15 m)- use #16 AWG minimum
runs up to 80 ft (24 m)- use #14 AWG minimum.
136
Gas Technician 2 Training- Module 11
© Canadian Standards A撼。ciation
MILUVOLT SYSTEMS
UNITS
Assignment 5
When you have completed the following questions, ask your instructor for the
Answer Key.
I.
The point at which the two dissimilar metals are joined on a thermocouple is known as what?
2.
Thermocouples are used with which type of pilot?
3.
What does a thermocouple power when it is being heated?
4.
What portion of the hot junction should be heated by the pilot flame, and what should the
temperature difference be between the hot and cold junctions?
5.
Approximately how many thermocouples does a powe甲ile contain, and how are 由ey
connected?
6.
Powerpiles with outputs of250 to 750 mV are able to power what?
7.
Upon inspection, the pilot flame of a powerpile-equipped appliance is observed to be blue in
colour, burning steadily, and contacting 也e top 0.5 inch of the powe叩ile tip. Is this
acceptable?
8.ηrreethin豁出at can
cause a small, blue pilot flame are:
、、马喻，，
Gas Technician 2 Training - Module 11
@Canad阳n
Standards A”。ciation
137
MILLIVOLT SYSTEMS
9.
UNITS
Is an external power source required for a control circuit operating on a millivoltage?
10. Thermocouples and thermopiles produce what type of current?
11. 孔'hat
type of test is performed to check the polarity of a millivolt meter?
12. A thermocouple must be under load to perform an open circuit test. True or False?
13. What does a closed-circuit test show?
14. During a pilotstat coil test, at what point and at what m V reading should the coil drop out?
15. Excessive millivolt drop indicates excessive resistance. What is the cause of the resistance?
16. The three available thermopile outputs are:
17. A 750 mV powerpile should be used when?
18. Testing a 750 mV circuit is essentially the same as testing a 500 mV circuit, except for what?
138
Gas Technician 2 Training - Module 11
© Canadian Standards As回ciation
UNIT 5
MILLIVOLT SYSTEMS
19. The voltage rating of a millivolt thermostat is:
20. Total electrical resistance in a system includes the heat anticipator in the thermostat. True or
False?
21. Name three components of a self-powered heating control system.
22. The manufacturer recommends maximum lengths of wiring runs for self-powered control
systems. True or False?
Gas Technician 2 Training- Module 11
© Canadian Standards Association
139
岛1odule
12
Table of Contents
Unit 1
Fundamentals of controls
Contr。I
concepts and components ..................... 3
The basic control system .................................. 11
Operating controllers. ………··….........……........... 13
Limit and safety
c。mbustion
contr。llers ....................…........ 19
safety c。ntrols ............................... 25
Ignition control modules ...........…………............. 31
Valves and regulators ....................................... 39
Assignment 1 .......................…................…....... 53
Unit 2
Control circuits
Diagrams for
c。ntrol
circuits ............................. 57
Auxiliary devices in a control system ................ 61
p。larity ................…·························…............... 67
Electrical sequence
of 。perati。n ....................... 71
Assignment 2 .......……….......…….......…….......... 75
Gas Technician 2 Training- Module 12
© Canadian Standards Association
v
Unit 3
Servicing and troubleshooting
circuits and components
Servicing controls and components .................. 79
Troubleshooting control system problems. ….... 81
Testing and tr。ublesh 。oting intermittent
pilot ignition control modules .........….......……… 87
Testing and troubleshooting direct spark
ignition control modules ...庸································ 93
Testing and troublesho。ting hot surface
ignition contr。Im。dules ..........………........…...... 99
Recalibrating and replacing components ...四… 105
Assignment 3 .......................................……….. 107
Unit 4
Motors
Nameplate information .......…………................ 113
c。nstructi。n and operation of electric mot。rs
Operation and
applicati。n
117
of three-phase
m。tors ..............................….......…..................
121
Operation and application of single-phase
motors .........…·················…............................. 125
Single-phase motor sta此up and overload
protection devices .........................…….......….. 129
Additional
comp。nents
of AC electric motors. 135
Variable speed DC m。t。rs .........................… .139
Assignment 4 ................................………......... 143
vi
Gas Technician 2 Training- Module 12
© Canadian Standa『ds Association
Unit 1
Fundamentals of controls
Purpose
There are numerous types of controls that a gas technician will encounter
regularly. The fundamentals of the operation of these controls are also
numerous. Knowledge of how controls work, where they are applied and
how they interact with other controls, is important to understanding overall
systems.
Learning
objectives
1. Describe control concepts and components.
2. Explain the basic control system.
3. Describe operating controllers.
4. Describe limit and safety controllers.
5. Describe combustion and safety controls.
6. Describe ignition control modules.
7. Describe valves and regulators.
Gas Technician 2 Training - Module 12
© Canadian Standards Association
Topics
1.
Control concepts and c。mp。nen恒.............…........…….......... 3
Thermal expansion of solids ........…..............................…·······…........... 3
Thermal expansion of liquids ................….. •····•·•••··• ........…........……........ 5
Electro-magnetism .........….......……·······….........…………….......……….......6
Thermoelectric e仔·ect .........................................…·…….............................7
Electrical heating of a resistive element .....……·························….......……... 8
叭lheatstone bridge principle .......……·····································…….............. 9
Semi-conductor p时nciple ........................................................................... 10
2.
The basic control system ..........................................…......... 11
Four basic sections of a control system ..........…….............................…........ 11
3.
Operating controllers .................…··”..................................... 13
Thermostats ...........…......……....…......…................…·….......................... 13
Thermostat location .....................…………························…….................... 15
Operating aquastat ............................…………·················…........................ 17
Operating pressuretrol .........……·…········…··……........................................... 18
4.
Limit and safety controllers ............................”··”··”··”··”.... 19
Low-water cut。仔 switch .........…·················…且.......….................................... 19
High-limit aquastat.. ……·········…··········································….........……........20
Flow switch .............…………........….........…................………........................21
High-limit switch ..…························…......... ·········….......….........................22
Combination high-limiUfan control switch ...............….......….........................22
High-limit pressuretrol... .....…….........…........…..............................................23
Ga$-pressure switch ....................................…..............….............................23
5.
Combusti。n safety c。ntrols ....................…........................... 25
Flame recti币ers （何ame rod) ...........................................................................25
Optical flame sensor .................................….......................................…......28
Air-proving switch .........…·······……..............................................................30
6.
lgniti。n control modules H….........….......回.........….................. 31
Types of control modules. …·电·································································· ••••• 31
Basic operation .........................................................’·······….........................31
Intermittent pilot control m。dule .........…·························…............................33
Direct spark ignition control module .................….........…........….......…........35
Hot sur旬ce ignition control module .................................…··········…….........37
7.
Valves and regulat。rs ............…............................................. 39
Manual valves ............................…..................….......…........…......................39
Automatic, n。『1-elect『ic valves ........….......…..........................…·······…...........42
Aut。matic, electric valves ...............................................…........…................44
Regulators ........…..........…......................................…...................................52
Assignment
2
1 ........…........……”..........……”...........….................... 53
Gas Technician 2 Training - Modu幅 12
。 Canadian S隘ndards Association
TOPIC]
Contγol concepts αnd
components
Control systems used in the gas industry use the physical characteristics of
solids, liquids and gases to expand and contract, and to conduct or resist
electricity as a means of regulating the burner system. For example,
physical characteristics associated with the expansion of solids and liquids,
electromagnetism, the thermoelectric effect and electricity are all used in
varying capacities.
Each of the founding principles is discussed below, with examples of
controls that operate on these principles.
Thermal
expansion of
solids
Metals expand when heated and contract when cooled. The principle of the
thermal expansion of solids is used for several control devices that regulate
temperature change.
Temperature disc
The temperature disc (trademark Klixon) shown in Figure 1-1 responds to
temperature changes by moving 仕om a concave to convex shape, touching
electrical contacts and completing a circuit. The temperature disc can be
used in the thermal relay.
Kl ixon
disc
Figure 1-1 Temperature disc used in thermal relay
Gas Technician 2 Training - Module 12
Standards Association
。 Canadian
3
FUNDAMENTALS OF CONTROLS
UNIT 1
Bimetallic strip
The bimetallic strip operates on the fact that not all metals expand at the
same rate. This device uses the warping action created when two dissimilar
metals having different coefficients of expansion are welded together at
one end and exposed to temperature change. Since one end of the
bimetallic strip is anchored solidly, the free end moves up or down with an
increase or decrease in temperature. The resulting curling or bending
(Figure 1-2) is used to control the opening or closing of electrical contacts.
Low coefficient
of expansion
High coefficient
of expansion
1
€':
Figure 1-2 Bimetallic strip warps and bends with an increase in temperature
Rod and tube
卫ie
rod and tube control device also
works on the principle that some
metals expand more quickly than
others. In this control device the
sensing portion of the valve is
constructed of copper tube that has a
high expansion/contraction rate. The
copper tube encases an invar rod, a
metal alloy with a low expansion/
contraction rate.τhe invar rod and
copper tube are welded together at the
far end so the expansion and
contraction of the copper tube (Figure
1-3b and 1-3c) effectively moves the
invar rod back and forth, opening and
closing a switch.
(a) Unheated state
(b) Expansion from heat
(c)
C。ntraction
from
c。Id
Figure 1-3 Rod and tube c。ntrol
4
Gas Technician 2 Training - Module 12
© Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Thermal
expansion of
liquids
Like solids, liquids expand when heated and contract when cooled. When
liquid is sealed in a naηow tube (called a capillary) the force created by the
liquid expanding within the capillary is used to operate an electrical switch
or control mechanism.
Sealed bellows
In the sealed bellows control device, liquid inside a bulb at one end of the
capillary senses the temperature of the surrounding atmosphere and
expands or contracts. At the other end of the capillary an attached bellows
reacts to the pressure within the capillaηby expanding or contracting
(Figure 1-4a and 1-4b). One advantage of the capillary tube is that it allows
the bulb to be located remotely from the bellows.
The action of the bellows is used to operate:
•
a switching device-completing or interrupting an electrical circuit.
•
a mechanism that controls the gas valve
supply to the main burner.
Bellows expanded
Spri吁
outlet一－modulating
the gas
Bellows contracted
Jo
Springded
q
一一－飞＿－ －由
ntacts O ℃
Heated
bulb
Heated
Cooled
bulb
Cooled
Figure 1-4 Sealed bellows with 臼 pillary tube
The liquid in the bulb may be fluid fill or mercury, depending on 也e
temperatures that will be encountered.
Fluid fill
Sealed bellows used to operate thermostats have a temperature limit of
and usually contain a fluid similar to a light oil. The
expansion or contraction of this type of fill is quite linear and gives a
smooth operation of the thermostat.
650。F ~343 。C)
Gas Technician 2 Training- Module 12
© Canadian Standards Association
5
FUNDAMENTALS OF CONTROLS
UNIT 1
Mercury
For high temperatures, such as 3000。F (1648。C) reached in pilot safety
controls, the bulb must be filled with mercuη. The expansion of the
mercury is smooth up to approximately 650。F (343 。 C) at which point the
mercury vaporizes (boils). With vaporization, a rapid expansion takes
place, giving the control ” snap action." Similarly, upon cooling, there is a
rapid contraction as the vapour condenses to a liquid.
Electromagnetism
When an electrical current is passed through a metal rod (called a
conductor), a magnetic field surrounds the conductor. This principle has
been put to use in creating the electromagnet, which forms the basis for the
solenoid, used in many control devices. Most electrical control devices use
solenoids to produce physical motion.
Solenoids
A solenoid is a cylindrical coil that creates a magnetic field inside when a
cuηent runs through it. A piece of iron, called an armature, becomes a
temporaηmagnet when it 1s in the magnetic field. If it is partially inside
the coil, the temporary magnet will be pulled into the centre of the coil
when the circuit is closed (Figure 1-5). When the circuit is opened, the
magnetic field dies, and the armature is 仕ee to move to its original
position.
Solenoid
；专~／
Valve disk
Armature
Figure 1-5 Movement produced by a solenoid
6
Gas Technician 2 Training- Module 12
。 Canadian Standards Association
UNIT 1
FUNDAMENTALS OF CONTROLS
Thermoelectric
e仔ect
The thermoelectric e旺ect of producing electricity by heat is used for the
thermocouple and thermopile.
Thermocouple
A thermocouple uses the combined effects of temperature change and
electricity (Figure 1-6). It consists of.a bimetallic strip joined at one end
(called the hot junction). When the hot junction is heated, a DC voltage is
generated across to the other two ends of the strips (the cold junction).
The thermocouple is used to prove the pilot flame; if it goes out, the
thermocouple prevents the main gas valve 企om opening.
The magnitude of the voltage across to the cold junction depends on the:
•
two materials of the bimetallic strip
•
temperature difference between the hot and cold junctions.
Dissimilar
metals
Cold
ju~ction斗
Negative Positive
Figure t 毛
Hot
and cold junctions of a thermocouple
Thermopile
The output of a single 也ermocouple is very small: 20 to 30 millivolts
( 1,000 millivolts = 1 volt). By placing a number of single thermocouples in
series electrically, a device known as a thermopile can be created which
generates hundreds of millivolts.
Gas Technician 2 Training- Module 12
© Canadian Standards Association
7
FUNDAMENTALS OF CONTROLS
Electrical
heating of a
resistive
element
UNIT 1
All materials conduct electrical current to some degree and heat up as a
result. The amount of heat created depends on 出e current flow through the
resistor and the material ’ s electrical resistance.
Anticipator
The functions of the bimetallic strip can be tied in with a change in voltage
by wrapping a heat resistive wire around the strip. When voltage is applied,
the current drawn by the wire will create heat, causing the bimetal to warp
and open/close electrical contacts.
The anticipator is a bimetal strip wrapped with heat resistive wire and used
inside the thermostat (Figure 1-7) t。”anticipate” the heating requirements
of a rooin. When the heating system starts to produce heat, so does the heat
anticipator. The heat produced by 也e heat anticipator will raise the
temperature of the bimetallic strip inside a thermostat faster than the
ambient temperature of the controlled area. This then provides a more even
temperature control in the room.
Court，呵P
ofHoneywell Inι
Figure 1-7 Heat anticipator
Thermistor
写rpically，也e elec位ical
resistance of metals increases when heated. Some
metals, however, have the opposite effect and are used in control situations
when more current is required when 也e metal is heated.
8
Gas Technician 2 T1『aining-Module 12
© Canadian Standards Association
FυNDAMENTALS
UNIT 1
OF CONTROLS
Thermistors are made of semi-conductive material that, although ve可
resistant to the flow of electrical current, has less resistance when hot. The
current flow of a thermistor increases within specified temperature ranges.
The thermistor is used for motor protection, or where a momentary delay in
the flow of current is required.
Wheatstone
bridge
principle
The circuit shown in Figure 1-8 is based on the Wheatstone bridge
principle. The principle states that when the ratio of R1 to R2 is the same as
the ratio of R3 to R4, the circuit is in balance (i.e., there is no current flow
between A and B).
R1
RJ
R2
R4
自
A
+
Figure 1-8 Circuit based on Wheatstone bridge theory
Electronic thermostat
The Wheatstone bridge principle can be used in control devices and is used
in some electronic thermostat controls for water heaters. As long as a s切te
of balance is maintained in the circuit there will be no current flow between
points A and B. When the thermostat dial (R3) is set to a given temperat山e,
an imbalance occ田s which allows current to flow between A and B. This
current is used to energize a relay (Figure 1-9) which in tum energizes the
ignition control module. The circuit will remain energized until such a time
that the resistance of the sensor （~） changes sufficiently to rebalance the
ratio between R1/R2 and R3fRi. At this point, the current flow to the relay
ceases, de-energizing the ignition circuit.
Gas T~nician 2 Training- Module
© Canadian Standards A路。ciation
12
9
OF CONTROLS
。／
FυNDAMENTALS
υNIT
1
A
+
Figure 1-9 Circuit for electronic thermostat
Semi ”
conductor
principle
Solid state electronic control devices have contributed to the increased
control of processes. For example, in lighting circuitry, lights were once
either on or off. The invention of the diode and SCR (silicon controlled
rectifier) now allows a range from full intensity to very low intensity to off.
Solid state devices have not changed the control process, but have provided
more precise, instantaneous control over this process.
The diode allows the passage of current in only one direction. This device
is used for various purposes such as a switch within control modules, the
light-emitting diode, photodiodes, etc.
Like the diode, the SCR allows current to flow in one direction only.
However, the SCR has additional properties in that it can also vary this
current from its minimum to maximum value. The SCR is ideal as an
electronic relay.
销掰i
The triac operates like the SCR, but can conduct current in both directions.
It can also be used as an electronic relay.
10
Gas Technician 2 Training- Module 12
© Canadian Standards Association
TOPIC
2
The basic contγol system
The function of a control system is to operate gas-fired equipment in
response to variable conditions. For example, in a residential heating
system, the control system is designed to ensure safe firing of the furnace
in response to variable room temperatures. Likewise, in a commercial
boiler the control system fires the burner in response to the condition ofther实可
controlled variable (e.g., hot water boiler operator responds to water
出出
temperature; a steam boiler oper创or responds to steam pressure).
Four basic
sections of a
control system
There are as many di茸erent control systems as there are controls, but all
systems have certain functional similarities-certain parts perform similar
tasks. The four basic sections of a control system that you would find in a
typical residential heating system include:
•
operating controllers
•
limit and safety controllers
•
combustion safety controller
•
ignition control module.
因
Although these four sections are shown here separately for purposes of
discussion, actual hookups of control systems are complicated by the fact
that:
several functions may be combined in a single control
additional features may be performed by the control system
more 由an
one limit or controller may be used.
Each of the four sections is described briefly below and in more detail in
subsequent topics.
Gas Technician 2 Training- Module 12
© Canadian Standards Association
11
UNIT 1
FUNDAMENTALS OF CONTROLS
Operαting
controllers
Limit αnd sαifety
controllers
The safety and limit controllers take the command
away from the operating controls when continued
operation would cause an unsafe situation. Examples
of these controllers include: low-water cutoff
switches, high-limit aquastats, high-limit
pressuretrols, and flow switches.
Combustionsα户ty
The combustion safety control monitors the flame
initiation and allows the gas to flow only if a stable
flame is initiated and maintained. Examples include
flame sensors and air-proving switches.
control
Ignition control
module
12
These controls respond to changes in the controlled
variable (temperature, pressure, etc.) and make or
break a circuit. Examples of operating or actuating
controllers include: thermostats, operating aquastats
and operating pressuretrols.
The ignition control module sequences the safe
light-up of the burner system (providing the limit
controls indicate a safe condition). Examples
include intermittent pilot, direct spark ignition
and hot surf注ce ignition control modules.
Gas Technician 2 Training - Module 12
© Canadian Standards Association
TOPIC
3
Operating contγvileγs
As discussed previously, operating controllers respond to changes in the
controlled variable by making or breaking a circuit. The following
describes the thermostat, operating aquastat, and operating pressuretrol.
Thermostats
Thermostats sense the temperature of the air in the controlled area and
translate this information into on/off switching of the heating or cooling
equipment. Two of the variables that determine thermostat type are:
•
Load switching ability. Thermostat may be rated for direct switching of
line volta肘， low voltage, or millivoltage loads.
•
Purpose. Thermostat may be heating only, cooling only, or heating/
cooling combined. They may also perform any number of auxiliary
functions.
Thermostat operation with bulb
The following sequence of operation applies to the thermostat with bulb:
1. As the room cools, the bimetal strip contracts and moves the glass bulb.
2. The mercury in the bulb moves and engulfs the two contacts,
completing a circuit (Figure 1-10).
3. This closes the control module circuit and energizes the main gas valve.
4. As the room temperature rises to meet the setpoint, the bimetal strip
expands, moving the glass bulb in the opposite direction.
5. The mercury rolls to the opposite end and breaks the control module
CtrCUtt.
6. The gas supply to the main burner is shut off.
Gas Technician 2 Training- Module 12
© Canadian Standards Association
13
FUNDAMENTALS OF CONTROLS
UNIT 1
Move~~.削弱
问世主二三Bal~ ~
mercury
24
v
Bi metal
strip
Trans.
Figure 1-10 Thermostat operation with bulb
Thermostat operation without bulb
In Figure 1-11, the room a让 temperature is at the thermostat setting and the
switch conta＇眈 points are open. Assume that the room air then cools.
As the temperature of the bimetallic sensor drops:
1. The bimetal bends as one of its metals tries to contract more than the
other, and the right end of the bimetal slowly rises.
2. When the contact points come together, the automatic gas valve is
powered and opens, allowing gas to flow to the burner.
3. The furnace or boiler then supplies heat to the home.
4.
As 由e
room temperature around the thermostat rises, the bimetal
begins to bend slowly downward.
5. As soon as the contact points separate, the gas supply to the appliance
is automatically turned off.
14
Gas Technician 2 T1『aining - Module 12
@ Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Spring 10
loaded
lever
气二Bi metal
sensor
Burner
Used by permission of the copyright
American Gas Association
ho/de月 the
Figure 1-11 Room thermostat with bimetal sensor
.Thermos阳t
location
The room thermostat is a precision device and therefore a proper
installation is essential for correct operation.
1. Be sure that mere町y switch thermostats are level when installed. Use a
spirit level to check.
2. Install the thermostat:
-
In a room that is subjected to 由e average tempera阳re of the
dwelling.
-
Where it will be exposed to normal air circulation,
approximately 5 feet from the floor.
-
Where it is not subjected to 也e artificial effects of internal heat
or cold, such as television sets, lamps, direct sun, cold air
return, etc.
．臼i
an inside wall.
Multi-s阳ge thermos始t
Thermostats capable of switching more 也m one stage of heating, cooli11g
or both heating and cooling are available for line or low-vol阳ge switching.
Gas Technician 2 Training - Modu隐 12
©Canadian S恼ndards Association
15
UNIT 1
FUNDAMENTALS OF CONTROLS
In this thermostat, the stages of heating and cooling are mechanically
linked (both mercury tubes are connected to a single sensing element) to
provide a constant interstage.
Programmable thermos饭ts
The term programmable thermostat generally means a thermostat 由at can
be set to operate at different temperature settings at different times. They
range in complexity from units that use a simple time clock to units that are
operated by integrated circuits.
The programmable thermostat can reduce energy consumption by
maintaining a desired temperature only during the hours the dwelling is
occupied. The temperature can be maintained at an uncomfortable level the
rest of the time, which permits the heating unit to operate much less often.
Heat anticipators
Heat anticipators are added in the thermostat to reduce the operating
of the system. (Operating differential is the di他rence between
the highest and lowest temperatures actually obtained.) The anticipator is a
small resistive heater in the thermostat itself which heats when the system
is on. The heat produced by the anticipator raises the internal thermostat
temperat田e slightly faster than the surrounding room tempera阳re. This
causes the thermostat to shut off the heating system sooner than it would if
affected by room temperature only. In other words, the thermostat
” anticipates” the need to shut off the heating system.
硝fferentia/
Advantages
The heat added by the heat anticipator to the inside of the thermostat has
several effects:
16
•
it compensates for overshoot by shutting off the heating equipment
before the ac阳al room temperature reaches the shutoff point. This
permits the residual heat delivered by the system to carry the room
tempera阳m up to this point.
•
it has the e班ect of increasing the cycling rate since the ” on” time of 由e
burner is reduced.
•
it compensates for the mechanical lag of the thermostat by moving the
temperature of the bimetal element 伽ough its operating range 副 a
faster rate.
Gas T民hnician 2 Training - Modu始 12
© Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Setting the adjustable heat anticipator
Thepu甲ose of the adjustable anticipator, installed in the thermostat, is to
provide a single thermostat to match almost any type of gas valve or
heating control system load.
Heat anticipators are dependent on current flow. The current flm风 in turn,
is determined by the amperage draw of the relay, gas valve, etc., in the
primary heating system.
For best results, the thermostat should cause the 如mace to cycle about 4
times per hour. Should a longer or shorter cycle be required, further
adjustment of the heat anticipator would be necessary to obtain the correct
cycle rate of the furnace. Each type of thermostat has a different method to
set the heat anticipator. Read the manufacturer ’s instructions and set as
directed.
Millivolt systems
Because of the small voltage developed by a self-generating system，也e
anticipator must be small so as not to create too great a voltage drop. Also,
because the anticipator produces a very small amount of heat, it must be
placed against the bimetallic. Thermostats for millivolt circuits are
specifically manufactured and are for use with 750 millivolt systems only.
Operating
aquas蚀t
The operating aquastat (Figure 1-12a and 1-12b) is a normally closed
switch that controls the temperature of the water inside the boiler. If the
aquastat is set for 180。F (82°C), the contacts will remain closed until the
water reaches this temperature. At this point, the contacts open and cut off
power to the main gas valve.
The water will cool several degrees before the contacts close again.
Aquastats with fixed differential have a 2斗。F (1-3 。C) tem?erature
differential. Those with an adjustable differential can be 叫justed between
5。F and30。F (3 。C-17°C).
Gas Technician 2 Training - Module 12
© Canadian Standards Association
17
FUNDAMENTALS OF CONTROLS
UNIT 1
Set point
indicating dial
Differential
wheel
(a) Direct-mounted aquastat
with horizontal probe
Figure 1-12
Operating
pressuretrol
(b) Remote bulb aquastat
了wo
types of aquastats
The operating pressuretrol (Figure 1-13) is a pressure switch on a steam
boilers. As steam pressure in the boiler rises and reaches the setpoint of the
pressuretrol, the switch contacts open and de-energize the power to the
main gas valve.
If you set the pressuretrol to 3 psig (21 kPa），也e contacts stay closed until
the steam pressure reaches 3 ps1g (21 kPa). Once it has reached this
press田e，也e contacts open and cut off power to the main gas valve. The
contact~ close again when the steam pressure reduces to 由e differential
settmg.
The high and low setpoints on the operating pressuretrols are a司justable, as
are 也e differentials.
Pressuretrol
Pressure
gauge
Figure 1-13 Operating pressuretrol senses change in steam pressure
18
Gas Technician 2 Training - Modu悔 12
©Canadian S姐ndards Association
TOPIC
4
Limit αnd safety contγoilers
Limit and safety controls include all of the interlocking controls to ensure
that the burner cannot operate unless all associated functions to 也e burner
are normal. Thus, in addition to the standard pressure and temperature
safety limit controls used for the protection of the fired equipment, there
are several other controls used as limits or interlocks.
Low-water
cuto仔 switch
The /ow-water cutoff switch actuates in response to fluid movement. If the
water level in the boiler falls below the minimum level, the low-water
cutoff switch opens its contacts and cuts off power to the main gas valve.
There are two basic types of low-water cutoff switches.
Float type
The float type (Figure 1-14) is a normally open switch
is held closed by the float on top of the water. If
the water level falls below a predetermined point，出e
float mechanism lowers and breaks the electrical
contact.
由at
Switch
action
Figure 1-14 Float-type low water cut-o何 switch
Gas Technician 2 Training- Module 12
© Canadian Standards Association
19
FUNDAMENTALS OF CONTROLS
Probe type
UNIT 1
The probe type (Figure 1-15) is a normally open
switch. It has an electronic circuitry that uses boiler
water to conduct cuηent between the terminals on the
end of the probe. If the water falls below the level of
the probe, the electronic circuit between the terminals
is broken. In response to no circuit, the low water
cut-off switch opens, cutting off power to the main gas
valve.
h
e
hu
-/
Figure 1-15 Probe-type low water cut-o汗 switch (top view)
High-limit
aquas旬t
The high-limit aquas阳t is similar to the operating aquast剖 but is a司justed
to a higher water temperature se往mg (commonly 200。F [93°C]). It serves
as a backup safety switch in case the operating aquastat 臼ils.η1etwo
aquas阳.ts can be mounted side by side. In some cases, they are consolidated
面1to one component, even sharing a single sensing element.
Some models 缸e equipped with a manual reset device. For example, if the
water temperature reaches 200哩。3。C) and the contacts open, the switch
must be manually reset to close.
20
Gas Technician 2 Training - Module 12
© Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Flow switch
Flow switches (Figure 1-16) actuate in response to water movement. They
ensure that the pumps are circulating water in the piping system and the
boiler before the main burner can fire. Boilers that require flow switches
have small water capacities and their water may tum to steam if the flow of
water is inadequate.
Water flow
switch ~
。
0
Water-sensing
paddle
Extended paddle
for larger pipe
Figure t 斗 6 Flow switch that senses water 币。w
Flow switches can also be designed to detect air movement; these are
called sail switches (Figure 1-17). A common application of a sail switch is
proving air flow for burner systems.
Air-sensing
paddle
Airflow
switch
Figure 1-17 Flow switch that senses air flow (sail switch)
Gas Technician 2 Training- Module 12
© Canadian Standards Association
21
FUNDAMENTALS OF CONTROLS
High-limit
switch
UNIT 1
The high-limit switch actuates in response to an excessive rise in air
temperature. It is a normally closed switch that opens the control circuit if
overheating occurs.
The high-limit switch can be located in several different areas of the
heating equipment. A common location for a high-limit switch on a forced
warm-air furnace is next to the heat exchanger. If the temperature of the
heat exchanger reaches around 200。F (93°C) (the normal set point for the
high limit), the heat-sensitive bimetal will warp and break the control
circuit. Once the temperature lowers to around 175 。F (79。C), the contacts
will automatically reset. In this case, the differential between the opening
and closing temperature settings is 25°F (14。C). The differential is usually
not adjustable, although the high-limit set point may be adjusted.
Combination
high-limit/fan
control switch
The combination high-limit/fan control contains a normally open fan
switch on the left side and a normally closed high-limit switch on the right
side (Figure 1-18）.币1e two switches are connected together with a jumper,
which connects the same power source to both switches. (The jumper can
be removed and the limit could then be wired in the control circuit if
desired.)
As the temperature rises, the bimetal strip will first close the fan switch and
start the blower. If an overheating condition occurs, the bimetal strip will
continue to wa叩 until the limit cut-out temperature is reached (around
200。F [93。C]) and then open up the limit switch.
When the limit switch is open, the transformer circuit is interrupted. This
de-energizes the control circuit, causmg the main gas valve to close.
Meanwhile, the fan continues to run until the fan switch cools and opens.
22
Gas Technician 2 Training - Module 12
© Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
High limit
setting
To fan
To
阿ioto「
transformer
Normally
closed switch
Figure 1-18 Combination high-limit/fan control
High-limit
pressuretrol
Gas-pressure
switch
A high-limit pressuretrol works similarly to an operating pressuretrol
except that it is a司justed to a higher pressure setting. Some models are
equipped with a manual reset device.
Gas-pressure switches are required by Code on burner systems 也at operate
with gas pressures greater than Y2 psig (3.5 kPa) (Figure 1-19）.η1ey
automatically shut off the gas supply to the burner in the event of an
overpressure or an underpressure condition in the burner valve train
assembly.
Low gas-pressure switches are reverse acting (RA) in that 由ey open if
gas pressure falls below the setpoint of the appliance pressure regulator.
The Code requires that the switch open if the pressure drops to 50% of
the regulator setpoint.
High gas-pressure switches are direct acting (DA) in that they open
when gas pressure exceeds the outlet pressure of the appliance
regulator. The Code requires that the high press町e switch opens when
the appliance regulator setpoint is exceeded by 25% or more.
Gas Technician 2 Training - Module 12
© Canadian Standa『ds Association
23
FUN DAMξNTALS OF CONTROLS
UNIT 1
Me 「cury
switch
t
Scale
plate
Cutout
adjusting
wheel
Seal-o仔
diaphragm
Md
-aa
MHnv
a m
hHFE nuo
Safety vent
for 1/8 inch tubing
Flow
restriction
Figure 1-19 Gas pressure switch
24
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
TOPIC
5
Combustion sαifety controls
Under safe conditions, the combustion safety control system will allow the
burner startup sequence to begin.
Combustion safety controls have evolved from the simple thermocouple
that monitored the pilot flame to an electronic ignition control module that
not only monitors the flame, but also sequences the burner cycle.
Flame sensors are designed to detect the presence of a flame; whether it be
the pilot flame or the main burner. If the flame is not detected, the flame
sensor fails to send a flame signal to the control module.
Pilot relight kits are flame sensors/igniters in one unit that, upon a flame
failure, begin to spark in order to relight the pilot. This unit continues to
spark for a predetermined amount of time, until the pilot relights or the
control module goes into lockout.
Flame
rectifiers
(flame rod)
Flame rectifiers (flame rod) are the most common flame sensing devices.
They work on the principle of flame ionization whereby the heat from the
flame causes air molecules in and around the flame envelope to collide so
forcibly as to propel some electrons out of their atoms, thus producing ions.
When two flame rods (electrodes) are placed in the flame and a voltage is
applied across the electrodes, a current can be conducted through the flame
between the 阳o rods (Figure 1-20). Since electrici可 consists of electrons
moving 企om atom to atom, the ions in the flame conduct the movement of
these electrons.
Figure 1-20
Gas Technician 2 Training- Module 12
© Canadian Standards Assοciation
Current 臼n
be conducted through a flame
25
UNIT 1
FUNDAMENTALS OF CONTROLS
The amount of current conducted through the flame is dependent on the
relative size of the flame rods. In this system, the ground electrode (usually
the burner head) is much larger than the flame electrode. To ensure
adequate flame rectification, a minimum ratio of 4: 1 between grounding
area and the flame rod must be maintained. This means that the grounding
area must be four times the size of the flame rod. In some cases, additional
metal rods or plates are added to the burner to increase the grounding
surface area (Figure 1-21 ).
Metal
rods
Figure 乍到 Metal
plates or r。ds added to burner head (ground electrode)
The 句rpical
flame rod is made from kanthol, a high temperature alloy
capable of wi.thstanding temperatures up to 2462。F (1350。C) or globar,
a ceramic material having a maximum operating temperature of 2600。F
(1425 。C).
Figure 1-22 shows the typical flame rod setup for both a residential and
large applications.
26
Gas Technician 2 Training - Module 12
。 Canadian Standards As缸沁iation
FUNDAMENTALS OF CONTROLS
UNIT 1
Flame
electrode
Igniter/sensor
Ignition 一一一一+ji 、：
electrode
Pilot burner
(b) Large application
(a) Residential application
Figure 1-22
Typi臼l
flame rod setup
Principle of operation
Although powered by an AC source, the size difference between the burner
head and the flame rod creates a pulsating current that can be read by a DC
m1croammeter.
First half of cycle
1. AC voltage is supplied across the two electrodes. The flame rod is
positive and the grounding area is negative (Figure 1-23).
2. Positively charged ions flow to the grounding area. Since the grounding
area is large, it holds many electrons.
3. Positively charged ions pull a high stream of electrons into the flame.
This results in a high c旧rent flowing 丘。m 也e grounding area to 由e
flame rod during the first half of the cycle.
Gas Technician 2 Training- Module 12
© Canadian Standards Association
27
FUNDAMENTALS OF CONTROLS
UNIT 1
Second half of cycle
In the second half of the cycle, the reverse process occurs, but the flame
rod cannot hold as many electrons and the resulting current is weaker
(Figure 1-23).
The resultant current acts like a pulsating direct current. The flame signal
in a rectified system should be steady and can be measured with DC
m1croammeter.
骨－
4毒－
First half 。fAC cycle
+
一’
一＋
Second half 。fAC cycle
-+
First half
of cycle
Figure 1-23 Current flow in a flame rectification system
。ptical
sensor
28
flame
A flame radiates energy in the form of waves which produce heat and light.
We can only see approximately 6% of the radiation; the majori可（90%) of
the heat occurs at 也e in企ared end of the spec位um while a small percentage
(3%) occurs at 由e ultraviolet end of the light spectrum. (Figure 1-24).
Gas Technician 2 Training - Modu恒 12
@Canadian S恒ndards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Figure 1-24 Approximate breakdown of light emitted by flame
Ultraviolet flame sensor
The radiant energy in a flame can be detected by an ultraviolet sensing tube
(Figure 1-25). This tube is constructed of quartz and filled with an inert
gas. Two AC-energized electrodes within the tube will, upon detection of
ultraviolet radiation, create electrical pulsations. These pulsations are used
to signal the control module 出at ultraviolet radiation has been detected,
thus proving the pilot flame.
〉注司应
Figure 1-25 Small ultraviolet sensor used for
conventional commercial applications
Infrared flame sensor
The main element of the infrared sensor (Figure 1-26) is a lead sulphide
cell which is used as an electrical switch . The lead sulphide material is in
itself a semi-conductor but when exposed to infrared radiation it loses its
resistance and allows free movement of electricity. When installed in the
control circuit and (sighted) at the infrared .~art of the ~ilot flame, the lead
sulphide cell will energize the circuit only if it detects in仕ared radiation,
proving the pilot flame.
Gas Technician 2 Training- Module 12
Standa『ds Association
© Canadian
29
FUNDAMENTALS OF CONTROLS
UNIT1
Figure 1-26 Infrared flame sensor with lead sulphide cell
Air-proving
switch
Air-proving switches interlock the burner fan operation with the flame
safeguard control system by monitoring the air pressure developed by
the burner fan. Essentially, air-provmg switches are sensitive diaphragmoperated pressure switches (Figure 1-27) used in positive pressure or
differential pressure systems to sense air pressure changes.
Figure 1-27 Air-proving switch
30
Gas Technician 2 Training - Modu幅 12
©Canadian S幅ndards Association
TOPIC
6
Ignition
contγol
modules
Control modules provide ignition and main flame 也ilure protection for
automatically ignited gas burners. In conjunction with limit and operating
controls and interlock devices, these controls automatically sequence with
solid state logic the burner/blower motor, ignition, and main fuel valves.
The control cycles automatically when the operating controls close and
after a power shutdown. They must be manually reset after a safety
shutdown.
Control systems with electronic ignition were originally designed for
rooftop units, in丘ared heaters and other gas-fired appliances where access
to the pilot was difficult; or where environmental factors such as wind and
rain caused frequent pilot outages that involved expensive service calls.
Types of
control
modules
Depending on how the main burner is going to be lit, there are three types
of control modules:
intermittent pilot
direct spark ignition
•
hot surface ignition
Manufacturers make several models of each type, depending on the
specific sequence of operation required.
Basic
operation
On a call for heat, the thermostat ene电izes the control module. The control
module then sequences the safe light-up of the burner system. D叩ending
on the burner control system, this may include:
1. Performing a safe-start check.
2. Igniting the flame.
3. Powering the gas valves.
4. Proving presence of flame.
5. Monitoring flame during the run cycle of burner.
Gas Technician 2 Training- Module 12
© Canadian Standards As回ciation
31
FUNDAMENTALS OF CONTROLS
υNIT
1
When the call for heat is satisfied, the thermostat de-energizes the control
module. The control module then de-energizes both the pilot and main gas
valves.
Terminology
Following are common terms associated with control modules
开ial for
ignition
Lockout
Trial for ignition is the time allowed to establish
ignition. For modules that are part of a 100% safe
system, the trial for ignition period is stated on the
module. Modules that are part of a non-100% system
energize the pilot valve and source of ignition until
the flame is established.
Lockout is what happens to the control module if the
trial for ignition period of time expires. The module
then requires a manual reset to restart the ignition
sequence. Depending on the make and model, this is
accomplished either by depressing a reset button on
the control module or by turning the thermostat to its
lowest setting. This de-energizes the control module.
After a predetermined period of time (usually 1 to 3
minutes), the control module resets and can be
energized by turning the thermostat back to its setting.
Depending on the control and how it is wired, lockout
mode is accompanied with a visual (flashing LED) or
audio alarm to indicate that there has been an ignition
or flame 也ilure.
Flame fα·ilure
response time
32
Flame failure response time is the time it takes the
flame sensor circuits to react to a flame failure and
de-energize the main gas valve. Some control
modules go directly into lockout on a flame failure
while others recycle the trial for ignition.
Gas Technician 2 Training- Module 12
© Canadian Standards Association
UNIT 1
FUNDAMENTALS OF CONTROLS
Intermittent
pilot control
module
Unlike the continuous pilot, the intermittent pilot is present only during the
operation of the main burner. On a call for heat by the Control circuit, the
control module sequences the safe light-up of the pilot flame and then the
main burner. When the call for heat is satisfied，出e pilot and main gas
valves are shut-off.
Terminals
The terminals on the control module connect to the Control circuit, the
main and pilot valves, and the igniter” sensor (Figure 1-28). Each
manufacturer of an intermittent pilot control module designs a different
terminal layout. However, all types have terminals for input power, main
and pilot gas valves, ground, and the igniter sensor. Note that in Figure 1”
28 the gas valve is the redundant type.
L1才
N (L2)
／以cti
n
Appliance /
switch
气
Fan
motor
Transformer,
‘
Pilot burner
\
-
hunuu enH
『
AU
lvs
川
户
UHU
p
nt
而
gd
aE
p
此 nu
』Mhwo
，、，
宇
1oe
..0
Figure 1-28 Intermittent pilot control module with combination
igniter-sensor and redundant gas valve
Gas Technician 2 Training- Module 12
Canadian Standards Association
©
33
FUNDAMENTALS OF CONTROLS
UNIT 1
Sequence of operation
The control module is energized when the Control circuit is complete.
1. On a caJI for heat, the thermostat contacts close to complete the Control
circmt.
2. The Control circuit energizes the control module through the terminals
labelled ” 25V. ”
3. Once energized, the control module:
4. Energizes the flame sensor and performs a safe-start check. (If false
signal exists, it does not energize igniter.)
5. Energizes 伽 ign阳回
6. Energizes the pilot valve through terminal marked ”PV. ”
7. Lights the pilot flame with the igniter.
8. Proves the flame with the flame sensor.
9. De-energizes the igniter.
10.
Energiz叫e
main gas valv
hrough th
rmina
11. Monitors the pilot flame, through the flame sensor, during the entire
run cycle of the main burner.
If flame failure occurs, the control module:
1. De-energizes the main gas valve.
2. Re-energizes the igniter.
On 100% safe systems, if the control is unable to relight the burner within
trial for ignition period, the control module will go into lockout.
也e
For non-100% safe systems, the spark generator remains energized
indefinitely or until a pilot flame is finally established.
34
Training- Module 12
Canadian Standards Association
Gas 丁echniαa『12
©
υNIT
FUNDAMENTALS OF CONTROLS
1
Direct spark
ignition control
module
Direct spark ignition systems operate on a slightly different principle than
the intermittent pilot system. Direct spark ignition does not use a pilot
flame, but rather directly lights the main burner with a spark. The control
module, therefore, does not have the terminals 岛r pilot valves. If a
redundant type gas valve is used, both coils are wired in parallel and are
energized together.
Terminals
A direct spark ignition control module has terminals for input power, main
gas valve, ground, and the igniter-sensor (Figure 1-29).
Junction
box
L1 I N (,L2)
/~
Appliance
disconnect
switch
Transformer
\
F~ctory installed
二－ wires for second
Limit switch
·- =
@
coil
Redundant
gas valve
日｜
。
Igniter-sensor
and burner ground
Main burner
Figure 1-29 Direct spark ignition with combination igniter-sensor
Gas Technician 2 Training- Module 12
© Canadian Standards Association
35
FUNDAMENTALS OF CONTROLS
UNIT1
Sequence of operation
The control module is energized when the Control circuit is completed.
1. On a call for heat, the thermostat contacts close to complete the Control
ClfCutt.
2. The Control circuit energizes the control module through the terminals
labelled ”25V. ”
Once energized, the control module:
1. Energizes the flame sensor and performs a safe-start check. (If a false
signal exists, it does not energize igniter.)
2. Energizes the igniter.
3. Energizes the main gas valve through terminal ” Valve. ”
4. Lights the main flame.
5. Proves the flame with the flame sensor.
6. De-energizes the igniter.
7. Monitors the main flame with the sensor during the entire run cycle of
the main burner.
If flame failure occurs, the control module:
1.
Re－创iergizes
the igniter.
2. Goes into lockout if the control is unable to relight the burner within
the trial for ignition period.
36
Gas Technician 2 Training - Module 12
© Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Hot surface
ignition control
module
Hot surface ignition systems operate the same as direct spark ignition,
except that a hot su矿ace lights the main burner. The hot surface igniter
requires line voltage to heat the surface hot enough to ignite gas on contact;
it is therefore directly connected to the line voltage supply (Figure 1-30).
Redundant
gas valve
4←一－
Thermostat
Figure 1-30 Hot surface igniti。n with
Hot
surface
igniter-sensor
Junction
box
combinati。n
Appliance
disconnect
switch
igniter” sensor
τerminals
The terminals of a hot surface ignition are the same as direct spark ignition,
except for the terminals to the hot surface igniter. The line voltage input
terminals are labelled ” L1 ” and ” L1 ” and the terminals to the hot surface
igniter are labelled ” HSI. ”
Gas Technician 2 Training- Module 12
© Canadian Standards Association
37
FυNDAMENTALS
OF CONTROLS
UNIT1
Sequence of operation
The control module is energized when the Control circuit is complete.
1. On a call for heat, the thermostat contacts close to complete the Control
ClfCUit.
2. The Control circuit energises the control module through the terminals
labelled 吃4V. ”
Once energized, the control module does the following:
1. Energizes the flame sensor and performs a safe-start check. (If a false
flame signal exists, it does not energize igniter.)
2. Warms up the hot surface igniter for approximately 30 seconds through
terminals ” HSI. ”
3. Energizes the main gas valve through terminals marked ” valve. ”
4. Lights the main flame.
5. De-energizes the igniter.
6. Proves the main flame through the flame sensor.
7. Monitors the main flame with the sensor during the entire run cycle of
the main burner.
If flame failure occurs, the control module:
1. De-energizes the gas valve(s).
2. Re-energizes the ignition cycle.
3. Goes into lockout if the control is unable to relight the burner within
由e trial for ignition period.
Some modules are designed to cycle the ignition sequence three times
before lockout.
38
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
TOPIC 7
Valves
and γ~gulαtors
Valves and regulators open or close in varying amounts to control the flow
of gas, water, or steam. There are many different types of valves: some are
operated manually, others automatically.
Following are descriptions of the most cormηon valves and regulators.
Manual valves
A manual valve is one where a technician must manually open or close the
valve. These valves can be installed to control gas or water and are used to
isolate parts of the system.
Gas shutoff valve
A manual gas shutoff valve provides a method of ensuring that 由e gas has
been positively turned off to any area of the piping system or to a particular
appliance. The two main types of manual gas shutoff valves include the
plug type and the ball type.
Plug-type
Plug-type valves fully open or close with a quarter 阳m of a handle
(Figure 1-31). There are two basic types common to the gas industry.
•
The spring loaded valve is made of brass and approved only for indoor
use.
•
The lubricated plug valve is made of malleable iron and approved for
indoor or outdoor use. The common name for 由is valve is Lubeseal. It
is designed to be lubricated and maintained with the valve in place and
with no interruption of service. For outdoor use, the lubricated plug
valve may also be obtained wi由 a removable handle and a locking
accessory for security.
Gas Technician 2 Training - Module 12
© Canadian Standards A链。αation
39
FUNDAMENTALS OF CONTROLS
UNIT 1
Quick operation
1/4 turn opens
or closes valve
Figure 1-31 Manual plug-type valve
Ball type
Ball valves also open and close with a quarter-tum of a handle and are
approved for both indoor or outdoor 山e (Figure 1-32). They are
constructed with a Teflon seat and a stainless steel sealing ball. To control
the flow, the ball has a hole drilled through its centre and fits tightly against
the Teflon seat in the closed position. Lubrication is not a concern with this
type of valve.
(These valves can be used for both gas or water applications.)
Lever in
Lever 1/4 turned
to open ball valve
\:
/0仔 position
Flow
Closed
。 pen
Figure 1-32 Cross-section of manual ball-type valve
Application of gas shutoff valves
The Code clearly requires that a readily accessible gas shutoff valve for
each appliance be installed upstream and external to the valve train
assembly. This valve ensures that the gas has been positively turned off to
any area downstream of the valve.
In addition there will be a gas shutoff valve on the pilot line so 也at it can
be controlled independently of the main valve train.
40
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
υNIT
FUNDAMENTALS OF CONTROLS
1
Water shutoff valve
Water shutoff valves control the flow of water to hot water heaters, hot
water boilers, and steam boilers. They are normally open valves that can be
shut off to isolate an appliance for repair or servicing.
Three typical types of water shut-off valves are:
Gate valve
The gate valve (Figure 1-33) has a gate 也at moves up or down to open or
close the valve. Because of excessive vibration and wear caused by
partially opened gates, these valves are not intended for throttling or
regulating flow. They are designed to operate fully open or fully closed and
are typically used on water and steam installations.
Globe valve
Globe valves (Figure 1-34), unlike gate valves, are designed for steady use
in applications with frequent 仕rrottling or flow regulation. The design of
the globe valve keeps the seat erosion to a minimum.
Wheel
Handwheel
Yoke
Gland
Stuffing
box
Stem
Disk (gate)
Body seat
rings
Body
Disk
Courtesy of Toyo Valve Co., Ltd.
Figure 1-33 Gate valve
Gas Technician 2 Training- Module 12
© Canadian Standards Association
Figure 1-34 Globe valve
41
FUNDAMENTALS OF CONTROLS
Automatic,
non-electric
valves
UNIT 1
Automatic non-electric valves typically operate on temperature and
pressure changes.
Relief valves
Relief valves are safety devices designed to relieve high pressure or
temperature conditions.
Pressure-relief valve
The pressure relief valve is a mechanical valve used on hot water boilers. If
pressure in the system rises above the set point, the valve opens and dumps
water until the pressure drops to an acceptable level.
Combination pressure-temperature relief valve
Local and national codes require that storage water heaters be installed
with a combination pressure-temperature relief valve (Figure 1-35). The
sensing stem of this valve extends into the water within the top six inches
of the tank. It will open to dump water if the tank pressure or water
temperature is excessively high. Whenever a water heater is replaced, a
new valve should be installed and the old valve discarded.
Some less-sophisticated relief devices use a fusible plug as the sensing
device. Once the plug has melted it will continue to dump water until the
water supply is manually turned off.
Test
lever
Water
Thermostat
Extension
thermostat
Teml?erature
sensing zone
Figure 1-35 Combination pressure-temperature relief valve
42
Gas Technician 2 Training - Module 12
© Canadian Standards Association
υNIT
FυNDAMENTALS
1
OF CONTROLS
Unitrol
The Unitrol (Figure 1-36) is a multi-purpose valve typically installed in hot
water heaters. It contains, in one compact unit:
•
thermostat
automatic gas shutoff valve
overtemperature energy cut-off (ECO) device
•
main pressure regulator
•
main and standby gas cock.
The Unitrol actuates in response to changes in water temperature. Its
sensing device works on the rod and tube principle.
Regulator
adjustment cap
Reset
bu扰。n 一一，
Temperature 一一.＿，
Pilot
adjustment
cap
dial
Figure 1-36 Unitrol multi-purpose valve
Water pressure-reducing valve
The water pressure-reduc坦g valve (Figure 1-37) reduces the high pressure
(e.g., house line pressure of 40 psig) to a lower operating pressure (e.g., 15
psig for a low pressure hot water heating systems). The valve actuates in
response to a pressure drop in the low pressure side.
This valve is commonly called a water makeup valve.
Gas Technician 2 Training- Module 12
© Canadian Standards Association
43
FUNDAMENTALS OF CONTROLS
UNIT 1
Pressure
adjusting
screw
/Diaphragm
三J理
Figure 1-37
Automatic,
electric
valves
V也ter
pressure-reducing valve
The majority of automatic gas valves are electrically actuated and are
primarily found on the gas valve train to control gas flow to the burner.
Safety shutoff valve
η1e
gas safety shut off valve shuts off the gas supply when de-energized by
a combustion safety control, safety limit control, or loss of actuating
medium. Many different valves can be used as safety shutoff valves,
depending on the power supply: 120V, 24V or millivolts.
44
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Solenoid valve
Solenoid valves (Figure 1-38) are commonly used as safety shutoff valves
on pilot lines of large input appliances.
When the solenoid’s electromagnet coil is energized, a metal plunger is
drawn up into the coil’s centre. By coupling the plunger to the valve seat,
the rising action of the plunger is used to li丘 the seat off the valve port,
opening the valve.
呵曰
E』 S
四川
m et
huc
nue GMnH
FU
Lead
Armature
(moves up
to open)
Valve seat
Figure 1-38 Solenoid valve in closed position
There are three basic types of solenoid valves.
•
direct acting A direct acting solenoid valve has the seat directly
coupled to the plunger. Energizing the solenoid coil lifts the plunger
and seating surface, opening the valve outlet port.
lever In the lever-actuated valve, the seating surface is connected to the
plunger through a lever arm. When the solenoid is energized, the
plunger lifts the level arm arrangement, opening or closing 由e valve
with a greater force than if the seating surface was directly connected to
the plunger.
•
pilot operated The pilot-operated valve uses pressure differential to
assist the plunger in opening and closing the main valve. When the
solenoid is energized, the rising plunger opens the pilot valve causing
the gas above the piston to bleed off faster than it can fill. The pressure
below the piston assists the plunger to lift the seating surface and open
the main valve.
Gas Technician 2 Training- Module 12
© Canadian Standards Association
45
FUNDAMENTALS OF CONTROLS
UNIT1
Modulating valve
A modulating valve is a combination of two valves in a single unit. It is
designed to give precision temperature control with minimum cycling and
maximum operating efficiency. This valve operates in a sequence as
follows:
•
A snap-acting valve opens at the initial call for heat to provide the
minimum rate of gas flow. If this gas flow is sufficient to bring the
room up to 由e set temperature, the snap-acting valve closes.
If more heat is required, a modulating valve adjusts the gas flow rate
between the fixed minimum and full burner capacity.
The valve is provided with a minimum rate which is intended to match
the minimum gas flow requirement of the burner that it serves.
The temperature-sensing bulb, capillarγtubing and bellows are filled with
a temperature-sensitive liquid: Changes in temperature at the bulb contract
the liquid on temperature fall and expand 让 on temperature rise, causing the
bellows to shorten and lengthen respectively. This movement is transmitted
to the valve assembly by a horizontal pivot arm. The Modusnap
modulating valve shown in Figure 1-3 9 is used for space temperature
control. The liquid immersion model is similar but it has a larger top casing
to accommodate larger bellows.
Figure 1-39 Modusnap modulating valve
46
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Combination valve
The combination gas valve (Figure 1-40) was designed to combine several
controls into one unit in order to save on space. This valve is generally
found in appliances with inputs 400 000 Btu/h or less.
The compact body of a combination gas valve includes:
shut咱ff valve
•
a manual
•
an automatic gas valve
•
a pressure regulator.
The system’s ignition and control system determine what additional
controls are included in the combination valve. Some of the additional
controls found include:
100% safety shutoff
•
pilot gas a司justment
control module (in newer models called Smart Vialves)
Control switch to Screw to applianceand safety regula;or adjustment
shut-o仔 valves
_/
Electrical connector
to automatic
gas valve
儿cock
Thermocouple
connection to
electromagnet
Components of combination valve
1
2
5
6
7
Gas safety shut-o仔 valve
B-cock
A-cock
Appliance regulator
Automatic gas valve
Figure 1-40 Combination gas valve
Gas Technician 2 Training- Module 12
© Canadian Standards Association
47
FUNDAMENTALS OF CONTROLS
UNIT 1
Redundant valve
The redundant (in excess) gas valve is one of the most popular gas safety
controls used in the. field today. It is of the 100% safety shutoff type with,
as extra protection, a second shutoff valve incorporated in the valve body
(Figure 1-41). This second ~redundant) valve eliminates the possibility of
an operational failure allowing gas to enter the combustion chamber while
a proper ignition source is absent.
Pilot valve
operator
丁。 pilot
Indicates gas
burner
Figure 1-41 Redundant gas valve with both valves closed
before operating cycle
Motorized valve
白ie
motorized valve ~Fig町e 1-42) is com~letely opened by the rotation of
an electric motor and is generally automatically closed by a spring or other
mechanical means when the electrical circuit is broken. This valve can be
used 部 a firing rate valve.
48
Gas Technician 2 Training - Modu悔 12
© Canadian Standards A篇回国ion
FUNDAMENTALS OF CONTROLS
UNIT 1
Electric
motor
Hydraulic
pump
Check
valve
Travel limit
switch
Valve
pusher
Return spring
Union nut
Lock nut
Valve
seat
Figure 1-42 Motorized gas valve
Diaphragm valve
The diaphragm gas valve uses available gas pressure as the primary force
to open or close the valve (Figure 1-43).
1. On a call for heat the electromagnet is energized.
2. The electromagnet then pulls the armature into a position which blocks
off the pressure port, allowing gas pressure above the diaphragm to
bleed off through the vent port to a standing pilot flame.
3. The gas pressure below the diaphragm lifts the diaphragm and valve
disk 企om the valve seat.ηiis action allows gas to flow through the
valve.
4. When the heat call has been satisfied, the electromagµ.et becomes de”
energized and the armature return spring pulls the armature into a
position 也at blocks off the vent port.
5. Working gas enters the pressure port and press田izes the top of the
diaphragm.
6. When the pressures above and below the diaphragm are equal, the
spring will cause the valve to close.
Gas T以:hnician 2 Training- Module 12
© Canadian Standards Association
49
FUNDAMENTALS OF CONTROLS
UNIT 1
立二 Leads
Electromagnet
Diaphragm
Gas flow
一一~全
Valve seat
Figure 1-43 Cutaway view of a diaphragm gas valve
Feedwater valves
As a gas technician you may encounter an automatic electric valve that
controls water, such as the feedwater valve (Figure 1-44), which controls
makeup water to a boiler. This valve is mounted directly into the feedwater
line of a boiler. This valve operates in co时unction with low-water cutoff
limit controls to maintain the boiler water level above the safe minimum
level. Upon sensing low water condition, the boiler low-water cutoff shuts
down the burner and powers the feedwater control which lets in makeup
water.
‘’._ Out
Figure 1-44 Feedwater valve with low-water cuto仔
50
Gas Technician 2 Training- Module 12
© Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Two-stage valve
A two-stage gas valve is used with a two-stage thermostat to supply fuel in
quantities necessa叮 to meet staged demand. The valves are built to supply
less fuel on a first-stage heating call. When the second stage is energized,
100% 臼el flow is sent to the burner. Two-stage valves can be constructed
using magnetic diaphragms and bimetals to control the fuel flow.
Gas pressures in service piping are often much higher than the pressures
acceptable for appliances and equipment. Gas pressure regulators (Figure
1-45), when properly selected and installed, help maintain constant
downstream gas pressure over a wide range of upstream gas pressure
variations. There are essentially three categories of gas pressure regulators:
service, system and appliance.
Measuring
element
一＼
Restricting
element
Figure 1-45 Gas pressure regulator
、、、－
Gas Technician 2 Training- MOO,ule 12
© Canadian Standards Association
51
FUNDAMENTALS OF CONTROLS
UNIT 1
Regulators
Service regulators
For natural gas, service regulators are used to reduce the service-line
pressure to house-line pressure at the gas meter set, in order to deliver an
allowable pressure to the building. Most meter sets are provided with a
service regulator which is installed by the gas utility, rather than the gas
technician.
For propane, service regulators are installed by the technician between the
storage container and the building.
System regulators
In some cases, a system of appliances and/or equipment in a building
requires a different gas pressure than the building-line pressure delivered
by the service regulator. A system regulator is generally used to reduce the
building-line pressure accordingly.
Appliance regulator
Appliance regulators are typically found on appliances (often built into a
combination control) to reduce building-line pressure to that required for
the proper performance of the appliances.
52
Gas Technician 2 Training ”－ M创ule 12
© Canadian Standards Association
FUNDAMENTALS OF CONTROLS
UNIT 1
Assignment 1
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
What three types of controls work on the principle of thermal expansion of solids?
2.
What liquid in a capillary is suitable for high temperature operation?
3.
What is a solenoid?
4.
矶That
5.
What system
6.
Give three examples of operating controllers.
7.
Are position and location important f玩tors for thermostat installation? If so, what are 由e
requirements?
8.
矶That
9.
What is an operating pressuretrol?
two control components produce electricity when heated?
supervises 由e
operation of gas-fired equipment?
is an operating aquastat?
10. Name five limit and safety controllers.
Gas Technician 2 Training- Module 12
© Canadian Standa『ds Association
53
FUNDAMENTALS OF CONTROLS
UNIT 1
11. Is a thermocouple considered to be a combustion safety control?
12. Name three types of combustion safety controls that rely on flame sensing.
13. List the three main types of control modules.
14. List the basic sequence of operation for a control module.
15. Where would a Unitrol valve typically be installed?
16. List the three types of solenoid valves.
17. What does a basic combination gas valve include?
18. What additional controls may be included in a combination gas valve?
19. What is the primary force used to open or close a diaphragm gas valve?
20. Name the three categories of gas press田e regulators.
21. What feature acts as extra protection on a redundant gas valve?
54
Training - Module 12
Standards A弱。ciation
Gas 丁丽chnician 2
。 Canadian
Unit2
Control circuits
Purpose
Controls on gas fired appliances are installed to ensure that the appliances
operate safely, efficiently and appropriately. To achieve this pu叩ose, gas
technicians must have a clear understanding of how control circuits are
designed, how controls are installed, and the electrical sequence of
operation.
Learning
1. Explain diagrams for control circuits.
o同ectives
2. Describe auxilliary devices in a control system.
3. Explain polarity.
4. Explain the electrical sequence of operation.
Gas Technician 2 Training - Module 12
e Canadian Standards Association
55
Topics
1. Diagrams for control circuits ........................”.......….........….57
Wiring diagrams ...………….......…………·－……………国…. . ... 57
Schematic diagrams ...................…·．．．．．．，．．．．．．．．．．．．．．．．．．．．目，.............. 58
Electrical symbols .... . ... .. ... ......... . ......................................….. 59
2. Auxiliary devices in a control system .......….............…........创
Switches ...............………...................................................…··…...61
Time-delay relay (timers) ......…·‘…..... ·······……...…-……………..... 64
Contactors . . . ......………………………··...............,.....·………..... 64
Protective devices. ……………··…··－…目，..............……·……....... 65
3. p。larity ………………………………………………………………………·” 67
Polarization .........…..................... ············ ....“··”．．．．．．．．．萨............ 67
How to determine polarity . . . … · · · · · · · .•••••• •• • ••••••• • • • • • • •••••.• ••••••• ••••••• 67
4. Electrical sequence 。f operati。n .......….....................…........ 71
Electrical sequencing example ....................…..........…................... 71
Assignment 2 “….......................................................................... 75
56
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
TOPIC]
Diagiγαmsfo γ contγol ciγcu its
The control system ’ s schematic and wiring diagrams are the basis for
determining the specific sequence of operation as well as to identi今由e
electrical connections between safety controls.
wd
v nr
ga
UHF
-
ms
”
' iring diagrams are maps of electrical circuits. They are very useful for
initially wiring a circuit, and for tracing wires when you are
troubleshooting. They show exactly how and where the wires are
connected between devices. They also show, as clearly as possible, the
actual location of all the components of a circuit. The components are
usually shown as standard electrical symbols.
Figure 2-1 is a wiring diagram for starting and stopping two motors,
complete with running light indication.
Figure 2-1 Wiring diagram
To make the wiring diagram clearer and easier to follow, all wires are run
either horizontally or vertically. When the wires cross, a dot means that the
two wires are connected. If a dot is not shown, the wires cross each other
but do not connect electrically.
Gas Technician 2 T1『aining - Module 12
© Canadian Standards Association
57
CONTROL CIRCUITS
阳咆
QUVAU
C
-
U
UNIT2
us
c
an
mm
The basic means of communicating the language of control is through the
use of the schematic diagram. This type of diagram consists of a series of
symbols interconnected by line to indicate the flow of current through the
various devices. 在1e schematic diagram show basically two things: （的 the
power source and (b) how current flows through the various parts of the
circuit such contacts, coils and overloads.
The schematic diagram is intended to show the circuitry which is necessary
for the basic operation of the system. It gives no indication of the physical
relationship between the components.
This schematic is also called a ladder diagram. The left-hand side of the
ladder represents the incoming voltage, the right-hand side represents the
switches and loads. The wires connecting the two sides form the ” rungs ” of
the ladder. From the schematic, you see clearly how the circuit works
electrically and can use it to trace the electrical sequence of operation.
Figure 2-2 shows the same circuit as Figure 2-1, except it is drawn as a
schematic. As you can see, it is much easier to follow the flow of current.
/
Figure 2-2 Schematic diagram
Series and parallel circuits
Circuits often include more than one device or component. The several
devices may be arranged in their circuits in any one of many ways, but any
aηangement can be classified by two basic types of circuits: series and
parallel (or a combination of these).
58
Gas Technician 2 Training - Module 12
© Canadian Standards Association
UNIT 2
CONTROL CIRCUITS
Series circuits have the components connected in such a way that the
electric cuηent must pass through each one in sequence.
In parallel circuits, more than one path is available for current flow.
A complete electrical circuit may have some parts wired in series and
others wired in parallel. These are called series/parallel circuits.
Electrical
symbols
Wiring and schematic diagrams use symbols instead of pictures to
represent the switches and loads of a circuit. The symbols.in Table 2-1 are
the international symbols for the most commonly used electrical devices in
the gas industry.
Table 2-1
Comm。n
international schematic symbols
Component
Schematic symbol
SWITCHES
j ,,,,,
j
ta
Disconnect switch
Circuit breaker
Normally Normally
open
closed
Limit
‘『才吏
Pressure and vacuum
t曼
红’
Liquid level
丁
了
FUSES
Temperature actuated
i、Jrs1，·E
cl。sed
?
?
1
lowsw叫毗 W毗则’τ·
Normally
气’
c。NTACTS
~Q
Power or control
Instant opening
J_
T
WIRING
TRAN SF。RMERS
Iron core
~
Normally
open
；特令1
Gas Technician 2 Training - Module 12
。 Canadian S阳dardsAssoc阳tion
Ground
土
59
TOPIC
2
Auxiliα＇. ry
devices
contγol system
in α
In order for the loads to operate, auxiliary devices must be incorporated
into the control system. Auxiliary devices include: switches, relays,
contactors and protective devices.
Switches
Switches are the most common auxiliary device found in control systems;
they are used to start or stop a sys臼m.
All switch symbols in a wiring diagram are shown in the “ resting” position.
Resting means that the medium (heat, pressure, etc.) has not caused the
switch to change positions.
switches are normally open (NO) when the resting position of the
switch is open (Figure 2-1-3a). Typicall）「 actuating switches are in the
NO position.
If the NO switch symbol is show above the line, the switch will
close on a decrease in the activating medium (heat, pressure, etc.)
If the NO switch symbol is shown below the line, the switch will
close on an increase in the activating medium.
switches are designated normally closed (NC) when the resting
position of the switch is closed (Figure 2-1-3b). Typically limit
switches are in the NC position.
(a) Wired in
n。rmally
。pen p。siti。n
(b) Wired in normally
closed position
Figure 2-3 NO and NC wiring of switches
Gas Technician 2 Training - Module 12
Standards Assoc幅画m
@ Canadian
61
CONTROL CIRCUITS
UNIT2
Multiple terminals
In some cases, switches can be wired either as NO or NC, depending on
the application. These switches have three terminals, but only two are used.
For example, if wired in NO position the wire will be connected to the NO
terminal and the common terminal. Likewise, if wired in the NC position
the wire will be connected to the NC terminal and the common terminal
(Figure 2-4).
Normally
open
terminal
Common
terminal
\ 1
Normally
closed
terminal
I
'""" N/O
I C
Figure 2-4 Multiple terminals
Relays
In a broad sense, a relay (Figure 2-5a) is an automatically operated switch.
A switch could be operated by compressed air in which case it is a
pneumatic relay. For electric control systems, the relay can be operated by
an electromagnet or solenoid (Figure 2-5b).
Solenoid
-f-'arm刷re
(a) Relay
(b) Detail of the contacts
Figure 2-5 Solenoid relay
62
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
UNIT2
CONTROL CIRCUITS
In a solenoid relay the electrical contacts open and/or close when its coil is
energized or de唰energized in response to a change in the conditions of the
electrical circuit. The operation of the contacts affect the operation of other
devices in the same circuit or in other circuits.
It is quite common for relays to be powered by 24 volts, but to close a
120 volt circuit. This way, expensive 120 volt wiring can be kept to a
minimum. To illustrate, notice that in Figure 2-6 the contact relay's coil
(CR) is located in the 24 volt while its contacts (CR) are located in the line
voltage circuit. The low voltage coil thus controls the higher voltage
contact.
N
Fan motor
Fan
control
High limit
Burner motor
Contact
relay
Figure 2-6 Relay powered by 24V but closes a 120V circuit
Relays are available in many coil voltages to suit the particular application.
It is therefore important to check the relay coil for proper voltage.
Gas Technician 2 Training - Module 12
Standards Association
。 Canadian
63
CONTROL CIRCUITS
Time-delay
relay (timers)
UNIT2
There are many reasons for controlling the operation of heating, air
conditioning and refrigeration equipment according to predetermined time
intervals. Timing relays may be called by terms such as time-delay relays,
timers, etc. according to their purposes. For example, sequenced control of
several motors is often used in heating and air conditioning systems. If all
of these motors were to start simultaneously, the heavy current resulting
from the total of all these staring currents may be large enough to blow a
main fuse or circuit breaker. The starting of such motors can be made to
occur one after the other, instead of simultaneously, by putting a time-delay
relay in control circuits of the sequenced motors.
Co n饭ct ors
Heavy duty contactors are solenoid/armature operators for switching
heavy-duty electrical contacts. They are used to control the large amounts
of current and high voltages required by industrial equipment. Figure 2-7
shows a contactor that might be used to turn on a three-phase motor on a
larger boiler. Note that the insulators which hold the conductive crossbars
are attached to the T-bar armature which closes several sets of contacts at
once. The wiring diagram in Figure 2-7 shows the switch in the 110 volt
solenoid circuit which simultaneously activates the 240 volt three-phase
lines to the motor. (The overload protectors on the lower right of the
schem~tic are not shown.)
川
nqu a o,
llz
Conductive ：：＝工主司
~
crossbars
aTK
E
A
B
C
队…
c2.
Terminals
B·
2•
A
Ea2 ‘
c0 En
t cs
AE
--
…~ - - - … …
u
Figure 2-7 Heavy duty contact。
64
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
CONTROL CIRCUITS
UNIT2
Protective
devices
Protection of the control circuit against overct盯ent prevents the switches
and loads 企om overheating and causing a fire.
Fuses
Fuses are circuit-protection devices. They are connected in series with a
load. In the event of excessive current flow, the fuse melts. This opens 也e
circuit, and protects the load device and its supply conductors from
overheating.
Fuses have the following characteristics:
The fuse element is usually made of an alloy such as silver-tin.η1is
alloy combines the high conductivity of silver wi由 the low melting
point of tin.
•
A fuse is rated according to the value of current that may continually
flow through it without causing the fuse-element to overheat and melt.
Fuses have an inverse time characteristic. This means that 出e greater
the value of a fault current，位1e faster the fuse breaks the circuit.
Circuit breakers
Circuit breakers, like fuses, protect electrical conductors and equipment
仕om the effects of overload and overc田rent. The type of circuit breaker
shown in Figure 2"'8 is used in low-voltage distribution systems under 750
volt. It is of王en used to protect lighting and motor circuits.
When a circuit breaker trips to open a circuit, it can be reset by hand
without replacing any parts.
Figure 2-8 Circuit breaker
Gas Technician 2 Training - Modu悔
Standards As回ciation
@Ca阳伽n
12
65
TOPIC
3
Pola.γity
As more and more electronics are introduced to the gas industry, two
factors have become increasingly important during normal installation and
service calls: polarization and phasing. Some of the electronics boards
being used today, with flame rectification, will not function properly--or at
all-unless the polarization is correct.
Phasing of primary to secondary voltage on transformers: some electronic
boards also require phasing of step-down transformers.
Polarization
In a DC circuit, polarity refers to the direction of cuηent flow. In an AC
circuit, polarity refers to the differentiation between hot, neutral and
ground.
How to
determine
polarity
Hot wire
is any non-grounded conductor which carries cuηent.
Neutral wire
carries current when the circuit is closed
Ground wire
is connected to ground and only carries current when
there is a short to ground in the circuit. The electrical
resistance of the grounding wire is less than the
electrical resistance of a human body and thus the
electricity travels through the wire to ground.
Determining the polarity of the branch circuit leads-which is hot and
which is neutral-is easily accomplished with a voltmeter.
1. Set the meter to a voltage range higher 也an 也就 of the branch circuit.
Connect 由e voltmeter across L1 and N (L2) at the junction box, as
shown in Figure 2-9, to determine if there is a voltage potential
between them.
Gas Technician 2 Training - Module 12
© Canadian Standards Assoc阳lion
. 67
CONTROL CIRCυITS
UNIT 2
N (L2)
120 v
120 V reading
voltmeter
Appliance
junction box
Appliance/
disconnect
switch
(closed)
’
ol~
’
Figure 2-9 Voltmeter connected at L1 and N (L2) across the junction box
2. If there is a voltage potential, connect the meter from each wire to
ground, as shown in Figure 2-10, to determine which is hot (120 V AC
reading) and which is neutral (0 V AC reading). On 120 volt circuits,
L 1 is used to designate the hot lead and Nor L 2 the neutral.
L1
N (L?)
'120 v」二
J(
GVEOHU
nHAU
/,
。引／
口
m阳
M／
Appliance/
disconnect
switch
(closed)
/
/
/
Ag
vh
C
j
/
Ground
/
Figure 2-10 Connect meter from each wire to ground
The lead which shows a 120 V AC reading to ground is the hot wire
and is usually black.
3. Check the operation of the disconnect switch at this time to ensure it
will turn off the power on the hot lead. After you have disconnected it
(turned 让 to the offposition), you must check the hot lead to ground.
There should now be a 0 V AC reading (Figure 2-11).
68
Gas Technician 2 Training - Module 12
© Canadian Standards As四ciation
CONTROL CIRCUITS
UNIT 2
L1
一-I
N (L2)
120 v
Appliance －扩
disconnect I
switch
(open)
Figure 2-11 Checking hot lead to ground
Note that on line voltage circuits, the switches should be placed in series
before the load.
Phasing
Matching the polarity of the prim盯y and secondary sides of a transformer,
phasing, becomes important only when the secondary side of the stepdown transformer must be grounded. For example, you must ensure proper
grounding and phasing when the transformer is connected to certain types
of control modules that 山e a flame sensor circuit operating with flame
rectification. Some of Honeywell’s interinittent pilot, direct spark, and hot
surface ignition modules have one of the transformer terminals grounded.
Checking the phasing
You need a voltmeter to check the phasing of a transformer. Use the
following procedure.
1. Check which lead in the junction box is hot (L1) and connect it to 由e
black lead of the trans岛rmer. Connect 也e neutral lead (L2) in 缸
junction box to the white lead of the transformer.
2. Now connect one side of the transformer secondary to ground. Check
由e voltage between the hot and the ungrounded side of the secondary..
If the primary and secondary are in phase, the reading should be 96 V.
3. If the reading is 144 飞 the primary and secondary are not in phase.
move 也e ground to 由e other terminal of the secondary and now the
reading between L1 and the ungrounded side of the secondary will read
96
v.
4.αice
the primary and secondary sides of the transformer are placed in
phase, the hot and ~ounded side of the secon也可 can be connected to
the appropriate terminals on the control module.
Gas Technician 2 Training- Module 12
© Canadian Standards As回ciation
69
TOPI℃ 4
Electrical sequence of
opeγαti on
As a gas technician, you must be able to determine the operating sequence
of gas appliances based on the electrical circuitry provided by the
manufacturer. Since there are many variations on the type of control
systems installed, you will need a solid grounding in reading wiring and
schematic diagrams so that you can easily trace the electrical circuitry of
any system.
Electrical
sequencing
example
The circuit for a simple residential warm-air furnace is shown in Figure 212 (on page 71) and will be used to explain how to read an electrical
sequence of operation. (Note that control systems for large input appliances
will have a more complex sequence with more interlocks, safeties, etc.)
The wiring diagram on the right shows the electrical connections between
the switches and loads. The schematic diagram (ladder diagram) on the left
is laid out in order to follow the electrical sequence of operation.
Switches and loads
Switches connected to loads are normally located on the hot line-never in
the neutral line. (Occasionally manufacturers will wire in a switch or load
in the neutral line, in which case they provide a wiring diagram showing
this arrangement.) Table 2-2 shows the switches and loads in Figure 2-12.
Gas Technician 2 Training - Module 12
© Canadian Standards Association
71
CONTROL CIRCUITS
UNIT2
r一阳
…－
Table 2-2 Switches and loads in each circuit
v
α
一．
一M
－
四日 N －v
m
wmω －
山
αυ
Switches and loads
Appliance disconnect (NC)-not shown
• Door switch (NC)
• Induced blower motor (120V)
• Circulating air blower motor
(120V)
Furnace relay contacts (NO)
• Combination fan (NO) and limit
control (NC) switch
Transformer circuit-120/24V
Transformer 120/24V
Control circuit-24V
• Thermostat (NO)
• Flame rollout switch (NC)
• Vent safety switch (NC)
• Air proving switch (NO)
• Control module
Furnace relay
Igniter sensor
• Pilot valve
• Redundant gas valve
Reading down in Figure 2-12, from left (H) to right 仆。， the circuit would
respond in the following manner:
1.
w挝h the door switch and the limit switch in the closed position the 120/
24V transformer is powered.
2. Thermostat calls for heat and the thermostat switch closes. This powers
the furnace relay which in tum closes the furnace relay contacts which
in turn powers the induced blower motor.
3. Air proving switch closes
4. The powering of the induced blower will cause the air proving switch
to close. This powers the control module as the flame rollout switch
and vent switch are normally closed.
5. The control module performs safe start check (not shown). (Note that
the internal circui位y of control modules differ with each model and
勾rpe. The control module sequence as indicated here represents a
typical example.)
72
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
CONTROL CIRCUITS
UNIT2
6. If safe start is indicated, the igniter and pilot valve are powered
simultaneously. The pilot is proven through the flame sensor.
7. If pilot is proven, the main valve is powered and the igniter is 命，
energized.
8. At this point the main burner is firing.
9. As the temperature rises to the fan control setpoint, the fan control
switch will close energizing the circulating blower motor (fan).
10. The burner will continue to fire until the thermostat is satisfied.
11. The circulating blower motor will continue to operate after the
thermostat opens, until the temperature drops below the fan control
switch setpoint differential.
Note that the appliance disconnect (NC) is not shown
N
H
Turb。 blower
Furnace relay-1
Circulating air
blower 何回＇tor
，－、
EOE
C
＠＠』。
E王宝
LN
@
2E
au－
m国
w
su－
m田
~t
Red
B阳ck
Blue
N。te: Imp。rtant. 『 any of
the 。riginal wire as suppl帽d
mu剖 be replaced, the
用p阳出m回t wire mu刨出。f
伽e same type and size of its
equivalent.
Figure 2-12 Schematic and wiring diagrams for a residential foii四d warrr问ir 仙mace
Gas Technician 2 Training- Module 12
© Canadian Standards Association
73
CONTROL CIRCUl1 s
UNIT2
’
Assignment 2
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
What two diagrams are used to determine the specific sequence of operation?
2.
A map of an electrical circuit is called a
3.
轨电at
4.
A shematic diagram is also known as a
5.
What are the most common auxiliary devices found in control systems?
6.
What device would be used if sequenced control was desired for several pieces of equipment?
7.
Name two types of overcurrent protection devices.
8.
What does polarization in an AC circuit refer to?
9.
Matching the polarity of the primary and secondary sides of a transformer is
called
two things does a schematic diagram show?
Gas Technician 2 Training - Module 12
Canadian Standards Association
©
75
CONTROL CIRCUITS
UNIT2
10. If a dot is shown where wires cross on a wiring diagram, it means
76
Gas Technician 2 Training - Module 12
© Canadian Standards Association
Unit 3
Servicing and troubleshooting
circuits and components
Purpose
Servicing and maintaining gas equipment is part of a gas technician ’s
regular duties. Isolating problem areas, replacing components and
troubleshooting control problems is a learned skill that comes with
experience. An understanding of servicing and troubleshooting
procedures will help achieve this objective.
Learning
objectives
1. Describe the servicing of controls and components.
2. Describe troubleshooting procedures of control systems.
3. Describe the testing and troubleshooting of ignition control modules.
4. Describe the recalibration and the replacing of components.
Gas Technician 2 Training - Module 12
©Canadian S恒ndards Association
77
Topics
1. Servicing
2.
c。 ntrols
and
comp。nents .................................... 79
Troublesho。ting c。ntrol
system problems ..….................... 81
Troubleshooting procedure. …………………..............……………................ 81
Typi明l electrical checks and readings ...............…......….......……......….... 83
3. Testing and troublesh。。ting intermittent pilot igniti。n
contr。i m。dules ........……......................................….............. 87
Prelimina『y checks. …………................…·….........….......……………..........87
System troubtesh。。ting ........…......................…….........…........…............87
Component checks ............................….........................……·······….............88
4. Testing and
m。dules
tr。ublesho。ting
direct spark ignition
c。ntrol
.................…..............................”.........….................. 93
Preliminary checks .........................................................…................…........93
System troubleshooting .......................…........…...........…..........................94
Component checks ....................………················…………......…........……......94
5. Testing and
m。dules
troublesh。。ting h。t
surface
igniti。n c。ntrol
.................….................................................….......... 99
Preliminary checks ........…·········…............... :................................…..............99
System troubleshooting ........…·……......................….........…..........…......... 100
Component checks ........……........………··…............................................. 100
6. Recalibrating and replacing c。mp。nents .......................... 105
Rea吗ustment and recalibration .........…………........................….......…........ 105
Replacement. …..........................................…·························‘’……............. 105
Assignment 3 .............…...............…........................................... 107
78
Gas Technician 2 Training - Module 12
© Canadian Standards Association
TOPIC 1
Servicing controls and
components
In the field of equipment servicing, many appliance malfunctions are due
to dirt and debris accumulated 齿。m lack of maintenance. On service calls,
before adjusting, repairing or replacing components, complete the
following checks.
1. Electrical contacts may be corroded, causing them to not close a circuit
properly. Clean electrical contacts with a hard surface, non-oily paper.
2. Primary air openings may be blocked by lint or other material. Clean
dirty primary air ports.
3. Dirty furnace filters may cause the furnace to cycle on the limit control,
giving the appearance of a short-cycling thermostat. Replace dirty
furnace filters.
4. Failure of an ignition system may be due to dirty or partially blocked
orifice. Blow out or replace pilot orifice.
5. Low heat input may be due to di此y or partially blocked orifice. Clean
burner ort斤ces with a toothpick never with a piece of wire.
6. Dirt on the seat or pivot point in the valve may cause a valve to remain
partially open.
7. Appliance input r剖e needs adjustment. Readjust to nameplate value by:
changing manifold pressure,
adjusting gas regulator, or
putting in new orifice spuds if greater change is required.
8. Flush water heater or boiler to remove sediment from the tank bottom.
9. Make sure vents are clear and working properly.
Gas Technician 2 Training - Module 12
© Canadian Standards Association
79
TOPIC
2
Tγoubleshooting contγol
system problems
Troubleshooting control systems requires special tools and instruments
(electrical meters, flue gas analysers, manometers） .ηie proper use of these
tools and instruments is directly related to the proper diagnosis as well as
minimizing the time necessary for the repair or replacement.
Troubleshooting
procedure
In any troubleshooting situation, it is necessary to consider the entire
system-including not only the burner, controls, wiring, etc., but also air
supp队 fuel supply, and the condition and characteristics of the flame itself.
In order to cover all areas of burner operation, the trouble-shooting
procedure is broken down into a series of specific steps.
Step 1-Know the system
In other words,”Do yo町 homework. ” Study the manufactur，町、 technical
manuals. Know how the systems works.
Keep up with the latest service bulletins. Read them and then file them in a
handy place. The problem on your appliance may be in this month ’s
bulletin, giving 由e cause and remedy.
Step 2-Ask questions
Usually，也e
information available on 缸rival at the installation consists of a
simple statement such as ”The burner shuts down." Start by asking all the
questions possible of anyone 由at might have some knowledge of what
happened. For example:
•
When does the shutdown occur?
What part of the cycle?
•
How long after the s阳riup?
Does a shutdown occur after every s阳rt?
•
Howis 也e
Gas Technician 2 Training - Module 12
© Canadian Standards A”。c阳tion
light-off?
81
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT3
These are only sample questions－一the information needed will depend on
the individual situation.
Step 3-Evaluate your information
Use the supplied manufacturer ’ s manuals, charts, service suggestions,
together with your personal experience, to evaluate any information you
have concerning the problem.
The conclusions drawn at this stage only provide an idea of where to look
for the exact solution to the problem.
Step 4-Make a trial run
Cycle the burner system and observe.
Was each step of the startup according to the design sequence?
•
Did any deviations occur?
Did the shutdown occur exactly as described?
•
Did anything else happen?
•
Have any new facts been established?
While you perform the trial run, make a note of any new information.
StepιRe-evaluate
η1e
re-evaluation of available facts can often be made during the trial run.
Look over your list of possible causes and decide which are most likely and
which are easiest to veri命．
Remember that in some instances, more than one factor may be
con位ibuting to the problem and must be considered in the solution.
Reach your decision on the leading causes and plan to check them first.
Step 6-Test your conclusions
After determining the apparent cause(s) of appliance problem, perform a
second test run to see if the evaluation is correct. If the answer has not been
found, a new evaluation must be made that includes any new information
由at has been obtained during the second test run. More than one reevaluation test may be necessary to get all the information needed to
positively identi龟r the cause(s) of the problem.
82
Gas Technician 2 Training - Module 12
© Canadian Standards Association
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT3
Step 7-Correct the condition(s)
At this stage, you would be confident in adjusting or replacing the faulty
pa此（s). (Note that not all parts can be a司justed in the field-check with the
manufactur町、 manual.) Do a final run through to check 由at the problem
has been solved.
Typical
electrical
checks and
read~ngs
Performing a thorough electrical check on the system allows you to
pinpoint whether the fault is electrical or mechanical. Mechanical failures
include bent, damaged or seized components such as shafts, rods,
operators, etc.
The following procedures show how to conduct common electrical tests in
order to isolate a problem. 。吨。，te that this circuitry is only one of many you
will encounter.)
Figure 3-1 shows the fan, transformer and control circuit for a forced warm
air furnace. Each of the components has a letter designation for the wiring
connections. A grounded terminal is also provided for testing pu叩oses.
什
N (L2)
L,1
120 V
Junction
box
-1=
•
A
」寸二
G
i
五二
”
Figure 3-1 Fan circuit, transformer circuit and control circuit for forced warm-air furnace
Gas Technician 2 Training - Module 12
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SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT3
Problem ’1-No 120V power supply
1. Check for source voltage by testing A to Band A to G. It should be 120
volts.
2. If the switch is in closed (on) position and there is no voltage reading,
check whether the disconnect switch is closed. If it is closed ( o时，
check voltage S to G If you get a 0 reading, check whether the branch
circuit breaker at the main electrical panel has tripped.
3. If you obtain a 120 volt reading and switch contacts have failed to
close, replace the switch.
Problem 2-Fan motor fails to run
1. Check for source voltage in the junction box. Place a voltmeter across
A to B to see if 120 volts are present.
2. If you obtain a 120 volt reading in the junction box, check the voltage
across fan switch C-D. If the main burner is operating and the heat
exchanger is above the fan-on set point, the fan switch should be closed
(on) and the voltmeter should read 0 volts.
3. If the fan switch contacts are open and the voltmeter reads
120 volts, replace the switch.
4. Check the voltage at motor terminal E-G This should read
120 volts to indicate there is power to terminal E.
5. Check E to F. It will read 120 volts whether or not 由e motor windings
缸e good.
6. To check the condition of the motor windings, disconnect the wiring
from E and reset 由e meter scale to read ohms. Place the meter leads
across the motor terminals and watch the mete旦 If the ohms scale
moves to infinity, the windings are burnt out.
If the reading is 0 ohms, the motor windings have a dead short to
ground. A normal winding would display several ohms of resistance
produced by the la电e amount of wiring 坦白e motor winding.
Note
A voltmeter will display the same 120 volt reading across a properly
operating motor winding and one that is burned out.
84
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SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT 3
Problem 3-Transformer seconda 叩
powered
not
1. Check for source voltage in the junction box between the wire
connections A to B. If no power is available, refer to 由e
troubleshooting procedure in Problem I.
2. If you obtain a 120 volt reading in the junction box, check the voltage
across high limit terminals H-I. A reading of 120 volts indicates the
switch is open. The switch is faulty and should be replaced.
3. Check the voltage drop between L-Gηiis will indicate 120 volts if
power is present at terminal L.
4. Check J-L. It will read 120 volts whether or not the transformer coil is
in good working order.
5. To check the condition of the transformer windings, disconnect the
wiring from L and reset the meter scale to read ohms. Place the meter
leads across terminals J-L and watch the meter. If the ohms scale moves
to infinity, the coil winding is broken.
If the reading is 0 ohms, the transformer coil has a direct short.
Replace the transformer in either case.
If the coil is all right, several ohms of resistance will register.
6. Place the meter leads across terminals K-M and watch the meter. If the
ohms scale moves to infinity, the secondary winding is broken.
”
If the reading is 0 ohms，也e transformer coil has a direct short.
If the coil is all right, several ohms of resistance will register.
Note
A voltmeter indicates the same reading across normally operating
transformer windings regardless ofwhether or not the windings are
good. You must use the ohmmeter to determine the condition of the
winding.
Problem 4-Main burner fails to operate
1. Check the source voltage at terminals K-M on the secondary side of the
transformer. It should show 24 volts. If no voltage reading is obtained,
refer to 也e troubleshooting procedure in Problem 3.
2. Check the voltage across P-Q of 由e 也ermostat. On a call for heat, the
thermostat contacts 缸e closed and the meter reading should be 0 volts.
3. If the contacts have failed to close or the heat anticipator is burnt out,
the reading will be 24 volts. ＆叩lace 也etherm。“at.
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4. If the thermostat is all right, take a voltage reading across terminals N0 of the gas valve. It will read 24 volts, whether or not the valve coil is
still in good working order.
5. To check the condition of the valve coil, disconnect the wiring from N
and reset the meter scale to read ohms. Place the meter leads across
terminals N-0 and watch the meter. If the ohms scale moves to infinity,
the coil is burnt out.
If the reading is 0 ohms, the coil has a direct short.
If the coil is all right, several ohms of resistance will register.
86
Training - Module 12
Standards Association
GasTechniαan 2
。 Canadian
TOPIC
3
Testing and troubleshooting
inteγmittent pilot ignition
control modules
The following testing and troubleshooting procedures provide a general
method for testing intermittent pilot systems. For the pu叩ose of this
explanation, the Honeywell S86 control module will be used. (Although the
procedure for testing control modules follows a similar sequence as
outlined below, use the instructions and guides specific to the make and
model of the control module you are testing and troubleshooting.)
To service and troubleshoot efficiently, break the procedure into three
steps:
preliminary checks
•
system troubleshooting
component checks.
Preliminary
checks
The following preliminary checks should be done before troubleshooting
the intermittent pilot system:
1. Check the disconnect switch and fuse to the S86 control system.
2. Check that the manual shutoff valve in the gas line to the appliance is
open.
3. Ensure all wiring connections are clean and tight.
4. Check that the module is not in sa岛ty lockout. If it is in lockout, follow
the procedure described below under the heading: Reset system q斤er
lockout.
System
troubleshooting
Troubleshooting the system can be performed as follows:
1. Start the system by
temperature.
se忧ing 也e
temperature controller above room
2. Observe the system response.
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3. Establish the type of system malfunction or deviation from normal
operation by using manufacturer ‘ s sequence of operation or
troubleshooting charts.
4. Continue checking until a solution, or how to make the repair, is fully
clear to you.
Component
checks
There are several component checks 出at can be performed when using the
Honeywell 886 intermittent pilot control module in a control system.
These are:
reset system after lockout
•
check sp缸k ignition circuit
check spark igniter
check grounding
check flame sensor circuit.
Reset system after lockout
If a system with an 886 C, D, G, or H control module goes into safety
lockout (other 886 modules do not offer this featu时， reset 由e module
before attempting further operation or checkout. The system will remain in
safety lockout until it is reset.
1. Shut off the system by a司JUStmg 由e thermostat below room
temperature or a句usting the controller to Off, or disconnecting
electrical power.
2. Wait at least one minute, then tum the system on.
Check spark ignition circuit
The electronic module and step-up transformer h 由e 886 provides spark
ignition at 15 000 volts (open circuit). This circuit can be checked at the
886 module as follows:
1. Tum off the manual gas valve to prevent the flow of gas.
2. Disconnect the ignition cable at 由e 886 stud terminal to isola臼 the
circuit 丘。m the pilot burner/igniter-sensor.
3. Prepare a short jumper lead using heavily insulated wire, such as
ignition cable (Figure 3-2).
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SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT 3
A
Caution!
Do not touch any bare wires or terminals. This is a veηy high voltage circuit and electrical shock can result卢om improper handling of the cables.
4. Energize the S86 while touching one end of the jumper firmly to 血e
S86 ground terminal(GND).
。
Jumper
lead
Ignition
cable stud
Figure 3-2 Checking spark ignition circuit on intermittent pilot control
module
5. Do not disconnect the existing ground lead.
6. Move the free end slowly toward the stud terminal to establish a spark.
7.
Pull 也e jumper
lead slowly away from the stud.
8. Note the leng由 of the gap at which arcing stops. An arc leng曲 of 1/8
inch (3.2 mm) or more indicates satisfactory voltage output.
9. Replace the S86 if no 町c can· be established or the maximum gap is less
than 1/8 in. (3.2 mm), and the fuse and power to the S86 input terminal
were all right.
Check spark igniter
If 也e
troubleshooting procedure indicates a problem wi白白e ignitersensor, check the spark igniter and the ignition cable connections as
follows:
Check igniter-sensor
1. Check the igniter spark-gap to make certain it is correct: 1/8 inches {3.2
mm).
2. If necessary, use needlenose pliers and carefully bend the tip of the
outer electrode to 也e coη·ectpos让ion.
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3. Check that the pilot flame is properly adjusted to cover 3/8 to 112
inches (9.5 to 12.7 mm) of the tip of the igniter sensor.
Check ignition cable
1. The ignition cable must not touch metal surf如es or current-carrying
wires.
2. Use ceramic standoff insulators, if necessary.
3. Check the length of the ignition cable, which must not exceed 3 ft (0.9
m).
4. Check that connections to the igniter and control module stud are clean
and tight. (Loose connections may not conduct a flame current even
也ough the ignition spark is satisfactory.)
5. Check the electrical continuity of the cable.
6. Replace the cable if it is damaged or has deteriorated.
If the spark ignition circuity check was all right, yet no spark or a weak
spark occurs follow this procedure.
1. Disconnect the ignition cable at the igniter (or igniter-sensor).
2. Measure the arc from the cable end to the igniter stud.
A
Cautio.n!
Do not touch either the exposed end of the jumper or the stud terminal.
This is aveηy h电？h voltage circuit and electrical shock can result.
3. If the arc is correct, replace the igniter (or igniter-sensor).
4. If the arc is less than it should be, disconnect the 阳1ition cable and use
a jumper wire from the control module stud terminal.
5. If the spark is all right, replace the ignition cable.
6. If the arc is still less than it should be, replace the control module.
Check grounding
A common ground is required for the pilot burner, the igniter-sensor.，也e
GND terminal of the 886, and the main burner. The main burner generally
serves as 也e common ground.
If 也e
ground is poor or erratic, safety shutdowns may occur occasionally
even 曲。鸣h operation is normal at the time of the checkout. Therefore, if
nuisance shutdowns have been reported, be sure to check the grounding
precautions.
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UNIT 3
Note thatifthe ground circuit path is incomplete, the S86 C, D, G, and H
system control will allow one trial-for-ignition before going into safety
lockout.
Electrical ground connections at the pilot burner, igniter-sensor and S86
must be clean and tight. If the lead wire is damaged or deteriorated, use
only No. 14 or 18 gauge, moisture-resistant, thermoplastic insulated wire
with 105 。C (221°F) minimum rating for replacement.
Excessive temperature at the ceramic flame rod insulator can also permit
electrical leakage to ground. Examine the flame rod and mounting bracket,
and coηect if it is bent out of position. Replace the igniter-sensor if the
insulator is cracked.
Check control module flame sensor circuit
The control module provides AC power to the igniter-sensor which the
pilot burner flame rectifies to DC. If the flame signal back to the control
module is not at least 1.5 µA DC，也e system will lock out.
Since 伽 output of the flame sensing circuit cannot be checked directly,
check the flame sensing circuit indirectly by checking the flame sensing
current 企om the igniter-sensor to the control module as follows:
1. Connect a meter (DC microammeter scale) in series with the flame
signal ground wire.
2. Disconnect the ground wire at the control module.
3. Connect the red (positive) lead of the meter to 也e 企ee end of the
ground wire (Figure 3-3).
4.
Connect 由e
black (negative)
meter lead to 也e quick-connect
ground terminal on the control
module.
5. Restart the system and read the
mete汇 The flame sensor current
must be at least 1.5 µA, and the
reading must be steady.
6. If the reading is below 1.5 µA or
ie reading is unsteady, check the 、
pilot flame and electrical
connections as described above.
“
7.
Replace 由e igniter-sensor if the
ceramic insulator is cracked.
Gas Technician 2Training-Module12
©Canadian S恒ndardsAssc比iation
。
Multipurpose meter
ALARM
VALVE
VALVE
GND
IO
I I
Black(-)
Figure 3-3 Measuring flame current
intermittent pilot control module
91
TOPIC 4
Testing and troubleshooting
diγ~ctspαγk ignition contγol
modules
The following provides a general method for testing direct spark ignition
systems (DSI). For the pu叩ose of this explanation，也e Honeywell S87
control module will be used. (Although the procedure for testing control
modules follows a similar sequence as outlined below, use the instructions
and guides specific to the make and model of the control module you 町e
testing and troubleshooting.)
In order to service and troubleshoot efficiently, break the procedure into
three steps:
•
preliminary checks
•
system troubleshooting
component checks.
Preliminary
checks
The following preliminary checks should be done before troubleshooting
the direct spark ignition system.
1. Check the power to the appliance and control module.
2. Check the 缸se on the control module and replace if necessary.
3.
Check 出at 由e manual
shutoff valve h 由e gas line to the appliance and
the automatic gas valve are open.
4. Make sure all wiring connections are clean and tight.
5. Check that the module is not in safety lockout. If it is in lockout, follow
the procedure desc出ed below under the heading ” Reset system after
lockout. ”
6. Check the ceramic insulator on the flame sensor and spark igniter, or on
the igniter-sensor. A cracked insulator will allow current to leak to
ground.
7. Check the flame sensor and its mounting bracket. Correct its position if
it is bent out of shape.
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© Canadian Standards Association
12
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UNIT3
System
troubl臼hooting Troubleshoot the system as follows:
1. Start the system by setting the temperature controller above room
temperature.
2. Observe the system response.
3. Establish the type of system malfunction or deviation from normal
operation by using the manufacturer ’s sequence of operation or a
troubleshooting table provided by the manufacturer.
4. Follow the questions supplied by the manufacturer ’s troubleshooting
chart.
5. Continue checking until a solution, or how to make the rep缸瓦 is fully
clear to you.
Component
checks
There are several component checks that can be per岛rmed when using the
Honeywell 887 direct spark ignition module in a control system. These are:
reset system after lockout
check spark ignition circuit
•
check spark igniter
check grounding
check flame sensor circuit.
Reset system after lockout
If a system with an S87 control module goes into safety lockout.，由e
module must be reset be岛re attempting further operation or checkout. The
system will remain in safety lockout until it is reset.
1. Shut off the system by adjusting 也e thermostat below room
temperature or adjusting the con:位oller to Q在 or disconnecting
electrical powe旦
2. Wait at least 30 seconds, then 阳m 由e system on.
Check spark ignition circuit
咀1e electronic module and step-up tr缸tsformer in the 887 provides spark
i伊拉ion 剖 30 000 volts (open circuit). This circuit can be checked at 伽
S87 module as follows:
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SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT3
1. Tum off the manual gas valve to prevent the flow of gas.
2. Disconnect the ignition cable at 由e S87 stud terminal to isolate the
circuit from the igniter or igniter/sensor.
3. Prepare a short jumper lead using heavily insulated wire, such as
ignition cable (Figure 3-4).
4. Energize the S87 while touching one end of the jumper firmly to the
ground terminal (GND).
A
Caution!
Do not touch any bare wires or terminals. This is a very high voltage circuit and electrical shock can result.
5. Do not disconnect the existing ground lead.
6. Move the free end slowly toward the stud terminal to establish a spark.
7. Pull the jumper lead slowly away from 也e stud.
8. Note the length of the g.ap at which arcing stops. An arc length of 1/8
inch (3.2 mm) or more indicates satisfactory voltage output.
9. Replace the S87 if no arc can be established or the maximum gap is less
than 1/8 inch (3.2 mm), and the power to 由e S87 input terminal was all
right.
Ignition
cable stud
Figure 3-4 Checking spark ignition circuit on direct spark ign忧ion co巾。l module
Check spark igniter
If the troubleshooting procedure indicates a problem with the spark igniter,
check the spark igniter and the ignition cable connections, as 岛Hows.
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SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
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Check igniter
1. Make sure that the spark igniter is positioned so that the ground
electrode portion of the igniter is not blocking the gas flow.
2. Check the igniter spark-gap to make certain it is correct, 5/32 to 3/16
inch (4-5 mm).
3. If necessary, use needlenose pliers and carefully bend the tip of the
outer electrode to its correct position.
4. Immerse only the tips of the electrodes in the burner flame. Spacing
between tip assembly and burner head is generally 114 to 1/2 inch (613 mm).
5. Check for bent mounting bracket.
Check ignition cable
1. The ignition cable must not touch metal surfaces or current-carrying
wires.
2. Use ceramic standoff insulators, if necessary.
3. Check the length of the ignition cable. It must not exceed 3 ft
(0.9 m).
4. Check that connections to the igniter and control module stud are clean
and tight. Loose connections may not conduct a flame current even
though the ignition spark is satisfactory. Check the electrical continuity
of the cable.
5. Replace the cable if it is damaged or deteriorated.
If the spark ignition circuity check was all right, yet no spark or a weak
spark occurs 如llow this procedure:
1. Disconnect the ignition cable at the igniter (or igniter-sensor).
2.
A
Measure 由e arc 仕om
the cable end to the igniter stud.
Caution!
Do not touch either the exposed end of the jumper or stud terminal. This is
a very high voltage circuit and electrical shock can result.
1. If the arc is correct, replace the igniter (or igniter-sensor).
2. If the arc is less than it should be, disconnect the ig.nition cable and use
a jumper wire from the control module stud terminal.
3. If the spark is all right, replace the ignition cable.
4. If the arc is still less than it should be, replace the control module.
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UNIT3
Check grounding
For a DSI system to operate properly, the spark igniter, flame sensor,
control module, and L2 side of the transformer must all share a common
ground with the main burner. The S87 will internally ground one side of the
transformer. Any auxiliary controls or limits must not be in the grounded
leg.
Connect the ground wire as 岛Bows, using thermoplastic insulated wire
rated for 105。c (221 。F)minimum.
1. Fit one end of 由e ground wire with afemale 1/4 inch (6 mm) quickconnect.
2. Connect it to the male quick” connect at the GND terminal on the
control module.
3. Strip the other end of the ground wire and scrape it to remove any
coating.
4. Fasten it under the igniter mounting screw.
5. Use a shield to protect the ground wire from radiant heat, where
necessary.
6. The burner serves as a common grounding 盯ea.
If there is not a good metal白to-metal contact, run a lead from the
burner to ground.
7. If the flame sensor is mounted on a separate bracket, make certain 由at
there is good metal-to-metal contact with the main burner.
If there is not a good metal-to-metal contact with the main
burner, run a lead wire from 也e sensor to 也e same ground you
chose for 也e spark igniter.
Check control module flame sensor circuit
The control module provides AC power to 由e igniter-sensor which the
pilot burner flame rectifies to DC. If the flame signal back to the control
module is not at least 1.5 µA DC，也e sys臼m will lockout.
Since the output of the flame sensing circuit cannot be checked direct.机
check the flame sensing circuit indirectly by checking the flame sensing
current 企'Om the flame sensor to 也e control module as follows:
1. Connect a meter (DC microammeter scale) in series with the flame
signal ground wire.
2. Disconnect the ground wire at the control module.
Gas Technician 2 Training －阳lodule
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12
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SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT3
3. Connect the red (positive) lead of the meter to the free end of the
ground wire (Figure 3-5).
4. Connect the black (negative) meter lead to the quick-connect ground
terminal on the control module.
5. Restart the system and read the meter. The flame sensor cuηentmust be
at least 1.5 µA, and the reading must be steady.
6. If the reading is below 1.5 µA or the reading is unsteady, check the
pilot flame and electrical connections as previously described.
7. Replace the igniter-sensor if the ceramic insulator is cracked.
。
ALARM
VALVE
VALVE
GND
Black(-)
Figure 3-5
98
flame current on direct spark ignition
control module
Measu 川 ng
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
TOPIC
5
Testing α~nd troubleshooting
hot surfiαce ignition control
mo出'lies
Hotsu币1ce ignit归n
systems are used in a wide variety of central heating
equipment and on appliances found in agricultural equipment, industrial
heating equipment and pool heaters. For the purpose of this explanation,
the Honeywell S89 and S890 control modules will be used. (Although the
procedure for testing control modules follows a similar sequence as
outlined below, use the instructions and guides specific to the make and
model of the control module you are testing and troubleshooting.)
In order to service and troubleshoot efficiently, break the proced田e into
three steps:
•
preliminary checks
system troubleshooting
component checks.
Preliminary
checks
The following preliminary checks should be done before troubleshooting
the hot surface ignition system.
1. Check disconnect switch and fuse to the 889 or 8890 control system.
2. Check that the manual shutoff valve in 白e gas line to the appliance is
open.
3. Ensure all wiring connections are clean and tight.
4. Check that the module is not in safety lockout. If it is in lockout, follow
由e proced旧es described· below under the heading ”Reset system after
lockout. ’’
}
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。 Canadian Standards As斟x:iation
99
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
System
troubleshooting
UNIT3
Troubleshooting the system can be performed as shown below.
1. Start the system by setting the temperature controller above room
temperature.
2. Observe the system response.
3. Establish the type of system malfunction or deviation from normal
operation by using the manufacturer ’ s sequence of operation or
troubleshooting chart.
4. Continue checking until a solution, or how to make the repair, is fully
clear to you.
Component
checks
There are several component checks that can be performed when using the
Honeywell 889 or S890 hot surface ignition module in a control system.
These are:
reset system after lockout
•
check ignition system
check grounding
check flame sensor.
Reset system after lockout
η1e
889 and S890 provide 100% shutoff or safety lockout on ignition
failure, or on loss of established flame.
Module operation is in four phases: prep~e (for the S890 onl~）， igniter
warmup，位ial for ignition and burner operation. Modules offer either one or
也ree trials for ignition.
•
C, D and J models of the 889 and 8890 lock out after one trial-for1gn1tion.
•
G and H models lock out after 伽ee 创als-for-ignition.
One trial-for-ignition module
If no flame is sensed by the end of the timed trial－岛r-ignition，也e gas
control closes and the module locks out. It must be manually reset by
removing power or setting the thermostat below room temperature for at
least 45 seconds.
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If the burner lights normally but goes out during the run cycle, the gas
control closes and the module initiates a warmup period followed by one
trial for ignition. (30 second prepurge on 8890 models when used with
fan-assist blower), followed by one trial-for-ignition. If flame is not
established, the gas control closes and the module locks out, requiring
manual reset.
Three trial-for-ignition modules
If no flame is sensed by the end of the first timed trial-for-ignition, the gas
control closes and the module initiates a second 30 second minimum purge
cycle (8890 models only), followed by igniter wannup and a second trialfor-ignition.
If flame is not established, the purge, warmup, and trial-for-ignition cycle
is repeated a third time. If flame is still not established 岛llowing the third
trial, the gas control closes and the module locks out. It must be manually
reset by removing power or setting the thermostat below room temperatur~
for at least 45 seconds.
If the burner goes out during 由e run cycle, the gas control closes and the
module checks for the number of ignition trials performed during the
current call for heat. If the number is less than three, the module initiates a
purge, wannup and trial for ignition. After the third trial during a single call
for heat, the module locks out. The module must be manually reset
following lockout.
Check hot surface ignition system
You must ensure 由at 也e following conditions exist:
•
ignition wire does not touch any metal surface
•
connections to the module and the igniter-sensor are clean and tight
•
ignition wire provides good electrical continuity.
Check system grounding
Nuisance shutdowns are often caused in hot surface ignition systems by a
poor or erratic ground. A common ground is required for 出e module,
igniter, flame sensor and main burner.
咀ie 24 V ~GND) terminal intemall)' grounds one side of the tr扭曲nner.
Any auxiliary controls or limits must not be in the grounded leg. In
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SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
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addition, the appliance should be earth-grounded. Ensure you perform the
following tasks:
1. Check for good metal-to-metal contact between the igniter bracket and
the main burner.
2. Check the ground lead from the GND (burner) terminal on the module
to the igniter bracket.
3. If the wire is damaged or deteriorated, replace it with No. 14 or 18
gauge, moisture-resistant, thermoplastic insulated wire with 105 。c
(221 。F) minimum rating.
4. Use a shield if necessary to protect the ground wire from radiant heat.
5. Check the temperature at the igniter ceramic or flame sensor insulator.
Excessive temperature will permit leakage to ground.
6. Provide shields if temperature exceeds the rating of the igniter or the
sensor.
7. Replace the igniter and 也e sensor or the igniter-sensor with an identical
unit if the insulator is cracked.
Check control module flame sensor circuit
白ie
control module provides AC power to the igniter-sensor which the
pilot burner flame rectifies to DC. If the flame signal back to the control
module is not at least 1.5 µA DC, the system will lockout.
Since the output of the flame sensing circuit cannot be checked directly, so
check the flame sensing circuit indirectly by checking the flame sensing
current 仕om the flame sensor to the control module as follows:
1. Check that L1 (hot) and L2 (neutral) are wired to 由e proper terminals.
(IfL1 and L2 are interchanged, the S89 or 8890 will not detect the
flame, and will go into safe可 shutdown.)
2. Ensure that the burner flame is capable of providing a good
rectification signal. To ensure this, the flame sensor must be placed in
the flame according to the me邵阳ements as shown in Figure 3-6.
卡－
3/4 to 1 inch (19 to 25 mm)
Flame sensor
1/4 t。
1/2
inch (6 to 13 mm)
Figure 3-6 Sensor position for a good r时tifying flame
102
Gas Technician 2 Training - M叫ule 12
。 Canadian Standards Association
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT 3
1. Ensure, for the best flame signal, that about 3/4 to 1 inch of the flame
sensor or igniter-sensor is continuously immersed in the flame.
2. Bend the bracket or flame sensor, or relocate the sensor as necessa可－
3. Do not relocate an igniter or combination igniter” sensor.
4. Check for excessive (over 1000°F [538。C]) temperature at the ceramic
insulator on flame sensor. Excessive temperature can cause short to
ground.
5. Move sensor to cooler location or shield insulator if there is excessive
temperature. Do not relocate an igniter or combination igniter-sensor.
6. Check for a cracked igniter-sensor or sensor ceramic insulator, which
can cause a short to ground, and replace the unit if necessary.
7. Ensure that electrical connections are clean and ti酬．
8. Replace damaged wire with moisture-resistant No. 18 wire, rated for
continuous duty up to 105 。c (221 。F).
9. Visually check that the igniter does not develop an insulating layer on
its surface (over a period of time) which would prevent flame sensing.
Honeywell has approved only two igniters, the Norton 201 and 271,
because 由ey meet the following specifications:
·τbe
igniter reaches
AC being applied.
1000。c (1,832。F)
within 36 seconds with 102 V
It maintains at least 500 megohms of insulation resistance between the
igniter lead wires and the igniter mounting bracket.
•
The igniter current draw at 132 V AC does not exceed 5 A.
Gas Technician 2 Training - Module 12
©Ganadian S臼ndards Associ硝m
103
TOPIC6
Recαlibγαting
and
γeplαcing components
Most controls 町e factory set or set upon installation of appliances
according to manufacturer's instructions. For 由is reason, settings should
not be disturbed unless you have definitely determined 由at the appliance
malfunction is due to an improper se忧ing.
Readjustment
and
recalibration
Some controls may be recalibrated or rea司justed on the owner ’s premises.
Some examples include room thermostats, heat anticipators, oven
thermostats, improperly operating gas valves, spark ignition electrode
gaps, some pilots, and some solid s臼te control elements.
When recalibrating or readjusting controls, always follow manufactur町、
mstruct1ons.
Replacement
Field repair of controls is often not practical. In many cases, it is cheaper
and safer to replace controls than to repair them.η1is depends, of course,
on the nature of the control and the repair required.ηie solenoid may be
replaced on a solenoid valve for instance, but a broken expansion bulb
thermostat could be replaced for less expense than a repair would cost.
Once you have determined 由at a component needs replacing, yo町
decision of which replacement product to choose should be based on 也e
best interests of the customer. Your choices include:
•
to replace the component like-for-like.
simplest solution，也e component may be outdated
and difficult to locate.
Al也OU白白is is 也e
•
to replace with a universal component
advantages of universal components is 也at you can keep a supply
of the most standard ones in yo田 van and you will also become
familiarwi由 their installation and operation，白山 increasing yo町
efficiency on the job.
刀1e
、‘－
Gas Technician 2 Training - Module 12
~Canadian
Standards As缸>ciation
105
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT3
to upgrade the appliance by installing a new control system
This option, although more expensive initially for the customer, may
well save them money in the long run. Moreover, standards continue
to improve and so the homeowner will benefit 仕om current safety
standards as well as cuηent research and manufacturing technology.
When replacing components, review the Code for the Field Approval of
Fuel-Related Components on Appliances and Equipment (CANICGA
B149.3) for the field acceptance of:
ignition systems (e.g., from standing pilot to automatic ignition)
automatic safety
•
shut咱ff valves
pilot-operated safety shut-off valves
miscellaneous requirements.
Ultimately, your selection of replacement component should be based on:
•
pu甲ose
•
sequence of operation
•
mechanical characteristics
•
electrical characteristics (switching actions, amperage ratings)
•
differential settings
•
physical dimensions (mounting characteristics, size)
•
resets (manual or automatic)
•
availability
of operation
To ens田e proper and safe operation of the mechanical equipment it is
necessary that field replacement controls and wiring corrections provide
也e same operation and protection as was originally intended.
1佣
Gas Technician 2 Training - M。du梅 12
。 Canadian Standards As回ciation
UNIT3
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
Assignment 3
矶Then you have completed the following questions, ask your instructor for the
Answer Key.
l.
认Then
troubleshooting gas-fired equipment, is it necessary to look at other systems besides the
burrier and controls? If so, which ones?
2.
List the seven steps to be taken when troubleshooting.
.
.
.
.
.
.
3.
Suppose that upon testing a furnace, the fan motor will not run. The burner is operating, the
heat exchanger temperature is above the fan-on se甲oint and the fan switch contacts are open.
轨That should you do?
4.
Suppose the thermostat is calling for heat and you get a reading of 24 V across the lines.
a) Is it working properly?
b) If it is not working correct坊， what is the next step?
5.
List three controls that can be recalibrated or readjusted in the field.
.
.
.
Gas Technician 2 Training- Module 12
© Canadian Standards Association
107
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
6.
UNIT3
Figure Al is a wiring drawing of a forced warm-air furnace using an intermittent pilot system
(Honeywell S86 control module). An electrical meter is shown with the test leads in a position
to check the voltage in the junction box. Draw lines where you would place the meter test leads
to test each of the following (letter the meters for identification):
a) check power at transformer secondary
b) check power supply voltage to control module
c) check for open thermostat con饵cts
d) check for power to pilot valve
e) check for power to main valve
ηcheck
flame
cuηent
figure A1 Intermittent pilot control module with combination igniter-sensor and
redundant gas valve
108
Gas Technician 2 Training - Module 12
© Canadian Standards Association
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
UNIT 3
7.
Figure A2 is a wiring drawing of a forced warm-air 如mace using a direct spark ignition
system (Honeywell S87 DSI module). An electrical meter is shown with 由e test leads in a
position to check the voltage in the junction box. Draw lines where you would place the meter
test leads to test each of the following (le仗er meters for identification):
a) check power at transformer secondary
b) check power supply to control module
c) check for open thermostat contacts ,
d) check for power to main valve
e) check flame current
因
I
t
I
、
、
喝一一＿
F?ctory installed
wires for second
coil
喝一一一一一 Redundant
囚
gas valve
Combination
ignitersensor
Igniter-sensor
and burner ground
\
Main burner
Figure A2 Direct spark ignition with combination igniter-sensor
Gas Technician 2 Training - Module 12
©Canadian S恼ndards Associa阳、
109
SERVICING AND TROUBLESHOOTING CIRCUITS AND COMPONENTS
8.
UNIT3
Figure A3 is a wiring drawing of a forced warm-air furnace using a hot surface igniter
(Honeywell S89/890 control module) with a combination igniter-sensor. An electrical meter is
shown with the test leads in a position to check the voltage in the junction box. Draw lines
where you would place the meter test leads to test each of the following (letter meters for
identification):
a) check power at transformer secondary
b) check power supply to control module
c) check for open thermostat contacts
d) . check S89 terminals for power to redundant gas valve
e) check S89 terminals for power to the hot surf民e igniter
Redundant gas valve
↓囚
国
Hot
4一－
囚／
surface
igniter-sensor
、－’
。
－、＇－－－－－－ Burner
ground
：囚
L
,
2
0,<·
Figure A3 Hot surface ignition with.combination igniter sensor
110
Gas Technician 2 Training - Module 12
© Canadian Standards Association
Unit4
Motors
Purpose
Electric motors are a common component found on gas』red equipment.
Gas technicians must have a basic knowledge of how they work, as well
as the type of voltage and current on which 由ey operate.
Learning
1.
o均ectives
2. Describe the construction and operation of electric motors.
Inte甲ret
nameplate information.
3. Describe the operation and application of three-phase motors.
4. Describe the operation and application of single-phase motors.
5. Describe
single喃phase
motor startup and overload devices.
6. Identify additional components of AC electric motors.
7. Describe variable speed DC motors.
Gas Technician 2 Training - Module 12
© Canadian Standa『ds A路。ciation
111
Topics
1. Nameplate information .........…............................................刊 3
Typical nameplate information .....…...............................................……. 113
Additional nameplate information .....…·······……·······………….................... 115
2. c。nstructi。n and 。pera ti。n of electric motors ••••••••••••••••• 117
Stator ....................……·····················….......…………···············……..............117
Rotor ..................................................……..........................…..................117
3. Operation and application of three-phase mot。rs •••••••••••• 121
Squirrel 臼ge induction motor ..….....…….........….......….......……................. 121
Wound rotor m。tor .........….........….......…......…................................... 122
Synchronous motor. ................………...........................…….........…........ 122
Three-phase AC circuits ..........................“......................……········…......... 122
4. O~eration and application of single-phase m。tors •••••••••• 125
Split-phase induction motor .......................……………….............................. 125
Resistance-start motor. ................………...........…… …….......................... 126
Capacitor-start motor ...............................…...............................................126
Permanent-split 臼pacitor mot。r ..........................................................….. ,.127
Shaded-p。le inducti。n motor ..……..................................................…......... 128
a
5.
Single-phase m。tor startup and 。verl。ad protection devices
129
Sta此up
devices .................…..........................……..............……................129
External
startup devices ................................…·········…...............….........…............... 131
Over!。ad protection devices ....................................................................... 133
6.
Additi。nal c。mponents 。f AC electric mot。rs •••••••••••••••••• 135
Insulation ...................…·························…........................….......................135
Bea刘ngs….............................................................……·…………............... 135
7. Variable speed DC m。t。rs ...................................……......... -139
DC series motor ..…·································….................…...............…........... 139
DC shunt mot。r ...........................................................................................140
DC compound motor .........….................................…·················…............... 140
s。lid state devices in speed control ...............…......................….......…...... 141
Assignment 4 .......................…................…................................ 143
112
Gas Technician 2 Training - Module 12
©Canadian S恒ndardsAs回ciation
TOPIC
1
Nα·meplate infoγmαti on
Electric motors have nameplates that provide the technician with valuable
information for selecting and installing a motor.
Do not remove or d价ce nameplates
Typical
nameplate
information
Figure 4-1 shows a typical motor nameplate for a single-phase induction
motor. The name plate gives the 岛llowing information:
thermal protection: A large percentage of fractional horsepower motors
are provided wi由 built-in thermal protection. Individual manufacturers
may use their own systems to mark the kinds of protection and the type
of thermal protecto卫
•
、、‘－
type and application indicates a split-phase, fan and blower motor.
Motors fall into a number of different types of classifications as shown
in Table 4-1, which also indicates types of motors and their
applications.
model number as set by the manufacturer
•
horsepower of motor rated as 1/3
再peed
(a卢actional
horsepower motor)
of motor at full-load speed is 1725 rev/min
voltage operates on 115 volts (sometimes two voltage figures are given,
such as 115/230. In this case the motor is intended for use on either a
1l5V or 230V circuit.)
·卢II-load amperage
of5.5 amps.ηiis refers to 由e approximate current
drawn by the motor when developing rated hors叩ower on a circuit of
the voltage and frequency specified on the nameplate.
j步ame
sizes are classified by their diameter. Sizes are used to obtain
世邵阳 dimensions such as the overall leng由 and diameter of the motor,
and distances between mounting bolts. They also indicate shaft Ieng白，
diameter, and height.
.frequency designed to operate on a 60 Hz AC voltage
a single-phase motor
·由e locked rotor k阳 code is a type N sqUirrel cage rotor. (Locked rotor
kVA codes are used to determine the 创nount of locked rotor current:
the amount of current 也e motor will draw at the moment of starting.)
Gas Technician 2 Training - Module 12
C Canadian Standa『ds Association
113
MOTORS
UNIT4
•
B class of insulation (the class of insulation is related to the ambient
temperature of the running motor) maximum ambient temperature of
40。C in which the motor is capable of operating
continuous duty designation means it can run continuously without
needing to be cooled down such as an intermittently rated motor would
require
service factor of 1.35. The service factor is used to determine the
amperage rating of the overload protection for the motor.
bearings for fractional and subfractional horsepower motors normally
use sleeve bearings or ball bearings
motor r笔舟rence is part of the manufacturer ’ s identification of the
electrical and mechanical features of the motor
date code indicates when the motor was manufactured
囹咐法~~crroC主〉
SPLIT-PHASE
FAN&BLOWER
MOTOR
CONNECTIONS
R骂正主
nu明
Z』
E「』
脏如
阳π
刊盹
E』HU
T’M川
M问niM
nUFF 11
UOPnnuqH
T UH
-
民ELUBRICATE
WITH 3日 DROPS
SAE 20 NON-DETERGENT OIL
ONCE A YEAR
ABC MFG CO .. Vancouver . B.C.
WARNING:
GROUNDING-FA！凶RE TO CONNECT THE MOTOR FRAME TO
EQUIPMENT GROUNDING CON口υCTOR BY USING THE GROUNDING CORO. GREEN SCREW
OR GREEN WIRE PROVIDED. MAY RESULT IN SE阳OUS ELECTRICAL SHOCK.
THERMALLY PROTECTE口 AUτOMATIC RESET-MOTOR WILL RESTART WIT树OUTWARNJ”G
AFTER PROTECT•口R TRIPS. DO NOT INSTALL THIS MOTOR ON EQUIPMENT WHERE
AUTOMATIC sτ:ART UP COULD RESULT IN INJURY. ALWAYS DISCONNECT MOT口R FROM
POWER SUPPLY BEFORE WORKING ON EQUIPMENT.
Figure 4-1τypical motor nameplate
Table 4-1 shows the various motors used for specific applications.ηiis
姐.ble is a guide only. The manufacturer ’s manuals and instructions should
always be consulted before choosing or installing a motor.
114
Gas TE提出nician 2 Training - Module 12
©Canadian S幅ndards Association
MOTORS
UNIT 4
Table 4-1 Applications and types of motors
Application
Shaft-mounted fans and
blowers
Types of motors
Single-phase
Split-phase
Permanent-split capacitor
Shaded pole
Belted fans and blowers
Three-phase squirrel-cage
induction
Single-phase capacitor-start
Split-phase
Split-phase 饵pacitor
Air-conditi。ning c。ndensers
motors
Shaded pole
and e> aporator fans
Permanent-split capacitor
Split-phase
Domestic oil burners
＼、－
Additional
nameplate
information
Comments
Either totally enclosed or open;
designed for propeller fans or
centrifugal blowers mounted on
the motor with or without air
drawn over the motors.
Generally not suitable for belted
loads because not enough
locked-rotor torque is available
for this purpose
Intended for operating be协
driven fans or blowers that are
commonly used in conjunction
with heating and air-conditioning
installations
Very few shaded pole motors
are used today
Mot。r operates mechanicaldraft oil burners for domestic
applications
A variety of additional information may appear on the nameplate. This may
include instructions for connecting the motor to a source of supply,
reversing the direction of rotation, lubricatµig the motor, or operating it
safely.
、、‘－－
Gas Technician 2 Training - Module 12
© Canadian Standards Association
115
MOTORS
UNIT4
As the rotor turns, the bars swing across magnetic fields created by the
stator poles and current is induced in them (Figure 4-3).
r
ρuv
•
「「
Figure 4-4 shows how the current in
each copper rod of the rotor sets up
a magnetic field around the wire
which interacts with the magnetic
field caused by the stator poles. The
direction of current flow in the
conductor is indicated by:
a cross sign (x) for current away
from you (or the tail feathers of
an aηow)
<
U niu
ATill
-
a dot ( •) for current towards you Figure 4-3 Current-carrying conduct。r
(the head of an arrow).
in magnetic 币eld
Flux aiound
conduct。r
Moti。n upcurrent away from you
Field flux
M。tion downcurrent t。＇ward y。u
Figure 4-4 Current-carrying conductor in magnetic field).
118
Gas Technician 2 Training- Module 12
© Canadian Standards Association
MOTORS
UNIT4
The magnetic lines of force set up by the current in the conductor will be in
opposite directions above and below the conductor. This magnetic field
interacts with the magnetic field of the stator poles. Since “ like” magnetic
lines repel each other, and “ unlike” fields attract each other, the rotor starts
to turn inside the stator.
Figure 4-5 shows the forces produced by opposite currents in bars on both
sides of the rotor, causing the torque that makes the rotor spin.
Rotar bar
s
N
Rotar bar
Figure 4-5 Interacting magnetic for＇臼S 臼use rotation
Gas Technician 2 Training - Module 12
Standards As四elation
@ Canadian
119
TOPIC
3
Op er，α tion
and αrpplication
thjγee-phαse
of
motors
The electric motor changes electric energy into mechanical energy. Motors
are used to drive compressors, fans, pumps, dampers, and any other 由at
rieeds energy to power its movement.
Different motors are needed 岛r different tasks because motors have
diff社rent starting and running characteristics. For example, compressors
require a motor with a high starting torque and good running efficiency.
Small propeller fans use motors with a low starting torque and average
running efficiency. In general, motors are classified according to the type
ofacpower （由ree-phase or single phase) and the motor ’s principle of
operation. Each type ts described separately below.
Three-phase motors are efficient and economical. These motors are most
widely used throughout industry and are known for their constant speed
characteristics. They have various designs with a wide range of torque
characteristics.
There are three main types of three-phase AC motors:
squiηel
cage induction
wound rotor
•
Squirrel cage
induction
motor
synchronous
In a squirrel cage induction motoζthere 缸e no physical connections
between 由e rotor and the stator. Hence the magnetic field must be induced
into the rotor. Its construction is the simplest of the AC motors.
A squirrel cage induction motor has:
•
a frame that provides a magnetic circuit and supports the stator
windings
•
stator windings
•
a squirrel cage rotor (Figure 4-6)
•
end bells
Gas Technician 2 Training - Module 12
@Canadian S阳刚a『ds A撼。ciation
121
MOTORS
UNIT 4
Depending upon their design,
these motors can have a
starting torque from normal to
ve可 high. These wide
variances in starting torque
allow for extensive variation in
applications. Therefore, when
combining the range of starting
torques, e茸iciency, and
economic considerations, these
motors are very useful within
the industry.
Figure 4-6 Squirrel cage rotor
Wound rotor
motor
The difference between wound rotor motors and squiηel cage motors is in
their rotor design. The wound rotor has insulated windings.
Like squirrel cage motors, these motors are used widely throughout
industry to drive fans, compressors, machine tools and process pumps.
Synchronous
motor
The speed of a synchronous motor is exactly proportional to the line
frequency, which is regulated on all large 60-Hz power systems so closely
that synchronous motors are widely used for clocks and timing motors.
Synchronous motors are so built that they lock into step with the rotating
magnetic field and rotate at exactly the same speed as the latter.
Three-phase
AC circuits
In three-phase induction motors, the separate phase coils of the stator may
be connected in delta （~） or wye (Y), as shown in Figure 4嗣7.
In the delta connection, the winding insulation is normally subjected to a
higher voltage than that of the wye connection. The delta connection is
usually not grounded, so 也at a (single) ground on one phase will not affect
the operation of the motor; two or more grounds, however, constitute a
short circuit between the points of the grounds and result in improper
operation or failure of the moto汇
122
Gas Technician 2 Training - Module 12
© Canadian Standards Association
MOTORS
UNIT 4
The wye connection is generally grounded at the common point, and while
the winding insulation is usually subjected to a lower voltage (than the
delta connectio时， a ground on any of the phases will adversely affect the
operation of the motor.
A
Line
A
Line
B
Line
c
c
A
B
c
N
(a) Delta connecti。n
(b) Wye connection
Figure 4-7 Delta and wye connections for three-phase AC motors
A
Caution!
After a three-phase induction motor has been disconnected for service, it is
yeηy important to reconnect the line conductors to the correct terminals.
Failure to ensure this m吗Y result in the motor, and the load which it drives,
rotating in the wrong direction. This can cause damage.
Gas Technician 2 Training - Module 12
Standards Association
© Canadian
123
TOPIC4
Op erαtion
α·nd αrpplicαtion
of
single-phαse motoγs
Single-phase operate on the same induction principle as 也ree-phase motors
once they get up to speed, however, a single-phase motor needs a
supplementary device to make it self-starting.
Having no magnetic rotating field at start, it will have no starting torque. If
brought up to speed by some external methods, however, a current will be
induced in 也e rotor 由at will produce a magnetic field. This will interact
with the stator magnetic field, producing a rotating magnetic field. This，面
turn, will cause the rotor to continue to turn in the direction in which it was
started.
The solution is to find methods of producing out-of-phase magnetic fields
in the rotor 也at will interact with 由e stator magnetic field to produce the
starting torque necessary for the rotor to tum. Several methods accomplish
由is: split-phase motor, capacitor-st盯t, shaded pol~， among others.
Split-phase
induction
motor
The essential parts of a split-phase induction motor are shown in Figure 4Sa.ηiere are two separate and distinct windings on the stator:“ie run
winding and the start winding which are mutually displaced by 90
electrical degrees.
For starting purposes, both run and start windings are connected in parallel
across the line. In series with the start winding is a starting switch (usually
a centrifugal switch).
These motors are fractional horsepower units and are found in small
can use either wound or 吨uirrel-cage rotors, al由ough
squirrel-cage is the most widely used.
pumps.ηiey
Gas T昭mician 2 Training - Modu悔 12
@
Canadian Standards As鼠>Ciation
125
Starting switch
(centrifugally
operated)
UNIT4
二。
MOTORS
T1
T4
T8
L1
L2
Counter-clockwise
rotation
T1 Ta
T4 Ts
Clockwise rotation
T1
T4 Ta
Ts
{b)
{a)
Figure 4-8 The split-phase motor and its c。nnections
Split-phase motors wi由 fo町 external line leads have had them identified in
a wide variety of ways. They may be identified by tags, colour, or by both.
In the connection diagram in Figure 4-8b the line leads are identified 岛r
clockwise and counterclockwise rotation.
ResistanceS钮rt motor
A resistance-start induction motor is a split-phase motor in which an
external resistor is connected in series with the auxiliary winding. Because
the start winding is highly resistive and the run winding is highly inductive,
由e currents through 由e two windings 缸e displaced by 30-50 electrical
degrees.ηiis creates a pulsating magnetic field, which induces rotor
currents resulting in development of torque.
Resis饵nee－剖art motors
have low starting torque and 缸e used for light load
applications
Capacitorstart motor
126
A capacitor-start motor is similar in construction to a split-phase motor,
except 也at it has a capacitor in series with the starter winding (Figure 49a）.咀iis permits a greater time displacement between the two winding
currents (approximately 90勺， resulting in a smoother rotating field and
greater torque development in the rotor.
Gas Technician 2 T1『aining - Module 12
。 Canadian Standards As部:>ciation
MOTORS
UNIT 4
Capacitor-start motors use the capacitor only while starting. It is
disconnected once the motor reaches approximately three-quarter speed.
This is done by means of a centrifugal switch which opens to bypass the
capacitor in the circuit.
飞一飞一飞
Startino switch
(centrifugally
operated)
口。
These motors are used in applications where a high starting torque is
required, such as conveyors, pumps, and reciprocating compressors.ηiey
are also available with normal starting torque and are used for such things
as centrifugal pumps and fans. These motors are either 仕actional
horsepower or integral horsepower as high as 15 hp.
问仨二
L1
L2
Counter-clockwise
rotation
T1 Ta
飞 T5
Clockwise rotation
T1 T5
T4 T8
(a)
(b)
Figure 4-9 Capacitor-start motor
In the connection diagram in Figure 4-9b the line leads are identified for
clockwise and counterclockwise rotation.
Permanentsplit capacitor
motor
The permanent-split capacitor motor is defined as a capacitor motor that
uses its start winding and capacitor continuously, without change 旭
capacitance.ηtls definition shows why no starting switch or relay is
required. As shown in Figure 4-1 Oa，也e arrangement of windings and
connections is exactly the s叙ne as the capacitor.:.sta.rt motor, exc叩t 由atthe
starting switch is omitted.
Generally speaking, permanent-split capacitor motors are not suitable for
belted applications or for any other continuous -duty application requiring
substantial locked-rotor torque. These motors 缸·e, however, ideal for
grinders and sanders.
Gas Technician 2 Training - Module 12
Standards As曲cialion
。 Canadian
127
MOTORS
UNIT4
:
T1
T4
TB
。＼
Counter-clockwise
rotation
Clockwise rotation
(a)
Ts
L1
L2
T1 Ts
T4 Ts
T1 Ts
T4 Ts
(b)
Figure 4-10 Permanent-split capacitor m。tor
In the connection diagram in Figure 4-1 Ob the line leads are identified for
clockwise and counterclockwise rotation.
Shaded-pole
induction
motor
A shaded-pole motor (Figure 4-11) may be de由ied as a single-phase
induction motor 也at uses a shading coil or low resistance copper/
aluminum loop as its starter winding.η1is shaded coil is mounted on one
side of each of the stator poles. This setup produces a moving magnetic
field perpendicular to the field pole and starts the rotor turning.
These economical, reliable motors are used in a wide variety of
applications such as: fans, humidifiers, etc.
Line
vol恒ge
Shaded coil
(sta『twinding)
Rotor
Figure 4-11 Shaded-pole induction mot1。r
128
Gas Technician 2 Training - Module 12
© Canadian Standards As甜C幅画。n
TOPIC
5
Single-phαse motoγ startup
α： ndoverloαd pγotection
devices
As described earlier, single-phase motors draw ave叩 heavy c町rent upon
startup, but this cuη·ent rapidly drops off once the motor begins to run.
Various methods have been invented to provide the motor with this initial
inrush of current (capacitors, wound rotors, split-phase, etc.) Overload
devices are used to ensure that the motor, if subjected to an excessive
torque during s阳rtup or run time, does not overheat. Overheating 扭曲e
prima可 factor for deterioration of insulation and motor failure.
Startup and overload devices are typically set by the motor manufacturer,
however, here are some of the criteria used to specify the selection of these
devices:
motor type （由e st町t up and protection 4evices are matched 明白白e
motor’s startup specific创ions)
motor application (if the motor requires high initial starting torque;
requires continuous run or intermittent run)
load requirements and amperage draw (the start current, run current
under light or heavy loads)
operating tempera阳re (heavy loads incur higher running temperatures)
location (temperature of 也e ambient air; outside or inside)
Startup
devices
Single-phase motors ( 1120 hp to 5 hp) need additional current to start up.
Built-in s饵rtup devices include the centrifugal switch and the capacitor.
External s饵”up devices (for hermetic motors) include the current relay,
potential relay and solid-state relay.
Gas Technician 2 Training - Mαiule 12
Canadian Standards As部ciation
@
129
MOTORS
UNIT4
Centrifugal switch
The split-phase motor contains a centrifugal switch 由at has its flyweights
mounted on the rotor shaft. As the motor accelerates, a centrifugal force
moves the flyweight outward against the force of the spring (Figure 4-12).
As the flyweights move out, they force a collar to move along the r创or
shaft and push the switch open. This occurs when the motor reaches about
75% of its rated speed.
As the motor slows down, the centrifugal force on the flyweights decreases
and the spring forces them back in towards the rotor shaft. This permits the
switch to close again.
To starter winding
Figure 4-12 Centrifugal switch
Capacitors
τ'he
capacitor is usable in both the start winding and the run winding. If
used h 由e start winding only, it is called a capacitor-start moto卫 Being
used for a few seconds at a time, it should have no cooling problems.
H<~wever, if a motor is started too often, or if the start winding is used
· longer than it is designed 岛民 the capacitor insulation will overheat and the
capacitor may fail.
If the capacitor is used for the run winding, it is carefully designed to
discard any heat generated in it during operation.
Note
Never use a starting capacitor in the run circuit.
Both types of capacitors are tested in the same mann町．
130
Gas Technician 2 Training - Module 12
。 Canadian Standards Association
MOTORS
UNIT4
Capacitor testing
When a motor does not start or run properly，也ere is a good possibility that
the trouble is in the capacitor. The simplest capacitor 臼st is to substitute a
good capacitor (of the same specifications）岛r the one being tested.
A
Caution!
Never place fingers across terminals ofa capacitor. It m句y be charged and
give a shock. Always short out the terminals with a screwdriver 归fore
handling it.
If the motor operates with the new capacitor, the old one is faulty. The
replacement capacitor should be the same capacity as the old. If you must
use a di班erent one, it should be 5 to 10 percent over capacity rather then
under.
External
s恒阳p devices
External startup devices are needed when it is not possible to include
switches inside the motor, as in the case of a hermetic motor.
Starting relays
Starting relays are used to remove the starting winding from operation
when the motor reaches approximately 75% of its normal running speed.
There are 也ree types of starting relays in common use today:
cuηent
relays
•
potential relays
•
solid-state relays
Current relay
The current relay is sometimes called amperage relays, since it is 由e
amperage draw on the circuit 由at operates the relay. This electromagnetic
relay is normally used on small capacitor-start induction-run motors.
1.ηie
relay is connected in series with the motor’s run winding (Figure 4-
13).
2.η1e
magnetic relay is an electromagnet much like a solenoid. Either a
weight or a spring holds the starting wind加g contact points open when
the system is idle.
Gas Technician 2 Training - Module 12
C Canadian Standards As回cialion
131
MOTORS
UNIT 4
3. When the motor control contacts close and the high current flows into
the running winding, the magnetic current relay coil is heavily
magnetized. It lifts the weight or overcomes the spring pressure and
closes the contacts.
4. This action closes the starting winding circuit and the motor will
quickly accelerate to 2/3 or 3/4 of the rated speed. As it does, the
amperage draw of the running winding of the motor decreases. This
decreases the magnetic strength of the magnetic current relay enough to
be overcome by the pull of the weight or spring.
Current
relay
.－－’飞
L1一一寸p~
""-
L2
－，『－－－－
一f c
I Motor
Figure 4-13 Wiring diagram of current relay
Potential relay
Potential relays, sometimes called voltage relays, are usually used wi由
larger sizes of capacitor-start induction-run motors. Like the current relay,
the potential relay has a magnetic coil that, when energized, operates a set
of moveable contacts. However, the contacts in this relay are held closed
by gravity or a spring, and are open only when the coil is energized (Figure
4-14）.古iis normally closed feature is its biggest advantage since there is
no arcing of the relay points when the circuit closes.
L1
L2
、 4 ’
S ／丁＼；；~
由自由” i
Potential
relay
Figure 4
132
(if used)
Starti~g
capacitor
-” Wiring diagram of potential relay
Gas T假如nician 2 Training- Module 12
©Canadian S恒ndards Assoc阳tion
MOTORS
UNIT 4
Solid state relay
Relays using solid state transistors, diodes and triacs are being used to
control starting of hermetic motors. Changes in voltage in the motor as it
starts and then gathers speed, are used to open the start winding circuit at
the correct time.
These relays are not as sensitive to the size of the motor as other relays.
The same solid state relay can be used for motors va可ing from 1112 to
1/3 hp.
Overload
protection
devices
If a motor is overloaded, it heats up. This temperature rise is destructive to
the motor and, if left unchecked, will bum out the motor. Motor overload
protection devices are designed to sense the increase in motor temperature
and to shut it down if a damaging increase in temperat町e is detected.
There are two fundamental principles behind overload devices:
One operating principle is based on a thermostatic device sensing the
temperature of the motor; this is 也e motor thermostat.
The other operating principle is based on 也e meas町ement of the
current as an indication of the tempera阳re 由at will be reached in the
motor. The higher the current draw, the more heat is generated in the
motor. The more heat generated，出e higher 也e motor temperature. 羽iis
is the current-sensing device.
Temperature-sensing device
Temperature-sensing devices (called motor thermostats) directly sense 也e.
motor winding temperature. Current is not carried through this device as it
would heat up and give a false reading. Usually temperature-sensing
devices are automatic since 也可缸e located inside the housing and are
inaccessible.
Reset of a motor thermostat may take anywhere 丘'Om 20 minutes to an hour
for a small motor and up to many hours for a la理e motor.ηiis delay is
prolonged if 也ere have been several trips in succession, especially if the
motor is already hot from heavily loaded operation.
Motor thermostats are also available for mounting on motors；也is type
C缸mot sense changes in motor temperat山e as quickly as the internal type
and therefore does not provide protection 也at is as good as the internal
type.
\}
Gas Technician 2 Training - M创ule 12
@Canadian S恒ndards Association
133
UNIT4
MOTORS
Current-sensing device
One 勾rpe
of current” sensing device is the temperature disc (Klixon disc).
Current flows through the bimetal disc and heats it. A predetermined
amount of current heats the disc enough to cause it to waφso that it opens
a set of contacts. Af王er the contacts open to break the circuit, the disc cools
down and automatically resets. This type of current overload device is
usually mounted inside the housing of small motors.
This type can also be mounted externally and may be more easily replaced
when faulty. These devices must always be replaced with an exact
replacement or proper protection will not be provided; they must also be
placed where 由e manufacturer has designated.
134
Gas T民hnician 2 Training - Module 12
。 Canadian Standards Association
TOPIC
6
Additional components ofAC
electric motoγs
So far o町 discussion of AC electric motors has been with the construction
and wiring of the various types. Other important components such as
bearings and insulation play a part 坦白e operation of such motors.
Insulation
Motor insulation has two basic functions:
to separate the various electrical components from one another and
from the stator iron and all the structural parts
to protect itse旺 and the electrical components 企om contaminants and
other destructive forces
Coil windings are usually insulated with varnish-impregnated paper or
co忱。n clo也 The insulation is designed not only to withstand the normal
voltages to which they are exposed, but include a margin to take care of
surges 由at might occur in the supply. The insulation of the leads 仕om such
coils is usually deliberately made weaker so that, should failure occur, it
may be more apt to take place outside the stator or rotor where it would be
more easily repaired.
Motor heating is the primary cause of motor insulation failure. Heat causes
deterioration of the insulation, resulting in a breakdown in insulating
quali守， short circuits, and eventually motor failure.
Ambient temperature
卫ie stand缸d 缸nbient
temperature used 岛r insulation rating purposes is
the motor will begin to overheat when 由e
air or other contacting medium is higher than 40。c.
40。C(104。F）.刀iis means 由at
Bearings
Bearings are one of the most vital parts of the motor and, except for the
starting switch, are the only wearing parts in most types of fractional
horsepower electric motors.
、、－
Gas Technician 2 Training - M创ule 12
©Canadian S恒ndards Association
135
UNIT4
MOTORS
Depending on the size of motor and its application, bearings to
accommodate the shaft of the rotor may be of sleeve bushing, ball bearing
or roller bearing types. Sleeve bushings require periodic lubrication
whereas most ball bearing designs are sealed and self-lubricating.
Speed control
Speed control is often desirable in a large number of fan and blower
applications in heating and air-conditioning installations.
Direct drive motors
The direct-drive fan motor is directly linked to the fan wheel. Several
speeds can be obtained, dependmg upon which speed tap is wired (Figure
4-15).
For one-speed operations, only one of the speed taps is wired to the hot leg
of the power supply. The other unused hot wire leads are taped separately
to prevent them from coming in contact with an electrical ground. The
motor sits in the off position until there is a call to circulate 也e heated air
throughout the heating sys阳m.η1e fan motor then blows the heated air at
the determined speed (hi牌， medium, low).
响咿阳呐
白，
P
吨以 nunuHM
ut
TVPS
Lo
Med. Lo
c
Figure 4圃， s
136
Speed 恒ps
for four-speed direct drive blower motor
Gas Technician 2 Training - Module 12
©Canadian S恼ndards Association
UNIT 4
MOTORS
Two-speed fan operation
When more than one speed is required, a multiple speed motor can be
connected to a relay so that two speed taps can be used. For example, some
systems are designed so that the fan motor operates at a low speed on the
off cycle to provide building air circulation. It then operates at high speed
when the fan switch closes to provide heated air circulation.
A single pole, double-throw relay can open one circuit and close another
circuit at the same time (Figure 4-16). Therefore a relay connected to the
Lo speed tap, and to the Med.hi on a four- speed motor, will operate at low
speed until the fan switch energizes the relay. Once energized, the relay
switch powers the medium-high circuit, and the fan speed increases.
Neutral
国gh
Med hi
Med i。
Junction box
Fan switch
110 V relay
Figure 4-16 Two speed direct drive fan operation with relay
(
Gas Tee如nician 2 Training- Module 12
© Canadian Standards Association
137
TOPIC
7
Vαγiαble
speed DC motoγs
Where a load is driven by a motor and its speed needs to be varied, a direct
cu盯ent (DC) motor may be used. A DC motor includes two main circuits: a
field circuit th剖 is the stationary component and an armature circuit that
rotates with the drive shaft.
In general, DC motors have the characteristic of delivering momenta可
high torque under load conditions at speeds above zero to full speed. This
characteristic is also ideal for acceleration and deceleration applications.
There are three types of DC motors-the series, the shunt and the
compound. The only difference between these motors is in how the field
and armature circuits are interconnected. The most commonly used DC
motor is the shunt type, which is used for applications such as induced draft
fans.
DC series
motor
The speed of a DC series motor is controlled by varying 也e source voltage
which is applied in series with the field and armature circuits. Although its
starting torque is high, its speed regulation is poo旦 Figure 4-17 shows a
variable DC series motor.
Variable
DC voltage
Figure 4-17 Variable speed DC series motor
Gas Technician 2 Training- Module 12
Standards A岱ociation
© Canadian
139
MOTORS
DC shunt
motor
UNIT4
Where 岛irly
high torque is required and constant speed regulation under
any load is desired, a DC shunt motor is used. To control the speed of a DC
shunt motor, either 也e voltage to the field circuit or the voltage to the
armature is varied. Figure 4-18 shows both speed control methods.
－一
DC
voltage
~τ工：：－ DC
－一一－ voltage
F2
(a) Field voltage varied
Figure 4-18
DC compound
motor
(b) Armature voltage varied
Va时able
speed DC shunt m。tor
In applications where it is desired to have bo由 high torque and good speed
control characteristics, a DC compound motor is used. The two methods of
variable speed control are shown in Figure 4-19.
-
-
(a) Current 四rled In shunt field
Shunt
field
DC
voltage
(b)Vi。ltage
varied
aero崎 armature
circuit
” Variable speed control of DC compound motors
Figure4-
140
Gas Technician 2 Training- Module 12
。 Canadian Standards A撼。elation
MOTORS
UNIT 4
Solid state
devices in
speed control
Prior to the discovery of solid state devices, it was common to control the
speed of DC motors by using rheostats to adjust the DC voltage source.
Since solid state devices are much smaller in size and are more energyefficient (they do not dissipate heat like rheostat吟， these devices are now
used as speed control devices.
A typical variable speed control that you will likely encounter in your work
is shown in Figure 4-20. Note that the AC source is used in this diagram.
With solid state devices, there is no longer a need for a DC source because
these devices also convert AC to DC. The net result is that a DC motor can
be energized from an AC source.
「－
- - - - - - - - 1
SCR
;.....----
Variable
speed
_,, control
I~ ＇
AC
source
F2
Figure 4-20 Typical variable speed control of a DC motor using a
S甘icon-controlled rectifier
Gas Technician 2 Training- Module 12
Canadian Standards Association
©
141
MOTORS
UNIT 4
Assignment 4
矶Then you have completed the following questions, ask your instructor for the
Answer Key.
speed，也11
1.
Where would you find the rated horsepower, the
of a motor?
2.
What are the two main parts of an electric motor ?
3.
What is the difference between a wound rotor motor and squirrel cage induction motor?
4.
What two ways can the stator phase coils in a three-phase induction motor be connected?
5.
List the four types of single-phase motors most commonly used in the gas industry?
6.
List the three types of starting relays.
7.
What should you never do when removing or replacing a capacitor?
8.
What is the pu叩ose of an overload device?
Gas Technician 2 Training - Module 12
© Canadian Standards Association
load amperage and the date code
143
MOTORS
9.
υNIT
4
What is the primary cause of motor insulation failure?
10. From which vantage point is the motor’s direction of rotation viewed?
11. List the three types of bearings used on the rotor shaft.
12. 孔'hat
144
device is connected to a multiple speed motor to allow for more than one fan speed?
Gas Technician 2 Training - Module 12
© Canadian Standards Association
Module 13
The Building as a System
Technological advances in the construction industry that make
buildings more energy-efficient, comfortable and cost-effective
have carried with them the need for tradespeople to understand
the building as a whole system. Every piece of work done on the
building has an impact on other parts of the building’s construction.
As a gas technician, it is important that you understand the
principles of heat, moisture, air flow, and demands for air, and how
出ey interact with present-day construction requirements and
standards.
At the end of this module you will be able to:
Gas Technician 2 Training- Module 13
©Canadian S恒ndards Association
•
Describe key components
•
Describe building science principles
•
Describe energy c。nservati。n methods
•
Describe indoor air quality
-1
·1
·1
Ken Bales, Manager, Gas Information Products, CSA, wishes to acknowledge the following individuals
who contributed as members of a Review Panel during the development of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology (BCIT) is
acknowledged for its work in the technical development and editing of the original edition.
c。ntributors and members 。f the Review Panel
John Cotter
Bill Davies
E时c Grigg
Warren Hayes
Darrel Hilman
Ken Kell
W. John Lampey
Lorne Lowry
Jim Noseworthy
Gary Prentice
Nick Reggi
Rick Rogozinski
Ron Royal
John Semeniuk
Allen Sidock
John Simmons
David Stainrod
Terry Waters
iv
Canadore College
Union Gas Limited
Canadore College
Superior Propane Inc.
Southern Alberta Institute of Technology
Centra Gas Manitoba
Albe阳 Advanced Education & Career Development
Algonquin College
Durham College
Environmental Energy Consultants
Humber College
Union Gas
Fanshawe College
Northern Alberta Institute of Technology
Cambrian College
Loyalist College
D.J. Stainrod &Associates Ltd.
Enbridge Consumers Gas
Gas Technician 2 Training - Module 13
。 Canadian Standards Association
岛1odule
13
Table of Contents
Unit 1
Key components
Definiti。ns
................................…............…......... 3
Relationship to heat, moisture and air flow ......... 7
Minimizing negative impacts ..................…....... 13
Assignment 1 .........……········………·…................ 25
Unit 2
Building science principles
Heat,
m。isture
and air flow .........…........…........ 29
Controlling heat l。ss/gain, excess moisture and
air leakage ........………‘..........................…......... 41
Mechanical effects ..........................……............ 49
Assignment 2 .............................….................... 59
Unit 3
Energy conservation
Types of building construction .........….............. 63
lnsulati。n ........................................................... 65
Conservation measures and techniques. …....... 75
Assignment 3 .................................................... 81
Unit 4
Indoor air quality
Pollution ....................…···························…....... 85
Ventilation and filtration ......................……......... 89
Assignment 4 ........….........….........…………........ 99
Gas Technician 2 Training- Module 13
© Canadian Standards A览。ciation
v
Unit 1
Key components
Purpose
Significant advances in home building technologies and materials over
the past several decades, including energy conservation, air leakage
control, improved insulation, etc., also mean that a new approach is
necessary by the gas technician. Gas technicians must be thoroughly
familiar with prevailing construction methods and technologies that
support 由e concept of a building as a series of interdependent parts.
This concept is generally known as “ the building-as-a-system."
This unit describes the key components of building-as-a-system
construction and how they a的ct the gas technician.
g
e
LOwe
n
nd
n s
1. Define key components of the building as a system.
唱
均
-
2. Describe the relationship between key components to heat,
moisture and air flow.
3. Describe how to minimize negative impacts on the building of
heat, moisture and air flow.
Gas Technician 2 Training 『 Module 13
© Canadian Standards Association
Topics
1. De罚 niti。ns ...........…...........…............._.. ............................…....... 3
Building envelope ………………，，..........................『．．．，．．．四……··…4
Occupants ......…………......……胃口…· ............... ……··.... ..... 5
Mechanical systems ... . . .. . ..... . . . ....... ..... .... ... .. ........……........... 5
External environment.. ….......................…......…….........川............ 6
2.
Relationship to heat, moisture and air flow••••••.••••.•••••••.••••.•• 7
Building envelope 目’................…………......……·…......…………··…....... 7
Occupants. …····························· ............………·-··..............,...·…........ 10
Mechanical and electrical systems .....................................，…………·…·．．．．什
External environment. …··……….......‘…·町….. ········ ............................. 12
3.
Minimizing negative impacts ...........................…...............… 13
Control within the building envelope ....................…圄..................................... 13
Ventilation .............. . ...............……................…... ············ ....….... 21
External environment ．．．．．．．．．．．．．．．．．．．．．，．·－··－··目’.....…............................… .24
Assignment
2
1 ...................................................................…......... 25
Gas Technician 2 Training - Module 13
© Canadian Standards Association
TOPIC 1
Definitions
In treating a building as a system of interlocking structural and service
elements, be aware of the four essential components:
•
the building envelope
•
the occupants
•
the building ’s mechanical systems and services
•
its external environment
Gas Technician 2 Training- Module 13
© Canadian Standards Association
3
KEY COMPONENTS
川唱阳
·町 O
M 创
Be
umH
UNIT 1
The envelope (or shell) of a building is defined as the floor slabs,
foundation, walls, roof, windows and doors (Figure 1-1 ). Each of these
components is made up of a variety of materials which may include paint,
drywall, vapour barriers, insulation, studs, sheathing, building paper, air
spaces and exterior siding or cladding.
Windows/;
Buidling envelope
components
Figure 1-1 The building envelope
4
Gas Technician 2 Training- Module 13
。 Canadian Standards Association
KEY COMPONENTS
UNIT 1
The building envelope defines the indoor space, which is governed by
other systems and devices that relate to the activities taking place inside the
building. Besides supporting the walls and roof, the envelope helps to
control the flow of heat, air and moisture between the inside of the building
and the external environment.
Occupants
The occupants are the people who live or work inside the building. The
activities carried out by the occupants in different areas of the building can
have varying degrees of impact on structural and service elements of the
building. Occupants also include pets and plants inside the building.
Besides controlling the indoor environment through their activities within
the building, people, pets and plants release moisture into the indoor air.
They also emit and absorb many atmospheric pollutants that affect the
system as a whole.
Mechanical
systems
The mechanical systems of a building include most of the systems and
devices that control or affect heating, cooling, humidi马ring and air
purification of the indoor environment (Figure 1-2). Examples of
mechanical systems and services include:
•
central heating
•
air conditioners
•
air circulation equipment
•
e对iaust
•
washers
•
dryers
fans and vents
cooking appliances
lighting devices.
Gas T以如nician 2 Training - Module 13
© Canadian Standards Association
5
KEY COMPONENTS
UNIT 1
Supplemental bath
and kitchen fans
Heat recovery
ventilator (HRV)
is the principal fan
HRV outdoor air
into return air
HRV to be balanced
Combustion air
intake
Insulated cold
air ducts
~＇~：~~ra~
Figure 1-2 The building’s mechanical systems
External
environment
6
Elements in the external environment that impact on the building ’ s ability
to operate as a system include:
•
climatic and seasonal conditions, such as frequency of exposure to sun,
wind, rain, snow etc.
•
shade trees, other shade elements
•
location (above/below steep slopes, proximity to bodies of water, heavy
traffic 由at emits pollutants, etc.)
•
age of the building-new homes 缸e considerably more ai叫ghtthan
older homes. New buildings are subject to materials shrinking,
expanding, and settling and external conditions can accelerate or slow
down this process.
•
gravity-affects water running downwards, as from a roof or down a
window pane, door 企ame; also building settling.
Gas Technician 2 Training - Module 13
©Canadian S恼ndards Assoc重ation
TOPIC
2
Relationship to heat,
mo is tuγeαnd αiγ卢ow
For the comfort, safety and health of a building and its occupants, a gas
technician must understand the relationship of the four key elements of the
building as a system to the physical effects of heat, moisture and air flow.
You must also understand why it is important to see them as interdependent
elements that sustain the efficient functioning of the building as a whole.
Building
envelope
The building envelope has three functions: to shelter occupants and
materials from the weather, provide a comfortable indoor environment, and
maintain the building ’s structural integrity.
Heat flow
The effects on the building envelope of modern heating methods are
generally beneficial. All heating systems must contain methods for the
control of venting and recirculation of 台esh air. Cracks and openings that
permit the escape of heat and the ingress of cold air must be sealed up to
prevent loss of energy efficiency (Figure 1-3).
Gas Technicia 『12 Training-Module 13
© Canadian Standards Association
7
KEY COMPONENTS
UNIT 1
／叫织
Doors and windows
15-20%
Basement 20-25%
Figure 1-3 Typical heat loss through the building envelope
Moisture
There must always be a certain amount of moisture inside a building for the
health and comfort of the building ’s occupants.
However, without adequate moisture barriers built into the envelope, a
great deal of moisture in vapour form can be carried 丘om the outdoors by
air flow, or other means, to the building ’ s interior.
Be aware of the following definitions:
Water vapour
is microscopic water molecules which are suspended in
air.
8
Relative
humidity
(RH) is the amount of moisture air contains relative to
what it could contain at a given temperature.
Absolute
humidity
refers to the actual amount of water vapour contained in
a given amount of air, regardless of the temperat町e of
the air.
Dew point
refers to the point at which any body of air is saturated
with water (100% RH).
Condensation
is the process by which dew, or condensate, is formed. In
this process, moisture changes state 企om a gas (water
vapour) to a liquid (water).
Gas Technician 2 Training - Module 13
。 Canadian Standards Association
KEY COMPONENTS
UNIT 1
Moisture crumbles concrete, rots wood and makes paint and other coatings
crack and peel. In vapour or liquid form, it attacks the building envelope
from the outside through:
•
exposed cracks, holes and spaces in the building envelope
exposed, uncovered earth in crawlspaces
open sump pump holes
improper venting.
Although the shell is built to protect both the building and its indoor
environment 仕om external moisture penetration, the building envelope
itself can create humidity that will eventually undermine the structure. This
may be caused by the drying of 丘aming and drywall in new and renovated
buildings that are badly or inadequately ventilated.
Excess moisture from indoor use of clothes washers and dryers and other
moisture-creating household activities also undermines the building
envelope if the appliances or rooms in which the activities are taking place
are not adequately vented.
Air flow
New, air-sealed buildings having vapour barriers that effectively protect
occupants 仕om external humidity or extremes of climate can also
drastically reduce 仕esh air and increase moisture and heat inside the
building, sometimes to health-threatening levels. The thermal envelope
must therefore allow for a controlled amount of air to be brought into, and
exhausted from the building.
Although an exhaust fan removes moisture or pollutants from the indoors,
社 can adversely a岱ct air quality and create a health or safety hazard. This
can result from e证ects of draft upon a naturally drafted furnace, or 仕om
expelled gases or vapours re-entering the house through floor drain or
below-grade cracks. It is therefore important to view exhaust equipment or
appliances in relationship to other parts of the building as a system.
Uncontrolled air flow through the envelope can be a major source of heat
loss, which may lead to other problems. Since warm air can carry large
amounts of water vapour, air flow is also the main means by which
moisture is carried into the envelope. In winter, air is forced through the
building envelope. Air moving out carries heat and moisture, while air
moving in brings uncomfortable drafts and, depending on climatic
conditions, dry or moist winter air.
Gas Technician 2 Training- Module 13
© Canadian Standards Association
9
KEY COMPONENTS
UNIT 1
For air to move from one side to the other there must be a hole in the
envelope and a difference in air pressure between the inside and the
outside. This difference may be caused by:
•
wind
· “stack” effect in the home
•
combustion appliances or e址rnust fans.
Unit 2 describes the principles of air ventilation and flow.
Occupants
People, pets and plants have significant effects on heat, moisture and air
flow and quality. Differing living styles or business practices impact on
these three elements.
Heat
The amount of indoor heating required by people varies. Very hot, dry
indoor air needs regular ingress of moist air to keep indoor air at a healthy
level. A balanced heating system in every room is an important factor in
controlling the amount of heat vs moisture in the air.
Hermetically sealed gas fireplaces can add to excess drγness and the buildup of contaminants in the atmosphere
Moisture
Al由ough
not so good for the building envelope, moisture in a building is
good for people. Moisture problems occur from two sources: excess
moisture and over-cool surfaces.
Occupants create excess moisture 台om such things as:
•
breathing, sweating, bathing, showering, or washing clothes, dishes etc.
•
growing plants, particularly in enclosed solariums
clothes hanging indoors to 世y.
10
Gas Technician 2 Training- Module 13
© Canadian Standards Association
KEY COMPONENTS
UNIT 1
Air flow
Open areas, in contrast to small, tightly sealed rooms, along with fans,
ventilators and humidifiers, help to keep indoor air flowing and fresh for
people, pets and plants.
Mechanical
and electrical
systems
The building ’s mechanical and electrical systems include all service
equipment and appliances inside the building. This includes various types
of heat distribution systems, air conditioning, ventilation, phones,
plumbing, electricity, hot and cold water and waste disposal. The points at
which pipes and wires enter to provide these services to the building
envelope are potential places of heat, air and moisture leakage into and
out of the building.
Heat, moisture and air flow
Equipment and appliances that contribute to effects upon heat, moisture
and air flow include:
•
water heaters
•
dryers
•
motors
•
fireplaces
•
woodstoves
•
air cleaners
•
cooking stoves and ovens
•
central vacuum cleaners
re企igerators
lighting
natural draft appliances
•
air changers (heat recovery ventilators)
inadequately vented dryers
clothes hanging indoors to dry
•
hot tubs and jac回到s
aquariums
moisture in stored and burning firewood.
Gas Technician 2 Training-Module 13
© Canadian Standards A豁出国ti on
11
KEY COMPONENTS
External
environment
UNIT 1
Amount of exposure to sun, wind, rain, snow, proximity to shade trees and
the like are outdoor factors that can have a significant impact on the
building ’s heat, moisture and air flow. In Canada, buildings are built to
withstand the rigours of cold winters, and to a lesser extent, hot, dry
summers.
Heat flows from warm to cold areas and moves in any direction, not just
upwards, as many people believe: a heated room over an unheated garage
loses heat through the floor (Figure 1-4). Heat flows by conduction,
convection and radiation (described in Unit 2). In a building wall, heat may
be moving in all three ways at the same time.
Figure 1-4 Heat
moves 。ut
of a building in all directions
A difference in air pressure between the inside and the outside of a building
causes. air to move from one side to the other if there are cracks or holes in
the building envelope. When wind blows against the outdoor wall of a
building, it creates a high pressure area which forces air inside the building,
or to 由e side of the building with a lower air pressure (where air is forced
out through cracks or holes).
Holes and cracks in the envelope permit:
air moving out to carry with it heat and moisture
air coming in to bring drafts and dry (or wet) winter air.
12
Gas Technician 2 Training- Module 13
© Canadian Standards Association
TOPIC
3
Minimizing negative
impαcts
Modem building technology has introduced a variety of devices and
systems that minimize many of the negative impacts of heat, moisture and
air flow on a building and its occupants. However, demands for energyand cost-efficiencies, as well as for improved comfort levels, air quality
and construction quality, have brought with them some problems as well as
benefits, particularly if building as a system guidelines are not followed.
For example, if you were to replace a conventional natural gas furnace with
a high efficiency, induced-draft fan gas 如mace, the building ‘ s air flow
would be greatly reduced and moisture levels could increase.
Control within
the building
envelope
Many of the devices and materials that control the negative impacts of heat,
moisture and air flow are built into the following components of a
building ’s envelope (Figure 1-5):
the skin
•
insulation
•
moisture and vapour barriers
•
air barriers.
Insulation works by trapping
small pockets of air
Wind barrier Air barrier
Up to 1/3 of insulating value 臼n
be installed on the warm side of the
vapour barrier
Figure 1-5 Insulators and barriers
Gas Technician 2 Training- Module 13
Canadian Standards Association
©
13
KEY COMPONENTS
UNIT 1
Tables 1-1 and l 」 at the end of this topic list many of the materials used in
minimizing negative effects on the building and its occupants.
Skin
The skin or outer siding materials of the building envelope:
•
protect underlying materials
•
help maintain the building ’ s integrity
•
help reduce heat loss or heat gain.
Insulation
Insulation maintains the energy-saving efficiency of the building envelope
by blocking air leaks and protecting against heat loss from indoors to
outdoors. Four major types of insulation are used in walls, basements,
attics, and around windows and doors:
•
hart or blankets
loose fill
rigid or semi-rigid board
•
foamed-in-place.
Weatherstripping is used to block air leakage around doors and windows.
Some common types are shown in Figure 1-6.
c幸运事化
Closed cell form
《二
Spring vinyl
Ribbed
Tubular
《二运去
Spring metal
Magnetic strip
J彭也多 喝多
Door sweep
Full threshold
Spring loaded
Figure 1-6 Common types of weather-st『ipping
14
Gas Technician 2 Training - Module 13
。 Canadian Standards Association
KEY COMPONENTS
UNIT 1
Heating ducts running through unheated or cool basements, as well as
return air ducts which pass through unheated crawl spaces or garages must
also be insulated. Figure 1-7 shows duct work insulated with fibreglass
batting, with taping used to seal the seams of heating ducts.
Figure 1-7 Taping and insulating heating duct
Materials used for insulation of the building envelope and its components
are chosen for their effectiveness in:
•
keeping heat inside the building
ability to fill space
•
durability
ability to withstand effects of high temperatures and moisture and air
movement.
Refer to Table 1-1.
Gas Technician 2 Training - Module 13
© Canadian Standards Association
15
KEY COMPONENTS
UNIT 1
Table 1-1 Insulation materials
Insulation type
Materials
Characteristics
Location
• Batt or blanket
Batts or rolls of glass fibre,
mineral wool
Easy to install, can be
cut to fit, won't settle.
Some types are noncombustible.
叭/all
ranging 丘。m
Cellulose fibre made from
chemically treated,
shredded newsprint
!:tt~~：~an
Fire, fungus and
corrosion inhibiting Fills
around small
obstructions
Walls, floors, attics,
enclosed, irregular
spaces. Not belowgrade appli臼tions
Glass fibre, chopped up
Best in open, h。rizontal
surfaces. Some are
non-combustible
Attics
Mineral wool (slag and rock
to glass fibre
Treated with oil and
binders to suppress
dust and keep its shape
A位ics,
woo牛－similar
Vermiculite (expandedmica)
Usually hand-installed
w垣lls:
• treated
• water-repellant
• untreated
• absorbs moisture
• high-moisture
areas
Loose fill
(particles
poured)
cavities, a忧ics,
around base『nent
venting, duct work
inaccessible
areas such as woodframe roofs, walls
and floors
• sealed-off areas
where moisture
C缸mot penetrate
• Rigid board
• Glass fibre or foam plastic:
• fibre boards
• expanded polystyrene
High insulating value,
for either below-grade
exterior use or above』
grade sheathing
See manufacturer’s
instructions - some
must be protected
from prolonged
exposure t。 sun,
solvents, sealants
and water.
Mixed and sprayed 。n
site, can expand up to
28 times their 。riginal
size (not used in
Building surface,
but
must be protected
from prolonged
sunlight and must be
covered with fire•
resistant material
when used indoors.
• extruded polystyrene
• polyurethane
• phenolic foam
• Sprayfoam
• Polyurethane
• Semi-flexible isocyanurate
plastic
enclosed 臼.vities).
Can be used as air (not
vapour) barriers
16
walls，臼vities,
Gas Technician 2 丁丽ining - Module 13
©Canadian S恒ndards Association
KEY COMPONENTS
UNIT 1
Moisture and vapour barriers
Moisture barriers within the building envelope are located on the wa口m
side of the insulation material (Figure 1-8). Moisture and vapour barriers
minimize negative impacts of heat, moisture and air flow by:
•
reducing transfer of water and water vapour (condensation) that cause
mould, mildew, wood rot, structural damage
•
reducing air infiltration and exfiltration
•
controlling relative humidity (RH) and reducing costs of
humidification or dehumidification. RH is the amount of moisture air
contains relative to what it could contain at a given temperature
(described more fully in Unit 2).
Moisture barrier materials are chosen for their:
•
resistance to moisture penetration or vapour flow
•
durability
•
ability to cover as much of the building envelope as possible
•
ease of installation
•
ability to act as a secondary air barrier or insulation
appropriateness to particular work being carried out.
Effective vapour barrier materials include:
•
polyethylene
aluminum foil
m01sture-res1stant pamts
specific types of insulation
•
vinyl wallpaper
exterior grade plywood.
Areas where vapour barriers are most needed include interlocking ceiling
tiles and new dηrwall, particularly in areas like kitchens and bathrooms.
Gas Technician 2 Training- Module 13
© Canadian Standards Association
17
KEY COMPONENTS
UNIT 1
I \I
Interior dampprooing
to grade: moisture barrier
••••
‘,,,.- 4
·LV
ag
..
飞。
Figure 1-8
Moistu『e
barriers in the building envelope
The key to dealing wi也 moisture in the indoors is establishing a balance
between the needs of the occupants and the needs of the building structure.
Air barriers
白1e air barrier system (Figure 1 －到 is the major protection of the building
envelope .and its insulation from the effects of moisture penetration.
Requirements of air barriers are:
•
resistance to air movement
continuous ability to surround the building envelope
18
Gas Technician 2 Training - Module 13
© Canadian Standards Associatiα，
UNIT 1
KEY COMPONENTS
ability to withstand storm conditions, particularly wind pressure
durability
ease of installation
•
compatibility with other building materials
•
ability to perform also as insulation and a vapour barrier.
Sometimes building materials like drywall, baseboards or structural
members are incorporated into the air barrier by sealing them to adjoining
materials. The air barrier ’ s most common components are:
•
sheet or rigid materials for large surfaces
•
caulking and gaskets for joints between materials that don ’t move
•
weatherstripping for joints that move.
Refer to Table 1-2.
Building
paper
4 mil
13 x 13 mm
urethane seal
poly
(vapour barrier)
13x13mm
urethane seals
Urethane seals
Figure 1-9 Air barriers
Gas Technician 2 Training - Module 13
© Canadian Standards Association
19
KEY COMPONENTS
UNIT 1
Table 1-2
Barrier type
Materials
Characteristics
Location
• Sheet
materials
Polyethylene sheeting
Durable, available in
wide sheets. Also
functi 。ns as a vapour
barrier.
walls, exterior t。
insulation below skin
(must be protected
from sun exposure)
Spunbonded olefin
As above, but also
e仔ective as a wind
barrier on exterior.
Does not function as a
vap。 ur barrier.
As above
• Rigid
materials
Most solid building components
including d叩wall, plaster,
plywood, glass, wood and
poured concrete. Includes rigid
foam insulati。n
Seams must be sealed
with caulking,
weatherstripping or
gasket
Throughout the
building envelope
• Sealants
(caulking
suitable to size
• Accoustical sealant
Refer to specific
Numerous locations
throughout building
envelope
• acrylic latex
『nanufacturer's
instructions relating to
~~｝Fa~：s and
• butyl rubber
bondability，负 re-
• silicone sealant
applied to)
• polysulfide sealant
resistance, ventilation
during application and
cu时 ng, etc.
• urethane foam alant
• stove or muffier cements
• Gaskets
Special designs
For sealing joints not
suited to caulking
Sill plates, electrical
and lighting fixtures
Neoprene
Flexible, durable, for
sealing where there is
Plumbing stacks
问iovement
Foam backer rope
• Weatherstrippmg
(Refer to
Figure 1-6)
• Compression strips
• Closed cell foam and
ribbed rubber
Filling
before 臼ulking
Durability,
ease 。f
inst剑 lation,
variety to
Deep gaps in areas to
be caulked
Do。rs, operable
of windows
pa此S
suit di何erent
applications
• tubular material
• tension strips
• door bottoms, sweeps and
thresholds
20
Gas Technician 2 Training- Module 13
© Canadian Standards Association
KEY COMPONENTS
UNIT 1
Ventilation
Ventilation is the process of supplying or removing air by either natural or
mechanical means to or from a space. Negative impacts of heat, moisture
and air flow on the indoor environment directly affect the building
occupants. Here the emphasis is on improving air quality and comfort, and
eliminating pollutants.
The mechanical systems that provide combustion air to heating and cooling
systems must also provide ventilation air. A well-designed and properly
installed ventilation system compensates for air exhausted and used in the
combustion process. Such systems replace stale, moist air with fresh,
tempered air (Figure 1-10).
Gas Technician 2 Training- Module 13
© Canadian Standards Association
21
KEY COMPONENTS
UNIT 1
Bathroom exhaust fan
intended for intermittent use
Manual
control
Kitchen exhaust
fan intended for
intermittent use
Normal
heating ducts
Manual or
automatic control
一 for HRV interlocked
to furnace fan
Manual
control
’Heat recovery
ventilator
Figure 1-10 Indoor air requiring ventilation
22
Gas Technician 2 Training - Module 13
© Canadian Standards Association
KEY COMPONENTS
UNIT 1
Heat recovery ventilators
Heat recoveηventilators (HRVs) exhaust warm, stale air while bringing in
fresh air from outside. They are primarily a ventilation system with the
added value of heat recovery.
An HRV consists of two fans一一one to bring in air, the other to e对1aust
air-creating a balanced air flow. The heat exchanger is a static device that
recovers the temperature difference between the two air streams.
Figure 1-11 shows the major components of a typical HRV system.
WOAR
Cool air
exhaust
Warm air ＼、’7
supply "<...... I
Heat recovery
core
Warm exhaust
Figure 1-11 A typical HRV system
Gas Technician 2 Training- Module 13
© Canadian Standards Association
23
KEY COMPONENTS
UNIT 1
External
environment
Many of the negative effects of heat, moisture and air flow in the building ’ s
external environment are related to·
location on the lot (e.g: above or below a slope, drainage)
•
orientation and exposure to elements (e.g: north/south facing)
landscaping (e.g: proximity of shade trees, retaining walls).
24
Gas Technician 2 Training - Module 13
© Canadian Standards Association
υNIT
KEY COMPONENTS
1
Assignment 1
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
2.
Define "occupants. ”
3.
Is a clothes dryer considered to be a part of the mechanical systems in a building?
4.
认That
two things are installed for moisture control in a building?
5.
认That
are the two sources of moisture problems?
6.
轨That
are the three methods of heat transfer?
7.
Can a building ’s air flow be altered by the installation of a furnace with an induced draft?
8.
Where are moisture barriers in the building envelope installed?
9.
DoHRVs e对1aust 仕esh air?
10. When should heat ducts be insulated?
GasTechniαan
2 Training-Module 13
© Canadian Standards Association
25
Unit2
Building science principles
Purpose
Understanding the building science principles that pertain to the
construction industry and related trades will assist the gas technician
in designing installations that provide comfort in the most efficient
manner.
Learning
1. Describe heat, moisture and air flow.
。同 ectives
2. Describe control of heat loss and gain, excess moisture and air
leakage.
3. Describe mechanical effects.
Gas Technician 2 Training - Module 13
Standards Association
。 Canadian
27
Topics
1.
Heat, m。isture and air fl。w ................................................… 29
s。urces of heat loss and gain ..........…........…............…·…........ 29
Sources of moisture. …………………··……… …………··-…. ········ .34
Air flow ....
......... 37
E
2.
Controlling heat loss/gain, excess moisture
and air leakage ....................................................................... 41
Air leakage control ............………….. …·-… ……·--…-……... 41
Excess moisture control .....…-…....... ········ ...................……町，..... 42
Air, vapour and moisture barriers ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．，目…........ ..45
Positive and negative pressure ..……··巴，．．．．．－．．．．，．．…··目’.....…阳......... .47
U
3.
Mechanical effects .............................................…................. 49
Combustion and exhaust appliances ........……………….........…….....……… 49
Passive depressuriz-ation testing .........................................…........且....... 54
Assignment
28
a
2 ………………….......…………………………………………… 59
Gas 丁丽chnician 2 Training - Module 13
© Canadian Standards Association
TOPIC
1
Heαt,
moisture and aiγflow
The three major principles in understanding the building as a system are
discussed here separately. However, a gas technician must always bear in
mind that they continually react with one another. The inter-relationship of
heat, moisture and air flow determines the state of a building system at any
pomt m time.
Sources of
heat loss and
gain
A building that is well-insulated but not properly sealed against air leakage
loses 30% or more of its heat. During colder seasons, heat is lost through
cracks and crevices in the walls, floor and roof of a building. Figure 2-1
shows how air leakage is distributed through different areas of a single
storey house.
Figure 2-1
of air leakage through
a single-storey house
Distributi。n
Heat flows from one place to another in three ways: conduction,
convection and radiation
Gas TE比如nician 2 Training-Module 13
© Canadian Standards Association
29
BUILDING SCIENCE PRINCIPLES
UNIT2
Conduction
Conduction is the transfer of heat from particle to particle within a
substance, or the transfer of heat directly from one part of an object to
another part. Conduction transfers heat through solid items, such as when
the handle of a cast iron frying pan gets hot, then passes its heat into your
hand. Air is a relatively poor conductor of heat since air movement carries
away and disperses the energy. Liquids are better conductors than gases,
but do not conduct as easily as solids.
Materials which resist heat conduction are called insulators. Cork, glass
fibre and air are excellent insulators.
•
Good conductors have high conductivity.
•
Good insulators have low conductivity.
For any given temperature difference, each material transfers heat at a
different rate. The ability of a material to conduct heat is called its thermal
conductivity. Figure 2-2 compares thermal units of conductivi-ty for
various materials, as shown on the bar graph. The formulas to calculate
thermal conductivity (Imperial and me位ic) are also shown.
SUBSTANCE
2700
Coppe 「
Aluminum
1390
Brass
Carbon steel
(boiler tube)
Cork
Glass wool
Wood ash
Dead air
Vacuum (0)
Units of thermal conductivity:
Imperial =Bt~ • inch I h • tt2 •。F
Metric =W m I m2 •。C
Figure 2-2 Conductors and insulators
30
Gas Technician 2 Training - Module 13
© Canadian Standards Association
BυILDING
UNIT2
SCIENCE PRINCIPLES
In the formulas shown in Figure 2-2:
British thermal units
Btu
-
thickness in inches
inch
--
hours
h
-
tt2
』
-
area in square feet
temperature change in degrees Fahrenheit
。F
-
w
m
Watts
-
thickness in metres
-
付12
area in square metres
temperature change in degrees Celsius
。c
-
R-values of insulators
Insulating materials are usually specified in terms of their R-value
(R 100 in metric systems). R stands for internal thermal resistance which
indicates the resistance of heat flow to conductivity. The R-value is
therefore the opposite of conductance.ηle higher the R-value, the better
the insulation ability of the material. Typical R-values are 19 for a six-inchthick layer of fibreglass and 1.2 for six inches of brick.
Conductive heat loss
An example of conductive heat loss in the building as a system is where the
outside wall studs have one side exposed to the interior of the house, and
the other side exposed to the outdoors. This is called thermal bridging.
Conductive heat loss through the studs is caused when the stud 丘ame is
tight up against the foundation wall. This type of heat loss reduces the
overall insulating value of the foundation wall.
Convection
Convection heat transfer requires the movement of a fluid, such as water or
air. Warm air can flow, or be blown, from a furnace to heat a room. Hot
water can flow through pipes to heat a substance some distance away.
In an uninsulated wall space, air picks up heat from the warm wall, then
circulates to the cold wall where it loses the heat. Some heat may be
transferred by the mixing of warm and cold air.
There are two types of convection: natural and forced.
Gas Technician 2 Training- Module 13
Standa『ds Association
© Canadian
31
υNIT2
BUILDING SCIENCE PRINCIPLES
Natural convection
Natural convection is caused by a change in buoyancy when a fluid is
heated.
1. When a fluid is in direct contact with a hot surface, the particles next to
the surf注ce are heated by conduction.
2. This heating causes the particles to expand and increase in density. This
increases their buoyancy.
3. The lighter, heated portion of the fluid rises and is replaced by a cooler,
heavier portion. So the liquid or gas circulates.
Air circulation through the Earth ’ s atmosphere occurs by natural
convection. Similarly, air circulates through a room when heated by
baseboard heaters.
In the hot water kettle in Figure 2-3, the water touching the heated bottom
receives heat energy by conduction. Its molecules move apart more,
making it less dense, so it becomes more buoyant and the water rises.
Colder water moves in to replace the warm, making the move-ment
continuous. So heat is carried throughout the water in the kettle.
边监尚
As 'the water is heated, convection
currents carry the heat energy
Figure 2-3 Convection heat transfer in a hot water kettle
Forced convection
Forced convection occurs when the fluid ’s particles are moved by some
outside mechanism or force. Liquids may be pumped, or gases blown by
fans. Buildings heated by hot water use a pump to force the water 也rough
pipes and heat exchangers. In a forced-air furnace, a fan circulates warm
air through a house.
32
Gas Technician 2 Training- Module 13
。 Canadian S姐ndards Association
BUILDING SCIENCE PRINCIPLES
UNIT 2
Radiation
Radiation is the transfer of heat energy by means of electromagnetic waves
(this is how the sun transfers energy). These types of waves are similar to
light waves, and the energy is transferred through air or through a vacuum.
Any object will radiate heat in the same way that the sun radiates heat. All
materials give up and absorb radiant heat energy.
If an object is hotter than its surroundings, it gives up more heat energy
than it absorbs. Its temperature decreases as this occurs.
If an object is cooler than its surroundings, it absorbs heat energy by
radiation and its temperature rises.
When you stand in front of a cold window, you radiate heat to the window
and you feel cold, even though the room temperature may be high. Figure
2-4 shows how energy waves from the hot rivet travel in a direct path
through the air to be absorbed into the person’s hand.
Figure 2-4 Radiant heat transfer through air
Gas 丁echnician 2 Training - Module
。 Canadian Standards Association
13
33
υNIT2
BUILDING SCIENCE PRINCIPLES
Reflection, refraction, absorption and transmissi。n
When radiant heat waves strike an object, they act like light waves. They
maybe:
reflected (sunlight striking a mirror or polished s田face)
refracted (bent)
absorbed
transmitted (passed through a magnifying glass and focused on a small
area of a piece of wood, the energy is absorbed by the wood, causing its
temperature to rise. The temperature of the wood may be raised
sufficiently high for combustion to commence.)
The texture and colour of a material ’s surface determine the amount of
radiant energy that is reflected or absorbed.
•
Smooth, shiny, light surfaces r拼ect radiant energy.
•
Rough, dull, dark surfaces absorb radiant energy.
Radiation heat loss
Window glass radiates heat out of the house, another reason you may
shiver when standing near a window since your body heat is first passed to
the window by convection.
Sources of
moisture
Moisture in the form of liquid, vapour, gas or ice penetrates the building
envelope 企om a variety of sources in the building and through the
activities of the occupants.
The following are typical daily sources of moisture in a building:
•
•
34
Inside (occupant related)
Occupants' activities (four people a day)
Indoor clothes dryer
Floor washing
Cooking
Drying firewood
Dishwashing
Outside/building related
Exposed uncovered earth in crawl space
Seasonal building storage (framing, d巧响all,
concrete)
New construction (drying of framing and
concrete over 18 months)
5 litres
12 litres
1.5 litres
I litre
5 litres
0.5 litre
40-50 litres
8 litres
4-5 litres
Gas 1忌chnician 2 Training - Module 13
© Canadian Standards A部ociation
8υILDING
UNIT 2
SCIENCE PRINCIPLES
F onns of moisture change according to the temperature:
•
warm air holds moisture in vapour h口口
•
cold air allows moisture to condense
•
very cold temperatures allow moisture to freeze.
Movement of moisture through envelope
In its different forms, moisture can move through the building envelope:
Gravi钞
Capillaηy
permits water to move sideways or upwards
is a surface tension effect in which liquids rise up
narrow tubes or through porous solids. It is caused
by the difference in attraction between the liquid
and air molecules for the material of the solid.
Dt如sion
permits water vapour to move directly through
materials. Diffusion depends on a difference in
water vapour pressure and the material ’ s
resistance to this pressure. Air will move through
an opening with very little pressure difference and
will caηy the water vapour with it. For the water
vapour to move through a material via diffusion
reqmres pressure.
Refer to Figure 2-5 on the following page.
Air movement
carries moisture as water vapour, for example,
where there is air leakage through a crack 扭曲e
building envelope.
Gas Technician 2 Training- Module 13
Standards Association
。 Canadian
action
即d
CGP ’’1,,,.or
causes water to move downward (water running
down a roof or condensation running down a
window pane)
35
BUILDING SCIENCE PRINCIPLES
UNIT2
Figure 2-5 shows two types of moisture movement through the building
envelope. Note that 100 times more moisture is ca时 ed via air flow than by
vapour diffusion.
1 metre
‘昏『回
1 门1etre
--”
J乞，
LJLJLJLJLJ LJLJ自由
口自由自由自由 30 litres
LJLJ自由自自由自
Transp。rt
via air leakage through 2 x 2 cm hole
4峰－
Transp。rt
1 metre
’白”
via diffusion through 1 sq. metre
Figure 2-5 Comparison of moisture fl。ws through the building envelope
Excess humidity
Excess humidity is one of the most common air quality problems in
residential buildings. Humidity is defined as the amount of water vapo町
contained within a given volume of air. There is a limit to the amount of
water 也at can exist as a vapour in air. The warmer the air, the greater the
amount of water vapour it can contain.
Humidity can be described in terms of the ratio of water to air, known as
the humidi.沙 ratio or absolute humidity which is:
the mass ofwater divided by the mass ofair containing
the water vapou只
36
Gas Technician 2 Training- Module 13
。 Canadian Standards Association
8υILDING
UNIT2
SCIENCE PRINCIPLES
Relative humidity (RH)
Relative humidity (RH) is defined as:
the amount of water vapour contained in the air expressed
as ape1℃entage of the maximum amount that could be
contained in the air at that same temperatu陀．
Air measured to have an RH of 50% contains half the amount of water
vapour that it could hold at that temperature. Air at an RH level of 100% is
saturated and has no potential for drying.
•
If a sealed house is heated, the RH decreases since the higher the
temperature, the more the air can contain moisture. The humidity ratio
remains the same since the amount of water vapour in the given volume
of air has not changed.
•
If the sealed house is cooled, the relative humidity will increase until it
reaches saturation at 100% RH. This temperature is called the dew
point. Continued cooling below the dew point will result in some of the
water vapour condensing into liquid water on a cooling surface. As the
temperature decreases below the dew point, the humidity ratio of the
remaining water vapour/air mix will decrease, since some of the water
vapour has been removed 企om the air as condensate. The relative
humidity however remains at 100%.
•
An example of this is in winter, where house air may cool below its
dew point as it passes over cold indoor surf如es, such as windows,
around doors, or cold corners, causing condensate on these surfaces.
Indoor air leaking into the walls or attic may drop water within the
structure as 让 is cooled below its dew point. This is called interstitial
condensation.
Air flow
In a similar way to heat flowing through a material because of a
temperature difference, air flows into or out of a structure because of a
difference in air pressure. Airflows｝争·om higher to lower pressure.
Pressure di他rences may be caused by:
a difference between indoor and outdoor air temperatures which creates
“ stack effect”(see below)
wind direction and velocity
•
ventilation and exhaust fans
chimneys used for combustion appliances or fireplaces
leaks in the ductwork of a forced-air heating system.
Gas Technician 2 Training- Module 13
© Canadian Standards Association
37
BUILDING SCIENCE PRINCIPLES
UNIT2
Air flow does not occur if there are no openings in the building envelope
for air to pass through. The process of air flowing in through openings is
called i听ltration; air flowing out through openings is called e拼ltration.
Internal air pressure governs the infiltration and exfiltration of air
throughout a building and must be factored into any tests of air flow.
Stack effect
The difference in temperature between indoor
air and outdoor air creates a pressure diff与rence
caused by the difference in air densities. This
pressure difference causes the house to act as
a large chimney. Cold air infiltrates through
openings in the lower levels of the building, is
heated, rises and exfiltrates through the upper
levels. This process is called stack 吃[feet. Refer
to Figure 2-6.
The level at which infiltration changes to
exfiltration is called the neutral pressure plane.
Note:
the greater the temperature difference between the
indoor and outdoor air, the larger will be the stack
笔庐ct.
Wind pressure
Stack effect
Figure 2-6 Wind pressure and stack e何ect
38
Gas Technician 2 T1阳ning - Module 13
。 Canadian Standards A路。c阳tion
BUILDING SCIENCE PRINCIPLES
UNIT2
Wind effect
Figure 2-6 also shows how wind causes positive
pressure on the windward side of the building and
negative pressure (suction) on the leeward side
and the sides parallel to the direction of flow.
Pressures inside the house due to wind action
depend on 由e amount of air flow through cracks
and openings in the building exterior and their
location in relation to wind direction.
Wind action does not usually pressurize or
depressurize the building. The overall effect of
wind action is that localized "pockets”。f positive
pressure may develop in some areas of the
building, but these will usually be balanced by
negative pressures in other areas.
Distribution systems
Forced-air heating systems distribute warm air
through pressurized supply ducts and return cool
air through depressurized return ducts. Since
many return-air systems utilize a joist space over
which sheet metal is nailed, it tends to be very
leaky. However, because the return duct system is
depressurized (it contains a negative pressure), air
does not leak out of the return system, but leaks in,
usually 企om the basement. This enhances the
stack effect by 且rrther depressurizing 也e
basement.
The effect can be compounded by basement
return-air inlets, poor fitting external furnace filter
assemblies, and leaky furnace blower doors.
Flue effect
Gas Technician 2 Training- Module 13
Standards Association
。 Canadian
A pressure difference can be caused by a
combustion appliance or fireplace with a chimney.
The appliance or fireplace takes in air for
combustion and dilution and exhausts it out 由e
chimney, causing a lower pressure in the building.
This causes increased infiltration known as flue
effect.
39
BUILDING SCIENCE PRINCIPLES
UNIT2
Ventilation effect
Ventilation effect results from the operation
of mechanical devices that exhaust air. The
expulsion of air from bathroom fans, range hoods,
clothes dryers and the like reduces indoor air
pressure, in a similar way to flue effect. Removing
air and reducing indoor air pressure causes an
equal amount of air to infiltrate.
House
depressurization
When exhaust equipment (fans, clothes dryers,
fireplaces) operate, they blow air out of the house,
lowering the indoor pressure relative to the
outside. This is house depressurization.
The greater the amount of exhaust and the tighter
the building is sealed, the more it will be
depressurized.
Backdrq斤ing
As greater house depressurization occurs, the
chimney must increasingly compete against
suction exerted by the exhaust devices.
Sometimes, this depressurization is great enough
to cause the flow of combustion gases in the
chimney to reverse. Cool chimneys are least
effective in combating house depressurization,
since cool chimneys have a weak draft. It is
therefore more common for chimneys to backdraft
when the heating appliance is not operating.
Since backdrafting can cause significant
cool-down of the chimney, when the appliance
begins to operate, it must fight against the
backdrafting c山rent of cold air. This may often
cause an appliance to spill combustion gases into
the house for prolonged periods before the
appliance can re-establish an upward draft in the
chimney. This type of spillage is called pressureinduced spillage. This spillage of chimney gases
may include carbon monoxide and other toxic
gases which can easily poison the building
occupant.
Combined effect
40
The combined effect on air flow of stack,
distribution system, flue, ventilation and wind
effects will change with such environmental
factors as outdoor temperature, wind,etc.
Gas Technician 2 Training - Module 13
© Canadian Standards Association
TOPIC
2
Contγoiling
excess
heat loss/gαin,
moistuγeand αiγ
leαkαge
Although control of heat flow and moisture are important considerations,
control of air leakage has the most significant effect on maintaining the
integrity of the building as a system. Controlling leakage into and out of the
building improves comfort levels for the occupants, saves energy and
heating costs, controls ventilation, and helps to control moisture migration
into walls and attic areas that will attach the building envelope.
Air leakage
control
Ideally, air leakage control is done from the inside to stop warm moist air,
in the winter, from entering walls or attic and possibly condensing. Air
sealing is best done at the top first (attic floor and top storey walls) to stop
warm, moist air from entering wall and attic cavities and causing damage.
Minimal work at the basement may still allow sufficient air for combustion
products.
A perfectly installed exterior air barrier can also stop movement of
moisture laden air 企om inside the building into the wall cavity, because
two holes are required to allow air to travel across the building envelope.
The air barrier would block off the holes on the outside of the envelope,
leaving only the cracks on the 句rwall side. Air cannot enter the wall cavity
if it is unable to exit on the other side.
Control of conductive heat loss
Conductive heat loss can be controlled by breaking the direct connection
between two solids with insulating material, since insulation works by
reducing heat flow through tiny pockets of air which are relatively poor
conductors of heat.
Taking the earlier example of a stud frame built tight up to the foundation
wall, if the wood 仕ame is built out from 也e wall and insulation laid behind
the studs and vertically between them, the conductive heat loss is
minimized. Extruded or expanded polystyrene is glued to the wall to
further reduce heat loss.
Gas Technician 2 Training - Module 13
Standards Assoc泪tion
。 Canadian
41
BUILDING SCIENCE PRINCIPLES
UNIT2
Control of convective heat loss
In large spaces such as wall cavities, heat can be lost across the air space by
convection and radiation. Insulation divides the air space into many small
pockets of still air, inhibiting convective heat transfer.
Control of radiation heat loss
If a person feels chilled when close to a window or wall, even though there
are no drafts, the person is experiencing radiation heat loss. This can be
resolved by improving the thermal resistance of the building envelope
surface (new windows, drapes or insulation). As with convective heat loss,
the many small pockets of still air provided by insulation, inhibits radiation
heat loss.
Insulation value
Insulation is manufactured and sold by its thermal resistance value一－
R value in Imperial measurement and RSI (Resistance System
International) in metric measurement. One brand of insulation may be
thicker or thinner than another, but if they both have the same R value，由ey
will control heat flow equally well.
The higher the resistance value, the slower the rate of heat transfer through
the insulating material.
Excess
『noisture
Controlling high humidity problems can be summarized in four steps:
control
•
Reduce moisture generation.
•
Provide spot ventilation.
•
Raise the surface temperature.
•
Ventilate the building as a system.
Control of excess moisture
Modem construction techniques are designed to:
avoid very cold surface temperatures by increasing insulation levels
•
prevent indoor leaking 由rough the building envelope through air
sealing and avoidance of pressure imbalance
reduce indoor humidity levels through adequate ventilation.
42
Gas Technician 2 Training - Module 13
。 Canadian Standards Association
BUILDING SCIENCE PRINCIPLES
UNIT2
All moisture problems are controlled by taking into consideration one or
the other of the following ways of reducing RH levels.
•
increase or decrease the temperature
•
increase or decrease the amount of moisture.
In winter, ventilation reduces indoor humidity by replacing the moist
indoor air with dry outdoor air. Indoor humidity levels must be below 40%
RH to avoid condensation on double-glazed windows at 0°C.
There are a number of ways of controlling excess moisture in winter. These
can be divided three ways:
•
no/low cost
•
medium cost
•
high cost.
No/low cost
The following measures involve little or no cost:
•
Open a window while producing moisture
•
Use exhaust fans
•
Keep lids on simmering pots
•
Vent dryers to outside
•
Remove wood piles from inside house
•
Reduce the number of plants, fish tanks, etc.
•
Cover hot tubs
•
Remove blockages from heat vents and radiators 企om windows so that
heated air can circulate freely
•
Open drapes
Install shrink-wrap plastic on windows
•
Use ceiling fans
Cover earth floors with 6 mil poly sealed with acoustical caulking at
edges
•
2 Training - MOO.ule 13
Standards Association
Gas 丁echnician
。 Canadian
Air seal cracks to reduce hidden condensation (but since this may
increase interior moisture levels, ensure you are using exhaust fans).
43
BUILDING SCIENCE PRINCIPLES
UNIT2
Medium cost
The following methods involve slightly more cost and can be used in
conjunction with other methods described here:
Install and use exhaust fans
Install a magnetic interior storm window
Add more insulation to localized areas (e.g.: in the attic over comer
wall or ceiling joints)
Install a fresh air supply duct on a forced air system, with a damper to
the cold air return plenum.
High cost
Higher cost remedies include:
Install magnetic interior storm window
•
Add exterior storm windows
Install new double-glazed, low-E, argon gas casement windows
Install a whole house ventilation system.
De-humidifiers
On a hot, muggy summer day, outdoor air may have a higher absolute
than the indoor air. Here, introducing outdoor air will increase
humidity levels. Indoor summer humidity levels can be reduced using a
dehumidifier or air conditioner.
hwηidity
Dehumidifiers are not effective in winter because they cannot lower the
indoor humidity level below 60--65%. Few buildings are above this
percentage on a regular basis in winter.
44
Gas Technician 2 Training - Modu陆 13
© Canadian Standards Association
UNIT2
Air, vapour
and moisture
barriers
BUILDING SCIENCE PRINCIPLES
A current concern in the building industry is the effects of "hidden
condensation，，。n a building. Hidden condensation refers to moisture that
enters wall and a饥ic cavities by diffusion and air leakage. This moisture
penetration problem is lessened by the proper installation of air and vapour
barriers.
Air bα！rriers
Air barriers stop moisture in vapour form from
being carried by moving air through a crack in the
house envelope. They can be installed on the
interior or exterior of the thermal envelope, and are
effective provided that they are taped at the seams
or joints. See Figure 2国7.
Vapour
barrier
Wind barrier
Air barrier
Figure 2-7 Wind and air barriers
v.αrpour bα！Triers
Gas Technician 2 Training - M~ule 13
Standards Association
© Canadian
Vapour barriers (usually 6 mil polyethylene)
restrict moisture in vapour form from travelling by
diffusion. They are always installed on the wa口n
side of the insulation, overlapped at the seams and
stapled to studs (Figure 2-8).
45
BUILDING SCIENCE PRINCIPLES
UNIT2
Air/Vapour bαrriers
This type of barrier stops moisture in vapour from
travelling with air and restricts the passage of
moisture travelling by diffusion through the
building envelope. Air sealing is relatively easy to
do, inexpensive and effective. Caulking and
weatherstripping play a key role in creating a
continuous thermal envelope air barrier, if
materials installed are of good quality and
appropriate to the job.
Moisture barriers
Moisture barriers protect insulation, studding and
wall finishes from water that might penetrate the
basement wall to the bottom plate of the stud
企ame wall from outdoors.
First sheet over
a solid member
Bead of
acoustical
caulking
Second sheet
pressed into bead
Staples
through bead
Wallboard or
batten for
mechanical support
Figure 2-8 Installation of a vapour barrier
46
2 Training - Module 13
Canadian Standards Association
Gasl忌chnician
©
BUILDING SCIENCE PRINCIPLES
υNIT2
Positive and
negative
pressure
Air pressure inside the building is defined in terms of positive and negative
pressures.
Positive pressure
Positive pressure (pressurization) means that air pressure inside the
building is greater than the pressure outside. This happens when the
amount of air supplied to the building by mechanical or other means
exceeds the amount of air removed by mechanical or other means. (The air
being added to the building exceeds the air being taken from the building.)
As the pressure inside the building increases relative to outdoors, it forces
the excess air out through any openings in the building envelope. Refer to
Figure 2-9.
Negative pressure
Negative pressure (depressurization)"means 由at the air pressure inside the
house is lower than the pressure outside the building. This happens when
the amount of air removed from the house by mechanical or other means
exceeds the amount of air supplied by mechanical or other means. (The air
being removed from the building exceeds the air being added to 由e
building.) As the pressure inside the building decreases relative to
outdoors, outside air is sucked in through any openings in the building
envelope to make up the difference in air flow. The openings may include
the chimney (Figure 2-9) .
...
...
Positive pressure
Negative pressure
Figure 2-9 Positive and negative pressures on a house
Gas Technician 2 Training - Module 13
Standards Association
© Canadian
47
BUILDING·sc!ENCE PRINCIPLES
UNIT2
Static pressure
Static pressure is defined as
•
a measure of pressure available from a fan to move a given amount of
air
•
the pressure required to use or deliver a given amount of air across a
resistance (e.g.: a filter, coil, length of duct).
External static pressure
External static pressure is the pressure di班时ence developed from the inlet
port to the outlet port of a packaged ventilator such as an HRV when the
unit delivers a specific air flow. It is the pressure available from a fan to
push air through the ductwork after pressure drops across, filters, cores or
coils etc. inside the ventilator case have been factored out.
Pressure drop
Pressure drop is the static pressure loss caused by air movement through a
duct，自lter coil, HRV core, etc.
48
Gas Technician 2 Training - Module 13
© Canadian Standards Association
TOPIC
3
Mechα＇nical
Combustion
and exhaust
appliances
effects
Air flow can have a significant effect on the combustion venting process.
Three basic concerns relate to the mechanical ventilation of a house:
•
bringing the proper amount of ventilation air to the house
•
distributing the air to the required locations in the house
•
avoiding excess pressurization or depressurization of the house.
This topic discusses combustion and exhaust appliances that help resolve
these problems. Refer to Figure 2-10.
厅·~；即n
…
Infiltration
makeup
飞且λ
τ＝－－ ·vacuum
exhaust
Dryer
exhaust
Figure 2-10 Air flow from combustion and exhaust appliances
Gas Technician 2 Training- Module 13
© Canadian Standards Association
49
BUILDING SCIENCE PRINCIPLES
UNIT2
Different types of air
The following is a brief review of the different types of building air.
Combustion air
is air required to provide adequate oxygen for fuel
burning equipment in the building. It often refers to
the total air requirements of a fuel-burning appliance,
including air to support both combus-tion and to
control chimney draft (dilution air).
Dilution air
is the ambient air that is admitted to a venting system
at the draft control device of the appliance. It is used
for two purposes:
to cool the hot vent gases
to control the draft 由e draft influence on the
combustion chamber.
See Figure 2-11.
Exhaust air
is air removed from a space and not reused (air from
kitchen and bathroom exhaust fans, clothes dryers,
vacuum cleaners). It is mechanically expelled to the
outdoors.
Make-up air
is outdoor air supplied to replace exhaust air. Makeup air can enter the house by infiltration，由rough a
make-up air duct or supply fan, etc. It does not
include air entering the building as combustion air to
replace exfiltration air.
Relief αir
is air that is mechanically removed 齿。m the building
or which exfiltrates from the building to reduce the
degree of mechanically-induced house pressurization.
It is the opposite of make-up a让．
· Circulation air
50
is produced by air moving devices such as ceiling
fans, portable fans, or summer fans on furnaces.
Natural
ventilation
is outdoor air supplied to a living space by natural
forces through openings in 由e building envelope
(open doors and windows, etc.). It is unreliable and
random.
Outdoor air
is air 仕om the outdoors taken into the building
and not previously circulated through the ventilation
system.
Gas Technician 2 Training - Module 13
© Canadian Standards A部ociation
UNIT 2
BUILDING SCIENCE PRINCIPLES
Recirculation air
is removed from a space for conditioning (heating,
cooling, cleaning, hun
and then returned to the space. Buildings without
forced-air heating or cooling systems have no
recirculation air.
Return air
is recirculation air being removed from a space.
Supply air
is the recirculation and ventilation air jointly supplied
to a space after being conditioned.
陆ntilation
is outdoor air mechanically supplied to a building.
supply air
Combustion
air
Figure 2-11
Dilution
air
Diluti。n
air
Resolving competing air problems
To keep the air in balance you need to make sure that the same amount of
air is coming in as is going out. Natural draft appliances can be affected by
an unbalanced air system which can lead to spillage of the flue products out
of the combustion chamber or draft hood. This can eventually lead to
incomplete combustion
Spillage-susceptible and non-spillage田·susceptible combustion
appliances and exhaust appliances
Exhaust fans create negative pressure and may cause spillage of
combustion appliances. Spillage is where flue gases spill out of the
combustion chamber or draft hood due to blockage or insufficient draft.
Gas Technician 2 Training - Module 13
Canadian Standards Association
©
51
BUILDING SCIENCE PRINCIPLES
UNIT2
Naturally drafted appliances, such as
atmospherically fired vented gas furnaces,
water heaters or fireplaces and other
appliances vented into a B-vent, are
spillage-susceptible.
nHHHHHHHHHHHHU
Draa“u hHooAU
If backdrafting occurs, it may go unnoticed
by building occupants. The products spilled
may contain carbon monoxide (CO) and
other dangerous contaminants.
Figure 2-12 Spillage-susceptible
conventional domestic
hot water system
Exterior wall 1/
v 11
Compare the spillage-susceptible
conventional gas 臼mace or domestic
hot water system shown in
Figure 2-12, with the non-spillagesusceptible, forced-draft and
sealed-combustion heating systems
shown in Figure 2-13.
Air inlet
‘/
/Exterior
wall
－－~－］ ¢Exhaust
\
outlet
Air inlet
陆？
Figure 2-13
52
Non-spillage-sus臼ptible
domestic hot water system
Gas Technici.~n 2 Training - Module 13
© Canadian Standards As豁出C陋的on
BUILDING SCIENCE PRINCIPLES
UNIT2
Code requirements for combustion air supply
The gas technician must consider the following factors when determining
combustion air requirements for gas appliances:
•
the tightness of the building envelope
the total input of the appliances in the room.
The Gas/Propane Codes require that outdoor air supplies must be provided
to either an enclosure or a structure in which an appliance is installed
“ when the structure either:
a) has windows and doors of close-fitting or sealed construction, and the
exterior walls are covered by a continuous sealed vapour barrier and
gypsum wallboard (drywall), pl沪.vood, or similar materials having
sealed joints
or
b) has an equivalent leakage area of 78 square inches (0.05 m) or less
at a di旺erential pressure of 0.00145 psig (10 Pa) as determined by
the recognized Canadian fan depressurization test procedure. ”
The reason for these requirements relates to the change from traditional
building construction to cuηent methods of construction. Older building
construction was loose and leaky enough to provide adequate amounts
of combustion and dilution air to installed gas appliances. Present-day
air-sealed building methods do not provide sufficient natural air
infiltration. So the Code requires that any building constructed with an
airtight envelope (such as R-2000 requirements) must be provided with
an adequate air supply.
The methods for calculating combustion air requirements change as the
factors change. The relevant factors, methods of air supp妙， and various
sizing requirements are detailed in Module 22.
Gas Technician 2 Training- Module 13
© Canadian Standards Association
53
BUILDING SCIENCE PRINCIPLES
UNIT2
Passive
depressuriz国
ation testing
To determine the required amount of make-up air, the gas technician uses
depressurization testing, usually through field testing. Determine the
appliances that may cause a negative pressure. Then test the house’s
pressure with a hand-held Magnahelic or manometer. These instruments
can measure pressure differences in the 0.0 to 0.25 in w.c. (0 to 60 Pa)
range.
Use the following depressurization testing procedure:
1. Close and latch all windows, doors and other openings. Fill floor drains
and plumbing traps with water or seal.
2. Seal combustion air inlets and chimneys or flues for combustion
appliances, including fireplaces and wood stoves.
Note:
Sealing of combustion air inlets and chimneys or flues is not required if the
combustion devices αre operated during the test and there is no combustion
spillage 斤。m any appliance during the test.
3. Set an exterior pressure tap approximately 25 ft (8 m) from the building
and connect to the measurmg device. Locate the measuring device at or
near grade level inside the building (Figure 2-14 ).
4. Switch off the ventilation equipment and any other appliances that
exhaust air to the exterior. Record the measured pressure difference.
This is the starting or “ rest” pressure.
5. Switch on all equipment used to provide the minimum ventilation
capacity (MVC). Record the pressure difference. The difference
between this measurement and the rest pressure is the MVC or
“ continuous” depressurization.
6. Switch on the dryer and the individual piece of exhaust equipment that
creates the highest intermittent air exhaust. Record the pressure
di能rence. The difference between this meas田ement and the rest
pressure is the r价rence exhaust condition or “ intermittent”
depressurization.
Note:
1页is step is required for systems which are installed according to CSAF236 rules. It is not required for “ Simple Exhaust 砂•stems ” installed
according to NBC rules.
7. Unseal any openings that were sealed for the test.
54
Gas Technician 2 Training- Module 13
。 Canadian Standa『dsAs回ciation
BUILDING SCIENCE PRINCIPLES
UNIT2
Pressure tap from dwelling
minimum 25 负（ 8 m)
Connect inside dwelling at
or near grade level X
Figure 2-14 Depressurization testing
What to do when the test indicates a problem
If the values you measure do not fall within the accepted limits as shown
on the NBC pressure limits table (shown in Figure 2-15), some solutions to
the problem are listed below:
Determine which appliance can be adapted or changed.
R叩lace or upgrade a standard furnace with a balanced ventilating nonspillage appliance.
•
Replace a standard fireplace with a direct vent fireplace.
Replace a conventional domestic hot-water heater with a direct-vent
domestic hot-water heater system.
•
Replace bathroom and kitchen exhaust fans with an E王RV.
Revent the central· vacuum system indoors.
Do not vent dryers indoors, since this introduces contaminants (odours,
dust and moisture) to the house.
Gas Technician 2 Training- Module 13
Standards Association
© Canadian
55
BUILDING SCIENCE PRINCIPLES
UNIT2
NATIONAL BUILDING CODE
PRESSURE LIMITS
1. For houses with SPILLAGE SUSCEPTIBLE combustion appliances
阳 allow创
I
I
Not
Rec ommemded
0 Pa
OK
-5 Pa
-15 Pa
0.K.
『 10
Pa
Rm
O.K.
nu
-5 Pa
-p
vu
－
-20 Pa
O.K.
。。
O.K.
tm 把一
Not
Re cornmended
NUm
朋－a
2. For houses with NON-SPILLAGE SUSCEPTIBLE combustion appliances
(or no combustion appliances)
-
AU
-
Test Conditions: • All fans of the
• Fans which are not part of the vent system are
not operated, other appliances, e.g. dryers,
cook-tops etc are not operated.
CSA F326/R2000 PRESSURE LIMITS
1. For houses with SPILLAGE SUSCEPTIBLE combustion appliances
Not allowed
O.K.
-5 Pa
O.K.
Not
Re commemded
O.K.
叫 O Pa
continuous
+5 Pa
0 Pa
2. For houses wit~ NON－~PILLAGE SUSCEPTIBLE combustion appliances
(or no combustion appliances)
No
Intermittent
Limit
O.K.
O.K.
Pa
-5 Pa
continuous
斗O
O.K.
0 Pa
Not
allowed
O.K.
+5 Pa
+10 Pa
continuous
Test Conditions ，℃ONTINUOUS”＝ Vent System 的“Minimum
· Ventilation Capacity" Mode
• "INTERMITTENT"= Vent system as above plus
Any appliance s) with exhaust capacity 75 Us
or greater (Reference Exhaust Condition)
Figure 2-15 Pressure limits
56
Gas Technician 2 Training - Module 13
。 Canadian Standards Association
BUILDING SCIENCE PRINCIPLES
UNIT 2
The
HRAI provides
a
Depressurization Test Report (Figure 2-16)
which the technician should
fill
out on completion of the testing procedure.
NOTES
1.
2.
Indicate units by circling where appropriate.
Do not conduct test with more than 12.5 km/h
(9 mph) wind.
BUILDER
Type of Home
(Bungalow etc.)
House address
3.
Test to be carried out at time of Final Inspection
or when house is substantially complete
4.
Maximum allowable pressure difference is 5 pa
in all conditions if any non-direct-vnt*fuel-fired,
vented combustion appliances are present.
5.
Maximum allowable pressure difference for
ventilation system only test condition is 10 pa
where there are no non-direct-vnt*fuel-fired,
vented combustion appliances present.
Reference Exhaust Condition
a. Ventilation system in operation
b. Dryer in operation (simulate
at 75 Ifs exhaust if not present
at time of test.)
c. All exhaust appliances over
75 Ifs exhaust capacity in
operation. (May include HRV
in defrost mode.)
*direct-vent refers only to sealed combustion units
6.
TEST EQυIPMENT
Make:
Type:
TEST CONDITIONS
Date of Test Note 3
km/h( mph)
Static Envelope P「essure STAR下一＿ Pa
END ＿一 Pa
SEE OVER FOR COMPLETE PROCEDURE DESCRIPTION
EXHAUST APPLIANCES
4123456
dd/mm/yy
Wind Note 2
TEST RESULTS
Ventilation System Pressure Change note 5 ＿一－－甲 Pa
阳erence Exhaust Condition PressureCh叫e note ＇.＇.＿＿一＿ Pa
TEST FIRM INFORMATION
Name
Address
CERTIFICATION
COMBUSTION APPLIANCES
4tnJL 句JA
I CERTIFY THAT THIS TEST HAS BEEN PERFORMED IN
ACCORDANCE WITH THE TEST PROCEDURE SET OUT
IN CSAF326-M91, PARAGRAPH 11.2.2(A1) OR 11.22.2(6)1)
DATE
mm/dd/yy
Tel:
斗
Name
FDRO
HRAI Certification #
Signature
Available from: The R2000 Home Program in
Ontario and The Heating, Refrigerating and Air
Conditioning Institute of Canada
Figure 2-16 HRAI Depressu 时zation Test Repo『t form
Gas Technician 2 Training- Module 13
© Canadian Standards Association
57
UNIT 2
BUILDING SCIENCE PRINCIPLES
Assignment 2
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
Define insulators.
2.
What are the two types of convection heating?
3.
Does cool air contain more water vapour than warm air?
4.
Cooling below the dewpoint causes water vapour to
5.
Air flowing in through openings is called
6.
轨That
7.
Can backdrafting cause spillage of flue gases? If so, could it be dangerous and why?
8.
Are dehumidifiers very effective in winter?
9.
If a building is pressurized, what happens to 也e excess air?
causes stack 写{feet?
Gas Technician 2 Training - Module 13
© Canadian Standards Association
59
BUILDING SCIENCE PRINCIPLES
UNIT2
10. Air that is removed from a space and not re-used is called
11. Air required for fuel-burning appliances is called
12. Recirculation air removed from a space is called
13. What is done to keep the air balanced in a building?
14. 孔'hat
60
instruments are used to test for depressurization of a building?
Gas Technician 2 Training - Module 13
。 Canadian Standards Association
Unit 3
Energy conservation
Purpose
The present-day emphasis on energy conservation is a major 也ct or
in the ongoing changes in building construction. To ensure that gas
equipment helps rather than hinders this process, gas technicians must
keep current on recent innovations iii materials and technologies.
Learning
objectives
1. Outline common types of building construction.
2. Describe insulation.
3. Describe conservation methods and techniques.
Gas Technician 2 Training- Module 13
© Canadian Standa『ds Association
61
Topics
1. Types of building c。nstruction ............................................. 63
House construction 1920 to present (Ontario) ...………·……………,...... 64
2. lnsulati。＂·····················….................….................................... 65
Historical levels …－…………·町．．．．．．．，．．．．．．…...………….......... ········ .. 66
Insulating throughout the building .......………··…··.......….....… ….. 67
u
3. Conservation measures and techniques ................….......... 75
Priorities. ……........... ·····,……………….....……·---…………·…, 75
Installing air sealing products ……·………………··….....…..…........ 76
Assignment 3 ............圄…………………·回........................................... 81
62
Gas Technician 2 Training- Module 13
© Canadian Standards Association
TOPIC
1
Types of building
canstγuction
In considering energy conservation, the gas technician should be familiar
with the three main types of house construction:
•
platform framing
•
balloon 仕ame
•
double/solid brick.
Of the three, platform framing is the most common.
Plα飞iform
framing
Balloon frame
Platform framing, used with brick, stucco or vinyl
veneer housing, has each floor built as a platform and
separate 丘om other floors. The brick serves no support
pu甲ose. Air leakage is a problem at the box headers
and the Building Code now requires an air barrier
wrap. Platform framing is now the most common type
of residential construction.
Continuous wall cavities from first floor to attic
(16 丘 studs) create flue-like cavities for air to escape
into the a忧ic. Wall insulation is easily blown into the
cavities.
This 句rpe
of house was popular at the tum of the
centu可·
Double/solid
brick
A double layer of brick replaces stud framing. This
of construction makes it difficult to add wall
insulation, unless rigid boards are attached to lath and
plaster and drywalled ove卫
句rpe
Until 1965, coinciding with the first Building Code
wall insulation requirements, the double brick type of
building was most common.
Gas T创业！nician 2 Training- Module 13
© Canadian Standards Association
63
ENERGY CONSERVATION
House
construction
1920 to
present
(Ontario)
UNIT3
Pre-1920
Solid brick houses had no central heating, plumbing or
electrical wiring. All these services were retrofitted in,
causing leaky construction.
1920-1945
Solid brick houses of leaky construction: knob and
tube wiring and galvanized plumbing.
1945-1970
Platform/brick veneer gradually dominated. These
houses had some attic insulation, but still leaky
construction and sliding windows of poor quality.
1970-1985
There is a gradual increase in insulation use, causing
“ tighter” houses, but increased moisture problems.
1985-1990
64
Awareness was increasing of R-2000 construction,
possibly without adequate ventilation.
Gas Technician 2 Training - Module 13
。 Canadian Standa『'ds Association
TOPIC
2
Insulαtion
Whatever the age or type of building you are dealing with, along with air
leakage control, insulation is a major f如tor in a building’s energy
conservation. This topic discusses the historical progress in establishing
insulation levels throughout the building and its various components. It is
important to the gas technician to have an overview of the key factors in
installing and locating insulation in the building as a system.
Figure 3-1 shows the main locations of insulating materials in a residential
building.
Roofs and attics
Insulating walls
Windows and doors
Figure 3-1 Insulated areas of a typi臼l Ontario house
Gas Technician 2 Training- Module 13
© Canadian Standards Association
65
ENERGY CONSERVATION
Historical
levels
UNIT3
Insulating products used to be measured by their thickness. Nowadays
insulation is measured according to its thermal resistance value (R or RSI
value), a more precise way of measuring its resistance to heat flow. Table
3-1 shows R (Imperial) and RSI (metric) nominal values.
Table 3-1 Metric (R) and Imperial (RSI) thermal resistance values
N。minal
R value
Nominal RSI value
4
5
8
12
20
28
40
56
60
0.7
0.9
1.4
2.1
3.5
4.9
7.0
8.8
10.6
Table 3-2 shows historic Ontario Building Code insulation levels in 由ree
areas of a house. Note 由at basements, the area with the largest percentage
of energy loss through 比 leakage, were not required to have insulation
until the 1980s.
Table 3-2 Historic insulation levels under the Ontario Building Code
Walls
Years
Pre-1950
。
1950-1960
A忧ics
Base町1ent
7
。
7
8
。
。
1974-1980
8
10
10
12
。
1981-1982
12
20
8
1983-1989
12
<5000
2.2
19
28/32
31
38
31
8
12
12
12 full height
>5000
22
38
12 full height
1960-1974
1990-1993
1993-
<5000
>5000
19
Note: Additional requirements for under slab, cathedral cei~的＇YS and exposed nαm are curren仰的 the Code.
In 1990, a division in the Code w回S provided for houses built in r吨ionswi伽 more or le臼 than 5000 degr盼 days.
In 1993, specific requirements for hou揭S h回t回 electrically were added. They indude R40 ceilings, R27 main walls,
R19 回回ment walls and energy-rated wind仰s.
66
Gas Technician 2 Training -
13
M创ule
。 Canadian S饱ndardsAs部cia币。n
ENERGY CONSERVATION
UNIT3
Insulating
throughout
the building
Air leakage is the number one source of energy loss in most homes
(30- 40%). This represents all air leakage throughout the building,
including cracks around windows and doors, baseboards, sillplate etc.
Basements are 20- 25%, windows (through the glass and frame)
15 - 20%, walls 10- 20%, and attics 10 一 15%. These percentages
represent heat loss by conduction, convection and radiation.
Still air does not conduct heat well and is a relatively good insulator. In
large wall and ceiling cavities, heat can still be lost across the air space by
convection and radiation. Insulation divides the air space into many small
pockets of still air, thus inhibiting heat transfer by convection and reducing
radiation across the space (Figure 3-2).
Figure 3-2
lnsulati。n
traps small pockets of still air in a cavity
General guidelines
Proper installation of insulation is essential and each area of 由e house has
specific requirements which are discussed later in this topic. 白ie following
are general guidelines 由at apply throughout the house:
•
The insulation must fill the space completely and evenly to avoid
convection heat bypassing the insulation (Figure 3-3).
Gas Technician 2 Training - Module 13
Standards Association
© Canadian
67
ENERGY CONSERVATION
UNIT 3
•
Try to avoid "thermal bridges." A thermal bridge is any solid which
directly connects the warm side of the building envelope to the cold
side, allowing heat to escape by conduction. The wood studs shown in
Figure 3-3 provide a thermal bridge.
•
Install the appropriate thickness of insulation for the size of the space.
If the insulation is loose ensure it is at the proper density.
Figure 3-3 Thermal bridge and gaps in insulation
68
Gas Technician 2 Training - Module 13
©Canadian S饱ndards Association
ENERGY CONSERVATION
UNIT 3
Although the general rule is for vapour barriers to be on the warm side of
the insulation, you may occasionally come across insulation on both sides
of the vapour barrier. The rule here is that at least two-thirds of the
insulation value of the wall is on the cold side of the vapour barrier. Refer
to Figure 3蝴4.
1/3
Figure3-4 Two-thirds of the insulation value 。nthe
cold side 。f the vapour barrier
Gas Technician 2 Training - Modu胎 13
Standards Association
© Canadian
69
ENERGY CONSERVATION
UNIT3
Figure 3-5 shows a typical cross-section of new construction from the roof
to the footings. Note how both insulation and air barrier run continuously
without breaks or thermal bridging.
"'- Continuous vapour
barrier
Double glazed
windows
//
川 e
N
h由
Et -
JHRM
JHhH
nu
nHnH
nuq
Sloped
grade
/
Figure 3-5
lnsulati。n
and air barrier from
a忧ic
to basement
Attics
High levels of insulation, a continuous air and vapour barrier, and
ventilation are the features of an energy-efficient a扰ic. Roof trusses are
available that allow high insulation levels over the top plate of the outer
walls. These include the dropped chord truss, and scissors and parallel
chord truss for cathedral ceilings.
70
Gas Technician 2 Training 』 Module 13
© Canadian Standards Association
ENERGY CONSERVATION
UNIT 3
Basements
Although many people do not think of the basement as a m苟 or source of
heat loss, basements account for up to 35% of total heat loss. Earth, below
grade level, is a poor insulator and basements also loose air through ·
windows, cracks, and at the top of the foundation wall.
The following types of foundations have their specific problems:
concrete foundations can be insulated from the outside or inside
provided there are no serious water or structural problems
rubble, brick, stone foundations are rarely damp-proofed and usually
have a history of moisture problems and should be insulated from the
outside, or replaced with concrete foundations
preserved wood foundations are found in newer residential buildings.
They are made with specially treated wood studs and sheathing and are
generally fully insulated.
Inside or outside insulation?
There are advantages and disadvantages to both inside and outside
insulation of basements.
Advantαrges
of
inside insulation
Work can be done at any time of year. It is often
easier and cheaper than insulating the full wall, yet
achieves high insulating values. Landscaping around
the house is not disturbed.
Disadvantages
of inside
insulation
Inside insulation cannot be attempted in basements
with a moisture problem without corrective measures
being taken to eliminate the moisture problem.
Obstructions such as electrical panels, wiring,
plumbing, stairs, partition walls, the oil tank etc., make
也e work more difficult and the insulation and air
barrier less effective.
Figure 3-6 shows types and locations of interior
basement insulation, including air and moisture
barriers.
Gas Technician 2 Training- Module 13
© Canadian Standards Association
71
ENERGY CONSERVATION
UNIT3
-
11l1EE
- n
nH C hH
nUM
Figure 3-6 Basement interior insulation
72
Advantages
of exterior
insulation
The outside wall tends to be more insulation
continuous and easier to insulate once 也e soil around
it is removed. You can coηect any moisture problems,
including damp-proofing and the installation of a
drainage system. There is no disruption inside 由e
house and no loss of inside space.ηie mass of 也e
foundation is within the insulated portion of the house
and tends to even out temperature fluctuations.
Disadvantages
~f exterior
insulation
Exterior insulatio~ involves excavating a trench which
can be tedious, and storing of dirt can be problematic.
Seasonal variations can cause problems in a high
water table location. Non-removable steps, paved
ca甲orts, shrubbery, trees or fences can be obstacles.
Gas T假如nician 2 Training - Module 13
© Canadian Standards Association
ENERGY CONSERVATION
UNIT 3
Figure 3-7 shows the work involved in exterior insulation.
Figure 3-7 Exterior insulation
Gas Technician 2 Training- Module 13
© Canadian standards Association
73
ENERGY CONSERVATION
UNIT 3
Walls
The type of insulation used in walls depends on the materials used in
Solid walls
Walls of brick, concrete block, log and wood plank do
not have a cavity that can be insulated. The only way
to insulate these types of walls is to add insulation to
the exterior or the interior. Air sealing of concrete
block walls is important.
Frame walls
Frame walls that have an empty cavity are easily
insulated using blown loose-fill insulation.
Adding insulation to the interior walls
Insulating interior walls (Figure 3-8) involves:
rebuilding the existing wall, usually done by removing the existing wall
board or plaster and insulating the cavity
building a new wall on the inside of the existing one. This work is done
on both wood frame and masonry walls, where a new wall is built
inside the existing one and then insulated.
Horizontal insulation
between the strappi_ng
Option of extending the
insulation past partition
walls
Insulating the
old wall
Applying the air
and vapour barrier
Figure 3-8 Insulating interi。r walls
74
Gas Technician 2 Training- Module 13
© Canadian Standards Association
TOPIC
3
Conservαlion meαSUγes αnd
techniques
Priorities
There are a few places that you need to pay particular attention to when
looking for air leakage areas. These are not the only places that you may
experience leakages, but they are the most common.
Inside the main living area, you should check:
•
around the windows
around the doors
•
the electrical outlets
•
exhaust fans and vents
•
corners where walls meet
light fixtures in the ceiling
•
interior trim and baseboards
•
cracks in the wall finish or ceiling
•
the joint where a wood 企ame wall joins a masonry wall or chimney
•
entrances into unheated attics
fireplace dampers and bricks
•
behind bathtubs and under sinks
•
above sliding pocket doors
•
around plumbing pipes and duct works.
Inside the basement, you should check:
•
where joists penetrate 也e masonry wall
•
where the wood frame wall meets the masonry
•
any holes in the walling for cables or pipes
•
leaky ducting and fittings for hot air registers or cold air intakes
•
around windows and doors
•
for cracks inthe foundation wall and slab
•
floor drains.
Gas Technician 2 Training- Module 13
© Canadian Standards A豁出iation
75
ENERGY CONSERVATION
UNIT3
inside the attic, you should check:
around the plumbing stack and pipes entering the attic
around wires or ceiling light fixtures that penetrate the attic floor
around ducting that enters the attic 齿。m inside the house (kitchen
exhaust fans, bathroom vents, etc.). No exhaust fans should discharge
into the attic, nor directly below the eave vents. Ducts should stay
below the insulation or be wrapped with insulation
at the junction of the ceiling and interior wall partitions
at the top of interior and exterior attic walls
•
around attic hatches
around the chimney
along the edge of shared walls.
Installing air
sealing
products
The first thing that you need to do is identify the place of the leak. This can
sometimes be quite difficult, and you may need to hire a contractor to find
the leak. You can also make a simple draft detector and check all the
pnonty areas.
Checking for leaks
To make a leak detector you require a few sticks of burning incense. Hold
these sticks together and check the priority areas for leaks
(Figure 3-9). Powerful leaks will cause the ends of the sticks to glow and
the smoke to dissipate. Slower leaks will cause the smoke to trail away or
move towards the leak.
Figure 3-9 Leak detection using incense sticks
76
Gas Technician 2 T1『sining - Module 13
。 Canadian Standards Association
ENERGY CONSERVATION
UNIT3
Caulking
Air seal any cracks and penetrations on the inside surface of exterior walls,
ceilings or floors. Note that any moisture that does reach the wall space
should be allowed escape to the outside. Caulking should only be used to
seal cracks that will allow water to penetrate the building.
Use a caulking gun and a caulking compound to perform the task. Make
sure that you use the right caulking compound. If you use the wrong
product it may not properly seal the crack. Also, ifthe temperature is below
5 。C the compound will become stiff and be difficult to work with. Once
you have identified the area to be caulked you proceed as follows:
1. Make sure that the area to be caulked is clean and free of dirt, loose
paint and old caulking. Replace deteriorated wood and renail loose
boards. If it is a large crack fill it first with a proper filling compound.
Push this into the crack to a depth equal to half the crack width.
2. Cut the nozzle of the tube at a size that will allow the bead of caulk to
overlap both sides of the cracl5.. Make the cut square and then push a
piece of wire or long nail down the nozzle to break the seal.
3. Push the caulking gun along at right angles to the crack or joint. The
caulk is then forced into the crack to fill the gap completely as shown in
Figure 3-10. Make sure the caulk adheres to both sides of the crack and
由at there is sufficient caulk to allow for movement or shrinkage.
Figure 3-10 Laying a bead of caulking
Gas Technician 2 Training - Module 13
© Canadian Standa『ds Association
77
ENERGY CONSERVATION
UNIT3
4. It should also look good. "Tooling”( finishing) the bead can be done
with a wetted sponge or finger before the caulk sets, but don’t use your
mouth to wet your finger.
5. Latex and silicone caulk can be cleaned off with water before they set.
For other caulks check the manufacturer's instructions.
6. When moving from place to place be sure to relieve the pressure lever
on the gun to prevent dripping.
There are a number of other materials that can be used to seal different
areas in the building. These include special gaskets and tapes, as well as
sheet materials. If you use sheet materials the installation techniques are
critical. You should also ensure all seams, edges and penetrations are
sealed.
Problem areas
Electrical outlets
Before you begin fixing an air leakage through an electrical outlet, you
must turn the power off at the circuit breaker, or remove the fuse. Check
that the power is off. You must use the special CSA approved foam pad that
fits between the cover plate and the receptacles. It will seal better if you
caulk the gasket first.
Caulk the penetration for the wire and seal the new air and vapour barrier
to the edge of the box. This is shown in Figure 3-11.
Figure 3-11 Sealing electrical outlets
78
Gas Technician 2 Training - Module 13
© Canadian Standards Association
ENERGY CONSERVATION
UNIT3
Trim areas
In many cases leaks in these areas can be sealed by using a flexible caulk.
A more effective method is to remove the trim and seal behind it. Insulate
wide cracks with polystyrene backer rod and seal them with caulking,
polyurethane foam, or other suitable material. Figure 3-12 shows the
sealing behind the window trim.
Putty or glazing
compound
/Glass
Figure 3-12 Sealing behind window trim
Glass panes
The seal between the glass and the wood frame should be tight. Check
the glazing carefully and ens田e that all seals are h臼ct, with no cracks
or missing sections. If 由e seal is not tight, r叩airwi也 putty or glazing
compound.
Fireplaces
Check 由at the fireplace damper seals properly, and 也at it is closed when
there is no fire burning. If it does not seal then it should be replaced. Even
with the damper closed, a great deal of heat escapes up the chimney.
Ideally you should install an outside combustion air duct to the fir叩lace.
This is usually available in kit form. Unused rreplaces should be sealed
off.
、马－
Gas Technician 2 Training-Module 13
© Canadian
Standa『dsAssoc湖1ti。n
79
ENεRGY
CONSERVATION
UNIT3
Chimney
Check the place where a masonry chimney rises through the attic. Cut two
pieces of sheet metal to fit around the chimney and seal the joints with a
heat-resistant sealant. If it is a factory-built metal chimney install a collar
of metal, or other fire resistant material, around the chimney, and caulk to
prevent air leakage into the attic. Note that you should not insulate closer
than 2 inches (50 mm) to a metal chimney.
Windows that are never opened
If a window is never opened, and it is not a fire exit, the best way to seal it
is to use caulking. You can use a special strippable caulk that can be
removed should you ever want to use the window again.
The main ways of improving the energy efficiency of windows is by
weatherstripping and double- or triple-glazing. Window coverings insulate
and help reduce radiant heat loss from windows.
Doors
Doors should fit snugly to their frames and incorporate weather-stripping
as air barriers around the frame and at 由e door bottoms.
Other energy saving methods
Domestic hot water systems consume more energy than all lighting and
appliances combined. Ensure that storage tanks are wrapped with
additional insulation. Use only insulation blankets 由at meet the latest
edition of the Canadian General Standards Board (CGSB) specification
51.65M Insulating Blankets for Domestic Hot Water Heaters.
Do not insulate over wiring, cover the controls, or obstruct the vent
connections, drq斤 hoods, or combustion air openings!
Lighting only specific work areas （细sk li~ting) reduces energy
consumption, and new lighting technologies also help increase ene电y
efficiency. PL lamps (pencil 也in fluorescent tubes bent into a U-shape)
are ideal for task lighting: a 11 W PL lamp gives ten times 伽 life span
of a 60 W incandescent bulb.
•
Try to install new major appliances 也at have a good EnerGuide rating
which provides the mon也ly ene电y consumption in
kilowatt-hours.
Check 岛r signs of moisture damage or structural deterioration and 阳ke
action immediately on any trouble spQts. Inspect your attic during the
cold months. Extensive 企ost build-up is a good indication of moisture
problems.
Important Check:
Any time installation is added or air leakage is sealed, gas-burning eψ中mentmustbe
checked to assure it is receiving ad1呵uate air for combustion, ventilation, and venting.
(See Module 22).
•
80
Gas Technician 2 Training-Module 13
。 Canadian Standards Association
ENERGY CONSERVATION
UNIT3
Assignment 3
When you have completed the following questions, ask your instructor for the
Answer Key.
I.
、That
is a major factor in a building’s energy conservation besides air leakage?
2.
认That
is the number one source of energy loss in most buildings?
3.
Insulation is measured by:
4.
How much of the insulation value of the wall is on the cold side of the vapour barrier?
5.
Should exhaust fans discharge into the attic to provide air circulation?
6.
Should an attic be ventilated?
7.
认That
8.
To improve energy efficiency of windows, what can we do?
9.
Frost build up in the attic indicates what?
percentage of total heat loss does the basement account for?
Gas Technician 2 Training - Module 13
© Canadian Standa『dsAs臼ciation
81
ENERGY CONSERVATION
UNIT3
10. Cracks and penetrations on exterior walls should be sealed where, and with what?
11. Caulking should be done at what temperature?
12. Insulation should be kept how far away from a metal chimney that penetrates the attic?
82
Gas Technician 2 Training - Module 13
。 Canadian Standards Association
Unit4
Indoor air quality
Purpose
Indoor air quality is directly related to levels of air pollution.
Ventilation and moisture-control must work in conjunction with
all gas equipment to provide a high level of air quality.
『
LO
a nd
eb
nge
e
j”
-
ws
1. Describe pollution and its sources.
2. Describe the principles of ventilation and filtration.
、）
Gas Technician 2 T1『邵阳ng 甲 Module 13
©Canadian S饱ndards A路ociation
83
Topics
1. Polluti。n ..............…........................….........….........….........….. 85
Sources of pollution ..…...……...……··－………...町…… E ……......... 85
Control methods and priorities .......凋.....................…·町…··…….. 88
2. Ventilati。n and filtration ......................…............................... 89
Ventilation systems ………······…........................................…….....90
National Building Code requirements for ventilati。n ………......……….... 91
Mechanical ventilation systems: advantages and disadvantages ................ 93
Filtration systems..... .…‘….....………..…… ……….........,…··-…..... 97
a
Assign町、ent 4 .................................................…........................... 99
84
Gas Technician 2 Training- Module 13
。 Canadian Standards Association
TOPIC
1
Pollution
Poor indoor air quality is described by the Heating, Re仕igeration and Air
Conditioning Institute of Canada (l虫Al) as “ when the inside air contains
enough of a substance to adversely affect the comfort, health or safety of
the occupants. ” Poor air quality is a direct result of the combination of high
pollutant levels and inadequate ventilation and other control methods that
e址iaust or neutralize polluted indoor air. Frequent air exchange ensures
that pollutants from household air are removed with speed and efficiency.
Sources of
pollution
Sources of indoor air pollution can be divided into two main categories
(refer to Figure 4-1 ):
chemical (from building materials, cleaning fluids, cigarette smoke,
furniture and rug finishes, etc.)
•
biological (from people, pets and plants).
Figure 4-1 Sources of indoor air pollution
Gas Technician 2 Training- Module 13
Canadian Standards As叙沁iation
©
85
INDOOR AIR
QUAL仔Y
UNIT4
Chemical pollutants
The following table summarizes the main chemical pollutants and their
sources.
Table 4-1 Sources of indoor air p。 llution (gases and liquids)
Description
Pollutant
Sources
Radon
Colourless, odourless, radioactive gas, !Air leakage from the ground or rock
generated from the decay of radium, a Ibeneath the building, from ground water,
lor construction products (concrete and
mineral in the ea同h’s crust
masonry)
Formaldehyde
(HCHO)
Strong-smelling, colourless gas
Construction materials, glues in
pa『ticleboard, plywood, furniture and
textiles. Also in tobacco smoke.
Carbon monoxide
(CO)
Colourless, odourless, tasteless gas, at
times released during combustion
IFireplaces, woodstoves, unvented gas
Iappliance, automotive engines in attached
garages
Carbon dioxide
(C02)
IColourless, odou叫essgas
Nitrogen dioxide
(N02)
IColourless, odourless, tasteless gas
Combustion appliances (kerosene
heaters), smoking
Volatile organic
compounds (VOCs)
!Visibly undetectable, but detectable
!odour
Fumishings, adhesives, .solvents,
pesticides, cleaning and cooking products
陆ter
!Humid, condenses on walls and
windows
Cooking, showering, new furnishings and
leaky basements
IPa此icles less than 0.25 microns in air
Ithat 臼n be drawn into lungs
Unvented combusti。n appliances, some
humidifiers, house dust, wood smoke and
tobacco smoke
(H20)
Respirable
particulates (RSP)
Respiration, fuel, burning equipment,
smoke
tobaα:o
Biological pollutants
咀ie sources of air-borne biological pollutants include (refer also to
Table 4-2):
•
humanhair
•
skin flakes
•
animal dander
•
pollen
•
mold spores
•
dust mites and dust mite debris
．如ngi
86
Gas Technician 2 Training - Module 13
© Canadian Standards As四elation
INDOOR AIR QUALITY
UNIT 4
•
lint
•
bacteria and viruses
•
tobacco and wood smoke
•
household dust.
Table 4-2
Airb。 rne
biological pollutants and their e何ects
Source
Airborne unit
Human effects
Main indoor sources
Bacteria
(Legionelle,
Thermoactinomyces,
Endot6xin, Proteases)
Organisms, spores,
products-toxins,
antigens
Pneumonia,
pontiac fever,
hypersensitivity,
pneum。nitis fever, chills,
asthma
c。oling towers, hot
water sources, stagnant
water reservoirs,
industrial processes
Fungi
(Altermaria, Hisoplasma,
Cladosporium,
Aspergillus, Penicillium,
Aflatoxins, Aldehydes)
Organisms, spores,
Asthma, rhinitis,
antigens, toxins, volatiles allergies, systemic
infection, cancer,
mucous membrane
irritants
Damp surfaces, bird
droppings
Protozoa
(Naegieria,
Acanthamoeba)
Organisms, antigens
Infection, hypersensitivy,
pneumonitis
Contaminated water,
reservoirs
Viruses (Influenza)
Organisms
Respiratory infections
Human hosts
Algae (Chlorococus)
Organisms
Asthma, rhinitis, allergies Outdoor air
Green plants (Amborsia)
Pollen
Asthma, rhinitis, allergies Outdoor air
A『thropod
(Dust mites,
cockroaches)
Faeces
Asthma, rhinitis, allergies House dust
Mammals (Humans,
horses, dogs, cats)
Skin scales, saliva, urine Asthma, rhinitis, allergies House dust
It can be seen from the preceding tables that excess moisture, dust and
inadequately vented air contribute in varying degrees to increased chemical
and biological pollution of the indoor environment. Most control methods
relate to ways of removing indoor contaminants and replenishing stale or
over-moist air with 企esh air drawn 齿。m the external environment.
Gas Technician 2 Training- Module 13
© canadian Standards Associ_ation
87
INDOOR AIR
QUAL阿Y
Control
methods and
priorities
UNIT 4
The priorities for improving the air quality inside a building are: to reduce
or eliminate the source of the pollutants, and minimize their 吃所cts through
better ventilation and, to a lesser extent, filtration.
Control at source
Although there are many and varied ways of controlling indoor air quality
(Figure 牛匀， often a combination of several approaches is most effective.
Ways of controlling the indoor air include:
removal (store chemicals outside the living space)
substitution (non-polluting products should be chosen in preference to
polluting products)
containment (store household chemicals in an airtight, vented cabinet)
control (at the design stage of new construction or renovation)
air treatment
•
humidification and dehumidification
local exhaust (range hoods, bathroom exhausts use filtration and
ventilation).
' - Innovation
and design
Figure 4-2 Methods of controlling air contaminants
88
Gas Technician 2 Training - Module 13
。 Canadian Standards ASl如ciation
TOPIC
2
Ventilation α＇ ndfiltγαtion
Ventilation and filtration are the two commonly used methods of pollutant
control.
Ventilation
A good ventilation system has the overall capacity to
ventilate the house, distribute fresh air to habitable
rooms, include mechanisms to control pollutants
through removal at source, provide for make-up or
relief air if necessary, and include an appropriate
ducting and control system.
Filtration
Filtration is 由e process of passing a liquid through a
device or porous substance to remove solids or
impurities-the removal of particulates (not gases)
from the air stream
As a gas technician, your main concern will be with
v~ntilation systems since you may be required to
provide ventilation air to areas containing gas
appliances. It is therefore important that you be
familiar with the current National Building Code
(NBC) and the Heating, Re企igerating and Air
Conditioning Institute O虫AI) requirements related to
the mechanical ventilation of residential buildings.
Note the Propane and Natural Gas Codes pertaining to
air supply requirements.
Gas Technician 2 Training - Module 13
e Canadian Standards Assc回ation
89
INDOOR AIR
QUAL盯Y
Ventilation
systems
UNIT 4
There are many ways of ventilating residential dwellings. Although codes
and standards play a large part in deciding what type may be appropriate,
other factors influence the choice:
type of heating system(s)
availability of equipment and parts
owner preferences
size, type and budget of the house.
Figure 4-3 shows a number of common ways of providing ventilation.
Open
window
‘----+
Holes in the
envelope
Duct to return
- air plenum
Central ventilation
system
Figure 4-3
90
叭lays
of providing ventilation to a dwelling
Gas Technician 2 Training - Module 13
© Canadian Standards Association
INDOOR AIR QUALITY
UNIT 4
National
Building Code
requirements
for ventilation
The National Building Code of Canada details requirements for the
ventilation of rooms and spaces in residential occupancies by natural
ventilation and to self-contained mechanical ventilation systems serving
only one dwelling unit.
General
1. Every dwelling unit shall incorporate provisions for non-heatingseason ventilation in accordance with the Building Code. If supplied
with electrical power, provisions for heating ventilation must be in
accordance with the Code.
Non-Heating 唰Season
Ventilation Required
1. Rooms or spaces in dwelling units must be ventilated during the nonheating season by natural ventilation or by conforming mechanical
ventilation systems.
2. If a habitable room or space is not provided with natural ventilation as
described above, mechanical ventilation must be provided to e址iaust
inside air 企om or to introduce outside air to that room.
•
•
one-half air change per hour if the room or space is mechanically
cooled during the non-heating season, or
one air change per hour if it is not mechanically cooled during the
non-heating season.
Natural Ventilation Area
1. The unobstructed openable ventilation area to the outdoors 岛r rooms
and spaces in residential buildings ventilated by natural means must
conform to Table 9.32.2 of the Building Code (following page).
2. Where a vestibule opens directly off a living or dining room within a
dwelling unit, ventilation to the outdoors for such rooms may be
through the vestibule.
3. Openings for natural ventilation other than windows must be
constructed to provide protection 仕om the weather and insects.
4. Screening must be of rust-proof material.
Gas Technician 2 Training- Module 13
©Canadian S恒ndards Association
91
INDOOR AIR
QUAL门Y
UNIT4
NBC Table 9.32.2
Natural ventilation
Location
Within
dwelling
unit
Other
than
within
dwelling
unit
Minimum
Unobstructed Area
Bathrooms or water closet rooms
Unfinished basement space
0.09 m2
0.2% of the floor area
Dining rooms, living rooms,
bedr。。 ms, kitchens, combined
rooms, dens, recreation rooms and
all other finished ro。 ms
0.28 m2 (per room or
combination of rooms)
Bathrooms or water closet rooms
0. 09 m2 per water cl。set
Sleeping areas
0.14 m2
Laundry rooms, kitchens, recreation
rooms
4% 。f
Corridors, storage rooms and other
similar public rooms or spaces
2% of the floor area
Unfinished basement space not
a shared basis
0.2 % of the floor area
the floor area
used 。n
Heating Season (mechanical ventilation)
required
Every dwelling unit that is supplied with electrical power must be provided
with a mechanical ventilation system complying with CSA-F326 and
various articles and sections in the Building Code.
Design and
ins恒 llation
Aspects of mechanical ventilation systems not specifically detailed in the
Building Code must be designed, constructed and installed in accordance
with good practice such as described in the ASHRAE Handbooks and
Standards, the E亚AI Digest, the Hydronics Institute Manuals, and the
SMACNA Manuals.
Total Ventilation Capacity
1. The minimum total ventilation capacity of the ventilation system
required in the Building Code must be 由e sum of the individual room
capacities specified in the Building Code.
92
Gas Te<为nicia『12 Training- Module 13
。 Canadian Standards Association
INDOOR AIR QUAL汀Y
UNIT 4
NBC Table 9.32.3
Ventilation capacity
Room
Mechanical
ventilation
systems:
advan姐ges
and
disadva n蚀ges
Capacity， υs
Master bedrooms
10
Other bedrooms
5
Living room
5
Dining room
5
Family room
5
Recreation room
5
Basement
10
Other habitable rooms
5
Kitchen
5
Bathroom 。r water closet room
5
Laundry room
5
Utility room
5
Until recently, mechanical ventilation was not considered important in
residential buildings. It was assumed that the natural ventilation through
the actions of wind and “ stack effect” and the operation of heating
appliances would create sufficient air movement through the leaks and
cracks in the building envelope to flush out home contaminants. In new
houses or older homes brought up to current air tightness standards, it is no
longer sufficient to rely solely on accidental ventilation.
The Heating, Re仕igeration and Air Conditioning Institute of Canada
defines three basic concerns related to the mechanical ventilation
of a house:
。现AI)
bringing 坦白e proper amount of ventilation air
•
distributing the air to the required locations
avoiding excessive pressurization or depressurization.
The following excerpt 仕om the HRAI manual, Residential Mechanical
陆ntilation Systems, outlines some of the advantages and disadvantages of
each system in meeting these concerns.
GasTechnic』an 2 Training-Module 13
©Canadian S恼ndards Association
93
INDOOR AIR QUALITY
UNIT 4
Exhaust fan systems
Figure 4-4 Exaust fan
system
This negative pressure can create problems, such as accentuating drafts
through the remaining holes in the envelope. If the suction forces are
high enough (for example, if the e油aust fans are strong enough or the
building envelope is tight), it can cause problems with the venting action
of fuel-fired appliances, creating combustion product spillage or
backdrafting.
There is also a concern that contaminants originating from below-grade
sources (soil gases) can be increased with high negative pressures.
Supply fan systems
Supply fan systems (Figure 4-5) draw fresh air into the house and create a
positive pressure in the building. This eliminates some of the concerns
found with exhaust fan systems but the positive pressure can force warm,
moist indoor air through holes m the building envelope and increase the
risk of problems due to condensation in walls and attics. Supply fan
systems should only be used in buildings with good air barriers.
Figure 4-5 Supply fan
system
Another problem with supply systems is that, in the winter, relatively
large quantities of cold outdoor air are brought into the house at one or
two locations. The outdoor air should be preheated, mixed with the
indoor air, and distributed in a manner which avoids cool air blowing on
the occupants of the house. This can increase installation costs.
Balanced systems
•
Figure 4-6 Balanced
System
94
Balanced systems (Figure 4-6) are designed to have no impact (either
negative or positive) on the pressure balance of the house.η1is
eliminates the problems caused by both positive and negative pressures,
but at some additional cost. In most cases, two fans work in tandem to
provide ventilation. These fans must be interconnected elec位ically and
may be connected physically. As with supply systems, the incoming air
must be warmed before distribution.
Gas Technician 2 Training - Module 13
© Canadian Standards Association
INDOOR AIR QUAL町Y
UNIT 4
Running a ventilation system will increase the operating costs of a home
when compared to the costs of operating a poorly ventilated dwelling.
Exchanging warm indoor air with cold outdoor air will require more
heating and electricity will be consumed to operate fans.
•
Note that controlled ventilation in a house with a tight envelope will cost
less than the uncontrolled ventilation resultingfrom “lea炒” construction
掉一 techniques.
Figure 4-7 Balanced
HRVsystem
One way to minimize additional heating costs is to extract heat 仕om the
outgoing air, using it either to heat the incoming air or to meet some other
energy requirements, such as domestic hot water. A type of balanced heat
recovery ventilator (HRV) system is shown in
Figure 4-7.
Distribution systems
The ventilation air distribution system distributes the ventilation air to the
·appropriate locations in the house. Three types are described below. In all
cases, exhaust air is exhausted from odour- and moisture-producing
areas, such as kitchens, bathrooms and utility rooms, through dedicated
e址ia山t ductwork.
Dedicated, independent or separately ducted
Dedicated, independent or separately ducted systems dis.tribute
ventilation air using an ind叩endent or dedicated set of duct work (Figure
4-8). Each habitable room in the house should have its own ventilation
Figure 4-8 Separately air supply outlet or e对iaust air inlet. 白iese systems are commonly used
ducted system
in houses with baseboard or radiant heating systems.
Gas Technician 2 Training - Moclu始 13
。 Canadian Standa叫s Assoc阳tion
95
INDOOR AIR
QUAL阿Y
UNIT4
／〈＼阳也g硝d …bined
Integrated or combined systems utilize the forced-air heating and/or
cooling systβm to distribute ventilation air throughout the house. The
ventilation air supply is connected to the forced-air recirculation system
return duct (Fig町＠牛肉. The forced-air recirculation fan (which must be
capable of ope1回ing continuously) distributes the ventilation air
throughout the house while mixing it with return air.
Figure 4-9 Combined
distribution system
Through-the-wall
Through-the国wall
distribution systems utilize exhaust fans to induce
infiltration into the house. Through-the-wall diffusers introduce outside
air directly to each room in a controlled fashion. Refer to Figure 4-10.
Figure 4-10 了hrough
the-wall system
A
Caution!
Note the following hazards and warnings related to ventilation:
•
If a house is well sealed and a series of 由rough-the-wall e由aust fans
are installed, their operation can lead to serious health hazards since the
depressurization that would result 仕om operating the exhaust fans
could cause the furnace or fireplace to backdraft .and draw poisonous
gases into the house.
Installing a supply-only system in a leaky house can lead to problems
with moisture-laden air being driven into the wall cavities.
96
•
Too much ventilation can cost the homeowner more 也m necessary to
adequately ventilate 由e home. If the cost is significant, the home。，wner
may be tempted t。”m the ventilation system off, defeating 也e
pu甲ose of installing it in 也e first place.
•
Too little ventilation can lead to a build-up of pollutants in the air. In
new house, for example, furnishings, floor coverings, and building
materials give off formaldehyde. If the ventilation system is inadequate
to dilute the levels of formaldehyde, health problems may develop 岛r
individual house occupants.
Gas Technician 2 Training - Module 13
© Canadian Standards Association
UNIT 4
Filtration
systems
INDOOR AIR QUALITY
Although there are many types of air filters available for the residential
market, the majority are designed to protect coils and heat exchangers of
mechanical equipment and have little impact on air quality. Be aware of
two ways of measuring that have proven effective in the building industry:
Arrestance
which is a measure by weight of particles. Since even
poor filters will pick up heavy particles most filters
demonstrate a relatively high efficiency in this area.
Dust spot
efficiency
which is a measure by volume of particulate at
various size ranges. It is a better indicator of filtration
effectiveness against the range of household dust
particulate.
Gas Technician 2 Training - Module 13
。 Canadian Standards Association
97
INDOOR AIR QUALITY
UNIT4
Assignment 4
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
Wood is a form of biological pollution. True or False?
2.
What is the word used to define the circulation and purification of air in an enclosed space?
3.
What is the minimum ventilation rate in a room with an 8 ft ceiling?
4.
If a room is mechanically cooled in summer, what is the ventilation rate required?
5.
An exhaust fan system in a dwelling causes a positive pressure due to suction force within the
dwelling.True or False?
(Explain your answer)
6.
Name the three terms used to describe ventilation distribution systems.
a)
b)
c)
、、－
Gas Technician 2 Training -
Modu梅 13
@ Canadian Standards Association
99
INDOOR AIR
QυALITY
UNIT4
7.
What is the problem with supply-only systems in leaky structures?
8.
What is the danger of having too little ventilation in a dwelling?
9.
Name the two ways of measuring effective air filtration in the building industry.
a)
b)
100
Gas Technician 2 Training - Module 13
© Canadian Standards As献副ation
Module 14
Domestic Appliances
A thorough understanding of domestic appliance installation, servicing and maintenance is an important part of a gas technician ’ s
training. Common gas-fired domestic appliances include: cooking
ranges and ovens, clothes dryers, barbecues, and lamps.
At the end 。f this m。dule you will be able to:
•
Install, service and maintain ranges and ovens
•
Install, service and maintain cl。thes dryers
Install, service and maintain barbecues
Install, service and maintain
Gas Technician 2 Training - Module 14
© Canadian Standards Association
gas－币red
lamps
-1
·1
·i
Ken Bales, Manager, Gas Information Products, CSA, wishes to acknowledge the followi 「1g individuals
who contributed as members of a Review Panel during the development of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology (BCIT) is
acknowledged for its work in the technical development and editing of the original edition.
Contribut。rs and members of the Review Panel
John Cotter
Bill Davies
Eric Grigg
Wa「「en Hayes
Darrel Hilman
Ken Kell
W. John Lampey
Lorne Lowry
Jim Noseworthy
Gary Prentice
Nick Reggi
Rick Rogozinski
Ron Royal
John Semeniuk
Allen Sidock
John Simmons
David Stainrod
Terry Waters
iv
Canada「e College
Union Gas Limited
Canadore College
Supe 「io「 Propane Inc.
Southern Alberta Institute of Technology
Centra Gas Manitoba
Albe 阳 Advanced Education & Caree 「 Development
Algonquin College
Durham College
Environmental Energy Consultants
Humber College
Union Gas
Fanshawe College
Northern Alberta Institute of Technology
Cambrian College
Loyalist College
D.J. Stainrod & Associates Ltd.
Enbridge Consumers Gas
Gas Technician 2 Training - Module 14
。 Canadian Standards Association
Module 14
Table of Contents
Unit 1
Ranges
Types of gas ranges ...............................…......... 3
Installation requirements ........……....................... 7
Piping .........................................…...............….. 17
Electrical ....................…….........…..................... 25
Burners and ignition systems ...........….............. 27
Oven c。ntrols ...........….................................…... 37
Oven c。ntrol calibration and testing ...........…... .43
Operation ........…............................................... 51
Service ...................................…·”.......……......... 53
Assignment 1 ...........…………·圄….......….............. 61
Unit 2
Clothes dryers
lnstallati。n
requirements .......................…......... 65
Piping ”.............…..................….......................... 71
Electrical
................................”．．．．．．，’．．晴............... 75
Moisture exhaust vents ..................................... 79
Burner ig 『liti。n systems ..................................... 85
C。ntr＇。Is .............................................’........’...... 93
Operation ．．．圄．．．．．．．．．．圃........................................... 99
Service ............................................................ 103
Assignment 2 ..............................圄................... 111
Gas Technician 2 Training - Mαjute 14
©Canadian S恼ndards Association
v
Unit 3
Barbecues
Installation requirements ..............................… 115
Components ............…………·············………...... 119
Operation .................…”................................... 123
Service 圃………·········……………….........….......... 127
Assignment 3 ...............………·······…··········…... 129
Unit 4
Lamps
Installation requirements ................................. 133
Components. ……································………… .135
Operation ........................................................ 141
Service ..........曹．．．．‘·····················’．．．．．’................ 143
Assignment 4 ................................盟．．．．．．．．．’....... 147
Appendix A t。 Unit4 ....................................’.. 149
instructions
丁ypical 『nam』facturer's
VI
Gas Technician 2 Training - Module 14
© Canadian Standards Association
Unit 1
Ranges
Purpose
Cooking with gas has never been more popular. Numerous gas ranges,
types of ignition systems and temperature controls are used. The gas
technician must be aware of old as well as new technology that may be
encountered when installing and servicing gas ranges.
Learning
objectives
1. Describe the different types of gas ranges.
2. Describe the installation procedures for gas ranges, including
piping and electrical connections.
3. Describe the burners and ignition systems.
4. Describe oven controls and their calibration and testing.
5. Describe the operation of gas ranges.
6. Describe the servicing of gas ranges.
Gas Technician 2 Training 呻 Module 14
Canadian Standards Assoc阳lion
©
Topics
1.
Types 。f gas ranges ................................................................ 3
Major types of gas ranges .........…........…········…回…......…...................... 3
M司or features of gas ranges ……..................................…·.........…........4
Heat transfer meth。ds ..........……………··….........………………..........…........ 4
2.
Installation requiremen恒”··”.................................................. 7
Manufacturer’s specificati。ns ............................……............………............... 7
Code requirements ........…........................……….........……..............................9
General considerations .......’.............................….......…....... •·•·••·•• •••.•.•.••• 12
Fuel conversion ..........….......……..............…..................….........……........... 15
3.
Piping .............….......…….....................................…................. 17
Connection ........…..............………............................. ••••••••·••·••·· •·•••·•••· .••.•.. 17
Regulators .......................................…........…................................................ 17
Burner orifices ..........…·······….......…...........................................….............. 18
Leak testing ........................…..............….....................................…..............20
Removing old appliances. …................……·····································…............20
Test pressures .......................…········……................…··············………...........21
Connecting components ...….................…………........…··············……............23
4.
Electrical ．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．瞿................................................ 25
Electrical Code requirements .............................…........................................25
5.
Burners and igniti。n systems ...........................…….............. 27
Top burners ........................…·······························…........….......……….........27
Top burner ignitors .............….................….................………….......................29
Oven burners .............................….......................................…·……..............3 丁
Oven ignition systems. …································….................…...........….........32
Extinction pop .................……..............……......................….........................36
6.
Oven contr。Is .............................…......................................... 37
Cycling oven controls ........…·….........................................……........…..........37
Set-back controls ...............…······················….......…·······…...........................40
Self-cleaning oven .................….........…................................….....................41
Programmable cl。cks .........….......................................................................41
7.
Oven c。ntrol calibrati。n and testing.….................…............ 43
Mechanical 叫ustments ...............................................................................43
Electro” mechanical adjustments .........….....................…·················…...............46
Electronic adjustments ..................................................…·….......…...............50
8.
Operati。n
.......................................…...............….......….......... 51
Gas pressure .......................…..................….........….....................................51
Primary air supply .................…...................….........………..............................51
9. Servi饵”··”…........................................................................... 53
Proper servicing practi臼．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．．臼
Ignition system faults ..................................…········································…….56
T。p burner faults .....................….................………······································…58
。ven burner faults ....................…..................................…............................58
Assignme’唱t 唱...................................”．．．．”．．．．．．．．．．．．．．．．．．．．．．．．”......... 6 唱
2
Gas Tee如nician 2 Training - Module 14
© Canadian Slandai:ds Association
TOPI℃ l
吟pes
Major types of
gas ranges
ofgas
γanges
A gas technician will encounter many different types and designs of
gas-fired domestic ranges in the field. Major types of gas-fired ranges
include:
•
free-standing ranges
•
built-in ranges
•
gas and electric combination units
dual 如el
units.
Free-s阳 nding
ranges
Most residential service gas-fired ranges are 24 to 30 inches wide,
free-standing units with an integral oven. Free-standing means that they
are not built-in or permanently installed.
Built-in ranges
Built-in ranges are permanently installed as part of the kitchen cabinetry.
A gas-fired wall oven is a separate built-in unit. It is installed and operated
independently from the drop-in countertop cooking unit that it is usually
paired with.
Gas and electric combination units
Gas and electric combination units allow the use of one or the other energy
source.
Dual fuel units
Dual fuel gas ranges can be operated on propane or natural gas. The switch
is usually accomplished by means of an adjustable orifice device.
Gas Technician 2 Training - Module 14
© Canadian Standards Association
3
RANGES
Major features
of gas ranges
UNIT 1
The m碍。r features of gas-fired ranges are included below.
Selj-cleαning
feature
肌喀
o
e
『
Heat transfer
methods
4
脯’加
dn
cd
n
na
-w
.., UFE
4
An oven equipped with a self-cleaning feature
incinerates the baked on dirt in the oven by heating it
to high temperature during a cleaning cycle. For
safety, the oven door locks when the cleaning cycle is
selected, and remains locked until the oven cools after
the cleaning cycle ends.
In a continuous cleaning oven, the dirt is baked off the
oven surfaces on a continuous basis while food is
cooking.
Broiler
Some gas-fired ovens are equipped with broiler units.
The broiler is a special burner located in the top of the
oven. Heat from the burner is directed downward
towards the food to be broiled.
Warming
drawer
Some gas-fired ovens are also equipped with warming
drawers. A warming drawer maintains food that has
already been cooked at 也e desired serving temperature.
The three methods of heat transfer in cooking appliances are:
•
convection
•
conduction
•
radiation.
Gas Technician 2 Training - Module 14
© Canadian Standards Association
UNIT 1
RANGES
Convection
Convection is the transfer of heat by heat cuηents. Ovens use one of two
methods of convection heating: natural convection or forced convection.
Natural
convection oven
Warm air rises and cool air descends in the process of
natural convection. In a standard, natural convection
oven, the hottest area is at the top of the oven and the
coolest is at the bottom, no matter where the burner is
located.
Thermostats located in the oven can control the burner
on-off cycle within a certain temperature range, but
the temperature may vary as much as 50。F from one
area of the oven to another. This makes it difficult to
cook 岛od evenly.
Forced
convection oven
In a forced convection oven, the heat produced by the
burner is circulated evenly throughout the oven by a
fan. The circulating heat cooks food 也ster and more
evenly than a natural convection oven.
Conduction
Conduction is the transfer of heat through direct contact. An example of
this method of heat transfer is a pot of water on a range top burner being
heated through direct contact with the burner flame.
Radiation
Radiation is the transfer of heat by means of heat rays emitted 企om a heat
source. An overhead broiler burner employs this method of heat transfer.
Gas Technician 2 Training - Module 14
Canadian Standards Association
©
5
TOPIC 2
Installation γequiγements
Before installing a gas-fired range, the following information must be
reviewed to ensure the installation will conform to the necessary
reqmrements:
Manufacturer’s
Specifications
•
manufacturer ’s specifications
•
applicable Codes
•
installation instructions.
The manufacturer ’s specifications are found on the model and serial
number identification plate (rating plate) attached to the appliance at the
factory. The rating plate includes the following information:
•
Btu/h (k矶＇） rating of the appliance
approvals by regulating authorities and agencies
operating voltage and current
operatmg pressure.
Input rating
The input rating of the appliance in Btu/h (or kW) will be stamped on the
rating plate. The rating plate specifications allow the appliance installer to
determine the correct pipe or tubing size for the service and to set the
burner inputs correctlv.
Approvals
Gas industry and gov rnmental regulatory agencies must approve all gas
appliances before they are sold by the manufacturer. Regulatory authorities
recognize the service f third-party certification organizations and provide
the approval by insistftig that gas appliances be certified by a recognized
certification organiza ion.
Gas Technicia 『12 Training- Module 14
©Canadian S蚀ndards Association
7
UNIT 1
RANGES
The official logo, symbol, or seal that indicates the certification of the
appliance will appear on the appliance ’s rating plate. The approval symbols
that must appear on the rating plate of a gas appliance sold in Canada
include those of CSA International (CSA). Local provinces may recognize
other agencies.
Operating voltage and current
The range must only be connected to an electrical circuit that conforms to
the operating voltage and current rating specified on the identification
plate. For example, if a range designed to operate on 120 volts is connected
to a 220 volt supply, the components will bum out from the excess voltage.
Excess voltage will also cause motors to overheat and gas valves to
malfunction. Some flame rectification ignition systems will not operate if
the polarity of the range supply voltage is reversed.
Operating pressure
Gas supply pressure is normally higher than that required for burner
operation. An appliance pressure regulator is used to reduce the supply
pressure to the manifold pressure required at the burner and maintain it at
that level.
It is important to maintain the correct manifold pressure setting in order to
avoid service problems and hazardous conditions such as:
•
delayed ignition
sooting
•
flash-back
extinction pop
•
damage to components
•
poor operating efficiency
limit cycling.
Typical inlet gas pressure to the appliance regulator is 6 inches w.c. (1.5
kPa) for natural gas and 10 inches w.c. for propane. Typical outlet
(manifold) pressure would be 3.5 to 5 inches w.c. (0.9 to 1.25 kPa) for
natural gas, and 10 inches wι （2.5 kPa) for propane.
8
Gas Technician 2 Training- Module 14
© Canadian Standards As就沁iation
RANGES
UNIT 1
The regulator is usually pre-adjusted for use with the type of gas specified
on the rating plate and for a specific outlet pressure. Many ranges are
equipped with a regulator that can be a司justed for use with propane or
natural gas. If the range is to be used with a different gas, the regulator
must be a司justed accordingly. The regulator is a司justed by changing the
position of a simple converter fitting (reversing cap or spring and disc
assembly) on the regulator.
It is important to measure the inlet pressure to an appliance while it is firing
at its rated input. If the appliance is not firing or is being under-fired, the
input pressure reading will be static. A static reading does not reflect the
pressure loss that results from gas flowing through the system.
The input pressure to an appliance is measured with a manometer or
pressure gauge installed in a tee fitting in the supply line just before the
appliance.
Code
requirements
All range installations must conform to the requirements of applicable
Building, Gas and Electrical Codes.
Electrical connections
Most gas ranges require electrici可 to power clocks, timers, and other
control devices. The electrical connection will usually be 120 V 60 Hz,
two-wire, with ground. The minimum size and type of wire that can be
used 岛r a 120 V, 15 A indoor appliance is #14 AWG NMD-90.
All electrical connections between an appliance and the building wiring
must comply with applicable Electrical Codes. All electrical devices
associated with the appliance must be connected in accordance with the
wiring diagram supplied by the manufacturer.
A range must be connected to the electrical circuit receptacle by means of
an approved power supply cord wi也 a 3-prong grounding plug. Extension
cords may not be used.
Under no circumstances should the grounding prong of a power supply
cord be removed, or replaced with a two-prong plug or adapter.
Gas Technician 2 Training- Module 14
© Canadian Standards Association
9
RANGES
UNIT 1
Piping connections
The Code requirements for gas range piping and tubing connections can be
found in the Natural Gas and Propane Installation Code (B 149 .1 ). We will
refer to this requirement as the Code.
Ranges may be connected to the gas supply by means of rigid or flexible
connectors. Metal (flexible) connectors must be installed in accordance
with the following Gas Code requirements:
connectors must be protected 企om potential damage
•
connectors must not pass through walls, floors, ceiling, or partitions
•
connectors must be connected to rigid pipe or tubing in the same area
as the appliance, with a shutoff valve located in the same room as the
appliance
a gas-fired appliance (range) must not be installed or operated in any
location where it could create a hazard
a gas-fired appliance (range) must not be installed in a room where
corrosive vapo町s may damage the appliance or its venting system.
Prohibited practices
咀ie
following practices are prohibited for gas piping installations, for
reasons of safety and proper system operation:
•
defective sections of pipe or tubing must be replaced and not repaired
bushings must n时 be nested (installed within one another)
•
fittings wi由 both left- and right-hand threads, thread protectors, or
running threads must not be used
concealed piping runs must not contain a union or combination of
fittings intended to act as a swing joint
field bending of piping is not permitted
•
gas piping and tubing must not be used as an electrical ground
•
piping and tubing must not be used in lieu of electrical wiring except
for a low voltage control circuit, ignition circuit, or flame detection
device circuit incorporated into an appliance
piping must not contain a street elbow or street tee.
10
Gas Technician 2 Training - Module 14
。 Canadian S恼ndards Association
RANGES
UNIT 1
Flexible metal connectors
You may use flexible metal connectors to connect appliances that may be
subject to vibration, expansion and contraction, or other movement that
might damage or loosen a rigid connection.
Figure 1-1 shows installation details for a flexible connector.
1/2 inch
nipple
Flexible metal
connector
Recommended
shut-off location
Figure 1-1 Flexible metal
connect。r
installation
Flexible connectors allow an appliance to be moved for cleaning and
servicing without disconnecting the gas supply. You can use them to
connect a range under the following conditions:
the length of the connector must not exceed 6 feet (2 m)
when used to connect the appliance to rigid piping, a shutoff valve must
be installed in the piping immediately upstream of the flexible
connector.
Gas Technician 2 Training - M。dule 14
© Canadian Standards Assoc泪tion
11
UNIT 1
RANGES
Facilitating repairs
There are a number of things that can be done during the initial installation
of a range to make 如ture repairs and servicing easier. These include
installation of:
a flexible connector to allow movement of the appliance
a shutoff valve upstream and as close to the appliance as practical
a quick-disconnect device attached to the flexible connector.
General
considerations
The following factors must be considered when installing a gas range:
specific installation requirements, including manufacturer ’s
mstruct10ns
levelling the range
•
anti-tipping devices
clearance to combustibles
•
power supply and polarization.
Failure to follow the manufacturer's instructions may result in:
•
fire or explosion hazards
•
personal injury or fatalities
•
operating and service problems.
Specific installation requirements
Specific installation requirements include such things as proper positioning
and adequate space for the appliance, including:
compliance with clearance to combustibles requirements, as per
manufactur，町、 instructions, the rating plate, and applicable Codes
access for cleaning, repairs and servicing
•
proper distance to venting hoods, flues, or ductwork if installed
•
proper positioning with respect to adjacent cabinets, countertops and
other appliances.
A range must not be installed in a bedroom, because of the possibility that
it might produce carbon monoxide. However, a range may be installed in a
bed-sitting room if the range is not used as a space heating appliance.
12
Gas Technician 2 Training - Module 14
© Canadian Standards Association
RANGES
UNIT 1
Levelling
If a range is not levelled, fluids will not fill the cooking containers
properly. This may lead to overflow and spillage that could create a fire
or personal in ury hazard.
Anti-tipping devices
Some ranges may be equipped with anti-tipping devices. These devices,
which are installed at the time of installation, prevent accidental tipping of
the range. Anti-tipping devices may consist of a chain connecting the range
to a wall bracket, or a rigid bracket attached to the back of the range and
secured to the wall behind it.
Clearance to combustibles
Different types ofranges have different clearance requirements. For
example, storage cabinets and other combustibles must be installed at a
safe distance above the cooking top of a range, while the rear and side
walls of the range may be approved for zero clearance.
The manufacturer's instructions and rating plate will speci命 the approved
clearance to combustibles distance for the appliance. Where not covered in
the manufacturer ’ s instructions or on the rating plate, follow Code
appliance clearance requirements.
For example, combustible cabinets or walls located next to a range cooking
surface must be protected with a 28 MSG metal shield, spaced out 0.25
inch (6 mm) from the combustible surface and extending 企om 5 inches
(125 mm) below to 30 inches (750 mm) above the cooking surface.
Zero clearance range requirements
A range certified for zero clearance must comply with the following
requirements:
there must be no combustibles within 30 inches (750 mm) of the top of
the range
combustible surfaces protected by a shield of 0.25 inch (6 mm)
millboard covered with 28 GSG (0.3 mm) sheet metal, may be within
24 inches (600 mm) of the top of the range
there must be at least a 1 inch (25 mm) space between the back of the
range and a combustible surface.
Gas Technician 2 Training- Module 14
© Canadian Standards Association
13
RANGES
UNIT 1
Power supply and polarization
Ranges equipped with electric components require a power supply cord
with three-prong grounded plug. Check the manufacturer ’ s instructions for
the coηect type and size of wire and plug assembly to use.
The range receptacle must be properly grounded. The 岛llowing simple
check can be used to confirm if 由e range is connected safely
(Figure 1-2).
1. Use a voltmeter set to measure AC volts. Check the voltage across the
line and neutral conductors at the range receptacle. The meter should
read 120 V，土 10%.
2. Next, check the voltage across the line and ground conductors. The
meter should read 120 V.
3. Finally, check the voltage across the neutral and ground conductors.
ηie meter should read 0 V.
Readings that differ 企om those above indicate that the circuit or recep阳cle
wiring is incorrect or defective and must be corrected before the range is
installed.
Note:
For determining the correct
polarity of a wall receptacle
Neu叫 i→／L1
Neutral side
(white wire)
蹄。VAC
Used by permission of the copyright holder ,
the American Gas Association
Figure 1-2 Range receptacle p。larity ch民k
14
Gas T由却nician 2 Training - Modu』e 14
© Canadian Standards Association
RANGES
UNIT 1
FC
lv
en
uo
e S On
FE
Conversion from one fuel to another may be required for a number of
reasons, including the following:
•
tural gas may become available in an area previously serviced only by
propane
•
a natural gas appliance may be purchased for use in an area where only
propane is available.
Three common types of gas pressure regulators are shown in Figure 1-3.
Each one nas a different method for converting from one gas to another. It
is important to ensure that an appliance regulator is adjusted to operate
with the gas being used.
Propane
~
Natural
gas
⑧、 Cap ~crew
~
Propane
。 ggqp
ggq
用γ
Natural
gas
＇，，洽／／
Propane
⑧
~
Courtesy ofFrigidaire Home Products
Figure 1” 3 Gas pressure regulators for conversions
The requirements for converting an appliance 丘om one fuel to another are
covered in detail in Module 9, Unit 6.
Gas Technician 2 Training - Module 14
© Canadian Standards Association
15
TOPIC
3
Piping
Piping for a gas range must be installed according to the manufacturer ’ s
instructions and Code requirements.
Connection
The piping connection for ranges must be done so that the components are
easily accessible for servicing.
Branch piping
The size of the pipe or tubing should be large enough to provide adequate
flow. See Modules 8 and 10 for information on proper pipe and tubing
sizing methods.
The piping or tubing of a final drop serving a range does not require a dirt
pocket.
Appliance connections
Ranges must be connected to the gas supply with piping, tubing or other
means, as discussed in Topic 2. If connections are made with copper
tubing, a loop should be formed in the tubing to facilitate movement of the
appliance for cleaning and servicing.
Regulators
An appliance regulator is used to reduce the gas supply pressure to the
operating pressure of the appliance. The regulator must be 叫justed for the
gas being used and the burner must have the proper orifice to ens町e that:
．也e
出e
Gas Technician 2 Training- Module 14
© Canadian Standards Association
appliance input is coηect
proper flame characteristics are maintained.
17
RANGES
Burner
orifices
UNIT 1
An orifice is a hole or opening used primarily to control the direction and
volume of gas flow into a burner. The size and design of an orifice depends
on the following factors:
．由e
type of gas
the appliance input
manifold pressure
number of burners.
Types of orifices
d,
dLV
泸
阳
There are three types of orifice used for gas service.
or ce
The fixed orifice (Figure 1-4a) is the most common
type of orifice. It is simply a hole drilled in a brass
spud (burner fitting）.ηiegas ’ angle of approach to the
orifice hole varies with the 句rpe andpu叩ose of the
burner.
Adjustable
orifice
Most gas ranges are equipped with orifices that can be
manually adjusted to increase or decrease the flow of
gas 也rough 也e orifices (Figure 1-4b).
Cap or
universal or泸ce
The cap or universal orifice (Figure 1-4c) is used
primarily on dual-fuel (propane and natural gas)
appliances.ηiis orifice requires only a simple
a司justment to burn either fuel. When the hood is
screwed 恤， gas will only flow through the fixed drilled
needle (propane setting). When the hood is screwed
out, gas will flow through the needle and around it
through the orifice 坦白e hood.
。rifice
sizing
A gas orifice is sized using tables based on an orifice sizing formula. The
size of an orifice is designated according to DMS drill numbers. OMS
stands for Drill Manufacturer s Standard. Sizes range 丘om No. 80
(the smallest) to No. 1 ；也en 齿。m A 也rough Z (the largest). Table 1-1 is
a partial capacity table for natural gas orifices.
18
Gas Technician 2 Training - Module 14
。 Canadian Standards As回ciation
RANGES
UNIT 1
Type2
Type 1
Type 5
Type4
Type3
(a) Fixed gas orifices
Moveable orifice hood
(a 司usted for natural gas)
Moveable orifice hood
Moveable orifice hood
(closed …叫．＼＼
Fixed orifice hood
Fixed drilled needle
Gas
(b) Adjustable
gas 。rifices
(c) Universal
gas 。rifices
Figure 1-4 Burner 。rifices
Table 1-1 Partial natural gas orifi臼饵pacity table*
Gas pressure at 。rifice (inches of water c9lumn)
3.0
3.5
4.0
5.0
6.0
7.0
8.0
9.0
10.0
50
12.85
13.88
14.84
16.59
18.17
19.63
20.98
22.26
23.46
49
13.98
15.11
16.15
18.05
19.78
21.36
22.84
24.22
25.53
48
15.15
16.37
17.50
19.56
21.43
23.15
24.74
26.25
27.67
47
16.15
17.45
18.65
20.86
22.85
24.68
26.38
27.98
29.49
46
17.19
18.57
19.85
22.19
24.31
26.26
28.07
29.77
31.38
45
17.62
19.03
20.35
22.75
24.92
26.92
28.78
30.52
32.17
。rifice
size**
* Basedonn，础11ral gas with a specific gravity of 0. 60 and an orifice c侃iffici，回t dis char军e ofO. 佣
” α听ce size =
decimal or DMS drill size
Gas Technician 2 Training - Module 14
© Canadian Standards Asst.副ation
19
RANGES
UNIT 1
Selecting the correct orifice
An orifice is selected as follows:
1. The required gas flow rate through the burner orifice is determined
from the information on the appliance ’ s rating plate, using the formula:
flow rate in cu ft斤l = rated input in Btu/h÷1000 Btu/cu ft for natural
gas or 2500 Btu/cu ft for propane.
2. The required burner manifold pressure is determined from the
information on the appliance ’s rating plate.
3. The correct pressure column is located on the orifice capacity table and
traced down to the required flow rate value.
4. The correct size orifice to use is indicated in the orifice column at the
far left of the flow rate value row.
Leak testing
After an appliance has been installed and before it is reactivated, the piping
and connections must be checked for leaks. Leak testing methods are
covered in detail in Module 8, Unit 3.
Removing old
appliances
The following procedure must be followed before either permanently
removing an existing range, or installing a replacement:
1. Locate and identify the gas shutoff on the branch piping that supplies
the range.
2. Shut off the gas supply to the range and any other appliances attached
to the same branch piping.
3. Disconnect the range 企om the gas supply.
4. Use thread dope and a properly fitting pipe cap to secure the gas pipe
opening. If the shutoff valve is accidentally opened, an improperly
capped pipe could allow gas to accumulate in the building and an
explosion could result.
20
Gas Technician 2 Training - Module 14
© Canadian Standards Association
UNIT 1
Test
pressures
RANGES
Operating and supply pressure testing
A武er
the appliance has been installed and the gas system checked for
obvious leaks, the gas supply and operating pressures must be checked
to ensure they are correct.
For residential and light commercial installations, natural gas manifold
operating pressure, at the burner, downstream of all control valves is
typically 3.5 inches w.c. (0.9 kPa) The rating plate will show the correct
manifold pressure.
Normally, natural gas supply pressure at the outlet of the gas meter or
system regulator should be 7 inches w.c. (l.75 kPa) Typical propane
pressure is 11 inches w.c. (2.74 kPa) at the inlet. The rating plate will
show the correct manifold pressure.
Pressure testing instruments
Two basic pressure measuring instruments are used in the gas industry:
•
a water-filled manometer
•
a bourdon-tube pressure gauge.
The manometer is usually more accurate, since normal gas pressure
which is measured in inches of water column is relatively low. Manometer
operation is covered in detail in Module 2, Unit 4. A pressure gauge is
more convenient to use, but is not as reliable and accurate as a water
manometer.
Pressure gauge
A bourdon-tube pressure gauge (shown
in Figure 1-5) operates as follows:
1. The gauge is connected to a pressure
source.
2. The pressure forces the bourdon
tube in the gauge to expand.
3. The expansion of the 阳be acts on
a system of gears and linkages to
move the indicator on the gauge
dial.
Gas Technician 2 T1『aining-Module 14
Standards A蹈。ciation
© Canadian
Figure1-5 B。urd。n-tube
pressure gauge
21
RANGES
UNIT1
4.
The gauge is calibrated so that the value of the pressure being
measured will be indicated on 由e dial in inches of water column,
or ounces per square inch ( osi), or kPa.
Uses of manometers and pressure gauges
Manometers and pressure gauges can be used to test pressures at various
points in a gas supply system, as shown in Figure 1-6 and Figure 1-7.
Service line
pressure
typically
60 psig
Typical
meter
outlet
pressure
7.0 inch w.c.
(1.75 kPa)
Appliance
inlet pressure
minimum
6.0 inch w.c.
(1.5 kPa)
Reduced
pressure
Appliance
burner manifold
pressure 3.5 inch w.c. (0.9 kPa)
Appliance
Customer gas
houseline
Service
regulator
Appliance
drop line
Figure 1-6 Points of gas pressure in a natural gas system
Appliance inlet
pressure mini町ium
10 inch w.c. (2.5 kPa)
刊 inch
w.c. (2.75 kPa)
house line
pressure
Appliance
Typically
10 psig (69 kPa)
Firststage
regulator
I
Secondstage
regulator....－冽
Customer gas
柳lia1:ce_/J
drop line
Minimum
5 psig (34.5 kPa)
Figure 1 ·7 Points of gas pressures in a propane system
22
Gas T创业mician 2 Training - Module 14
0 Canadian Standards Association
RANGES
UNIT 1
Figure 1-8 shows the manometer connection method for determining inlet
pressure upstream and downstream of the combination control valve.
765432101234567
Figure 1-8 Manometer connection methods
Connecting
components
The following components are used to connect appliances to gas systems:
•
control valve and shutoff valves
•
flare fittings
flex connectors.
Control and shutoff valves
Control valves are used to control gas flow to appliances. Shutoff valves
are used to stop gas flow for system repairs and servicing. The location and
installation requirements for control and shutoff valves are specified in the
Code. In addition to Code requirements, the gas technician must take the
following factors into consideration when selecting the proper valve for the
application:
the location where the valve is to be installed
valve gas flow and pressure capacity
access for repairs and servicing.
Gas Technician 2 Training - Module 14
© Canadian Standards Association
23
RANGES
UNIT 1
Valve
c。nnecti。n
The size of a valve generally determines the method of its connection to the
gas system:
•
medium-size valves generally have threaded connections
smaller valves, used with copper tubing, are connected with flare
fittings.
Flare fittings
Brass flare fittings are used to join copper tubing. Connections between
copper tubing and steel pipe are made with threaded-to-tubing adapter
fittings. Although short阳 and long-neck forged flare nuts are acceptable for
natural gas or propane installations, short-neck forged flare nuts are
preferred because 也ey are stronge卫
Flex connectors
ηie
Code and installation requirements for flexible connectors were
discussed in Topic 2.
24
Gas Technician 2 Training - Module 14
。 Canadian Standards A岱ociation
TOPIC4
Electricαl
When a gas appliance requires an electrical connection, it is important to:
check 由at
the circuit wiring and components are rated for the circuit
voltage and current values and the operating requirements of the
appliance
arrange 岛r
safe and secure electrical connections to the appliance
ensure 也at
the installation conforms to applicable Electrical Code
reqmrements.
Electrical Code
requirements
Each kitchen must have a sufficient number of split duplex receptacles
located along the wall behind counter work surfaces and isolated work
surfaces less than 300 mm long at the wall line, so that no point along the
wall line is· more than 900 mm from a receptacle (measured horizontally
along the wall line).
There must be an electrical receptacle within safe and easy reach of the
appliance cord-you may not use an extension cord.
All appliance receptacles must be grounding句pe receptacles, able to
accommodate parallel blade attachment plugs (Figure 1-9).
Figure 1-9 125 V, 15 A grounding-type
appliance receptacle (CSA configuration 5-15R)
Gas Technician 2 Training -
Modu幅 14
© Canadian Standards Association
25
TOPIC
5
Burneγ~
and ignition systems
Top burners
Figure 1-lOa shows a typical top bwner for a gas” fired range. Figure 1-lOb
shows the va巧ring burner port designs. The design chosen depends on the
burner firing rate and tumdown range.
~0000000000000001
Single row drilled
lo~叽、叽、 0ifo~》oj
SI。tted
and drilled
Double row drilled
(b)
(a)
Figure
”。但） Typi臼l
top burner (b) burner port designs
Thermostatically controlled top burner
The thermostatically controlled top burner (Figure l甸 11 a) is equipped with
a thermostatically controlled sensing element and valve. A spring-loaded
sensing unit 如r the thermostat is located in 由e centre of the burner. It
extends slightly above the burner grate so 由at when an utensil is placed on
也e bwner, the sensing unit maintains a positive contact with the utensil
bottom. 百1e process of burner flame ignition varies slightly from 也e
ordinary top bwner.
Gas Technician 2 Training - Modu悔 14
@Canadian S恒n匈rds Associa.tion
27
RANGES
UNIT 1
1. When the control knob is turned on, gas begins to flow to a secondary
pilot called the tower卢ame assembly.
2. The tower flame is ignited by the constant burning pilot flame.
3. The main burner lights from the tower flame.
The tower flame is only present when the control is turned on. This
flame acts as an auxiliary ignition pilot light for the burner. It is lit by
the primary pilot light and serves as a standby pilot flame for fast
ignition to the burner. The flame on the tower should be about 3/16 inch
(5 mm) high and bright blue in colour. There is usually an air shutter
adjustment at the base of the tower and the gas flow to the tower flame
is controlled by its orifice.
4. The control system keeps the utensil contents at the desired setpoint
temperature. Figure 1-11 b shows the location of the calibration screws
for the tower flame and sensor.
Turn right to lower temperature
Turn left to raise temperature
(each notch= 5° F)
Tower flame
adjustment
(a)
Figure 1-11 (a) Thermostatically controlled burner (b)
28
(b)
I。臼tion of 臼libration
screws
Gas Technician 2 Training - Module 14
© Canadian Standards Association
RANGES
UNIT 1
Top burner
ignitors
Top burner ignitors may be one of two basic types:
standing pilot
•
electric ignitor.
S阳 nding
pilot
The standing pilot type of ignition system has a continuously lit pilot. Each
top burner is controlled by a standard or 阻击伍D-LO push-to-turn valve.
When a top burner control valve is turned on to allow gas flow into the
burner, the pilot ignites the gas.
There are three basic designs of top burner pilot ignitor systems:
•
one pilot for each burner
•
one pilot 岛r two burners (Figure 1-12)
one pilot for all four burners.
When only one pilot is used for more than one burner,jlash tubes are used
to direct the pilot flame to each burner.
Figure 1-12 Standing pilot for two burners
Gas T~nician 2 Training-Mcx,1ule 14
Canadian Standards Association
©
29
RANGES
UNIT 1
Flash tube
The flash tube runs from the top burner ignition port to the pilot flame to
provide a direct path for the ignition flame (Figure 1-13).
When the burner control valve is turned on, gas flows out of the burner
ignition port and into the flash tube, drawing combustion air into the flash
tube behind it. The gas and air mix as they travel down the tube toward the
pilot flame, where it is ignited. The resulting flame “ flashes ” back to the
burner, where it ignites the gas at all the burner ports.
Top
burner
Courtesy of Consumers Gas
Figure 1-13 Flash tube (plan view)
Improper ignition
If a flash 阳be fails to light the burner when the burner is manually lit and
there is no flame at the end of the tube, there may be too much air in the
mixture.
If the top burner will not Ii民t off the pilot, but there is a flame at the end of
the flash burner, there may be too little air in the mixture or too much gas.
If the ignition at the range burner is delayed, the operator could be burned.
If a range has two top pilots controlled by one a司justment and they are
unequal in size, the pilot orifices should be cleaned or replaced.
30
Gas Technician 2 Training - Module 14
© Canadian Standards Association
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UNIT 1
Electric ignitor
An electric ignition system consists of a spark generation device, a switch
on each burner valve, and spark ignitors (Figure 1-14). Typically there are
two spark ignitors, one each for the le企－ side and right-side burners. Both
sets of burners have flash tubes 由at run between a top burner ignition port
and a central spark gap.
When a burner valve
is switched on,
electric current is
applied to the spark
generator and gas
begins to flow into
the burner. The
gas-air mixture from
由e burner port flows
down the flash tube,
is ignited by 由e
spark, and flashes
back to ignite the top
burner ports.
卢卡7
Figure 1-14 Electric ignitor
Oven burners
The slotted port burner, shown in Figure 1-1 旬， is often used in range ovens
and broiler units. It has a series of thin slots that distribute 也e g缸ne.
(a)
(b)
The ribbon port burner in Figure
1-15b has a single, long slot.
An assembly of thin, straight
and crimped metal strips
produces a solid, continuous
flame along the length of the
slot. Ribbon po此 burners are
used in larger gas-fired ovens.
Figure 1-15 (a) Slo忧eel port burner (b) Ribbon p。同 burner
Gas Tee才mician 2 Training - Module 14
© Canadian Standa叫sAssoc丽lion
31
RANGES
Oven ignition
systems
UNIT 1
There are several types of oven ignition systems:
mini-pilot
•
constant pilot
spark-ignited
•
hot surface ignitor
•
match-lit.
Mini-pilot (thermocouple) igniter
A mini-pilot ignition system employs a flame 也at is considerably smaller
than typical pilots. A mini-pilot thermocouple generates approximately 20
millivolts (open circuit）.η1is voltage is used to operate an electromagnetic
safety switch to prove the flame.
Gas flow to the burner is turned on and off by 由e control valve, in response
to oven temper削re (sensed by the thermostat). When 由e thermostat is
satisfied, the oven burner reduces to a minimum by-pass flame. When the
oven cools，由e sequence repeats, maintaining an even temperature at 由e
control setting.
The millivolt values for a mini-pilot system should be as follows:
•
open circuit test-20 mV
closed circuit test一 lOmV
magnet drop-out test-4 mV or less.
Constant pilot
Constant pilot ignition system consists of a thermostat valve, safety gas
valve, constant/heater pilot and mercury sensmg bulb. （白山 system is
sometimes called standby pilot.)
咀ie
constant pilot ignition system (Figure 1-16) works 部岛Hows:
1.ηie
oven is controlled by the thermostat valve which is mounted on 由e
manifold. From the valve are g部 lines to 也e oven burner, and one line
to the pilot. A small amount of gas flows continually throu且也is valve
阳也e oven constant pilot.
2. When the thermostat is set and the thermostat bulb is calling for heat,
two things happen simultaneously:
32
Gas Technician 2 Training - Module 14
© Canadian Standards As叙>ciation
UNIT 1
RANGES
gas flows through the thermostat to the safety valve at the burner.
ii. the gas flow to the constant pilot increases thus causing a heater
pilot.
i.
3. The flame deflector spreads the heater pilot flame over a mercury-filled
bulb.
4. After this bulb is heated, 1t causes the safety valve to open.
5. The safety valve allows gas to flow to the oven burner.
6. The burner is lit by the heater pilot.
7. The burner continues to operate until the preset temperature in the oven
is reached.
8. Once temperature is reached the heater pilot is reduced to the regular
constant pilot flame until the thermostat again calls for heat.
Constant pilot
何am~
@
Flame
deflector
Heater pilot
何 ame
Mercury-filled
bulb
Figure 1-16 ConstanUheater pilot
To light the constant pilot in the oven:
1. Make sure the oven is turned off.
2. Remove the oven racks.
3. Hold a lighted match to the opening in the top of the pilot at the rear of
the oven burner. (No pilot 叫justments are required.)
Spark ignition
The spark ignition system (Figure 1-17) operates similarly to the constant
pilot system, except that the pilot flame is lit by a spark and only burns
while the oven control is turned on.
Gas Technician 2 Training- Module 14
Standards Association
© Canadian
33
RANGES
UNIT 1
In the spark ignition system:
1. Gas first flows to the pilot when the oven control is turned to the
desired cooking temperature.
2. At the same time as gas flows to the pilot, the capacitive discharge
ignitor produces a spark to ignite the pilot.
3. When the oven reaches the setpoint temperature, the pilot flame
reduces in size, but does not go out. This allows the burner to cycle on
in response to a call for heat without having to re-ignite the pilot each
time.
4. Once the oven control is turned to off, the main burner and pilot flame
extinguish.
Spark
ignito『＼
Constant pilot
flame ~1
Heater pilot
flame
Mercury-filled
bulb
Figure 1-17 Spark igniti。n system
Hot surface ignitor
A hot surface ignition system (Figure 1-18) eliminates the need for a pilot
flame in the oven. It operates on standard household current of 120 V AC
and ignites the oven burner electrically.
When the thermostat calls for heat:
1. The cycling contacts 缸e made and the hot surface ignitor is energized.
2. As current begins to flow, the ignitor starts to heat and its resistance
decreases.
3. As the ignitor resistance decreases, the current flow 也rough the low
resistance coil of the bimetal valve increases. The bimetal valve will
not open until the ignitor has reached gas ignition temperature.
4. The gas valve opens and ignition occurs when approximately 4 V 缸e
developed across 也e bimetal valve ’s heater coil.
34
Gas Technician 2 Training - Module 14
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UNIT 1
When the oven temperature reaches the thermostat setting:
1. The thermostat cycling contacts open and the electrical circuit is
broken.
2. The ignitor cools and the bimetal valve closes, shutting off gas flow to
the main burner.
3. This cycling action will repeat until the thermostat is turned off.
Thermostat
bulb
Oven burner
Hot surface
ignitor
Main gas
supply.
~一~
Manifold
Figure t 斗 8 Hot surface ignitor
Match-lit ignition
As the name implies, this type of system requires the burner to be lit
manually with a match; the flame from the main burner lights the standby
pilot. When the oven control is turned off, gas flow to the burner and
standby pilot stops.
Match-lit ignition works as follows:
1. The oven door is opened and a lighted match is held to the end of the
flash tube running between the burner ignition spud and the pilot flame.
2. The oven control valve is then turned fully on to start gas flow to 由e
burner and standby pilot.
3. The gas-air mixture ignites at 由e burner when it comes into contact
with the match flame.
4. The flame travels down the flash tube to ignite the standby pilot.
5. The thermostat is turned to the desired cooking temperature
Gas Technician 2 Training - Module 14
Canadian Standards Association
©
se创ng.
35
RANGES
UNIT 1
6. When the oven reaches the desired temperature setting, the oven burner
reduces to a minimum (by-pass) flame and the pilot remains lit. When
the temperature in the oven drops below a certain setting, the burner
returns to full flame to maintain cooking temperature.
Extinction pop
Extinction pop or flashback can occur when the burner is turned 。在 Even
after gas flow to the burner is shut off, primary air can still flow into it.
When this occurs, the gas唰air mixture in the burner is replaced by air only.
During this time when the gas pressure quickly decreases, the burning
velocity can exceed the flow rate of the gas-air mixture and flashback
results. The small flashback explosion or "extinction pop” is not a hazard,
but may be annoying.
36
Gas Technician 2 Training - Module 14
© Canadian Standards Association
TOPIC6
Oven controls
Cycling oven
controls
An oven heat control system is activated by changes in temperature to
control gas flow to the oven burner. A typical cycling oven heat control
system (Figure 1-19) consists of:
an oven thermostat and temperature sensing probe which controls
heater pilot operation
a constant pilot which lights the heater pilot
a heater pilot which controls safety valve operation
a safety (cycling) valve which controls main burner operation
•
the oven burner.
Oven
thermostat
Capillary
tube
Burner
orifice
~:i~~ s响ty ...＿＿＿＿＿＿、
Courtesy of Co阳umers G回
Figure 1-19 Cycling oven control comp。nents
、、，，
Gas Technician 2 Training - Module 14
Standards Association
© Canadian
37
RANGES
UNIT 1
Cycling control operating sequence
1. The constant pilot, which is located at the base of the oven burner,
remains on at all times.
2. When the oven thermostat dial is turned on and adjusted to the desired
temperature, the thermostat supplies gas to the heater pilot.
3. The heater pilot heats the capillary tube or bimetal element of the sa也可
valve, depending on the design.
4. Within 60 seconds, the safety valve opens to allow gas flow to the main
burner.
5. The main burner is lit by the pilot system as soon as gas starts to flow
into the burner.
6. When the thermostat senses that the desired temperature has been
reached, the pilot flame reduces back to the stand-by rate. This shuts off
由e safety valve and gas flow to the burner.
7. When the oven cools to below the thermostat temperature setting, the
cycle r叩eats to maintain a constant temperature 扭曲e oven.
Oven thermostat
The oven thermostat (gas thermostat) is 也e main component of the cycling
control system (Figure 1-20).
A gas thermostat is a hydraulic control device which responds to expansion
and contraction of a liquid contained in the oven probe bulb. The probe
bulb is connected to the thermostat by a capillary tube. This device opens a
valve in the thermostat to increase gas flow to the pilot when heat is
required, and closes the valve to reduce gas flow when the desired
temperature is reached.
-
n
o
38
aubu“耐
Figure ’－20 。ven
。
////,,
d 才
ESS
BWmm
thermostat
Gas Technician 2 Training - Modu梅 14
@ Canadian Standards Association
υNIT
RANGES
1
The oven thermostat also provides a positive shutoff for the main burner
gas supply (manual gas valve). The oven burner gas supply passes through
the shutoff portion of the thermostat to ensure that no gas flows to the
burner when the thermostat dial is turned to the offposition.
The thermostat can be set to operate on natural gas or propane, and it can
be adjusted (with the calibration screw) to increase or decrease the
temperature.
Safety valve
The gas safety valve controls gas flow to the oven main burner. It is usually
located in the bottom rear area of the oven, attached to the oven cabinet or
to a bracket extending 仕om the burner.
The safety valve (Figure 1-21) contains a diaphragm mechanism that is
controlled by the action of the pilot flame on a liquid-filled bulb. The liquid
in the bulb expands or contracts in response to the amount of heat it
receives from the pilot flame. The valve diaphragm opens and closes to
control gas flow to the burner.
Burner orifice
Gas
inlet
Courtesy of Frigidaire Home Products
Figure 1-21 Safety valve
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© Canadian Standards Association
39
RANGES
UNIT 1
Set翩back
controls
Set-back controls reset the oven cooking temperature to a lower “ hold and
serve” temperature. Three types of controls are used for this pu甲ose:
•
a heat motor
a mechanical turndown
•
a substitute thermostat.
Heat motor
Oven control systems equipped with thermo-mechanical heat motors can
automatically reduce oven temperature from “ cooking” temperature down
to “ hold and serve” temperature after the cooking cycle is completed.
There are two types of heat motors:
Bellows type
The bellows type has an electrically heated, fluidfilled bellows mechanism built into the thermostat
When the cooking cycle is finished, a pair of contacts
in the oven timer close to ene电ize 也e set back control
circuit. When the bellows is heated it expands,
resetting the thermostat mechanism to maintain the
oven at serving temperature - typically 170。F (77。C).
Bimetallic type
刀ie
bimetallic heat motor operates similarly to the
bellows type, except 也at the bimetallic element is
heated instead of the bellows. Typical坊， the bimetallic
heat motor only reduces the temperature to 15 5 。F
(86°C) below the cooking temperature.
Mechanical turndown
· The mechanical turndown consists of a small, low-rpm electric motor
connected to 由e oven thermostat spindle by a series of gear wheels. When
the cooking cycle is completed, the switch mechanism of the oven timer
energizes the elec位ic motor.τ'he motor then rotates the gear wheel
mechanism, which turns the thermostat temperature control dial to 170。F
(77°C).
40
Gas Technicia『1 2 Training - M创ule 14
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UNIT 1
RANGES
Substitute thermostat
This type of set back control uses two separate thermostats. One thermostat
is adjustable for setting cooking temperatures. The second (substitute)
thermostat is set to maintain only 170°F (77°C). When the cooking cycle is
completed the oven timer mechanism switches over 企om the cooking
thermostat to the substitute thermostat, which maintains the oven at 170°F
(77°C).
Self-cleaning
oven
Many modem ranges are equipped with self-cleaning ovens. This is
accomplished by operating the oven on a cleaning cycle of elevated
temperature for a set period of time. A typical cleaning cycle has three
phases:
I. After the clean cycle is initiated, the radiant broiler burner heats the
oven to approximately 650。F (340°C). The oven door then locks
automatically.
2. A disc thermostat (thermodisc) senses when the oven temperature
reaches 650。F (340°C) and switches electrical power 仕om the radiant
broiler burner to the oven burner, which 臼rther heats the oven to
approximately 950。F (510°C).
3. At the end of the cleaning cycle (typically two hours), the oven cools
down and the door unlocks when the oven is at a safe temperature.
Programmable
clocks
Many modern ranges are equipped wi也 programmable clocks (timers) that
allow “ programmed cooking. ” There are usually four cooking programs
available:
cook and off
cook and hold
•
delay, cook and hold
•
delay, cook and off.
Cook and off
When the clock and thermostat are set to the cook and off program, the
oven will operate at the set point temperature for the length of time
required. When the cooking cycle is finished, the oven shuts off and cools
down to room temperature.
Gas Technician 2 Training- Module 14
Standa『ds Association
© Canadian
41
UNIT 1
RANGES
Cook and hold
When the clock and thermostat are set to the cook and hold program, the
oven will operate at the set point temperature for the length of time
required. A short time before the cooking cycle is finished, a set back
device will reduce the oven temperature to “ hold and serve temperature. ”
Delay, cook and hold
This program allows the user to pre” set the clock and thermostat so that the
oven will operate automatically without the user being present. At the preprogrammed times, the cooking cycle will start and the oven will operate at
the set point temperature for the length of time required. A short time
before the cooking cycle is finished, a set back device will reduce the oven
temperature to “ hold and serve temperature. ”
Delay, cook and off
This program also allows the user to pre-set the clock and thermostat so
that the oven will operate automatically without the user being present. At
the pre-programmed time, the cooking cycle will start and the oven will
operate at the set point temperature for the length of time required. When
the cooking cycle is finished, the oven shuts off and cools down to room
temperature.
42
Gas 丁丽chnician 2 Training- Module 14
。 Canadian Standards Association
TOPIC
7
Oven contγvi calibγa ti on
testing
αnd
Accurate calibration and testing of oven controls is a critical factor in
ensuring safe and fuel-efficient range operation and satisfactory cooking
results. If an oven control is significantly out of calibration the oven could
overheat, resulting in fire, damage to the range, or personal injury to the
consume立 There are 由ree basic classes of oven calibration and testing:
Mechanical
adjustments
•
mechanical
•
electromechanical
•
electronic.
Mechanical adjus伽tents include such things as:
•
a司justing
the thermostat temperature by means of its calibration screw
a司justing
the thermostat temp町ature setting knob
standby pilot flame a司justment
•
bypass flame a司justment.
Oven
thermos阳t
calibration
The thermostat calibration screw is located in the centre of the thermostat
shaft. Figure 1-22 shows two different thermostats and the location of their
calibration screws. The calibration screw is turned clockwise to decrease
the temperature and counterclockwise to increase the temperature. Note,
however.，由at some thermostats are rtot designed to be calibrated in the
field, and have their calibration screw 回aled in place to prevent tampering.
Before calibrating an oven 也ermostat, it is important to verify 由e location
of the thermostat sensor bulb and capillary tube in 由e oven. The bulb
should only con臼ct its mounting clip•- it must not con饵ct the racks or any
oven sur鱼饵s.
」
Gas Technician 2 Training - Module 14
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43
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UNIT 1
A reliable temperature measurement probe or mere町y thermometer should
be used to veri命 temperatures when calibrating an oven thermostat.
Aluminum foil should be used to shield the temperature sensing probe
from the effects of radiant heat in the oven, unless the probe is specially
designed for this pu甲ose.
Temperatures should be measured on the middle rack of the oven, with the
thermostat set to 350。F (l 75°C). For accurate results, a gas oven should be
operated for at least fi白een minutes at 350。F (175°C) before beginning the
calibration sequence.
Calibration
Courtesy of Fr胆daire Home Products
Figure 1-22 Location of thermostat calibration screw
Temperature setting knob adjustment
An oven temperature setting knob can be adjusted to increase or decrease
factory settings, over a range of 土50°F （土30°C) in 10。F (5°C)
mcrements.
由e
ηie
oven temperature setting knob shown in Figure 1-23 consists of a
knob handle and temperature indicating plate attached by two screws to an
44
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UNIT 1
adjustable shaft. The shaft of the temperature setting knob is adjusted as
follows:
1. The knob is turned to the OFF position, then removed by pulling it
straight off the thermostat shaft.
2. An aηow on the back of the knob ’ s temperature indicating plate
points to the centre of the upper screw, indicating the original factory
se位ing of the shaft. When the upper and lower screws are loosened,
the shaft can be rotated to the right or left to increase or decrease the
setting.
3. A screwdriver is used to loosen both screws approximately one full
tum, or until the shaft will rotate freely in both directions.
Cοurtesy of
Frigidaire Home Products
Figure 1-23 Oven
temperature setting
knob adjustment
4. The knob handle is held in place while the shaft is turned in the
desired direction. Notches or teeth in the shaft assembly indicate the
amount of temperature mcrease or decrease. Each notch represents a
change in the se忧ing of 10。F. The shaft can be rotated five notches in
either direction.
5. When the knob has been adjusted to the desired temperature, both
screws are tightened.
6. The knob is reinstalled by pushing it straight onto the thermostat
shaft, ensuring that it is first properly aligned with the shaft.
Standby pilot flame adjustment
Oven thermostats that control the flame of a manually lit burner are
equipped with a standby pilot. The thermostat controls the gas supply to the
standby pilot, which is lit only when the oven valve is turned on. The
pu甲ose of the standby pilot is to re-ignite the flame of the oven burner if it
is extinguished for any reason.
The proper length of the pilot flame depends on its position with respect to
the oven burner flame. A pilot flame may be 仕om 0.25 to 1 inch in length,
and should have only a trace of yellow at its tip. The pilot flame should not
touch any part of the burner, and should ignite the oven burner within one
second.
The standby pilot flame should normally only require adjustment when the
range is first installed, or if it is converted 仕om one fuel to another. If a
standby pilot does require rea司justment, consult the manufacturer ’s
instructions for the proper procedures and specifications.
Gas Technician 2 Training - Module 14
© Canadian Standards Association
45
RANGES
UNIT 1
Bypass flame adjustment
The main oven burner bypass flame should be adjusted to the minimum
size at which it remains stable. For most pu叩oses, a properly adjusted
bypass flame should be the same size as the standby, with blue “ beads” of
flame. The bypass flame is adjusted as follows:
1. The oven temperature setting knob is turned to
2. The oven is heated up to
350。F
350。F
(175°C).
(175°C).
3. When the oven has reached 350°F (175°C), the burner flame must be
checked to ensure it has reduced to its bypass state.
4. The oven temperature setting knob is turned to 250。F (120°C) to ensure
that the thermostat valve is completely closed and that the burner flame
will remain in bypass mode.
5. The coηect tool is used, in accordance with the
instructions, to adjust the bypass flame.
Electromechanical
adjustments
manufactur町、
Electromechanical a司justments and tests are sometime required on electric
gas control systems. An electric gas control system operates on 120 volts
AC, and consists of three main elements:
•
the oven thermostat
•
a flame switch or silicon“ carbide ignitor
•
a solenoid valve.
An electric gas control system with a flame switch operates di旺erently than
one with a silicon-carbide ignitor. In both systems, the oven burner gas
supply is controlled by a solenoid valve. The solenoid valve, which is in
series with the thermostat and flame switch or ignitor, is normally held
closed by a spring. The valve opens when the solenoid is energized.
Flame switch system
An electric gas control system with a flame switch operates as follows:
1. The constant pilot is manually lit. The pilot flame heats the flame
switch causing it to close. ·
2. When the thermostat temperature setting knob is 阳med to the desired
temperature, the circuit connecting the thermostat to the flame switch
and solenoid valve is completed.
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Gas T以如nician2T1『aining - Module 14
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RANGES
UNIT 1
3. The energized solenoid valve opens to allow gas flow to the oven
burner, where the gas is ignited instantly by the pilot flame.
4. When the oven set point temperature is reached, the circuit opens,
closing the solenoid valve which, in tum, shuts off the gas supply to the
burner.
5. The on-off cycle continues until the thermostat temperature setting
knob is turned OFF.
If the pilot flame is extinguished, the flame switch will cool and the circuit
will remain open until the pilot is re-ignited and the flame switch heated to
operating temperature.
Flame switch test
As discussed above, the flame switch is connected in series with the
thermostat and solenoid valve (Figure 1-24), and is normally closed as long
as there is a pilot flame. The solenoid valve cannot open unless the
thermostat and flame switch are both closed.
The flame switch is a safety device and must be replaced immediately if it
is defective. It is tested as follows:
1. With the power on, the pilot burner ignited, and the thermostat closed, a
voltage test across the flame switch terminals should indicate 0 V. If
voltage is indicated, the switch is defective.
2. A continuity test is performed by turning off power to the circuit and
disconnecting one wire from the flame switch terminals. With the pilot
l让 and the flame switch heated to operating temperature, a continuity
test across the flame switch terminals should indicate continuity. If
continuity is not indicated, the switch is defective and must be
replaced.
3. Continuity across the flame switch terminals when the unit is cold,
indicates that the switch has a short circuit. This means 出at 也e system
will still operate, but the safety feature will not be operational. The
switch should be replaced.
Gas Technician 2
T1『·aining-
Module 14
©Can8d阳n S恒ndards A弱。ciation
47
UNIT 1
RANGES
The 「mo
stat
L1
丁
1650 Ohms
Flame switch
Oven thermal
valve
Figure 1. -24 Flame switch system and test
Thermostat
The following procedure is used to determine if the oven thermostat
requires recalibration:
1. A temperature test probe or mercury thermometer is placed in the
centre of the oven ’s middle rack.
2. The oven is turned on and the temperature set to
oven is allowed to heat up 岛r 15 to 20 minutes.
400。F
(200°C). The
3. After the oven has heated up, observe the temperature reading to
determine when the oven burner cycles on and off. Record the
temperatures at which the burner turns on and off for several cycles,
and calculate the average time.
•
An average temperature within 10。F ( 5°C) of the setpoint is
satisfactory.
A temperature more than 10。F (5°C) higher or lower than the
setpoint means that the thermostat should be recalibrated.
Thermostat recalibration
A typical electric gas control system thermostat is shown in
Figure 1-25. This type of thermostat is calibrated as follows:
48
Gas Technician 2 Training - Module 14
© Canadian Standards Association
RANGES
UNIT 1
1. Remove the temperature setting knob assembly by carefully pulling it
straight off the thermostat shaft. It is important to ensure that the “ D"
stem does not rotate, otherwise the original thermostat setting will
change.
2. Insert a screwdriver carefully into the calibration screw slot.
Tum the calibration screw clockwise to reduce the temperature
Tum the screw counterclockwise to increase it.
Do not to move the “ D ” stem during these
a司justments.
1. Observe the temperature change on the test instrument and adjust the
calibration screw as necessary until the desired temperature is
maintained.
2. When the adjustment is completed, reinstall the temperature setting
knob and tum it to the OFF position.
飞‘主
Heater
/
pilot flame /
adjustment /
Courtesy of Consumers Gas
Figure 1-25 Calibrating electric gas control therm。stat
Solenoid valve test
The solenoid valve is normally closed, and opens when it is energized.
Solenoid valve operation can be tested by observing its opening and
closing action while turning the power to it on and off.
•
If there is no continuity across the solenoid coil, and the valve does not
open when the power is turned on, the valve or its coil must be
replaced.
Gas Technician 2 T1『aining - Module 14
Standards Association
© Canadian
49
RANGES
UNIT 1
If any gas continues to flow through the valve when it is shut and the
power is off, it should be replaced.
Electronic
adjustments
Electronic adjustments include such things as digital oven temperature
controls. These microprocessor-controlled devices are operated by a pushbutton keypad. A digital LED or LCD window displays temperature
readings, cooking times, etc.
There are as many designs of digital temperature controls as there are
manufacturers. One typical unit is calibrated as follows:
1. Depress the BAKE push-bu忱。n on the keypad.
2. Tum the rotary temperature selection switch to 500。F (260°C) or
highe巳 then immediately (within 1 second) depress the BAKE pushbutton and hold down 岛r 5 seconds. The display will then indicate the
factory se忧ing ofOO.
3. Tum the rotary temperature selection switch to enter a hotter or cooler
oven temperature, as desired. The temperature can be increased or
decreased 土35 。F （土20°C) m 5 。F （土2.5°C) increments.
4. When the desired temperature has been selected, depress the STOP/
CLEAR push-button to set and store the new tempera阳re se忧ing in the
controller's memory.
Principle of thermistor operation-temperature
control
A thermistor is a temperature-sensitive semiconductor device 也at has a
negative temperature coefficient. This means 也就由e thermist町、
resistance decreases as its temperature increases. The resistance of the
thermistor varies non-linearly with tempera阳re. The tempera阳re range of
a 由ermistor can be designed to almost any convenient or required value.
Because its resistance increases so rapidly over a very narrow temperat町e
range, the thermistor can be used as a switching device to switch the gas
valve and ignitor off and on. In oven temperature control systems，也e
thermistor is in series with the thermostat which operates wi由in a specified
resistance range.
50
Gas Technician 2 Training - Module 14
© Canadian Standards Association
TOPIC 8
Operation
As with all appliances, the operation of a gas-fired range requires
gas pressure and primary air adjustment.
coηect
Gas pressure
After installing and before servicing a gas range, check the gas manifold
pressure with a manometer. It must have gas flowing through in order for
its pressure setting to be correctly read and adjusted.
If it is incorrect, adjust the regulator to achieve the correct manifold
pressure. (Adjusting pressure regulators is discussed in Module 15, Unit 1.)
Primary air
supply
A stable flame with the correct characteristics is required for proper
combustion and range operation. (Flame characteristics are discussed in
Module 3, Unit 2.)
hF
cwm
z
-
咆w
－
哪町
The characteristics of a flame depend mainly on the primary air supply. A
stable, blue flame will be produced at the burner when the proper amount
of primary air is premixed with the gas before ignition. Increasing or
decreasing the primaηair supply will change the shape and colour of the
burner flame.
Deereαsing
primαηαfr
Gas Technician 2 Training - Module 14
Canadian Standards Association
©
As the percentage of primary air in the fuel mixture is
increased, the flame sharpens and the inner cone gets
smaller.
When the percentage of primary air in the 也el mixture
is decreased, the flame gets longer and burning speed
decreases, because more secondary air is then required
to complete combustion. If the primary air supply is
reduced further, a yellow tip appears on the flame and,
if the primary air supply is cut off, the flame will
become completely yellow.
51
RANGES
UNIT 1
Primary air adjustments
The following information is typical of manufacturers instructions for
adjusting the primary air.
•
For each of the top burners and oven burners the primary air shutter is
located at the open end of the venturi tube and is locked in place.
Should the air shutter need adjusting, loosen the Phillips head screw
and gradually rotate the air shutter to allow more or less air into the
burner tube as needed.
If the air is properly adjusted, the flame will be steady, relatively quiet
and have approximately Yi inch sharp blue cone. This type of flame is
usually found in the centre of the air shutter adjustment.
•
Other colours or flame patterns indicate problems that should be
corrected. Table 1-2 shows a number of common undesirable flame
p硝em characteristics, their causes and remedies.
Table 1-2 Flame pa忧em problems and remedies
Flame pattern problem
Lifting 何ame
when cooking vessel
Possible cause
了。。 much
Corrective acti。n
air
Reduce primary air
in place
Fuel mixture velocity higher Reduce appliance
than flame speed
input
Not a problem
No correction
necessary
Simmer set too low
Adjust simmer se忧ing
Oven burner flame larger at back
than front
N。t a problem (this is
common)
ne臼ssary
Radiant bumer makes a loud
popping s。und
Deteriorated radiant panel
Replace radiant panel
Li食ing 洞ame
when burner
uncovered
Flame blows out on simmer
se悦ing
52
No correction
Gas Technician 2 Training - Module 14
C Canadian Standards As叙汩汩tion
TOPIC
9
Service
Proper
serv1c1ng
practice
Proper appliance servicing practice requires the following disciplined
approach to solving problems:
properly diagnosing customer complaints
following
manufactur町、 instructions
and specifications
interpreting wiring diagrams and schematics
•
practicing safe work habits and perform all prescribed safety
procedures
making a司justments to controls and burner ports
removing faulty components and replace 由em with new or
reconditioned components
•
verifying operation of replaced components.
Each of these steps is described in more detail below.
Diagnose customer complaints
On initial contact wi由 a customer, use the following techniques to
determine what the problem is:
listen attentively to 由e customer
•
have the customer show where the equipment is
ask the customer questions regarding specific symptoms
restate 由e problem to 由e customer to ens田e 由atbo由 parties
understand what the problem is.
Note
Determine 扩the
customer is experiencing any symptoms of carbon monoxide poisoning such as headache or na附＇ea while operating the range.
Carbon monoxide can be produced by a gas range when large containers of
fluid are heated over a long period of time. Carbon monoxide can 岛m
when a gas flame impinges on the cold bottom of a container.
Gas Technician 2 Training - Module 14
C> Canadian
Standa时sAssc抱iation
53
只ANGES
UNIT 1
Follow manufacturer's specifications
In order to service appliances properly, the gas technician must follow the
manufacturer’s instructions and specifications as found in:
appliance operating and service manuals
established troubleshooting procedures.
Interpret wiring diagrams and schematics
Each appliance has its own wiring diagram or schematic. These drawings
may be attached to the appliance or located in its operating manual. In
some cases, a third pa吗r service and repair book may have to be consulted
for the information required.
Practice safety
General safety procedures to be completed prior to servicing an appliance
include:
•
disconnecting electrical power to the appliance if necessary
•
shutting off the gas supply to the appliance if necessary
•
wearing and using prescribed safety clothing and equipment.
Some situations may require additional safety measures. It is always best to
consult the applicable Code and the manufacturer’s instructions for any
special safety precautions regarding a particular appliance.
Remove faulty components
After tests proves a component to be faulty, it should be removed in
accordance wi也由e manufacturer’s instructions. Potentially hazardous
materials, such as mercury-filled capillary devices, must be disposed of in
accordance with applicable envrronmental legislation.
Some parts of the range may need to be disassembled in order to get to
components.ηiis may include removing the back splash and access
panels. The sequence of disassembly for these and other components will
be 岛und in the manufacturer ’s instructions and the applicable appliance
service manual.
54
Gas Technician 2 Tr亩ining-M创ule 14
。 canadian Standards Association
υNIT
RANGES
1
Install replacement components
When it is necessary to install replacement components, it is important to
ensure that 由ey are the correct part number, type, size, and rating for the
application. Always consult the manufacturer ’s instructions for the
component part number and other necessary specifications. When in doubt
about the su让ability of a component, consult the manufacturer or their
nearest representative.
Install replacement parts in accordance with the manufacturer ’s
instructions and the appliance service manual.
Verify operation of replacement components
An important part of the servicing operation is verification of the operation
of replacement components, both mechanically and electrically.
To ensure operator safety, and safe and efficient appliance operation, it is
important to check the function of all replaced components. The following
items should be checked when any servicing procedure has affected, or
could possibly have a能cted, their function or safe oper创ion:
an operational check to veri命伽at 也e appliance is in proper working
order
calibration of control components
•
thermocouple output
oven thermostat calibration
•
gas leaks at fittings or other connections
igmtion system operation
•
flame characteristics.
Gas Tee如nician 2 Training - Module 14
C Canadian Standards Assα垣ation
55
RANGES
Ignition
system faults
υNIT
1
There are various ignition systems used on gas-fired ranges. The faults
encountered and the solutions vary depending on the system used.
Spark ignition faults
Electric ignition systems may fail due to electronic component failure or
burned circuit wiring. You can use continuity checks of system components
with a multimeter and visual inspection of wiring runs to determine the
source of faults. Defective components and wiring should be repaired or
replaced in accordance with the manufacturer ’ s instructions. Table 1-3
Lists common problems for spark ignition systems.
Table 1-3 Spark ignition faults and causes
Faults
Possible causes
Corrective action
No sparking occurs for one of the
top burners
Valve switch not operating
Replace valve switch
Sparking occurs at two of the top
burners only
Shorted wire
Replace wire
Defective ignition control
Replace control
Poor grounding
Ground properly
Incorrect gap
Adjust gap
Intermittent sparking at burner
electrode
Partial short to ground from
No sparks at any burners
Constant or random sparking
after the burner is lit
Clean spillover
Ignition control or poor grounding
Replace c。ntrol and／。r
ground properly
Reversed polarity
Check
Improperly grounded
receptacle
range 。r
wall
pola 时ty
Check grounding
Extremely low flame which 臼nnot be
detected by the flame sens。r
Reposition sensing
element
Flame may be blown away from the spark
electrode by a draft
Eliminate draft
Electrode
56
spillo巾er
insulat。r
may be cracked
Replace insulator
Electrode lead may be short circuited
Repla臼 lead
Spark gap between the electrode and the
burner base may be too small or to。 large
Check gap
Repla出 faulty wiring or
Electrode may be sparking up to the burner
cap instead of down to the burner base
electrode
Gas pressure may be too low.
Adjust pressure
Gas Technician 2 Training - Module 14
© Canadian Standards Association
RANGES
UNIT 1
Constant pilot faults
Table 1-4 details the common fault associated with constant pilot ignition
systems in ovens and top burners.
Table 1-4 Possible causes and corrective action for pilot flame outage
Possible causes
Corrective action
Too much air going into burner causing
flame to lift and blow out.
Adjust
Drafts in oven
Completely enclose oven cabinet
Pilot set too low
Adjust
Oven burner flame playing directly on
pilot tip
Adjust pilot tip so it is 3/8 inch below
oven burner p。rt
Loose connection in pilot supply line
Tighten connection.
Pilot flame out of adjustment
Adjust flame length
Defective thermostat
Replace thermostat
Defective automatic oven gas control
Replace control
p时 mary
pil。t
air shutter.
valve for longer flame
Mini-pilot system faults
Table 1-5 details the common faults associated with mini-pilot ignition
systems m ovens.
Table 1-5 Mini pilot faults, causes and corrective action
Faults
PossJble causes
Corrective action
Mini-pilot flame
goes out
intermittently
Pilot size inadequate
Adjust flame length so that
flame has yellow tip
叭leak magnet 。n
Check millivolt dropout
reading
mini-pilot
system
Mini pilot goes out
when reset
mechanism
released
Gas Technician 2 Training - Module 14
© Canadian Standards Association
main 霄ame
input
Overtired or smothered
main burner flame 臼using
smothering of pilot
Check
Bent rod
Replace oven control
Defective mini-pilot
thermocouple
Replace therm。couple
Defective magnet
Replace magnet or valve
57
RANGES
UNIT1
Top burner
faults
A properly adjusted burner flame should extend between one and two
inches above the burner ring or grate. The flame will spread out when a
cooking vessel is placed on the burner.
It is important to ensure that the inner blue cone of the flame is not broken
by a cooking vessel on the burner. If the inner blue cone of the flame is
disturbed in this w町， carbon monoxide can be produced by the incomplete
combustion that results. Carbon monoxide (CO), is a colourless, odourless,
poisonous gas.
Burner adjustments include:
•
gas input adjustment
•
air shutter adjustment to regulate primary air flow
•
burner and orifice cleaning and alignment.
The correct gas input is indicated on the appliance rating plate. When the
coηect gas input to the range is verified, the orifice hood of each burner
can be adjusted to maintam the coηect gas-air mixture for proper
combustion. Dirty burners and burner orifices must be cleaned and
misaligned orifices repositioned.
Oven burner
faults
Table 1-6 gives the corrective measures for typical oven burner faults.
Faults
Oven too hot
Table 1-6 Typical oven burner faults
p。ssible causes
c。rrective action
Standby pilot set to。 high,
Adjust standby pilot
preventing burner from
cycling o仔
Heat control sensing bulb
Replace sensing bulb
broken or leaking
Recalibrate
Heat control out of
臼librati。n
丁hermostatic
Baking takes too long
valve di『ty
Burner underfired, causing
excessive preheat time
Heat control out of
Clean or replace
Inc『ease orifice size
Recalibrate heat c。ntrol
calibrati。n
Uneven baking
58
Burner ove『fired
Adjust burner orifice
Gas Technician 2 Training - Module 14
。 Canadian Standards Association
RANGES
UNIT 1
Faults
Oven will not turn on
manually
Table t 毛（Continued) Typical oven burner faults
Corrective acti 。n
Possible causes
Relight
Pilot light out
Dirty or defective
thermostat valve
Clock not set for manual
operation
Defective flame switch
Defective solenoid valve
Electric power o仔
Oven burner cannot be
turned o仔 by thermostat
Defective component or
wiring
Clean or replace
Set cl。ck for manual
operati。n
Replace
Replace
Check for blown fuse or circuit
breaker
Disconnect plug from wall socket
If burner stays on, replace
valve
the 回lenoid
If burner goes out, inspect
wiring and terminals for
shorts.
No main burner flame
Oven does not maintain
temperature
Broil burner will not come
on when thermostat set to
BRO比
If no short is e> ident, turn
calibration sc陪w clockwise
several turns. This will shut 。仔
gas if thermostat is out of
calibration.
Thermostat out of calibration Recalibrate therm。stat
Thermostat se忧ing lo响·er
Recalibrate temperature se忧 ing
than actual oven
control knob
temperature
Replace safety switch
Defective safety switch
Mercury bulb does not get
Check pil。t flame position
hot en。ugh
Check gas pressu用
Defective thermostat
Replace thermos恒t
Repositi。I") or clean oven bulb
Oven temperature sensing
bulb 。ut of po创tion or dirty
Thermos阳t not properly
Recalibrate thermostat
calibrated
Sa币＇ety switch not closing
Check 臼fety switch 。peration
Aerated pilot not
functioning
Check that aerated pilot flame:
is ignit创
is hard and about % inch long
reaches above
pil。t
shield
倪。附 around the 臼pillary
of
the flame switch.
Check pilot a吗usting screw to
make sure it is open
、、－，
Gas Technician 2 Training - Module 14
© Canadian Standards As曲ciation
59
UNIT1
RANGES
Table 1-6 (Concluded) Typical oven
Possible causes
Faults
Broil burner will not come Orifice dirty or incorrectly
on when thermostat set to sized
BROIL (Cont'd)
Air supply tube restricted
burner faults
Corrective action
Check orifi饵 for correct size. If
correct size, clean orifice
Check air supply tube:
for foreign material
for kinks or restrictions
is securely attached to
mounting bracket
Upper oven broil burner
pilot gas goes out
Restricted vents
Pilot flame to。 small
Air supply tube blocked or
out of alignment
Oven bake burner ove『fired
Vent passages blocked
Check air supply tube for proper
location (approx. % inch to 5/8 inch from the oven burner box)
Check pilot 。rifice size. Replace if
incorrect
Adjust orifice
Clear blocked vent passages
Dirty pilot
Clean pilot orifice
。efective
Replace pilot
Set for natural gas
Clean or replace regulator disk
and seat
Incorrect orifice size
Burner will not turn on and
mercury is not glowing
bright red
Burner cycles rapidly
(every 1"'-2 s) a负er it
reaches setp。int
Pilot does not expand
when control temperature
set
Pilot expands and heats
mercu『y bright red, but
burner fails to ignite
60
fittings to make sure they are
tight
Check vents
Check whether adjusting screw is
open en。ugh to provide maximum
flame
Check air tube for restriction
pilot
Oven control set to LP
Regulator is faHing to lock
up，但using the heater pilot
fo SU咱e when main burner
goes out
Clock has not been reset
(may have been activated
while cleaning)
Mercury safety is defective
Set to manual operation
Replace mercury safety
Gas Technician 2 Training - Module 14
© Canadian Standards Association
RANGES
UNIT 1
Assignment 1
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
Where is the input rating of a range located and what pu叩ose does it serve?
2.
How must the range be connected to the electrical circuit?
3.
孔That
4.
What is the allowable clearance to combustibles for a range certified for zero clearance?
5.
What is the purpose of the appliance regulator?
6.
Why must there be gas flowing to properly read and adjust pressures?
7.
Describe what is happening when a flash tube ignites a burner from a pilot.
8.
Why is it important to verify the calibration of an oven-control?
are three ways to determine the required clearance to combustibles for a range before
installing it?
Gas Technician 2 T1『aining-Module 14
Standards AS1.始ciation
。 Canadian
61
RANGES
9.
UNIT 1
How long should a gas range operate before adjusting the oven temperature calibration?
10. What could be the causes of intermittent pilot outage on a range equipped with a mini-pilot
system?
62
Gas Technician 2 Training - Module 14
。 Canadian Standards Association
Unit2
Clothes dryers
Purpose
咀1e
operation of a gas clothes dryer is somewhat different than that of
other common gas appliances. The gas technician must have a 缸11
understanding of installation procedures, service and maintenance to
ensure 由e equipment operates safely and efficiently.
Learning
objectives
1. Describe the installation requirements for clothes dryers.
2. Describe the installation procedures for gas ranges, including
piping and electrical connections.
3. Describe the moisture exhaust venting.
4. Describe burner ignition systems.
5. Describe clothes dryer controls.
6. Describe the operation of clothes 世yers.
7. Describe the servicing of clothes dryers.
Gas Technician 2 Training - Module 14
©Canad阳n
Standards As部>elation
63
Topics
1.
Installation requiremen恒..............…..................................... 65
Responsibility of the installer .......................…···································· ...... 65
Clearan臼s ........………........…….................……….................….............. 66
Gas supply piping .................…·············…........…··…….........….........….....66
Moisture exhaust vent... ....................…........…·......…..................…............68
Levelling the dryer . .........................…............................…...........................69
Electrical supply ........…··················…··…..............…………......................... 70
2.
Piping ......................….........…...............................…............... 7’
Fuel conversion ........………·”……………...................................................... 71
Inlet pressure ..........................….........…........…….........…….........……........71
Making the gas connecti。n ..............................…......... ·················….......... 71
Pressure regulators ................…........……·······………............…....................72
3.
Electrical ...........................…................................................... 75
Power supply ........….............…………….....,..............……........…..................75
p。larity and grounding ........……........................……………............................75
Installing the dryer ...............…···········…·········…................….........……........77
4. M。isture exhaust vents ....”··”··”......................................”... 79
Types of vents ............................................……······························…….......79
Exhaust hoods .......................................................…....................................80
Vent length .........................................................................................…........81
Vents in unheated areas ........…….......…………..............................................82
R。uting the vent. ...........................................................................................82
T。。Is required ........................................…························…….....................83
5.
Burner igniti。n systems ....................”..............”.................. 85
Constant pilot burner .......................…........................…………........…...........85
Glow coil system .....................….........................………….......…...................86
Spark ignition bumer .....................................................................................88
GI。－Sil burner .........................….......... ·········…........................................….. 90
6.
c。ntrols
.......................................................................…........ 93
Drum motor and door switch ............................……..............……...................93
The drying cycle ..........…...............….........…….......….......…..........................94
Temperature controls .......................…................”…......................................95
Timers ...................................................……….............................凰................. 95
Automatic cycle ...............................................….....................~－…................. 95
Cool-down period ..……..................................................................................96
Start switches ..................….........................…................................…...........97
Thermostats ..................................................................................................97
7.
Operati。n
.............................…................................................ 99
Heating the air .............................…·········…································…...............99
Air movement... ......….......................................….........…..........…................ 101
Exposing clothing to heated air ................................................................... 102
8.
Service ……”··”..............”··”............…...................”··”··”.... 103
Electrical sequen臼 of operation ..…............................................................ 103
General electrical troubleshooting ........…...............................…..........…·….103
Troubleshooting the burner ignition .........................…................................ 105
Troubleshooting d『yeroperati。n .................圄…............................................ 107
Assignment
64
2 ........”··”............................”··…”.........…”...........’”
Gas T职加1ician 2 Training - Modu悔 14
。 Canadian Standards As叙回ation
TOPIC
1
Installation γ~quiγem en ts
It is important to know 由e procedures that must be 岛llowed when
installing a gas-fired dryer. The Natural Gas and Propane Installation
Code (B149.l), which will be called the Code from now on, contain the
code requirements for installing gas appliances.
Responsibility
of the ins饵”er
All ~as a~pliances must be installed according to the manufacturers ’
certified instructions and the Code requirements. If there is a di能rence
between the manufacturers' instructions and the Code requirements then
the instructions set by the Code must be followed.
Failure to read the manufactur町、 instructions before installation can
result in:
•
fire
•
explosion
•
personal
•
service problems.
ii飞jury
or death to 出e operator
The Code places a lot of responsibility on the installer. If replacing an
appliance, check to ensure 也at 由e new appliance or replaced parts 町e
compatible with, and suitable for.，也e current system.
If the new appliance uses a di他rent type of energy to 由e old one--such as
a different type of g邸， or elec往icity-check that the old energy supply is
臼fely shutoff and sealed. The Code outlines how this must be done.
When an appliance is installed, it must be tested to see that it is working
safely and correctly. Included in these tests are pressure tests which are
described in Module 8, Unit 3.
Finally, ensure 由at 由e user of the appliance knows how to safely operate
gas-fired clothes dryer.
也e
Gas Technician 2 Training - Module 14
© Canadian Standards A路∞剧。n
65
CLOTHES DRYERS
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Clearances
The rating plate on the clothes dryer specifies the clearances required
between a gas-fired appliance and combustible material. The Code must
also be checked for specific requirements for dryers. These requirements
must be taken into account before the dryer is installed.
Since the appliance will need to be serviced, minimum clearances need to
be left at the service points of the appliance. These clearances are given by
the manufacturer and are in the Code.
Gas su.pply
piping
The following gas supply piping items must be considered when installing
a clothes dryer.
Material
The Code states that all gas piping shall be steel, copper or plastic. There
are very specific requirements if piping, tubing or fittings are to be re-used,
or if the piping is to be used with a different type of gas. If re-using the
piping, it must be equivalent to a new one. To do this the old piping needs
to be:
JU
m．，由
mh 比
－
..
创
cleaned
eAU
All piping and tubing must meet the Code requirements.
Size
All piping, hoses and tubing must be checked to ensure 由ey are large
enough to provide the required amount of gas needed by the connected
appliances. It is also a good idea to take into account any appliances that
may be added later. Tables in the Code can be used to help determine the
size of the piping required. The procedure for pipe sizing is covered 面
Module 8, Unit 2.
The gas pressure required for the various appliances can be found:
66
•
on the appliance rating plate
•
from 也e
manufacturer if it is not shown on the appliance.
Gas Technician 2 Training - Modu梅 14
。 Canadian Standards Association
CLOTHES DRYERS
UNIT2
Location
The Code specifies where gas piping, tubing, connections and fittings may
or may not be placed. These requirements must be checked when planning
where to locate the appliance.
It is important that all piping and tubing is properly protected from passing
tra伍c, weather conditions, and other substances. The piping and tubing
must not sag, and nothing may apply external press山e on them as this may
cause damage. The piping or tubing must also be clear of all appliance
doors and access points.
Joints and connections
Joints and connections must be properly installed:
All pipe jointing sealants must be certified.
•
When an appliance is connected to the gas supply lines it must be
properly supported. The appliance must not place any s位ess or load on
the piping or connections.
The Code does not require that a dirt pocket be installed on a domestic
clothes dryer.
A quick disconnect device can be used to connect a dryer to 也e
building gas supply. In 也is case there must be a readily accessible
manual shutoff valve immediately upstream of the disconnect device.
The shutoff valve should be as close as possible to the disconnect
device.
Prohibited practices
Note that the Code specifies ~rohibited practices. See Unit 1, Topic 2 of
module for a list of prohibited practices.
也is
Markings
All ~as piping and tubing needs to be clearly identified according to 由e
requirements of the Code.
Manual shutoff valves
The Code specifies the type of manual shutoff valve required，副 well as
wh町e it must be placed. All appliances must have manual shutoff valves
installed. These valves need to be readily accessible; If the valve for the
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67
CLOTHES DRYERS
UNIT2
clothes dryer is not installed in the drop to the dryer, or within a few feet of
the dryer, there must be a metal tag attached to the valve, or a permanent
sign placed next to the valve, indicating the appliance it se凹es.
Hose and hose fi忧ings
Hoses may only be used with an unvented appliance, and they are therefore
not permitted to be used for connection to a dryer.
Connectors
Flexible metal connectors are 也e most common connection method for
clothes dryers. Details on flexible connectors are included in Unit 1 of this
module.
Moisture
exhaust vent
The dryer must be exhausted to the outdoors. The Code sets 叩ecific
placing and 可pe of moisture exhaust vents that may
be used.
requirements 岛r 也e
The vent must be either non-combustible, or certified as meeting the
requirements for Class 1 Air Ducts as contained in CAN凡JLC-SllO
Standard for Air Ducts. Plastic vents are only acceptable if they have been
stamped with this number.
Do not connect a moisture exhaust vent into a vent connector, vent or
chimney. The exhaust vent must also vent clear of combustible materials.
Do not use sheet metal screws to
secure a moisture exhaust vent. If
screws are used, lint may be caught
by them in the outlet.ηiis can cause
blockages and fire hazards. Instead,
use duct tape to connect the
moisture exhaust vent to the dryer as
shown in Figure 2-1.All joints should
also be sealed with duct 饵：pe.
An access for inspection and
cleaning of the e由aust system must
be provided. 白iis should be done at
least once a ye町．
68
Figure 2-1 Use duct tape to a忧ach
vent to dryer
Gas Technician 2 Training - Module 14
。 Canadian Standards Association
CLOTHES DRYERS
UNIT2
Levelling the
dryer
A dryer should be installed on a solid and level floor, and the dryer should
be level when it is operating. Floors are often not completely level. In this
case the levelling legs will have to be a司justed to make the dryer level (see
Figure 2-2).
Note
Do not install a dηer on α weak or spongy floor.
区®
Dryer
base
Leveling leg
Figure 2-2 Adjusting the levelling legs of a dryer
ηie proced田e
for installing a dryer and a司justing its levelling legs is as
follows:
1. Prepare to protect 由e floor and the appliance:
•
•
•
Check 也at the
legs are not extended. If a dryer is dragged across the
floor after the legs have been extended, the legs or the dryer may be
damaged.
Make sure the locknuts are tight.
Slidethe 由yer onto cardboard or hardboard before moving it across
the floor.
2. Move the dryer close to its permanent location.
Leave enough room to connect 也e e对iaust vent.
Note the clearance requirements specified on the rating plate or as
specified in the Code.
3. Remove the cardboard or hardboard from under the drye卫
Gas Technician 2 Training- Module 14
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69
UNIT2
CLOTHES DRYERS
4. Check the levelness of the dryer by placing a level on top of the dryer.
•
•
Check side to side.
Check front to back.
5. If the dryer is not level, loosen the locknuts and adjust the legs until the
dryer is level.
•
•
Keep the dryer as close to the floor as possible.
All four legs must rest firmly on the floor so that the dryer does not
rock when it is operating.
6. After the dryer has been levelled, tighten the locknuts securely against
the bottom of the dryer base.
Note
扩the
/ocknuts are not tightened secu陀秒，
during operation.
Electrical
supply
70
they will
vibrate out ofposition
All electrical connections must conform to local codes and ordinances.
Check the local electrical code for the approved size and type of wire
required for the particular dryer installation. The electrical supply is
discussed further in Topic 3 of this unit.
Gas Technician 2 Training - Module 14
© Canadian Standards Association
TOPIC
2
Piping
Many of the requirements for hooking up a dryer to a gas system in a
building are contained in the Code. Additionally, some of these subjects
have been covered in Topic 1.
Fuel
conversion
Conversions of clothes dryers follow the same procedure as described in
Unit 1 of this module and Module 9, Unit 6.
Inlet pressure
The typical inlet pressure for a dryer operating on natural gas is 6 inches
w.c. (1.5 kP时， and 10 inches w.c. (2.5 kPa) for an appliance operating on
propane.
The inlet pressure is measured in the piping just be岛re the appliance. It is
measured while the appliance is fir切g at its rated input so 由at 由e pressure
loss 由at occurs while the gas moves through the system can be taken into
account.
Making the
gas
connection
The following are typical manufacturer ’ s
connection.
1. Before the dryer is
connected, close the manual
shutoff valve to the piping
where the dryer is being
installed.
2. Remove the shipping cap
from the gas pipe at the rear
of the dryer (Figure 2-3).
3.
instructions 岛r
making the gas
Shipping cap
Figure 2-3 Shipping cap
Check 也e
rating plate on the dryer to see 也e type of gas it requires. If
be converted this must be done before it is connected
to 也e supply.
也e dryer needs to
)
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© Canadian Standards A斟扮ciation
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UNIT2
CLOTHES DRYERS
4. Apply a certified pipe-joint compound to the supply pipe and flexible
connector JOlllt.
5. If the dryer is connected to the gas supply using copper tubing, form a
loop in the tubing so that the dryer can be moved when it is serviced. A
0.125 inch NPT plugged tapping should be installed immediately
upstream of the gas supply connection to the dryer. This tapping must
be readily accessible to be used for the test gauge connection.
6. Once the installation is complete, soap-test any piping or tubing that
was not previously tested.
Testing for leaks
The easiest way of checking for leaks is to use a soap bubble test. First
make sure that the gas supply to the dryer is on. Use a soapy solution such
as a liquid detergent. Wi由 a paintbrush, spread some of the solution around
all gas joints and connections. If bubbles are seen then there is a leak. Turn
off the gas supply and tighten the connections. Once this has been do时，
check the connections again for leaks.
Every time a dryer is serviced, a soap test should be done to check for
leaks.
For more information on soap tests, refer to Module 8, Unit 3.
Cautions!
Do not use a soapy solution that contains ammonia as this can damage
brass piping and connections.
Always clean the soap solution aw咿 after pe功rming a test, as over time
this can be corrosive to the piping or tubing.
Pressure
regulators
币ie press旧e
regulator on a 由yer:
reduces the incoming gas pressure
keeps 也e pressure
supplied to 也e dryer at a constant level.
Pressure regulators are covered extensively in Module 15, U时t 1.
Location of the regulator
Figure 2-4 shows a cut-away view of the controls and gas flow system in a
dryer. :Note the location of the pressure regulator.
72
Gas Technician 2 Traini咱－ Module 14
e Canadian Standards Association
CLOTHES DRYERS
UNIT 2
Unlatch solenoid
Main burner solenoid
Pilot orifice
‘
e 阻
民
趴闹
P
su,..
mmM
rE
AV<>
Pilot valv
A
4
Section through ~ilot
valve showing 9~桶。ow
from body to pilo~
Figure 2-4 Cut-away view of the controls and gas flow system,
showing lo臼tion of pressure regulator
。 peration
of the regulator
Although the operation of a regulator is covered in more detail in Module
15, some points are highlighted here.
The balancing pressure of the regulator is typically set at 3.5 inches w.c.
(0.9 kPa). Variations 丘。m this press田e will change the burner input and
can cause 由e dryer to fire incorrectly. If the pressure on 由e regulator needs
to be adjusted, a manometer is used to veri鸟r the pressure adjustment. The
actual manifold pressure is marked on the rating plate.
Gas T缸如nician 2 Training - Module 14
© Canadian Standards Association
73
CLOTHES DRYERS
UNIT2
Adjusting the regulator
The pressure regulator is adjusted at the factory to provide the correct
operating pressure. If someone has tampered with it, it may need to be
adjusted. Typically, the 0.125 inch NPT pipe plug on the side of the burner
is used to give access to test the pressure.
Tum off the main gas supply before connecting a manometer or test gauge.
Then tum the gas supply back on. Adjust the pressure on the regulator up
or down as the burner is firing.
74
Gas Technician 2 Training - Module 14
© Canadian Standards Association
TOPIC
3
Electγicαl
Power supply
All gas dryers are equipped with a power cord incorporating a common
parallel-blade plug （由ree-prong plug) which will fit into a household
receptacle. This receptacle must supply a nominal 120 V, 60 cycle current,
and should be within 5 f王（ 1.5 m) of the rear of the machine. It is better if
the receptacle used is on a separately fused ( 15 A) circuit.
Note
Do not use an extension cord, an adapter or a heavily loaded circuit.
All electrical service to the dryer must conform with local codes and
ordinances, as well as the latest edition of the National Electrical Code
(CSA C22.l).
Polarity and
grounding
Ensure that the dryer is supplied wi由 a 也ree prong grounding plug.ηiis is
for the protection of everyone. It should be plugged directly into a properly
grounded three-prong receptacle.
Caution!
Never remove the grounding prong from the plug.
If a mating wall receptacle is not available, it 扭曲e responsibility and
obligation of the customer to have a suitable grounded three-prong
rec叩臼cle installed by a qualified electrician.
Figure 2-5 shows the power cord from the dryer control housing to the wall
receptacle. It also shows the polarity check for the wall receptacle.
」，
Gas Technician 2 Training- Module 14
。 Canadian Standards A篇。~tion
75
CLOTHES DRYERS
UNIT2
The neutral, hot and ground wire of an appliance cord can be determined
without taking the plug apart. In a cord with black, white and green leads:
•
black is hot
white is neutral
•
green is ground.
In a moulded flat cord with no wire colours except green:
•
smooth is hot
ribbed is neutral
•
green is ground.
N。te:
For determining the c。rrect
polarity of a wall receptacle
叫且／L1
Vk~~~VA
Used by P_ermission of the copyright holder,
the American Gas Association
Figure 2-5 Polarity and grounding of a plug
Note 也at the
76
ground wire is also referred to as 由e bond wire.
Gas Tee才mician2T1『aining - Module 14
。 Canadian Standards A捕。ciation
CLOTHES DRYERS
UNIT2
Ins相 lling
dryer
the
Before plugging the dryer ’s power cord into the wall receptacle ensure that
也e power is off at the circuit breaker or 如se box. After plugging the dryer
in, tum on the power at the circuit breaker or fuse box.ηiis is to protect
you 仕om electrical shock if there is a problem with the electrical circuit.
、、－
Gas Technician 2 Training - M叫ule 14
© Canadian Standards A筒。ciation
77
TOPIC4
Moisture exhaust vents
The moisture exhaust duct removes the moisture 由at evaporates from the
wet clothing to the outdoors. It is important for this vent to be completely
sealed as any moisture leakage could damage the walls and floors.
Types of
vents
自由er
a rigid or flexible metal exhaust vent can be used to vent the clothes
dryer. Rigid metal vents are preferable as 也ey are less likely to be crushed.
If flexible metal venting is used, then it must be fully extended and
supported when it is installed on the dryer. It must not be enclosed in walls,
ceilings or floors.
Uncertified plastic and foil-covered vents (Figure 2-6) are not
recommended since this type of ducting can kink, sag, be punctured,
reduce airflow, extend drying times and affect dryer operation. If the
existing ducting is uncertified plastic, non-metal or combustible, replace it
with metal ducting.
Note
Do not use a vent with a diameter less than 4 inches ρ 02 mm).
Rigid metal
(preferred)
Flexible metal
(acceptable)
资额
Uncertified plastic
Flexible foil
Figure 2-6 Types of moisture exhaust ducts
Gas Technician 2 Training - Mα:lu饱
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14
79
CLOTHES DRYERS
Exhaust
hoods
UNIT2
In Canada, the exhaust system must be vented to the outdoors. This is to
prevent lint build up indoors, which is a fire hazard, and to prevent high
moisture levels within the building. Lint build-up, as well as excessive
moisture, can also lead to health problems to the occupant in the building.
Check for lint accumulation regularly.
The exhaust vent must therefore be capped with an exhaust hood to prevent
exhausted air from returning to the dryer. The following installation criteria
apply:
•
The exhaust vent must fit inside the hood.
•
The exhaust outlet hood should be at least 12 inches (305 mm) from the
ground, or any object that may be in the path of the exhaust.
The termination should present minimal resistance to the exhaust air
flow.
Use caulking compound to seal the exterior wall opening around the
exhaust hood.
Figure 2-7a shows the two preferred types of hoods. Figure 2-7b shows
another type that is acceptable.
q$)C回 q)
4 inches
(102 mm)
4 inches
(102 mm)
(a) Preferred
2 1/2 inches
(64 mm)
(b) Acceptable
Figure 2-7 Types of hoods
Vent flaps
Vent hoods are equipped with flaps that prevent exhaust and wildli岛 from
entering the system.
Check that the exhaust hood flapper is not stuck, missing or damaged in
any way. Figure 2-8 shows how a mirror can be used to check 也at the flap
is moving 仕eely. When the dryer is on the flap should be fully open.
80
Gas 丁echnician
2 Training -
© Canadian
Module 14
Standards Association
UNIT2
CLOTHES DRYERS
On an existing system check that the exhaust hood is not clogged with lint.
Also check that no wildlife has nested inside the hood.
Cautions!
Do not use exhaust hoods with magnetic latches. The flapper on the vent
prevents the flap斤。m swinging卢-eely.
Never install a screen over the outlet as it will cαuse lint build up and
blockages.
Flaps move
freely
Figure 2-8 Check the flap
operati。n
with a mirror
Vent length
The maximum length of the e对iaust system depends on:
•
manufactur町、 specifications
•
type of exhaust hood
•
type of material一-either rigid or flexible metal
number of elbows.
First choose the exhaust vent length chart 也就 corresponds to 也.etype of
hood being used. Then select 也e length based on the vent material and the
number of elbows needed. A typical chart for a 4 in ( 102 mm) vent hood is
shown in Table 2-1.
Do not use vent runs longer than those given in the chart. Exhaust systems
longer than these will:
•
accumulate lint, creating a fire hazard
•
shorten the life of the dryer
reduce performance ·of the 由yer, leading to higher energy costs;
、、－
Gas Technician 2 Training- Module 14
@Canadian Standards As配刚ation
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CLOTHES DRYERS
UNIT2
Table 2斗
A
Routing the
vent
vent length chart for 4 inch (102 mm) hood
Number of
Maximum length of me幅l vent
90° elbows
Rigid
。
64 食（ 19.5
m)
36 由（ 11.0
54 负（ 16.5
m)
31 ft (9.4 m)
2
44 负（ 13.4
m)
27 货币 .2
m)
3
35 负（ 10.7
m)
25 伐（ 7.6
m)
23 食（ 7.0
m)
4
Vents in
unheated
areas
Typical
127 负（8.2
m)
m)
If the ductwork runs through an unheated area, it should be insulated and
slope downwards towards the exhaust hood. This is to prevent the build up
of moisture and lint within the exhaust vent system.
The exhaust outlet is located at the rear of the dryer. Figure 2-9 shows some
possible options for routing the vent from the dryer.ηie e对iaust vent can
be routed up down, le鱼， right or straight out of the back of the dryer.
Flgure2-9
82
Flexible
R。uting
the vent
Gas Technician 2 Training - Modu始 14
©Canad国n S幅ndards Association
CLOTHES DRYERS
UNIT 2
Tools
required
Before starting an installation always ensure that you have all the tools
required. They may include the following:
•
caulking gun
level
safety glasses
•
knife
adjustable wrench
•
flat-blade screwdriver
•
Hex-head socket wrench
•
pipe-joint compound
•
nut driver
•
duct tape
•
pipe wrench
•
gloves
•
tin snips (to cut 由e metal ducting)
Make sure to include snips that cut to right and snips that cut to left.
Never use snips to cut wire as this blunts the blades on the snips.
a heavy-duty electric drill to drill through walls.
When selecting a drill bit, make sure it is sharp. Also check that the
bit shank and chuck jaws are clean. If they are dirty the bit may not
align properly.
To cut a hole through the walls that the venting must pass through,
use a 4.125 inch (100 mm) high-speed hole cu忧er. For brick or
concrete walls, use a masonry bit or coring machine.
Gas Technician 2 Training- Module 14
©Canadian S汩ndards Association
83
TOPIC
5
Burneγ ignition
systems
Burner ignition systems can be categorized into four basic types:
Constant pilot
burner
•
constant pilot
•
glow-coil
•
spark ignition
•
Glo-Sil.
The constant pilot is sometimes referred to as a match-lit, capillaη1 pilot, or
standing pilot burner. With this type of burner ignition system, the pilot
must be manually lit. Once lit, the pilot remains on at all times.
The standing pilot heats a mercury-filled capillary tube bulb; the pressure
is transmitted through the capillary to keep the spring-loaded shutoff valve
open (Figure 2斗。）．
If the pilot goes out, the mercu可 cools and the bellows release the springloaded valve to shut off the flow of gas to the pilot and burner.
/Mercury filled bulb
Zip
tube"J
Start
lever
Pilot valve plunger
Zip tube valve plunger
Figure 2-10 Constant pilot ignition system
Gas Technician 2 Training - Module 14
© Canadian Standards Association
85
CLOTHES DRYERS
UNIT 2
To light the pilot:
1. Push down on the start lever.
This lever lifts the pilot valve and latching cap; it also seals the tube to
the main burner. The gas flows into two different tubes: to the zip tube
and the pilot.
2. Light the air-gas mixture above the zip tube.
The gas lights along the full length of the tube, and lights the pilot.
3. Wait while the pilot heats up one end of the mercury-filled capillary
饥ibe.
As the mercury heats up it expands and pushes on the diaphragm
attached to the other end of the tube, operating a latching pin.
After about one minute the pin moves forward into the latched position,
holding the pilot gas valve open.
4. Release the start lever.
If the pilot goes out, the latching pin pulls back, shutting the pilot valve and
stopping all gas flow.
The main burner is ignited as follows.
1. When the timer dial is set to a heat setting, the circuit through the timer
is closed.
2. This completes a circuit through the thermostat to the main gas
solenoid.
3. Gas can now flow to the burner and be ignited by the pilot.
Glow coil
system
The glow coil is a resistance wire mounted on a ceramic block. As shown
in Figure 2-11, it is connected to a step down transformer that is mounted
on the valve body. When power is applied to the coil, it glows, producing
enough heat to light the gas.
As soon as the dryer timer is turned to one of the heat settings, the pilot
valve (not shown) is energized.ηie following electrical sequence of
operation occurs to light the main burner.
1. Power enters through the 1 V circuit.
At this point, the pilot switch is closed at three points simultaneously:
1.
86
Connection 午1 allows the current to travel throu白白e pilot
solenoid coil and wa甲 switch to the 3 V terminal.
Gas Technician 2 Training - Module 14
© Canadian Standards A部∞阳ti on
CLOTHES DRYERS
UNIT2
Connection 4-3 allows the current to travel through the wa甲
switch heater and the transformer (which powers 由e glow coil) to
the 3 V terminal.
iii. Holding circuit for the pilot solenoid and warp switch. The holding
circuit does not allow enough voltage through to open the pilot
solenoid coil, butjust enough to hold it once in the open position.
i1.
2. When the glow coil heats up to a brilliant white hot, it ignites the pilot
gas.
3. The pilot flame heats the mercury bulb, creating pressure in the tube
leading to the pilot switch.
4. This pressure causes 也e pilot switch arm to move, opening the 4-1 and
4-3 circuits, and closing the 4-2 circuit (see dotted line in Figure 2-11).
The following occurs:
The current travels 由rough 出e pilot switch and main burner
solenoid coil to the 3 V terminal.
ii. The current still travels through the holding circuit. The holding
circuit includes the 800 n resistor, the pilot solenoid coil and the
warp switch to the 3 V terminal.
i.
At this point, bo也 the main burner and pilot burner 盯e open, allowing gas
to flow through the main burner where it is ignited by the pilot.
1V
3V
ω…
Warp
switch
Pilot solenoid
coil
Figure 2－刊
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@Canadian S随时ardsAs曲ciation
Wiring
diagram of glow-coil ignition system
87
CLOTHES DRYERS
UNIT2
Opening the dryer door
If the dryer door should be opened at any time during the cycle:
1. Voltage to the main burner is cut off.
2. Both the main burner and pilot gas valves close, stopping gas flow.
3. Both the main and pilot burners go out, even though the door is closed
again. (The pilot valve will not open because of the 800 n resistor).
4. After about two minutes, the mercury cools and the pilot switch moves
back to connect 4-1 and 4-3 circuits again.
5. The burner ignition steps are then repeated.
Function of the warp switch
Thewa甲 switch
acts as safety device to break the circuit to the glow coil
and pilot valve when one of the following malfunctions occur:
•
The main burner does not light at initial start up because of interrupted
gas supply
•
The pilot fails to light
The pilot flame is faulty and not generating enough heat to cause the
pilot switch to operate.
Thewa甲 switch
is composed of a bimetal arm that wa甲s or bends when
heat (supplied by the resistance heaters) is applied to one side of it. Ifleft in
the circuit, the warp switch will open after three to four minutes. However,
under normal operating conditions, the pilot 增iites and the pilot switch
swings to the 4-2 circuit, removing the resistance heater from the circuit
before the warp switch can react.
Spark ignition
burner
The spark ignition burner is sometimes referred to as a direct ignition
burner. There is no pilot in this system as the gas is ignited directly by a
spark. Figure 2-12 shows a typical manufactur町、 wiring diagram for a
direct spark dryer burner. Refer to this diagram when reading how the
circuitry works.
When voltage is applied to the burner assembly:
1. A circuit is completed 企om 1 V through the normally closed flame and
ignitor switches, the ignitor coil, and the normally closed warp switch
to the 3 V terminal.
88
Gas Technician 2 T1『aining - Module 14
© Canadian Standards Association
CLOTHES DRYERS
UNIT 2
2. This circuit starts three circuits simultaneously:
The ignitor circuit
The ignitor assembly consists of a coil, a stationary contact arm and
a movable contact arm. The moveable contact arm is motoractuated by circuitry through the contact points. The arm oscillates
6 to 12 times a second and is returned to its normally closed
position by a spring.
Arcing occurs each time the contacts break to provide ignition.
The heat generated by arcing of the ignitor contacts ignites 由e gas
within one second or less.
ii. The main coil circuit
The circuit from the 1 V terminal, through the main coil and the
normally closed warp switch contacts, to 也e 3 V terminal.
Al也ough this circuit ene电izes the main coil, no gas flows to the
main burner at 也is time because of the resistor in the pilot coil
circuit.
iii. The relay coil circuit
The circuit from terminal 1GB through the relay coil and warp
switch heater, to the 3 V terminal. This circuit closes the normally
open relay switch which completes a circuit directly to the pilot coil
(bypassing the resistor).
The increased voltage across the pilot coil provides enough energy
to “ pull h”也e gas solenoid valve. Gas now flows through to 也e
main burner where ignition occurs.
i.
FS
3. Within 3 to 5 seconds after burner ignition takes place, the burner flame
heat applied to the heat probe of the
Flame
switch
flame switch will cause the flame
,,
1GB
switch contacts to open.
ηiis
action opens circuitry to the
ignitor, relay c9il and wa叩 switch
heater and stotis ignitor action.
lg阳 4. Pilot coil circu~町 is now 伽ough 伽
resistor, reducijlg voltage to the pilot
coil.ηtis voltasze is sufficient to
lgnitor
coil
maintain 也e pi~ot valve open.
1GB
立〈
~ι~
问gure
TOR
2-12 Wiring diagram of dir，回t spark ignition system
)
Gas Technician 2 Training- Module 14
©Canadian S幅ndards A槌∞阳加n
89
UNIT2
CLOTHES DRYERS
Failure to ignite
If, for any reason, the burner flame should fail to ignite, or the flame switch
should fail to open, heat generated by the warp switch heater will open the
normally closed wa叩 switch contacts. This opens the circuits to the pilot
and main burner coils, and stops the flow of gas.
Warp switches on spark ignition burner are typically actuated by a 1 000 n
heater and calibrated to open between 15 and 40 seconds.
Glo-Sil burner
The Glo-Sil type burner was developed to bring a hotter ignitor and a much
faster response to combustion in the firing of the dryer burner. It has been
used in production for many years. The “ K ” series was used until 1984
when the “ M ” series was phased into production. Although they look
different, both function the same way：础er the gas passes through the
regulator it encounters the first of two electrical solenoid control valves.
Both valves are spring-loaded closed and the solenoids must be energized
for them to open. Both valves must be open 岛r the burner to work.
Figure 2-13 shows the wiring diagram for an M series Glo-Sil burner
system.
Bk
1 V Bk
Bk
Bk
~ValveNo.1
Holding
coil
Bl I
FS1
As补〉
coil
lgnitor
w
Bl
3VBI
IGR
(R)
Main coil
Valve No.2
Radiant
sensor
R
IG
w
FS2
Figure 2-13 The Glo-Sil burner system
ω
Gas Technician 2 T1『ai『1ing - Module 14
。 Canadian Standards Association
CLOTHES DRYERS
UNIT2
。 peration
When line voltage is applied:
1. A circuit is completed from the 1 V terminal to the ignitor and sensor
back to the 3 V terminal. Simultaneously:
i. The hold coil is energized.
ii. The assist coil is energized through the sensor.
iii. Both the hold coil and the assist coil must have full line voltage
applied to lift valve no. I off its seat.
2. The ignitor is heating and valve no. 1 is open.
3. No gas flo隅， however, until valve no. 2 also opens.
The valve no. 2 coil is not energized because current is shunted 由ough
the sensor switch (the path ofleast resistance).
4. When the ignitor reaches a temperature hot enough to open the radiant
sensor contacts (about 2200°F or 1204°C), the only pa由 left is through
the valve no. 2 coil. 卫iis causes valve no. 2 to open.
5. Gas now flows through valve no. 2 and is ignited instantly by the hot
tgn1tor.
6.
Magnetism 由rough
the assist coil is reduced.
7.
Magnetism 由rough
the hold coil is enough to hold open valve no. 1
open.
If the voltage to 也e burner is momentarily interrupted from a power
也ilure, and then restored:
1. Valve no. 2 opens.
2.
Wi由 the reduced c田rent through the assist coil (now in series with
valve no. 2), valve no. 1 will not open.
3. When the sensor cools and its contacts re-close, ignition will resume.
The ignitor
The ignitor heats to a temp町ature of about 2200。F (1204。C) in about 15 to
30 seconds a伽r line voltage is applied to it. It is made 企·om recrystalized
silicon carbide and is very brittle so take care when servicing this type of
burner ignition system. Several different styles have been used but they all
function the same way. Figure 2-14 shows a typical ignitor.
Gas Technician 2 Training -Module 14
©Csnad阳n S恒ndards Association
91
CLOTHES DRYERS
UNIT2
Ceramic base
Electrical
Figure 2-14 Igniter
The radiant sensor
This is mounted on 由e side of the burner tube and it controls 由e opening
of Valve No. 2. A cut-out in the funnel allows radiant heat from the ignitor
and gas flame to contact the sensor. Its contacts are single-pole, single由row二 and are calibrated to open when 由e ignitor reaches its operating
temperature, about 2200。F (1204。C). Heat 企om the burner flame holds the
contacts open ai王er ignition. Figure 2-15 shows the placement of the radiant
sensor.
Radiant sensor
Burner funnel
Figure 2-15 Placement of the radiant sens。r
92
Gas Technician 2 Training - Modu始 14
。 Canadian S阳dards Association
TOPJC6
Controls
Figure 2-16 shows how the dryer controls and devices are situated within
the dryer bulkhead assembly. The bulkhead assembly is welded or bolted
together to form a rigid support for the drum.
The motor, blower housing and burner are mounted at the base of the
bulkhead. The top panel and console assembly consists of the timer, pushto-start switch and temperature selector. It may also have a buzzer attached
that indicates when the dryer has completed its cycle.
Temperature
selector
Push
to start
..
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r、
m
hM
们m HM
W灿
H
DmD
ONr
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Belt
Courtesy of Consumers Gas
Figure 2-16
Drum motor
and door
switch
Positi。ning
of comp。nents and controls within dryer
ηie m创or
is the driving 岛rce 由at turns the dryer drum and blower. Dryer
motors are double-shafted (Figure 2-17): a pulley sits on one end and the
blower on the other end.
．
ηie
dryer drum is rotated through a belt 由ive system. Idler pulleys are
used to keep the belt tight.
The blower is a centri缸gal wheel 也at supplies the air flow 伽·oughthe
、』－
命yer.
Gas Technician 2 Training - Mα~ule 14
@Canadian S恒ndards Assoc福tion
93
CLOTHES DRYERS
UNIT2
Motor
switch
Used by permission of the copyr也ht holder,
the American Gas Association
Figure 2-17
Typi臼i
clothes dryer motor
Every dryer has a door switch (Figure 2-16）也at opens 也e electrical circuit
to the motor when the dryer door is opened. A pin on the inner door panel
extends through the door latch strike plate opening to operate the switch
when the door is closed.
The drying
cycle
The dryer uses a number of electronic controls to control the drying cycle
of its load. The control system works on 也e principle of air passing across
a regulating thermostat in the e对iaust system.
1. At the beginning of a load cycle, damp clothing is placed into the dryer
and the control adjusted for a drying time.
2. The heat applied by the dryer evaporates the moisture in the clothing.
There is little rise h 也e tempera阳re of the air being exhausted 由rough
由e exhaust vent.
3. As the load becomes drier, less heat is used to evapora臼 moisture and
the air temperature in the dryer starts to increase. The temperature of
the air being exhausted also increases.
4. This heated exhaust air passes over a regulating 也ermostat.
5.
94
When 世ie
temperature reaches a se甲oint, the 由ermostat turns off the
supply of gas to 由e dryer.
GasTechn』cian 2 Training - Modu胎 14
@ Canadian Standards Association
CLOTHES DRYERS
UNIT2
6. The temperature of the air will start to decrease, and so will the
temperature of the thermostat.
7. When this temperature drops below the setpoint the thermostat turns
the dryer back on.
Temperature
controls
Temperature controls modulate the heat within a range selected by the user.
There is also a fixed high limit switch 由at is typically set between 190。F to
250。F (88。C to 121 。C).
Temperature control switches are actuated by the temperature of the air 出at
passes across them. When the temperature in the dryer rises above the
setting, the switch opens the circuit to the burner, cutting off the gas supply.
The temperature in the dryer consequently lowers. When the temperature
reaches the lower setpoint the temperature control closes, energizing the
burner circuit.
Timers
The timer is the main control mechanism since it controls the motor and
burner sequence. It is either a solid state device, or it consists of a timer
motor and cam that mechanically opens and closes circuits in the dryer.
、一
Time-dry timers
Time dry timers have the time motor operating all the time. Both the heat
source and the dryer motor are also operating at the same time, except
when the dryer is in the cool down cycle. In this case the heat circuit is
open.
Automatic
cycle
The automatic cycle of a dryer also includes a timer. When the control is
set to A盯O DRY it operates 扭曲e same way 部由e time dry timer except
也就 the timer motor is not on when the heat source is operating (Figure 218). A thermostat controls the switching between the heat source and the
timer motor.
、、町，
Gas Technician 2 Training- Module 14
。 Canad阳 Standards As四elation
95
CLOTHES DRYERS
UNIT2
Shaded area
timer run time
22
（比。
）EOSE←o
160
/Timer run out
140
120
80
Ambient
0
5
10 15 20 25 30 35 40
Time (minutes)
Figure 2-18
Typi臼l
automatic cycle timer ch创
The shaded area in the chart (Figure 2-18) indicates the ?eriods when the
timer is operating. The rest of the time the heating circuit is closed and the
timer circuit is open.
In the automatic cycle, the drying time depends on 岛ur things:
.
.
.
.
the amount of run time selected 岛r the timer
也e 守pe
and size of clothes loads
the wetness of the clothes in the dryer
the ambient tempera阳re and humidity.
Wi也 auto dry settings, the user can set the control for different cycles
depending on the clothing bein~ dried ‘ These settings a司just the drying
temperatures, the length of the timer operation, and 也e length of the cool
down period.
Cool-down
period
Whether set to timed dry or the automatic cycle, there is a cool down
This is just before the end of its timed cycle and
is used to prevent excessive wrinkling. In this case the dryer operates 如r a
longer period of time after the clothing is dry, with no heat being added to
the air.
~eriod when the heat is off.
Some dryers allow clothing to be damp dried. This is to pr叩缸e 也e
clo也ing for ironing. In this case as soon as the thermostat cycles the heat
off，由e timer motor advances to OFF.
ηiere may also be an air fluff cycle. In 也is case the dryer operates without
heat being supplied.
96
Gas Te曲nician 2 Training-Module 14
。 Canadian Standards Assoc涌tion
CLOTHES DRYERS
UNIT 2
Start switches
All dryers have a momentaη contact start switch which must be activated
for the dryer to operate. These switches are also called push圄t。”start
switches, and are a safety device on the dryer.
The switch is a single-pole, spring-return in series with the start windings
of the drive motor. It must be held in momentarily until the dryer motor
reaches approximately 1200 r/min, then the centrifugal switch in the motor
closes the circuit internally.
Should the electric motor circuit be interrupted from any source (this
includes opening the clothes dryer door), which stops the drum from
revolving, it is necessary to push the START button to start the dryer again.
Thermostats
Dryers typically have three separate thermostats to control and maintain its
safe operation.
Control
thermos饭t
The control thermostat is located on the exhaust vent and it controls the
amount of heat supplied to the dryer.ηiis control is discussed in Topic 2 of
this unit.
The safety thermostat
The safety thermostat (or safety limit) is wired in series wi由 the control
thermostat and heat source. If the heat in the dryer rises above a certain
temperat田e, normally about 250°F (121 。C), the thermostat opens 白e
circuit to the heat source and the dryer cools down.
This safety switch would also shut off the burner if the lint screen was
blocked. The blower creates a negative pressure in the heater box 也at is
monitored by 也e sa岛ty disc (a temperature sensing snap disc). This switch
is mounted over a hole h 也e burner box and normally air is drawn 尬，
keeping the snap disc cool.
When the lint screen or vent syst臼n becomes blocked, the negative
pressure in the heater box is reduced and 由e heat from the burner flows out
也e hole.ηtis increase in temperature is sensed by 也e safety thermostat
which then shuts off the burner and cycles them until the condition is
rectified. This action reduces 由e 世y坦g effect of the dryer b四ause 由e
burners are not on as much and the moist air c缸mσt escape as readily.
、、峙，
Gas Technician 2 Training - Module 14
Standards A弱ociation
@ Canadian
97
CLOTHES DRYERS
UNIT2
The cool-down thermostat
The cool-down thermostat measures the temperature of the air in the dryer
at the end of a timed cool-down period. When the air has dropped below a
set temperature, the thermostat advances the timer to the end of its cycle.
98
Gas Technician 2 Training - Module 14
。 Canadian Standards Association
TOPIC
7
Op eγαtion
Proper and efficient drying requires three things: heat, air movement, and
exposure to the air movement.
In a dηer:
the heat is provided by the burner
the air movement is provided by the blower
the exposure is enhanced by the speed of drum rotation and baffles.
Heating the
air
The flame should be blue and lively, but not too loud. It should not be
scrubbing the top of the burner cone (funnel), but should extend to the end
of the cone, tailing up slightly. Figure 2-19 shows the characteristics of an
ideal flame.
Rounded blue
outer flame
Sharp blue/white
inner flame
Figure 2-19 An ideal
cl。thes dryer 何ame
has no yellow in it
Air requirements
The air involved in the burning process can be divided into the primary air
and the secondary air.
Gas Technician 2 Training- Module 14
Canadian Standards Association
©
99
UNIT2
CLOTHES DRYERS
Primαry αir
The primary air is the air mixed with the gas before
ignition. This air affects the characteristics of the
flame.
The amount of primary air supplied to the burner can
be adjusted by opening or closing the air shutter. The
location of the air shutter will be included in the
manu臼ctur町、 literature. It is normally locked in
place with a locking screw. With the burner operating,
loosen the locking screw and gradually slide the
shutter open or close until the flame meets the
manufactur町、 suggested flame characteristics.
Secondaηy
air
The secondary air is the air around the flame during
burning.
Properly adjusted primary air shutter
A properly adjusted flame ensures that the air is heated efficiently and
within the set tempera阳re ranges. If it is not, it can lead to unburned carbon
particles dirtying the clothing in 也e d~er, as well as 由e 岛rmation of
dangerous gases and dryer inefficiencies.
The following flame characteristics can be used to indicate burner
problems. Note, however, that flame characteristics are only a guide and
other checks and tests must be done to confirm the problem.
Lifting
(blow in回
η1e
Yellow t伊'[Jing
刀1ere
Yellow flame
A yellow flame is lack of primary air which may be
caused by dirt in the venturi or a mala司justed venturi.
Orange flashes
Oranges flashes 坦 the flame 缸e caused by dust h 由e
air and do not indicate a problem with the burner.
的 the.flame
Flashback
flame will look as though it has lifted off the
mouth of the burner. It is caused by either too much
primary air, high gas press町e, or both.
is a yellow tip on the end of the flame. 币1is is
caused by a shortage of primary air or poor burner
design.ηie fuel gas is not burning completely and
carbon is being formed.
The flame will appear to have travelled back through
burner tube to the orifice. 咀iis is caused by a low
velocity gas-air mixture.
也e
100
Gas Technician 2 Training - Module 14
© Canadian Standards Association
CLOTHES DRYERS
UNIT 2
Lαzy芦αme
A lazy flame is one that wavers and hits the top of the
cone. This indicates an airflow problem.
Air movement
The air movement within a dryer is shown in Figure 2号O and described
below. In summary, areas of air upstream of the blower experience negative
pressure and areas downstream experience positive pressure.
Lint trap
Outside air 圃’
Flue products __..
panel
Figure 2-20 Dryer air fl。w
1. The blower draws air in through the access panel at the bottom of the
dryer.ηiis creates suction and thus a negative pressure in the heater
box.
2. A portion (approximately 30%) of this air is pulled into the combustion
chamber and heated by the gas burner.
3. This heated air passes up the back of the dryer through a duct, into the
diffuser.
4. The rest of the air (approximately 70%) is pulled up through vents into
由e diffuser and mixed wi由 the hot air.
Gas Technician 2 Training - Module 14
。 Canadian S恼ndardsAs臼ciation
101
UNIT2
CLOTHES DRYERS
5. The mixed hot air now passes through perforations in the drum. The
drum has a number of baffies in it to tumble the clothes so that the
heated air can pass through them.
6. The blower pulls the moist air out through the perforations in the front
of the drum, and down through a lint trap.
7. The air passes through the trap duct and into the blower where it is
pushed out the exhaust duct (under positive pressure) to the outdoors.
For the system to work efficiently:
the ）争·ont
and rear of the drum must be prope1命 sealed
If the drum seal is defective, air can bypass the heater box. This creates
a loss of negative pressure, reducing the drying efficiency.
the lint trap must be kept clean
If the lint trap is clogged, the negative pressure in the burner box is
reduced and the heat from the burner flows out the hole and is sensed
by the safety thermostat. Topic 6 of this module discusses the operation
of the safety disc. The end result of a blocked lint screen is that air will
not be able to move freely and the drying time will increase.
Exposing
clothing to
heated air
The clothes' expos田e to the heated air is enhanced by the speed of drum
rotation and the baffles inside the drum.
Drum rotation
The drum rotates at between 4 7 and 50 revolutions per minute. Engineering
studies have shown that this is the optimum range for drying the contents
of the dryer. If the drum turns any faster, the clothes would be pressed
against the outside of the drum and not tumble. If the drum turns more
slowly, the clothes ball up in the drum. In both of these cases the drying
times are greatly increased.
The drum speed on the dryer is affected by the belt diameter, belt alignment
and the condition of the belt, so be sure to check and replace the belt if
required.
Baffles
The baffles inside the dryer are positioned so 由at the clothing is tossed
around, increasing its exposure to the heated air. Without the baffles, the
clothing would not dry as quickly.
102
Gas Technician 2 Training - Module 14
。 Canadian Standards As四ciation
TOPIC
8
Service
A gas technician is often faced with a dryer that has already been installed
but is not operating properly. It is then necessary to determine the cause of
the problem by troubleshooting the problem and running tests on the dryer.
Properly testing the components of a dryer requires that you be able to read
and interpret wiring diagrams. This has been covered in Module 11, Unit 2.
Electrical
sequence of
operation
Knowing the sequence of operation for the electrical start up of the dryer
will make it easier to determine possible faults.
A typical sequence of operation occurs as follows. As soon as the timer is
turned on:
1. All the circuits close.
2. The circuit from the timer to the door switch is completed through the
door switch to the timer motor and drive moto汇
3. The timer motor circuit is completed.
4. The drive motor circuit is completed.
5. The centrifugal switch is closed.
6. The circuit from the timer through the thermostat to the main coil valve
is closed.
7. The neutral 企om the main coil valve is completed through the limit
switch and the centrifugal switch.
8. The burner is activated.
9. The circuit from the timer to the panel and drum lights is closed (this
may differ from dryer to dηrer).
If this basic sequence of operation does not occur then there is a problem
with the dryer.
General
electrical
协喇eshooting
Isolating the source of the problem is the first step in fixing the problem. To
locate the general problem area, tum on the dηrer and set the temperature to
high. Then check the power at the burner and test switches and loads.
Gas Technician 2 Training- Module 14
© Canadian Standards Association
103
CLOTHES DRYERS
UNIT2
Check power to the burner
There are only two possible results when checking power at the burner:
there is power to the burner-concentrate your tests on the burner
there is no power to the burner-check the operating switches in the
dryer circuit.
Test switches and loads
Check the wiring diagram and use the three-point test described in Table 22 to test the switches and loads. This will help in locating the most
electronic faults. (A good quality multimeter is required to do these tests.)
Table
2-2 丁hree-point
test
Testing conditions What to expect
Open switch
voltage reading across the switch
voltage r冠ading on the inlet terminal to ground
•
Closed switch
no voltage on the outlet terminal to ground
no voltage reading across the switch
voltage reading on the inlet terminal to ground
voltage reading on the outlet terminal to ground
On a load
voltage reading across the load
voltage reading on the hot terminal to ground
On a load that has
lost the neutral
104
•
no voltage reading on the neutral terminal to
ground
•
no voltage reading across the load
•
voltage reading on the hot terminal to ground
•
voltage reading to the neutral terminal to ground
Gas Technician 2 Training- Module 14
© Canadian Standards A键。ciation
CLOTHES DRYERS
UNIT 2
Troubleshooting
the burner
igniti。 n
Due to the various ignition systems, troubleshooting the burner ignition is
dependent on the system used in the dryer. The sequence of operation for
each of these burner ignition systems is discussed in Topic 5 of this unit.
The Glo-Sil and spark ignition systems
When line voltage is applied to the Glo-Sil ignitor, it should heat up to its
operating temperature in 10 to 30 seconds. The resistance across the
terminals of a good ignitor should be between 50 and 250 n in the Glo-Sil
coils.
The
GI。”Sil
ignition can be checked as follows:
1. If there is power to the burner, then shut the power off.
2. Disconnect the leads to the burner.
3. Use a multimeter to check the sensor switch and Glo-Sil.
4. Check for cracks in the Glo-Sil.
5. If the Glo-Sil is fine, check the radiant sensor for continuity.
Never apply line voltage directly to the senso卫
The ignitor and motor of a dryer using a spark ignition burner can be tested
by applying direct power to the ignitor terminals.
The main complaint that a user may have with the Glo-Sil and spark
ignition systems is that the clothing smells of gas. Possible causes and
solutions to this problem are contained in Table 2-3.
Table 2-3 Troubleshooting the Glo-Sil and spark ignition burner when there is a
smell of gas
Cause
Soluti。n
lgnitor points welded
Sand down or replace
Ove而red
burner
Check input
Broken fan
Rep la四 fan
Valve bypassing
Re pl a臼 valve
Sensor opens before reaching 2200。F
Replace sensor
(1200。C)
Gas Technician 2 Training - Module 14
© Canadian Standards A部ociation
105
CLOTHES DRYERS
UNIT 2
Constant pilot burner
If the dryer is equipped with a constant pilot burner, check Table 2-4 as a
guide to troubleshooting common dryer problems.
Table 2-4 Troubleshooting constant pilot burner system
Faults
Possible causes
Corrective action
Pilot extinguishes
Drafts coming in
Check outside vent flapper
Dirty pilot
Remove and clean
Mercury switch not holding
plunger up
Replace mercury switch
Door not staying closed
Repair d。or latch
Blown fuse
Replace and check cause
Unplugged
Plug in
Plugged lint trap
Clean lint trap
Open limit switch
Check for blocked lint trap
and exhaust vent
Broken belt
Replace belt
Defective gas valve
Replace valve
Control set to AIR (FLUFF)
Set to HIGH
Pilot lights but no
heat to dryer
Glow coil ignition faults
The transformer, wa甲 switch and wa甲 switch heater are all combined into
one unit. If any one of the three components fail, they must all be replaced
as a complete assembly. To check the unit:
1. Apply 120 V to the burner with the gas supply turned off.
2. The glow coil should glow for approximately 3.5 to 4 minutes, then go
out as the warp switch opens.
3. Turn the dryer off and af王er 10 to 15·minutes the wa叩 switch heater
will cool sufficiently to allow the warp switch to again close.
Table 2-5 details the common faults along with the possible causes and
corrective action to take when troubleshooting glow coil systems.
106
Gas Technician 2 Training - Module 14
© Canadian Standards Association
CLOTHES DRYERS
UNIT2
Table 2-5 Glow coil faults, causes and corrective action
Faults
叭/arp switch
does
Possible causes
Corrective action
Defective warp switch heater
Test heater with an
ohmmeter and replace
warp switch, heater and
transformer unit
Corroded terminals on
transformer
Clean terminals
Transformer defective
Measure the voltage at
the glow coil terminals
Defective pilot switch
Replace
Defective glow coil
Replace glow coil
Screen plugged with lint restricts
primary air
Clean screen
Glow coil warped out of position
Reposition glow coil
Defective glow c。ii
Replace
Pilot coil is not energized
Test pilot switch
Defective pilot switch
Replace
not open
Glow coil does
not glow
Glow coil glows
but does not
ignite gas
No pilot flame
创
铺位
M邮机
h
MUfmO
n
’n
nMM
Table 2” 6 gives many of the operating problems that might be encountered
when working with dryers. It also lists probable causes and solutions.
τable
。perating
problem
The motor runs but the
drumd。es not turn
2-6 Troubleshooting dryer operation
Cause
Solution
Broken or loose belt
Replace or tighten belt
Lo。se m。t。r
Position and tighten pulleys
or idler pulley
Frozen drum sha负
Clean the shaft
Repla臼 bearings
if necessa叩
Lub到cate
1 Motors on dryers have an overload protector which is similar to a 仙se. It protects the motor from burning out if there is a mechanical
or electrical overload. When checking a motor, check 伽at the overload protector has not failed. If the protector has failed then the
motor will need to be replaced.
Gas Technician 2 Training - Module 14
Canadian Standards Association
©
107
CLOTHES DRYERS
UNIT 2
Table 2-6 (Continued) Troubleshooting dryer operation
Operating problem
Cause
s。lution
Motor hums and drum
does not turn
Centrifugal switch has defective contacts
Replace switch
Centrifugal switch
stuck
Sta叫 winding
Motor will not stop
Lubricate or replace
Incorrect wiring
Check wiring diagram
Grounded motor or wiring
Check motor and other
comp。nents for sho目s to ground
∞。led
down)
Mot。r 阳ns louder than
norm剑， stops, and de恒ct
a burning 。dour
u
- -e
TE
m 一．引
－
。nly re』start a负er
Replace motor
Drive components seized
BM －』H
(will
of motor open
Clean or replace
Replace motor
y7 阳
Motor runs intermittently
mechanism
Motor seized
EE
Motor does not start
activati。n
&
t
-
CAW
erEO
Check timer
-
s u
Replace fuse
limer is inoperative
Check timer
Motor is inoperative
Check motor
Dryer is not properly connected
Check that the dryer is connected
properly and the voltage is correct
Poor, or inoperative, door switch
connection
Test the door switch circuit
connections
Loading door is not closed properly
Check the door to make sure that
the strike is in the c。πect position
Motor cover创
Clean motor
with
lint
Motor bearings getting tight
Lubricate or replace motor
Dryer bearings or other rotating
equipment getting tight
Lubricate or replace
Centrifugal switch contacts failing to open Replace motor
Centri仙gal
switch activation mechanism
Clean or repla臼
stuck
Dryer smokes
108
Lint has accumulated in the
d『yer
Remove all lint
Wire insulation is burning
Check and correct a short circuit.
Replace or properly position all
wiring
Overheated motor
Check mot。r for lint build up and
air circulati。n around it
Gas Technician 2 Training - Module 14
。 Canadian Standards Assoc悔自α1
CLOTHES DRYERS
UNIT 2
Table 2-6 (Continued) Troubleshooting dryer operation
Operating problem
Cause
Solution
Clothes drying too slowly
A blocked lint trap or vent pipe
Clean the lint trap and vent
system
。efective
Replace drum seal
Clothes are not drying on
AUTO DRY
Dryer does not dry
properly
The drum turns but the
heater is not energized
drum seal
Vent pipe too long
Shorten venting system
Temperature control thermostat set too
low
Check the blow田 temperature at
which the thermostat turns o仔
Heat selector switch defective
Check program switch
Drum seal failure
Replace drum seals
Safety thermostat is tripping
Replace the thermostat if it trips in
normal operation
House voltage is fluctuating or too low
Call the power company
Timer advances to OFF too soon
Set timer for more time on AUTO
DRY
Open control thermostat to heat source
Check thermostat
The dryer is overloaded
Instruct the user on proper load
size
The blower assembly is plugged
Remove the lint
The lint trap is blocked
Remove the lint
。。。r
Adjust the cabinet door position or
replace the seal
not sealing tightly
Safety or c。ntrol thermostats not w。rking
correctly
Check the thermostats
Bad selector switch
Check selector switch
Inoperative timer
Check the timer
Faulty selector switch
Check the selector switch
Loose terminal
Check and tighten all connections
Inoperative thermostat
Check both the cycling and safety
thermostats
Inoperative motor switch
Check the motor
Broken wire in wiring harness
Check individual wire continuity
Gas Technician 2 Training - Module 14
© Canadian Standa『ds Association
109
CLOTHES DRYERS
UNIT2
Table 2-6 (Concluded) Troubleshooting dryer operation
Operating problem
Cause
Solution
Drum operates, but noisily
Drum warped
Replace drum
Lower drum guide sticking or out of place
Reposition 。r replace mechanical
lower drum glide
Idler pulley noisy
Replace idler pulleys.
does not last.
Belt squeaking
Use bar soap to lubricate the
outer surface of the belt，。r
replace belt
F。reign
Remove all foreign objects from
the drum
Main burner does not light
Main burner does not
operate properly
objects are in the drum
Lubri臼ting
Belt is frayed
Replace the belt
Drum supp。『t bearings are worn or need
lubrication
Lubricate 。r replace the bearings
Motor pulley loose
Position and tighten the pulleyset
screw
The front or rear drum seals or bearings
are worn out
Replace
Machine not level or levelling legs not all
on floor
Level
Safety thermostat wiring connections are
loose
Check the wiring or replace the
thermostat
Temperature control thermostat is
inoperative
Repl a臼 the thermostat
The motor centrifugal switch contacts are
bad
Clean contacts
了he
Check the motor
motor wiring connections are l。。se
or the timer is not working
seals 。r drum
bearings
Check the timer
Main burner does not light
Bad door switch
Repla饵 the do。r switch
Faulty temperature c。ntrol thermostat
Repla饵 the
Safety thermostat wiring
c。nnections
are
l。。se
Temperature control thermostat is
inoperative
The
bad
110
motor 臼ntrifugal
switch contacts are
thermostat
Check the wiring or replace the
thermostat
Repla饵 the therm。stat
Clean ∞嘟嘟
Gas Technician 2 Training - Module 14
© Canadian Standards Association
CLOTHES DRYERS
UNIT 2
Assignment 2
When you have completed the following questions, ask your instructor for the
Answer Key.
I.
What are the allowable clearances to combustibles for a gas dryer?
2.
What is the maximum length of a metal connector used to connect a gas dryer?
3.
What must be done to convert a propane dryer to natural gas (or natural gas to propane) to
avoid having to get a special inspection?
4.
How should a gas dryer burner flame look when the burner primary is properly adjusted?
5.
If the dryer burner fires but the drum does not turn, what could be the problem?
6.
If the dryer burner fires for the first cycle but fails to ignite on subsequent cycles and a
solenoid click is heard after the ignitor warms up, what could be the problem(s)?
7.
What will cause a gas dryer to keep running after its door is opened?
8.
Where can specific service information about a gas dryer be located?
Gas Technician 2 Training - Module 14
© Canadian Standards A斟如C悔自m
111
CLOTHES DRYERS
9.
UNIT2
What is the minimum exhaust vent diameter for a gas dryer?
10. What can cause insufficient drying, even if the lint screen is kept clean?
112
Gas Technician 2 Training- Module 14
© Canadian Standards Association
Unit 3
Barbecues
Purpose
Gas-fired barbecues, whether set up for natural gas or propane, are one
of the simplest gas appliances that the technician will encounter. However, there are service and installation procedures that must be 岛1lowed which will prolong the life of the unit and ensure satisfactory
operation.
Learning
1. Describe the installation requirements for barbecues.
o均ectives
2. Describe the components of barbecues.
3. Describe the operation of barbecues.
4. Describe the servicing of barbecues.
Gas Technician 2 Training - Module 14
Standards Association
。 Canadian
113
Topics
1. lnstallati。n requirements .....................…················….........刊 5
Conversion 。f the appliance ... .. . .……..………目，.......…………町… .115
Connections ............………-…............................ ········· .. 116
Testing …………... ············· .....…............…………··-…...….....….. 117
Pressure regulators ..........….....，…·町…………...........….........….......... 118
2. Comp。nents .........….........…................................................. 119
Burners ........................…...…·……........……................,…................ 119
Brique忧es and lava rock .. . ......………………… …........…………......... 119
The ignition system ……·－．．．，．．．．．．．．．．，．．….......”…－－‘…·凋….......... 120
Barbecue components. ……··………………··……·………................ 120
E
3. Operation ..............…...............…........................................... 123
The ignition sequence. …...…………………………. ·······………………… .123
The combustion process ...…………………..........”………………........ 124
4. Service .....................................................…....................…... 127
Assignment 3 ......…...................…........................….........…....... 129
114
Gas Technician 2 Training - Module 14
© Canadian Standards Association
TOPIC
1
Installation γequiγements
Where relevant, the Natural Gas Installation Code (Bl49.l) and the
Propane Installation Code (Bl49.2) must be consulted for all regulations
on piping and tubing.
The Code sets requirements for the use of piping and hoses, as well as for
the marking of different types of piping. Refer to the relevant sections in
the Code.
Conversion of
the appliance
All gas appliances, including barbecues, have an attached rating plate that
indicates the type of gas that must be used with the appliance. It is
sometimes necessa可 to convert barbecues so that they can be used with a
different gas than originally intended.
First check the rating plate to see what type of gas the barbecue is set up
for. If the appliance is set up for a different type of gas than the one being
supplied, the appliance must be converted.
Note
扩a barbecue is converted斤。m one gas to another, the rating plate must be
changed to indicate what 仰e ofgas the barbecue has been converted to.
The Code states that the manufacturer ’s guidelines must be followed when
converting an appliance. If there are no guidelines, the appliance must be
approved after conversion.
The most common type of conversion is to convert a propane barbecue for
a natural gas supp协 However, the same criteria and conditions apply when
converting a natural gas barbecue for propane supply. For more
information on appliance conversion, see Module 9, Unit 6.
If you have no previous conversion experience, it is a good idea to get an
experienced person to assist you.
Gas Technician 2 Training - Module 14
© Canadian Standards A部ociation
115
BARBECUES
UNIT3
Connections
Before installing any piping or tubing, consult the Code and contact the
local municipali可 to get any additional regulations.
Figure 3-1 shows a typical natural gas supply installation for a barbecue.
Inside
wall
To
Outside
wall
Sleeved and
caulked
Locking
shut off
Quick disconnect
~nstalled above
ground)
Courtesy of Weber-Stephen
Pγ oducts
Company
Figure 3-1 Typical natural gas supply installation
Underground copper tubing
A common practice when installing natural gas barbecues is to run copper
tubing underground. If this is done, the tubing must be connected by
brazing or approved mechanical compression fittings. Before the piping
enters a building, it must rise above grade.
Connecting hose
When a hose is used to connect a barbecue to 白e gas supply,，也e following
additional requirements must be observed.
116
Gas Techniαan 2 Training - Module 14
© Canadian Standards Association
BARBECUES
UNIT 3
The hose may not go from one room into another, and it may not pass
through walls, partitions, ceilings or floors.
Slip-on-ends are not permitted.
The hose must be replaced the moment any damage or wear is noticed.
The maximum length of the hose is15 ft (4.6 m).
The shutoff valve for the barbecue must be in the gas supply piping or
tubing, and as close to the hose as practical. The handle of a shutoff
valve on an independent connection must not be closer than 6 inches
(150 mm) from the handle of any other shutoff valve. The shutoff valve
must not be placed at floor level, or any other location where it may be
turned on by accident.
•
The hose must placed so that it is:
visible (it must not be routed under a deck)
ii. prevented from contacting a hot surface, and it must not be
subjected to tempera阳res in excess of 125°F (50°C).
iii. protected from dripping grease and other causes of damage
iv. protected from passing traffic, and placed so that the passage of
traffic over the hose is at a minimum.
1.
Most gas barbecue systems use a quick disconnect hook-up. If this is the
case, a readily accessible manual shutoff valve must be installed upstream,
and as close as practical to the quick disconnect device. A quick disconnect
device cannot be substituted for a manual shutoff valve.
．、Then
disconnecting a barbecue with a quick disconnect, make sure
that the shutoff valve is closed.
•
When connecting the quick disconnect hook-up, check 也at the
coupling on the quick disconnect is clean and free of debris.
Testing
Check the hose for any cuts, abrasions and nicks. Advise the user to do the
same every time the barbecue is used. If the hose is damaged it must be
replaced immediately.
All gas connections must be tested for leaks. A leak detector or soap test
can be used to do this. The soap test is described in Module 8, Unit 3.
When testing for leaks, make sure all burners are in the offposition and the
gas supply is on. As shown in Figure 3-2, the key positions to check are the
(a) hose to mani岛Id connection, (b) valves to manifold connection, and (c)
the hose to quick disconnect connection. Also test any other points where
there is a connection in the piping or tubing.
Gas Technician 2 Training- Module 14
© Canadian Standards Association
117
BARBECUES
UNIT3
Courtesy of Weber-Stephen Products Company
Figure 3-2 Gas leak checks
After testing the connections, turn the gas supply off and rinse all the
connections.
Pressure
regulators
Pressure regulators are used to:
reduce the incoming gas pressure
keep the pressure supplied to the barbecue at a constant level.
Pressure regulators are discussed in more detail in Module 15.
118
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。 Canadian Standards Association
TOPIC
2
Components
A barbecue may be attached to either a natural gas or a propane supply. If it
is attached to a natural gas supply, the gas is piped to the barbecue from a
main supply line outside the building. If it uses propane, the gas is supplied
仕om a cylinder. The component parts of a propane cylinder are covered in
Module 15.
Burners
Some barbecues have only one burner while others have two burners
placed side by side. Some barbecues are also equipped with side burners.
Figure 3-3 shows a typical burner and its coupling to the gas supply.
Venturi/
tube
Burner
coupling
Figure 3-3 Typical barbecue burner
Briquettes
and lava rock
Many barbecues use ceramic brique忧es or lava rocks. The gas flame heats
the surface of the briquettes or lava rocks which, in turn, radiate heat to
cook the food. Take care not to over do the lava rocks or briquettes. Too
many may cause premature burner bum-out.
Gas Technician 2 Training - Module 14
© Canadian Standards Association
119
BARBECUES
UNIT3
The ignition
system
The barbecue illustrated in Figure 3-3 uses a crossover or piezo ignition
system. When the piezo button is pushed, it energizes the ignitor electrode
inside the gas catcher ignition chamber. This creates a spark which ignites
the gas. Barbecues can also be manually lit through a match-light hole in
the 仕ont of the cooking box.
A
Barbecue
components
Caution!
Always have the barbecue lid open 归自re attempting ignition.
Figure 3-4 shows an exploded view of a Weber barbecue and Table 3-1 lists
the components. Most of these components are common to all barbecues.
Table 3-1 Barbecue components
Label
Label
Part
Lid
Part
abel
Part
Casters
1
Con tr＇。I panel
bu忱。n
2
Lid handle
2
Bottom tray
2
lgnitor
3
叭farm-up
basket
3
Catch pan holder
3
Screws
4
叭farming
rack
Catch pan
4
Crossover tube
5
Sh。此 flavorizer
Drip pans
5
Front and back
burners
6
Long flavorizer bars
Accessory trays
Center burner
7
Cooking grates
Frame c。nnectors
Nuts
8
Work table
Wheel hubcaps
Spider stopper
guards
9
Tubing plugs
Wheels
Manifold assembly
10
Bolts
Tool holders
Manifold bracket
11
Spacer bracket
叭/heel
lgnitor
12
Swing table end
bracket
Front panel
lgnitor lock nut
13
Le负 frame
Plastic buttons
lgnitor gasket
14
Bolts
Axle
Gas catcher ignition
chamber
15
washers
Hair pin cotters
lgnitor wire
16
Caster frame
Hinge pins
lgnitor wire
17
Swing table
assembly
Thermometer
Right frame
18
Left hand slide bar
assembly
Nut
Hose
19
Screws
Cooking box
Control panel
20
Nuts
Burner control knobs
120
bars
frame
inse付S
Gas Technician 2 Training - Module 14
© Canadian Standards Association
BARBECUES
UNIT3
/
38
39
7
8
44
9
10
49
17
51-56
57
30
58
Courtesy~川，eber-Stephen P酣ducts
Company
Figure 3-4 Components of a typi臼l barbecue
Gas Technician 2 Training- Module 14
© Canadian Standards Association
121
TOPIC
3
Operation
Each season, before the barbecue is used, a visual inspection must be made
to ensure that all piping and tubing is sound and that there are no visible
也ults. Failure to do this could result in inju可 or death.
The ignition
sequence
There are two common ignition systems used in barbecues: the piezo,
which- is an electronic ignition system, and the manual ignition system.
Piezo ignition
To light a barbecue using the piezo ignitor system, first ensure that all the
burner control knobs are off. Then use the following procedure:
1. Open the lid.
2. Turn the gas supply valve on.
3. Turn the burner control that is closest to the ignitor to START or HIGH.
4. Push the piezo button several times so that it clicks each time. Each
time it clicks a spark is created.
5. Check through the match-light hole 坦白e
see if the front burner is lit.
仕ont
of the cooking box to
6. If the burner is lit turn on the other burners. They will light from the
flame of the first burner.
Manual ignition
To manually light 由e barbecue, first close all the burner control valves.
Then use the following procedure:
1. Open the lid.
2. Tum the gas supply valve on.
3. Light a match and put it through the match-light hole in the 仕ont of the
cooking box.
4. Turn the front burner control knob to START or HIGH.
5. Check 由at the burner is lit by looking throu白白e match-light hole.
Gas Technician 2 Training- Module 14
© Canadian Standards Association
123
BARBECUES
UNIT3
6. Once the first burner is lit, turn on the other burners.
Barbecues using either of these ignition systems are extinguished in the
same way. First, turn the gas supply valve off. Then turn each burner
control knob off.
If faced with an unfamiliar situation, check the manufacturer ’s instructions.
A
Safety when igniting a barbecue
Adhere to the following safety precautions.
•
Always open the lid 问fore lighting the barbecue.
扩the
burner does not ignite, wait a few minutes for the gas 归 clear
to ignite the burner again.
In either case, gas may collect in an area and explode when an attempt
is made to ignite the barbecue.
before 的1ing
Never lean over the barbecue, or look through the match-light hole
when lighting the barbecue.
The
combustion
process
When the burner control valve 1s opened, gas flows into the burner tube
a venturi.ηie movement of the gas through the venturi reduces
pressure in the burner tube. As a result, primary air is sucked into the tube
through air shutters. The prim缸y air mixes with the gas in the burner tube,
and is ignited at 由e burner head. When the air-gas mixture ignites, it draws
in secondary air 企om around the burner to complete the combustion
process.
由ro鸣h
Flame characteristics
Figure 3-5 shows
the characteristics of
a good burner flame
for a barbecue.
Tips
occasionally
yellowish
Light blue
Dark blue
Courtesy q川Veber-Stephen Products Company
Figure 3-5 Flame characteristics
124
Gas Technician 2 T1『aining-Module 14
。 Canadian Standards Association
BARBECUES
UNIT3
Adjusting primary air
Each burner on the barbecue will have an air shutter that can be slid to
allow more or less primary air in to the burner tube. Before adjusting,
however, the spider guard will need to be removed.
Spider guards prevent spiders and other insects from nesting in burner
tubes. Without the guard, and with nests in the burner tubes, gas may flow
out of the air shutter causing a fire around the shutter.
A sign 由at the spider guard is blocked is a cooking flame that appears to be
yellow and lazy.
Gas Technician 2 Training- Module 14
© Canadian Standards Association
125
TOPIC 4
Service
Table 3-2 lists some of the problems that may be encountered with gas
barbecues as well as their causes and solutions.
阉吁吁－，
...na s
hu
－叫“
-
Table 3-2 Troubleshooting gas barbecues
翻一
b
o·m
c-um
Cause
Solution
Possible leak
Shut o仔 gas immediately
-
2M
Check for leaks
Repair leak
Leak detected at any connection
Quick disconnect coupling not
seated fully
Remove coupling
Check that the coupling is clean
Reconnect coupling
Gas leak in connection
Tighten connection
Perform leak test
Flame flashback beneath the
control panel
Gas leak in hose or control valves
Replace hose or control valves
The venturi tube is blocked
Remove the burner and clean the
venturi tube:
Use a pipe cleaner or venturi
brush to clean the venturi as
sh。wn in Figure 3-6
connecti。ns
Spark ignition failure
Poor ground connections
Burner will not light
Gas shuto仔 valve closed
Open gas shuto仔 valve
Fuel hose bent or kinked
Straighten fuel hose
lgnitor wire(s) not connect回
Connect the burner electrode
wires
lgnitor electrode
burner
lgnit。r
misaligned 。n
malfunction
Check and fix ground
Realign electrode
Manually light the burner
Venturi blocked
Remove the burner and clean the
venturi
Venturi not aligned with valve
orifice
Realign venturi to orifice
。而臼 block创
Remove burner
Clean
。而cewi伽 a pin 。r 币newire
、、－♂
Gas Technician.2 Training- Module 14
©Canad阳n
Standards Association
127
BARBECUES
UNIT3
Table 3-2 (Concluded)
TrOL』 bleshooting
gas barbecues
Problem
Cause
s。lution
Premature burner burn－。ut
Too many lava rocks
Reduce the number of lava rocks
Hot spots on cooking surface
Briquettes n。t evenly distributed
Spread brique扰es evenly on grate
Venturi blocked
Remove the burner and clean the
venturi
Excessive grease buildup 。n
briquettes
Clean briquettes as follows:
Flare-ups or grease fires
Remove the cooking grids
Turn the briquettes over
Light the burner
B时quettes
will self clean
Finish by placing the briquettes in
layer
。ne
Cooking surfaces and bottom tray
dirty
Clean thoroughly
Excessive heat
Turn burner controls to lower
setting ，。r
Raise c。。king grid to upper
position if possible
If yellow flame is excessive the
venturi may be blocked
Remove the burner and clean the
venturi
Spider stopper guard is blocked
Clean the spider stopper guard
Burner ports blocked
Remove the burner and clean with
a so筒 bristle brush or scraper
The flame is low in HIGH position
The fuel hose is bent or kinked
Straighten fuel hose
Inside 。f lid appears t。 be peeling
Caused by a build up of grease,
not faulty paint
Clean with stiff bristle brush or
scraper
Yellow er orange flame
:
如在
C三至2午三一－一－－－ ~弘
1
Ventu时 tube
Clean venturi tubes using a pipe cleaner or
ventri brush to eliminate any blockages
caused by spiders or insects.
Figure 3-6 Cleaning the venturi and burner tube
When installing parts on a barbecue, always refer to the manufactur町、
instructions.
128
Gas Technician 2 Training - M。dule 14
C Canadian Standards As拥ciatlon
BARBECυES
UNIT3
Assignment 3
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
What must be done if a barbecue is converted from one gas to the other?
2.
Is a shutoff valve necessary when using a quick disconnect device?
3.
Can barbecues equipped with a piezo ignition be match-lit?
4.
Is it possible to install insect guards on burner tubes?
5.
During lighting of a barbecue should the lid be open or closed?
Gas Technician 2 Training - Module 14
C Canadian Standards As四ciation
129
Unit4
Lamps
Purpose
Gas lamps are becoming more popular. Lamps must be installed and
set up properly by the gas technician, to ensure that they are both deeorative and practical.
e
LOwe
nnMMe
nd
均
-
ws
1. Describe the installation requirements for lamps.
2. Describe the components of lamps.
3. Describe the operation of lamps.
4. Describe the servicing of lamps.
Gas Technician 2 Training- Module 14
© Canadian Standa『ds Association
131
Topics
1. Installation requirements ........................................…......... 133
Rating plate and specifications ....……………·…，．町......……….....…............ 133
Clearances ...……··……………....………·…….......... 133
Piping and tubing ...................”……… …...................…….......... 134
E
2.
c。mponents ............….............…............….......…................. 135
Components of a gas lamp ...….................…········……….....................….... 135
Construction materials ………….......………......…........………….................. 136
Mantles ....……-…….......……·….........……·…….........……….....……........ 137
Gas lamp covers ..............................................................田….. 138
3.
Operati 。n ..........…................................................................. 141
Types of lamps .........… E 曹...........…….........…............................. 141
Principles of gas lamp operation ....................…··…-……........................... 142
4. Service ........…...................................…...........”….................”3
· Servicing and trouble- shooting .......................…….......……............. 143
Troubleshooting electrode ignition system ..... ……·················………· ··町町...... 144
Assignment 4 ........….................................................................. 147
Appendix A to Unit 4 ...............................….......….........…......... 149
Typical manufacturer’ S instructions
132
Gas Technician 2 Training - Module 14
。 Canadian Standards Association
TOPIC]
Installation requirements
Code requirements for installing lamps can be found in the Natural Gas
and Propane Installation Code (Bl49.l). All gas lam?s must be installed
according to the manufacturer's instructions, and the installation must
comply with the Code. Once a lamp has been installed, the operating
instructions must be left with the user.
Rating plate
and
specifications
All gas appliances m四 be fitted with a rati吨 plate that provides the
following in岛rmation:
•
type of gas
•
Btu rating
model number
serial number
•
cl卢arances.
·Most gas lamps operate wi也 a pressure of 6.3 inches w.c. and so the
pressure is not always noted on the rating plate.
Note
扩a gas lamp has been converted, this must be noted on the rating plate.
Gas lamps vary considerably in design, and it is difficult to find
standardized specifications. For example, not all lamps have a mantle;
some lamps “ flicker” which makes it difficult to gauge the consumption
and output of the lamp. Manufacturers’ specifications are 由ere fore
important to read during installations.
Clearances
Clearances 如r gas
appliances are stated on the rating plate of the gas
light.ηie Code also contains specific requirements for different types of
lighting.
The main ob~ective of the clearances 也r gas lamps is to prevent 由e globe
from contacting combustible materials. Note that ignition temperatures
vary for different materials. For example paper on wallboard ignites at a
~
飞
Gas Technician 2 Training - Module 14
@Canad幅n Standards Association
133
UNIT 4
LAMPS
lower temperature than wood or plastic. Therefore locate the lamp with
consideration for the temperature tolerance of the surrounding materials.
The Code does allow a reduction of clearance if:
it is approved as being safe to do so by an approved authority，。nd
•
the reduced clearance level is marked on the rating plate
or
•
the combustible material is protected, and
the reduced clearance is in accordance with the Code.
Piping and
tubing
All piping and tubing used with gas lamps must meet Code requirements.
The gas lamp must be properly mounted and supported to avoid putting
any pressure on the piping supplying the lamp.
Piping and tubing is discussed in more detail in Module 8. Installation of
underground piping and tubing is discussed in Module I 0.
134
Gas Techniαan 2 Training - Module 14
© Canadian Standards Assoc眩目。n
TOPIC
2
Components
There are many different types of gas lamps, and their components often
vary 企om one lamp to the next. The manu臼cturer ’s assembly instructions
normally list the lamp ’s components.
Components
Of a gas lamp
Figure 4-1 shows the components of a typical gas lamp valve assembly.
1/4 inch
lamp valve in
OFF positio
Valve
assembly
；：~：·
but
d回陇
powered
valve
？飞~~ead
Brass
hex nut
Slot above
door opening
(access sl0 t)
II
Valve
stem
@.,
cap
Counesy of Trimblehouse Corporation
Flgure4斗 Valve
Gas Technician 2 Training - Module 14
@Canadian
S恒nd司rdsAs四ciation
assembly
135
LAMPS
UNIT4
Figure 4-2 shows a venturi assembly with an electrode for a gas lamp.
Venturi
assembly
High voltage white
wire to spark
electrode's high
voltage coil
Green to ground
Blue/red to DC
powered gas valve
Courtesy of Trimblehouse Corporation
Figure 4-2 Venturi assembly
Note 由at
Figures 4-1and4-2 illustrate the components for sample lamps.
For specific information, always refer to the manufacturer ’s instructions.
Construction
materials
Most gas lamps use 由e same construction materials for their various parts.
The frame is usually made of iron, alum.inum, brass, copper or bronze.
Brass and copper 町e commonly used on gas lamps because of their
resistance to rust.
The burner will be either copper or ceramic, and is often enclosed by a
glass globe. The glass is tempered to withstand tempera阳re changes.
136
Gas Technician 2 T1『·atning - Module 14
。 Csnadian Standards Association
!AMPS
UNIT 4
Mantles
Lamps are equipped with mantles that are used to provide light. There are
two basic types of mantles as shown in Figure 4-3:
so白 mantles
•
(soft auto-form mantles)
pre-formed hard mantles.
睡
Soft mantle
Pre-formed hard mantle
Figure 4-3 Types of mantles
Installing the mantle
The installation method depends on 由e type of mantle being installed and
to a lesser extent on 由e 句rpe of gas lamp. However, the basic principles are
由e s缸ne for both types of mantles.
So'ft mantle
ηie
procedure for installing a soft mantle is as follows:
1.
Ensure the lamp valve is closed and the light has been off long enough
to cool down.
2.
Remove the old mantle.
3.
Loop 由e
4.
Use your fingers to enlarge the throat so it will fit over 由e burner.
5.
Fit the mantle over 由e burner so 由at it seats in the lower groove of
也e burner nose.
6.
Shape the mantle evenly.
7.
Pull the ends of the tie-on s位ings so 也at the mantle and strings are
seated securely in the burner nose groove.
8.
Tie a double knot h 也e string and cut off the ends.
Gas T础nician 2 Training - Module 14
@Canadian S饱ndarcls Assc刚ation
tie-on strings at the throat of the mantle.
137
LAMPS
UNIT 4
9.
Hold a lit match close to, but not touching, the mantle. The mantle
should smolder as its protective coating bums off. Once this is done,
the mantle becomes a form of chemical ash and must be handled
carefully. It may break if touched.
10. Let the mantle cool for a few minutes
after 由e
coating has burnt off.
11. Now tum the gas on and light the mantle without touching it with the
match. On a new installation it may take a while for the mantle to burn
because of air in the gas line.
12. Turn the gas on fully to allow the mantle to burn to its proper shape.
After about five minutes 硝 ust the gas control for the desired amount
of light.
When the gas light is burning properly the flame is a bright white and has
no visible outlines.
Pre-formed hard mantle
A pre-form@d hard mantle is installed as follows:
I.
Ensure the gas supply is turned off, and the light has been off long
enough to cool.
2.
Remove the old mantle.
3.
Take the mantle out of its box and place 由e throat over the burner
nose.
4.
Follow steps 6 to 12 from the procedure for soft mantles.
If the lamp is burning correctly, the flame should be bright white and have
no visible outline.
Gas lamp
covers
138
Gas lamp covers come in different forms. They can be similar to the type
shown in Figure 4-4, or they can be more like a globe 由at directly cov田s
the flame.
Gas Technician 2 Training - Module 14
© canadian Staitdards Association
υNIT
LAMPS
4
Figure 4-4 Gas lamp cover
The coveζincluding the glass, should be able to resist the sudden
temperature changes 由at occur when the lamp is switched on or off.
Gasl创np
covers se凹e a decorative purpose as well as protecting the flame
weather and other external e茸ects. It also safely encloses the burning
flame.
台om
Gas Technician 2 Training - Module 14
© Canadian standa晦 Association
139
TOPIC
3
Opeγαti on
Since there are many different types of gas lamps, it is important to read the
manufacturer ’s instructions for specific lamps. These instructions should
be left with the user after the lamp has been installed.
Types of
lamps
There are two basic classes of gas lamps: indoor and outdoor.
The appliance rating plate and manufacturer ’s instructions will specify the
of each type of gas lamp (i.e. whether for installation indoors or
outdoors).
pu甲ose
Indoor gas lamps
Indoor gas lamps serve both practical and decorative pu甲oses. Make sure
these lamps are used only in properly vented rooms. Carbon monoxide is
formed if there is incomplete combustion, and if the room is not properly
vented there may be a build up of dangerous gases.
The area around the lamp must also be kept 丘ee of combustible materials
including flammable vapours and liquids, such as gasoline.
Even thou白白e gas flame is small, it still requires primary air for
combustion. The gas flows through a venturi to the burner. The movement
of gas through the venturi sucks in air through the air ports. There should
be no obstruction to the flow of primary air. If the burner is dirty, or has
insects nesting in it, the air flow will be obstructed. The burner must be
kept clean.
Outdoor gas lamps
Outdoor gas lamps are used mainly for decorative pu甲oses. They can
usually operate in all types of wea由er, and are useful in the event of a
power outage.
Wi由 these
lamps there must be no obstruction to 由e primary air flow, and
the lamp must be properly vented. There should be no combustible
materials near the lamp.
Gas Technician 2 Training 叩 Module 14
© Canadian Standards Association
141
LAMPS
Principles of
gas lamp
operation
UNIT4
The selection of a lamp with or without a mantle depends on the intended
use of the lamp. Gas lamps without mantles give a “ flicker flame" and are
intended purely for decorative purposes. For functional lighting purposes, a
lamp equipped with a mantle is required.
Gas lamps with a mantle
In a mantle-equipped gas lamp，世1e mantle bums white hot and gives off
light. When burning properly, its flame should be bright white and have no
visible outlines. If this is not the case, then the air flow to the gas may need
adjustment. A yellow flame indicates the air-flow should be increased.
Poor flame quali可 may also result from a broken mantle, in which case the
mantle must be replaced.
Adjusting the primary air flow
η1e
primary air flow is controlled by adjusting the air-shutter rings near the
burner. (Check manufacturer ’ s mstructions to determine the exact
location.) Adjust the air-shu忧er rings until the optimal light is obtained.
ηie
gas pressure may also need to be a司justed. Check the manufacturer's
instructions to find the correct pressure setting.
Ignition
There are two ways in which gas lamps are ignited:
•
by an electrode 也at is operated manually wi也 a switch or
automatically with a photosensor
•
manually using an open flame, such as a match.
In automatic systems a solar cell detects 也e light falling below a certain
point and opens an elec位onic ctrcwt to the electrode. It also opens 也e gas
valve. The electrode will spark until the gas lamp is lit. A photosensor
detects when the lamp is lit and stops 由e elec位ode 企'Om sparking. When
the light in the area reaches a certain level (such as at sunrise), the solar cell
will close the gas valve and extinguish the lamp.
142
Gas Technician 2 Training - Module 14
。 Canadian Standards Association
TOPIC
4
seγvice
、、－－
Because there are so many different types of gas lamps available, it is
important that the manu岛ctur町、 instructions are consulted before
installing or replacing any components. A typical manufactur町、
instructfon sheet for installing a gas lamp is provided in the Appendix 1 at
the end of this Unit. It is important that manufacturer ’s procedures are
followed. Otherwise, the lamp may not work properly.
Servicing and
troubleshooting
Before starting any repairs:
•
Turn off the gas supply.
•
Wait for the lamp to cool.
Remove and clean the glass.
•
Replace the mantle if it is broken.
General maintenance on gas lamps include:
ensuring 由at
making
•
the venturi and all screens are clean and clear of insects
sure 由e
solar cell is clean, if so equipped
cleaning the glass casings.
At least once a ye缸， an outdoor gas lamp should be properly cleaned and
painted if necessary.
Leak testing
A
If there is a smell of gas, or if a new gas lamp or new E恼怒s have been
installed to 由e gas supply line, perform a leak test with soap solution or
leak detector. Refer to Module 8, Unit 3 岛r more information on leak
testing.
Caution!
Never use an open flame 归 testfor leaks.
Check all joints and connections. Tighten any connections 伽t maybe
loose.
Gas Technician 2 Training - Module 14
©Can甜ian 阳ndards Association
143
LAMPS
UNIT4
Flame impingement
Burned metal on a gas lamp indicates flame impingement or a flame that is
too hot. Flame impingement means that the flame is in contact with a
surface causing the flame to cool. When the flame cools, it cannot burn all
of the gas and so carbon or carbon monoxide (CO) is produced. To correct
this problem:
a司just the air openings,
•
and/or
a司just the gas pressure.
Troubl臼hoo回ng
electr。de
ignition
system
Table 4-1 lists some of the problems that may be encountered with both
manual and automatic electrode ignition systems.
Table 4-1 .Electrode igniti。n system
Pr。ble『n
Soluti。n
Electrode will not begin sparking
when it gets dark.
Check
ba忧ery
connection.
Check that ba忧ery voltage matches
manufacturer’s specifications.
Check s。lar cell connection and
polarization.
Check electrode wire and ground wire
connections.
Electrode will not stop sparking after
ignition.
Check the alignment of the mantle over
the ph。t。sensor.
Check that the photosensor is clean.
Check the alignment of the photosens。r.
Check the gas pressure'.
Lamp keeps burning after it gets
light.
Check solar cell connection and
polarization.
Check polarization of valve connection
to the circuit board.
Valve does not 。pen or allow
operation.
Check p。larization of valve connection
to the circuit board.
Check that ba忧ery voltage matches
manufacturer’s speci负臼tions.
144
Gas Technician 2 Training - Module 14
。 Canadian Standards Association
LAMPS
UNIT4
Table 4-1 (Concluded) Electrode ignition system
Problem
Solution
Valve open, electrode sparks, but the
mantles do not ignite.
Check the gas supply line is properly
bled of air.
Check the electrode is aligned with the
burner head.
Check the alignment of the mantle.
At night, lamp ignites, but then turns
o仔.
Check the alignment of the mantle over
the photosensor.
Check that the photosensor is clean.
Check the alignment of the
photosenso仁
Check the gas pressure.
Ba忧ery voltage lower than
manufacturer’s specifications.
Gas Technician 2 Training- Module 14
Standards Association
© Canadian
Check that solar panel is facing the sun,
and allow the ba忧ery to charge.
145
LAMPS
UNIT 4
Assignment 4
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
What are the two types of mantles used in gas lamps?
2.
What are mantles used for?
3.
What must you be s田e of when installing indoor gas I缸nps?
4.
Before starting any r叩airs what should you do?
5.
How often should a gas lamp be cleaned?
＼、－
GasTeclm』cian
2 Training -
Modu幅 14
© Canadian Standa『'ds Association
147
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Module 15
Pressure Regulators,
Overpressure Protection,
岛1eters and Fuel
Containers
Before installing any piping and appliance systems inside a building,
the location of gas meters, propane storage containers and gas
pressure regulators must be planned. These are key elements in
the supply of fuel gas to the installation, and will determ1ne many
important aspects of the work which follows. This module deals
with the nature of 由ese items and the installation and maintenance
procedures that apply to them.
At the end of this module you will be able to:
Choose and install the correct gas pressure regulator
for a system
•
Explain the need for overpressure
to achieve this
•
Read and clock meters
protecti。n
and
h。w
Identify and plan for the correct use of pr。pane
cylinders and tanks
il
---
Gas Technician 2 Training- Module 15
© Canadian Standards Assoc阳lion
Ken Bales, Manager, Gas Information Products, CSA, wishes to acknowledge the following individuals
who contributed as members of a Review Panel during the development of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology (BCIT) is
acknowledged for its work in the technical development and editing of the original edition.
c。ntributors and members 。f the Review Panel
John Cotter
Bill Davies
Eric Grigg
Warren Hayes
Darrel Hilman
Ken Kell
W. John Lampey
Lorne Lowry
Jim Noseworthy
Gary Prentice
Nick Reggi
Rick Rogozinski
Ron Royal
John Semeniuk
Allen Sidock
John Simmons
David Stainrod
Terry Waters
IV
Canadore College
Union Gas Limited
Canadore College
Superior Propane Inc.
Southern Alberta Institute of Technology
Centra Gas Manitoba
Alberta Advanced Education & Career Development
Algonquin College
Durham College
Environmental Energy Consultants
Humber College
Union Gas
Fanshawe College
Northern Alberta lnstitl」te of Technology
Camb时an College
Loyalist College
D.J. Stainrod & Associates Ltd.
Enbridge Consumers Gas
Gas Technician 2 Training - Module 15
© Canadian Standards Association
岛1odule
15
Table of Contents
Unit 1
Pressure regulators
The need for pressure regulators ........................ 3
Codes .........................................胃........................ 5
Basic operation of a regulator ..............………...... 9
Different types of regulators .........…........…....... 17
Selection requirements ..............................…… .29
Location and piping practice ..................…........ 35
Troublesh。。ting 。f
regulators .............…........... 37
Assignment 1 ....................…...........………........... 41
Appendix A to Unit 1 ...………............................. 43
Typical regulator selection guide
Unit 2
Overpressure protection
Introduction .................…·········………………........ 51
Relief valves ........................................…........... 53
Security ........…........……….......…….................... 61
M。nit。rs ......................................................…… 63
Assignment 2 ...........….........….........,…............. 67
Unit 3
Meters
Types 。f
meters ......................….........…........... 71
Care and handling of meters ........…........…....... 79
Installation procedures ...................................... 81
Determining flow rates ...................................... 83
Assignment 3 ........…......................................... 93
Gas Technician 2 Training - Module 15
© Canadian Standards A豁出；iation
v
Unit 4
Fuel containers
Cylinders, tanks and accessories. …………......... 97
Sizing and installing cylinders and tanks ......... 105
Assignment 4 .............………··…….......….......... 117
Appendix A to Unit 4 .....,…............…........….... 119
Vap。rizati。n rates for tanks and cylinders
Appendix B to Unit 4 ....................................... 121
Installation clearances for tanks and cylinders
vi
Gas Technician 2 Training - Module 15
© Canadian Standards A销。ciation
Unit 1
Pressure regulators
Purpose
Pressure regulators are installed in a gas piping system to maintain a
balance between downstream gas flow and downstream pressure. A
thorough understanding of the principle elements of pressure regulators and their operation is necessary in order to properly install and
service gas equipment.
e 剧，
LOwe
nd
nge
-
ws
1. Describe the need for pressure regulators.
2. Locate the codes and regulations pertaining to regulators.
3. Describe the basic operation of a regulator.
4. Distinguish between the different types of regulators.
5. Describe the selection requirements.
6. Describe the location and piping practices.
7. Troubleshoot common regulator problems.
Gas Technician 2 Training - Module 15
© Canadian Standards Assoc泊tion
1
Topics
1. The need for pressure regulators .................…........…............ 3
Purpose ...............................‘.......“................……·...”.....3
Main categories .....曹…………........……………·．．．．，，．．·…............…...... 3
Direction of flow .... . .... ............... . .......…………………－…··国..... 4
2. Codes ..................................….......……...................................... 5
Pressure inside buildings ........….........………....................... 5
Pressure regulators .……·······………··…….................… …........…-…..... 5
Line relief devices. . ... ..... ... .. .... .... .. ..... ... . .. . .. ....... . .…·-...,..,….......... 6
Hydrostatic relief devices........ . .. . . . ......... . .. ......... .. . ...... . . ............ 7
Venting ..… ……·…………............,……......…...………·…-…............. 7
2
a
3.
Basic 。peration of a regulator .....................................…........ 9
The loading element ..... . . .. . .. . . . . ... ...... .. .... . ... .... . . ...…............ 10
The measuring element .........…...…··-….....……………. ............ 11
The restricting element .....…·..,...………………······…·....‘……................ 11
The atmospheric vent ........阑................…．．．，．．．．．．．．．．．．．．．．，．．．阳………........ 12
The working system .........………··町….......…········….......... ·········· ......…… 12
Adjusting the pressure on non-utility regulators ........….........……................ 12
Safety features ..............…·….......................………··.......…......…............. 14
Materials of construction 回……………...............…………..................... 15
4.
Different types of regulators ................................................. 17
Appliance regulat。rs …．圄….......….............................……·－……………........ 17
Service regulators. ………·········…........................…................……..... 18
Bal~nced regulators ……………………………········…............................ 20
Servo valves ……,....... ····················· ..........………................. 22
Zero governors ......…················…………….......…………...….. . ........... 23
Proportional regulators ........….......….......…··…….................................... 24
Propane regulator systems. ……................................…·······…..............24
5.
Selecti。n requirements ......................….......…........…........... 29
Selection factors ...............…·······…………… ……….....................…........ 29
Sizing factors .................……·’.............…........…...........……………......... 30
Typr臼I selection guides ...….........…·············…......…...............…………....... 31
Additional issues for propane regulators ........…..................…....................... 31
a
6.
Locati。n and piping practice ......................…........”….......... 35
Preliminary planning ..…...................…·····································……............35
On-site considerations ..................…····························…················………....35
7.
Tr。ublesh。。ting 。f regulat，。rs ....................”….......…........... 37
Assignment
1 …..........................................................................41
u
Appendix A t。 Unit 1 .........…........…................................…......... 43
Typical regulator selection guide
2
Gas 丁ectinician
2 Training- Module 15
© Canadian Standards A豁出iation
TOPIC
1
The
needfoγpγes sure
γegulαtoγs
Gas pressures in supply mains (natural gas) and from storage containers
(propane) are generally higher than the safe operating pressures of
connected appliances. For this reason gas pressures must be controlled to
fall within an appropriate range, depending on the operating characteristics
of installed appliances.
Purpose
Gas pressure regulators have two main purposes:
•
to reduce the supply main pressure to safe operating pressures of
connected appliances
•
to maintain constant downstream gas pressure, regardless of changes in
the gas flow or upstream pressure variations.
If a gas appliance receives too much 缸el because the gas pressure is too
great, it will overfire. If the gas appliance receives too little fuel then it will
unde吃fire. If an appliance is overtired or underfired:
it will produce too much and too little heat respectively
combustion characteristics could change resulting in carbon monoxide
generation
·也e
Main
categories
appliance may not work properly or efficiently.
There are three categories of gas pressure regulators, each used to serve a
specific pu甲ose:
Service
regulators
Service regulators are used in natural gas systems to
reduce the service line pressure to building line pressure
at 也e gas meter set.
In propane systems they are used to reduce the service
line pressure to building line pressure. It is placed
between the storage contamers and the building.
Gas Technician 2 Training - Module 15
© Canadian Standards Association
3
UNIT 1
PRESSURE REGULATORS
Line pressure
regulators
Line pressure regulators sometimes named "system
regulators”, are used to reduce the building line
pressure in cases where the pressure required by a
system of appliances or equipment is less than the
pressure in the pipe where it enters the building.
Appliance
Appliance regulators are used to reduce the building
line pressure to the pressure required by the appliance.
This regulator is often built into a combination control.
reguliαtors
See also the definitions provided in the CSA B149.1 Natural Gas and
Propane Installation Code.
Most pressure regulators operate using the same principle. They also all
contain the same basic components. These are described in more detail in
Topic 3 of this unit.
Direction of
flow
When installing a pressure regulator, the direction of flow of the gas must
be taken into consideration. (Direction of flow will be covered in more
detail later in this unit.)
Two commonly used terms are upstream and downstream. This refers to
the placing of an item in the system according to the flow of the gas. So
when referring to gas downstream of the regulator, this refers to the flow of
gas after it has passed through the regulator. Conversely, gas upstream of
the regulator refers to the gas flow before it passes 伽ough the regulator. It
is important to know these two terms since 由ey are used often to explain
where to place appliances.
4
Gas T院如nician 2 Training - Modu抱 15
© Canadian Standards As曲ciation
TOPIC
2
Codes
The applicable code requirements for regulators are in the Natura/Gas and
Propane Installation Code (CAN/CGA-B149.l) and the Propane Storage
and Handling Code (CAN/CGA-Bl49.2). This topic explains some of the
reasons for these requirements.
Pressure
inside
buildings
The B149.1 Code sets maximum levels for the gas pressure inside
buildings. Higher gas pressures are permitted in certain areas in buildings
because problems that may be caused by leaking gas are reduced in these
areas. A manual shutoff valve must be installed upstream of the regulator
so that the regulator may be isolated for servicing or replacement.
Many line pressure regulators require an internal relief device or a line
relief device. This is to allow excess gas to be vented outdoors. In some
instances the vent contains a leak limiting device which restricts the flow
so that gas accumulatipn does not reach dangerous levels. These are not
required to be vented outdoors. (Venting is discussed in more detail in its
own section in the Code, and later in this unit when the various types of
pressure regulators are discussed.)
Pressure
regulators
The choice of regulator depends upon the range of supply pressures from
the gas utility or distributor.
Knowing the pressure range, and the specifications of the regulator, the
appropriate regulator can be selected. Ensure that the chosen regulator
supplies the required flow rate at both maximum and minimum flow.
As pressure regulators are extremely important, the B 149 .1 Code states
should be accessible, and protected from physical or chemical
damage. In particular，也ey should not be in a place where moisture is able
to form on 也em. A build-up of ice on a regulator can lead to serious
problems as the vent on 出e regulator may become blocked, restricting the
movement of the diaphragm. The regulator will then become unstable.
that 由ey
The B149.1 Code forbids the isolating or bypassing of a safety limit or
safety relief device. The only permitted exception is when a line pressure
regulator or second-stage regulator is bypassed in order to avoid complete
Gas Technician 2 T1『·aining- Module 15
© Canadian Standards Association
5
UNIT1
PRESSURE REGULATORS
shutdown of the operations for maintenance or repairs, especially in
large-scale systems. This may only be done:
if it is safe to do so
•
for the duration of the repair or replacement
if permission has been granted by the relevant authority having
jurisdiction.
If the inlet pressure to a line pressure regulator exceeds a level laid down in
the Code, then it must be a positive shutoff type regulato汇 This ensures that
in the case of a gas pressure surge, the system downstream of the regulator
is shut off and the appliances are protected.
Line relief
devices
A line reU吃f device (or pressure relief device) is used to relieve excess gas
pressure 企om a system. The Code says that the pressure setting on a line
relief device should not be higher than the lowest rated item downstream of
出e relief device. If it is higher, appliances could overtire and malfunction.
An installed line relief device should be able to handle the changes in
pressure in the normal gas supply that will occur 企om time to time without
discharging, but it should discharge if the gas supply pressure exceeds its
normal level.
Most natural gas, and all propane gas pressure relief devices must be
vented to the outdoors.
6
Gas Technician 2 Training - Mod响 15
。 Canadian Standards Association
PRESSURE REGULATORS
UNIT 1
Hydrostatic
relief devices
A hydrostatic relief device is used in propane systems. It has a similar
purpose to a line relief device. The Code states that these are to be installed
between two valves in a propane system. If liquid propane is trapped
between two closed valves in piping or a hose, it will begin to expand as its
temperature increases. The hydrostatic relief device relieves this pressure,
thus preventing the piping from bursting. The pressure should be set to take
into account the natural fluctuations of the pressure in the system. The
relief device should not discharge below this point.
Venting
When planning system venting, look at the following factors:
plan-place the pressure relief devices in such a way so as to simplify
the layout and installation of the venting lines
size--properly size the vent lines
point of termination一-ensure that the vent lines terminate safely and
are protected from damage, including water entry and insect damage.
Natural gas relieved by pressure relief valves should be vented outdoors to
prevent the buildup of dangerous gas indoors. There is an exception to this
in particular cases which are specified in the Code.
The B 149 .1 Code specifies that the vent line shall be made of approved
materials, and its size must be at least 由at of the nominal pipe size of the
vent outlet of the pressure regulator, but its inside diameter must not be less
than 0.25 inches (6 mm）.币ie individual vent lines may be connected to a
single vent line provided this single vent line is twice the area of the total
area of the connected bleed vent lines.
If specific manufacturer ’s instructions are not provided giving details on
the sizing of the vent line, the vent line must be increased by one pipe size
diameter for every 50 ft (15 m) or part thereof that the vent line extends
beyond the initial 50 ft (15 m). This increase must be made at the regulator
vent outlet.
systems 也e pressure relief valve must always vent to
is because propane is heavier 由an air and so sinks to 也e
ground, where it can pool in dangerous concentrations.
In propane gas
outdoors.ηiis
Gas Technician 2 Training - Module 15
© Canadian Standards Association
7
PRESSURE REGULATORS
UNIT 1
In a natural gas setup, if using a diaphragm valve or combination control
device to relieve the gas pressure on a low-inlet pressure appliance, the
Code allows the relieved gas to be vented into the combustion chamber.
The bleed line used to do this must be positioned in a fixed position relative
to the flame, and it should not affect the performance of the appliance. It
should also not be affected by heat. If such a venting system is being used,
the appliance must have a continuous pilot.
The vent 仕om a line pressure regulator and from relief device must
terminate outdoors. The specifications for these vent lines can be found in
the B149.1Code.
Always consult with the authorities having jurisdiction if unusual vent
lines or configurations are required.
8
Gasl忌chnician
2 Training - Module 15
© Canadian Standards A豁出iation
TOPIC
3
Basic opeγαtion
ofα
γegulαtor
Most service, system, and appliance regulators are direct-operated
regulators that work in basically the same way.
A direct-operated regulator is defined as any self-contained valve and
actuator combination. They automatically adjust the flow to meet the
downstream gas demand. Figure 1-1 illustrates a direct-operated regulator.
Loading
element
Atmospheric
vent~
Measuring
element
Restricting
element
Figure t 斗
Direct-operated
regulator
As shown in Figure 1-1, these regulators have four essential elements:
a loading element-usually a spring
a measuring element-usually a diaphragm
a restricting element-a valve, disk or plug
an atmospheric vent-a vent allowing the diaphragm to move freely.
Gas Technician 2 Training- Module 15
standards Association
© Canadian
9
PRESSURE REGULATORS
The loading
element
UNIT 1
The loading element is used to counterbalance the downstream pressure. It
is usually a spring. The position of the restricting element is determined by
the amount of spring pressure on the diaphragm. The amount of flow
through the regulator can be adjusted by changing the spring load. The
following terms relate to flow and pressure regulation.
Setpoint
The desired outlet pressure is known as 也e se伊oint. A
perfect regulator could maintain downstream pressure
equal to setpoint under all flow rates, but in reality, as
flow rate increases, the downstream pressure
decreases.
Lockup
The pressure above setpoint that is used to shut the
regulator off tight is called lockup. In many regulators,
the orifice has a knife edge while the disk is made of a
soft material. To make a tight seal, the regulator must
increase the downstream pressure to force the disk
onto 由e knife edge. 白tis extra amount of pressure
required is called the lockup pressure.
Service regulators provide a positive shutoff when no
flow is occu时ng in the line to the appliances.ηie
service regulator will usually lockup to within 10% of
the original outlet pressure setting.
Droopandq庐et
Droop and offset describe the downstream pressure
drop below setpoint. At this point, the valve is opened
and there is an increased flow of gas. Droop can be
expressed as a percentage of setp。如t pressure.
Manufacturers publish regulator capacities according
to their amounts of droop.ηiese are generally for 10%
droop and 20% droop. The accuracy of a regulator is
determined by the amount of flow it can pass for a
given amount of droop. The closer the regulator is to
setpoint，也e more accurate it is.
If plotting the performance of a typical regulator on a
graphσigure 1-2), the flow rate of gas is proportional
to the outlet pressure: as the gas flow increases, the
outlet (downstream) press田e drops.
10
Gas Technician 2 Training - Module 15
© Canadian Standards A翩翩ation
PRESSURE REGULATORS
UNIT 1
（~ockup
Setooint
。』刀的的。
E』
m巳
wo∞
b
CBOO
Droop
(o仔set)
Wide open
Flow rate
Figure 1-2 Graph depicting the performance of a typical regulator
The measuring
element
The restricting
element
The measuring element is usually a diaphragm. It is used to measure the
changes in the downstream pressure. The diaphragm is attached by a stem
to the restricting element so that they both move together.
When the downstream pressure changes the restricting element moves in
response to the measuring element. Usually the restricting element is a disk
or plug which controls the amount of flow by varying the orifice opening.
It is important that the orifice and seat are properly maintained. They must
be smooth and undamaged so that the seat may seal the orifice. If the seat is
damaged it must be replaced.
Gas Technician 2 T1『aining - Module 15
Standards Association
© Canadian
11
PRESSURE REGULATORS
The
atmospheric
vent
The working
system
UNIT 1
The atmospheric vent (regulator vent) allows the air above the diaphragm
to escape or enter as the diaphragm moves up or down. If the vent was
blocked, the diaphragm would not be able to move properly. Most small
appliance regulators vent to atmosphere, but this is restricted by the
appliance standards. Larger appliance regulators may pipe the vent opening
to the combustion chamber beside a constant pilot flame, or to the
outdoors. Note that we are only talking about venting of the area above the
diaphragm.
If the valve stem is in equilibrium, the force of the downstream pressure
across the bottom of the diaphragm equals the force of the spring pressure
pushing down on the top surface of the diaphragm. The downstream or
outlet pressure can be controlled by changing the compression of the
adjusting spring.
When the downstream pressure (under the diaphragm) drops below a set
level, the spring moves the diaphragm down and causes the valve to open
and create a wider space between the disc and the seat (orifice). As the
valve opening widens, the pressure drop across the valve is reduced and the
downstream pressure returns to its original level.
For example, when turning on the burners of a gas cooker, the downstream
decreases as the flow rate begins to increase. This pressure
decrease moves the diaphragm downward, le饥ing in more gas. The gas
flow continues to increase until the pressures on the bottom of the
diaphragm and on the loading spring of the regulator are balanced. This
process takes place whenever there is a change in the flow rate.
press田e
Adjusting the
pressure on
non-utility
regulators
12
η1ere
are three main types of regulators when it comes to adjusting the
pressure:
non-adjustable regulators
•
minimal adjustment regulators
•
fully adjustable regulators.
Gas Technician 2 Training - Module 15
© Canadian Standards Association
PRESSURE REGULATORS
UNIT 1
Before beginning any adjustments, consult the manufacturer's instructions
and check that the model numbers match. Always use the proper tools and
make sure that all pressure measurements used are accurate. In some cases
it may be better to order a more suitable regulator with appropriate factory
settings than to spend a lot of time tηing to measure and adjust the
pressure.
Measuring of outputs is discussed in Unit 3.
Reducing the pressure
If the pressure from the regulator is too high, use the following procedure
to reduce the pressure setting:
1.
Tum off the gas.
2.
Install the pressure test equipment.
3.
Remove the regulator adjusting screw cap.
4.
Tum on the gas.
5.
Tum the equipment on allowing the gas to flow.
6.
Tum the adjusting screw counterclockwise; this should reduce the
spring tension. Keep turning the screw until the coηect pressure is
achieved.
7.
Replace the cap.
Increasing the pressure
If the pressure from the regulator is too low:二 use the. following procedure to
increase the pressure setting:
1.
Tum off the gas.
2.
Install the pressure test equipment.
3.
Remove the regulator adjusting screw cap.
4.
Tum on the gas.
5.
Tum the equipment on allowing the gas to flow.
6.
Tum 也e a司justing screw clockwise; it should increase the spring
tension. Keep turning the screw until the correct press旧e is reached.
7.
Repla侃出e
Gas Technician 2 Training - Module 15
©Canadian S蚀ndards Association
cap.
13
PRESSURE REGULATORS
Safety
features
UNIT 1
A number of safety devices form part of the regulator.
Automatic safety vent limiting device
In certain regulators, such as 2 psig (14 kPa) line pressure regulators, an
automatic safety vent limiting device can be used. In this device a ball
check allows free inhalation of the regulato卫 This means a fast regulator
diaphragm response. However, in the case of a diaphragm rupture resulting
in an initial flow of gas, the ball check limits the flow of gas. This device
gives a sens1t1ve response.
Vent limiting orifice
This is used in appliance regulators. Its allows equal limits of inhalation
and escape of air from the upper diaphragm chamber. If the diaphragm
ruptures the leakage is limited to less than 1 cu ft/h (0.02832 m3届） at 7
inches w.c. (1.74 kPa) gas pressure.
Internal safety relief
This is used on service regulators. Service regulators 由at have this feature
have special seats located at the diaphragm and linkage connection. If the
downstream pressures exceeds the allowable levels then the seat opens.
The gas passes out of the regulator through the vent.
Lock-off mechanism
This is used on service regulators. There is an additional seat that closes,
shutting off the flow of gas through the regulator if the outlet pressure is
too high or too low. If the regulator locks off under these conditions then it
must be manually reset.
Two-way stabilizer vent valves
Two-way stabilizer vent valves provide quick, sensitive reaction to rapid
downstream pressure changes. As the diaphragm responds to rapid
changes, one of the flappers opens to minimize diaphragm lag due to air in
the spring case. Both flappers are closed during equilibrium.
14
Gas Technician 2 Training- Module 15
© Canadian Standards Association
PRESSURE REGULA TORS
UNIT 1
Materials of
construction
Regulators are made from corrosion resistant materials. This is because
many gases are corrosive. Typical construction materials are shown in
Table 1-1.
Table 1-1 Typical regulator construction materials
Part
Material
Body
cast aluminum
cast iron
steel
Spring case, I。叫ver diaphragm casing,
union ring, seat ring, disk holders
aluminum
0-ring, disks, diaphragms
nitrile
Cl。sing
neoprene
cap gasket, relief valve pad
Diaphragm head, adjusting screw
Delrin™
aluminum
Relief/monitor piston ring
graphite
Vent flappers
Cyc。lac™
nyl。n
Other metal parts
aluπlinum
brass
cast iron
Monel™
steel
stainless steel
zinc
Gas Technician 2 Training- Module 15
Standards Association
© Canadian
15
TOPIC' 4
Different types of regulα＇tors
Appliance
regulators
There are three types of appliance regulators. They are:
low capacity type appliance regulators-used to provide safe and uniform
gas pressure to residential gas appliances
high capacity type appliance regulators-used on larger residential and
commercial appliances
component of a gas control valve-performs the same function as a low
capacity type appliance regulator except that it forms part of the
combination control valve.
Low capacity appliance regulators
Low-capacity appliance regulators carry both main burner and pilot gas
loads. They are usually marked with the identification symbol “ P. ” This
indicates 也ey are suitable for pilot load capability. These regulators are
designed to produce a fine pressure control. They work with small pilot
flame flows that are mandatory operating requirements for some
appliances.
High-capacity appliance regulators
High-capacity appliance regulators are only used to regulate the gas
pressure to the main burner. The pilot flame receives the 7 inches water
column (w.c.) (1.75 kPa) gas pressure delivered downstream of the utility
gas meter or line pressure regulator. The volume of gas to 也e pilot flame is
controlled by a throttling valve (needle valve), sometimes called the
B-cock.
Operation of an appliance regulator
The most common type of appliance regulator is the spring-loaded type as
shown in Figure 1-3. The spring holds the valve in the open position.
Gas Technician 2 Training 『 Module 15
© Canadian Standards Association
17
PRESSURE REGULATORS
UNIT1
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创
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白M 户Ur
ns
ng
rrrrz
engaw(
町叫
e
’
－阳
）
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e 、啡，
nu
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muψ
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坦白叫
hd
e me t
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Restricting element
(valve disk and seat)
Inlet ¢
Figure 1-3 Spring-loaded, low-pressure appliance regulator
The appliance regulator works on the same principle as all other regulators.
Only changes in the downstream pressure cause the diaphragm to move
because the loading force of the spring is constant. Remember that when
the diaphragm moves it changes the position of the disk in the restricting
element. The downstream pressure is determined by the amount of loading
force created by the spring compression. The loading force (and
downstream pressure) can be increased or decreased by adjusting the
screw on top of the spring.
Service
regulators
The gas regulator at the utility service meter is the first regulator on the
piping system. It reduces the gas pressure from the utility company main
lines to the required building pressure. If the gas pressure in the house
piping exceeds 14 inches w.c. (0.5 psig) then more regulators must be
installed on the piping system. These extra regulators are called line
pressure regulators. (often called system regulators)
The service regulator is in the normally open position. It does not begin to
regulate gas pressure until pressure begins to build on its downstream side.
A typical service regulator is shown in Figure 1-4.
18
Gas Technician 2 Training- Module 15
© Canadian Standards Association
PRESSURE REGULATORS
UNIT 1
Internal
relief valve
Pusher post
Lever
D 叫 press
Seat ring
re
AU
Inlet pressure
Figure 1-4 A typical service regulator
The service regulator operates in the same manner as other regulators.
Most service and line pressure regulators have removable seats which form
an orifice to control the maximum flow rate through the regulator. Ensure
也at the proper orifice or seat size is installed to match the flow rat¢ of the
piping system. If the wrong orifice or seat size is used there will bq
insufficient flow rates or poor regulating perfo口nance.
1
Since the downstream pressure is controlled by the spring loading force,
service and line pressure regulators may offer a wide selection of springs
for di茸erent system pressures. Select the proper spring to provide t(he
required range of downstream regulated pressure.
'
Most service regulators have an internal relief valve that operates when too
much gas pressure builds up on the downstream side of the gas regµlator.
η1e internal relief valve is a spring-operated device which opens at a
predetermined setting to relieve excess gas press田e to the outside ·
atmosphere throu且也e atmospheric vent. If a gas pressure regulator is
equipped with an internal relief valve，也e atmospheric vent outlet µmst be
piped to 也e outdoors. Ensure that the vent outlet is covered by a bug screen
to prevent insects blocking the vent.
I
Gas Technician 2 Training- Module 15
Standa『ds Association
© Canadian
19
UNIT 1
PRESSURE REGULATORS
Service regulators also use a lever to help reduce the gas pressure from the
utility main line. Through the lever mechanism, these regulators provide
increased force for lockup without the extra cost, size and weight of larger
diaphragms, diaphragm casings, and other related parts. The extra
mechanical force also keeps the disk in a stable position. This stops the
disk cycling.
Balanced
regulators
Large changes in the inlet pressure makes it difficult for a regulator to
maintain constant downstream pressure. Many regulators therefore add a
second diaphragm or port to create a balanced regulator. Balanced
regulators are classified as:
single-ported
•
double-ported.
Single-ported balanced regulator
Single-ported balanced regulators have the four basic elements common to
all regulators. The regulator is also equipped with a Pitot tube and a
balancing diaphragm as shown in Figure 1-5.
Loading
element
Measuring
element
Disk
and seat
Inlet
Figure 1-5
20
Single』ported
balanced regulat。r
Gas Technician 2 Training- Module 15
© Canadian Standards Association
PRESSURE REGULA TORS
UNIT 1
Balancing diaphragm
The balancing diaphragm eliminates influences of changes in inlet pressure
on the regulating capabilities of a single-ported regulator. The balancing
diaphragm separates the lower main diaphragm area and the upper valve
section. The inlet pressure exerted downwards on the inner valve disk also
pushes upwards on the balancing diaphragm. The effective areas are equal,
so the forces are equal. The balancing diaphragm is attached and sealed to
the valve shaft. With equal forces pushing both ways, fluctuating inlet
pressures are balanced, resulting in minimum lockup with either high or
low inlet pressures.
Double-ported balanced regulator-basic type
Double-ported regulators have the same four basic elements of all
regulators, except 由at the restricting element has two disks and seats. This
is shown in Figure 1-6. The equal port diameters balance the opposing
forces across the valve disks, resulting in minimum lockup with_ either high
or low inlet pressures.
0-ring
seal
Double seat
and disks
Inlet
Figure 1-6 Double-ported balanced regulator
、
、一
Gas Technician 2 T1『aining - Module 15
© canadian Standards A撼。ciation
21
PRESSURE REGULATORS
UNIT1
The shaft connecting the two disks or plugs to the main diaphragm is
sealed with an 0-ring where it passes through the valve body. The doubleported regulator does not use a Pitot tube to sense outlet pressure. Instead, a
tapping is provided under the main diaphragm which must be connected to
the downstream piping.
Balanced regulators allow for more stable operation and precise control of
pressure.
Servo valves
Gas valves that use servo operation are combination gas valves
incorporating safety coils, A-cocks, B-cocks, and a pressure regulator.
Servo valves are limited to flow rates of about 400 cu ft/h ( 11.3 m3斤1), so
they are used on residential and commercial appliances with relatively low
volume requirements.
The bleed valve operator on a servo valve can be electromagnetic,
hydraulic or bimetal. Figure 1-7 shows a closed servo gas valve.
Quqd
町
Regulator
adjustment screw
1.
When the valve is
in the off position,
there is no call for
heat.
2.
Inlet gas press旧e
passes through the
restrictor and down
the bleed line to
build pressure
under the main
valve diaphragm.
The gas pressure is
equal above and
below 也e diaphragm.
3.
The force of the
spring, and the fact
that 也e area of the
lower diaphragm
surf注ce is greater,
keep the valve
closed.
Inlet
Main valve
(closed)
Figure 1-7 Servo gas valve closed
22
”
‘可。 3
e
Bleed valve
(closed)
札U
ρLW
To
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eo
vnu
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Gas Technician 2 Training - Module 15
。 Canadian Standards Association
PRESSURE REGULATORS
UNIT 1
Zero
governors
Zero governors, or regulators, are designed to deliver an outlet pressure
equivalent to atmospheric pressure. They are normally double-diaphragm
units equipped with an 0-ring seal diaphragm (balancing diaphragm), as
shown in Figure 1-8. This isolates the inlet gas pressure from the lower
chamber of the main control diaphragm. The balancing diaphragm is set so
that its effective area equals the effective area of the valve disk. The spring
of these regulators counterbalances the weight of the internal 阴阳. This
provides just enough additional tension to close the valve.
r 黑市ing
讪m
M创
nHnua
amHHdu
ee
己：＞
Figure 1-8 Zero governor
Gas Technician 2 Training- Module 15
© Canadian Standards Association
23
PRESSURE REGULATORS
UNIT 1
As the spring always just counterbalances 由e internal parts, the outlet
pressure of the governor will always be the same pressure 由at is applied t。
由e top side of the main diaphragm. Since the vent above the diaphragm is
open to the atmosphere (see Figure 1-8), the zero governor is also called an
atmospheric regulator. It can only provide gas pressure that is equal to
atmospheric pressure.
A zero governor is connected to an air-gas mixer in a burner system. This
creates a suction on the outlet of the atmospheric regulator. This suction on
the bottom of the main diaphragm causes it to open the regulator and try to
bring the outlet pressure back up to zero. The more suction applied to the
outlet, the more the regulator opens to increase the flow.
If a pressure reference line is connected from the combustion chamber to
the upper diaphragm chamber of the zero governor, the combustion
chamber press田e is counterbalanced in the mixer-governor system. This
allows the burner to operate under positive or negative combustion
chamber conditions. When operating these systems on combustion
chambers above 1 inch or 2 inches w.c. (0.25 or 0.5 kPa) positive pressure,
inlet gas pressures to the zero governor must be high enough to provide a
minimum pressure drop across the zero governor of 4 inches w.c. (1 kPa).
Proportional
regulators
Propane
regulator
systems
A proportional regulator is similar to a zero regulator except that air
pressure is applied to the top of the main diaphragm through a sensing line
connected to 由e vent connection. The outlet press山e ·is equal to whatever
positive pressure is applied to the top of the regulator diaphragm. If a
positive or negative pressure is applied to the diaphragm chamber, the
outlet pressure becomes equal to this pressure.
A big difference between natural gas systems and propane gas systems is
natural gas system press田es in service piping usually do not
experience 由e 回me change in pressures that propane systems do. Propane
storage container pressures may vary 企om as low as 8 psig (55 kPa) to as
high as 220 psig (1500 kPa) due to changes of temperature around the
cylinder.ηie propane regulator system must compensate 岛r 也is variation
and deliver a steady press田·e. The regulator must also be able to handle 也e
problems caused by the h阳mittent use of the appliances attached to it.
也at
It is possible to get single-stage regulator systems, but the Code now
requires all permanent installations make use of two-stage regulator
systems. Two-stage regulator systems have a number of advantages:
24
Gas Technician 2 Training - Module 15
。 Canadian Standards As四ciation
PRESSURE REGULATORS
UNIT 1
They deliver uniform appliance pressure. This is as a result of the
second-stage regulator receiving a relatively uniform gas flow from the
first-stage regulator.
They reduce freeze-ups and service calls since the expansion of the
propane gas is divided into two stages allowing the heat to be
transferred through the walls of two regulators. It also allows for the
use of a larger orifice. Both these operations reduce the extreme
chilling and freeze-up which can occur with single-stage pressure
regulation.
There is an economy of installation since the line between the first唰 and
second-stage regulators is much smaller than in single-stage systems.
The allowance for future appliances is enhanced as additional secondstage regulators may be added if the first-stage regulator still has
additional capacity.
These systems should also be used in non-permanent installations to get
full and proper use from the connected appliances.
Two-stage regulator system
There 缸e
two options for a two-stage pressure regulation system:
1.
A first-stage high pressure regulator (Figure 1-9a) with an inlet from
the storage container and an outlet to a second-stage low pressure
regulator (Figure 1-9b). This second-stage regulator acts as a service
regulator to the building.
2.
An integral twin-stage regulator which performs both of these
且mctions internally. An example is shown in Figure 1-10. Use these
when piping distances are 30 ft (9 m) or less. A big advantage is that
the regulator is compact allowing it to be used easily in mobile homes,
on-site filling and average size domestic installations.
Gas Technician 2 Training …·Module 15
Standards Association
© Canadian
25
PRESSURE REGULATORS
UNIT 1
High pressure first-stage regulator
Low pressure second-stage regulator
Copyrir;;ht Engineered Controls International Inc. (RegO ( j
Reproduced with permission
Figure t ” 9 Typical first- and second-stage propane regulators
High to low pressure twin-stage regulator
Copyr.也ht Engineered Controls Intematianal Inc. (RegO (
Reproduced with perm归sion
Figure 1-1
26
J
o A typi臼i high to low twin-stage propane regulator
Gas T臼:hnician 2 Training- Module 15
。 Canadian Standards Association
PRESSURE REGULATORS
UNIT 1
In colder climates, such as in Northern Ontario, the outlet pressure for the
first-stage regulator is 5 psig (34 kPa). In warmer climates, such as in
Southern Ontario, the outlet pressure for the first-stage regulator is 10 psig
(70 kPa). The second-stage regulator m山t maintain the appliance pressure at
11 inches w.c. (2. 7 kPa) except in recreational vehicles where the pressure
must be maintained at 13 inches w.c. (3.25 kPa).
Single-stage regulator
A single-stage regulator is used to reduce tank or cylinder pressures to
11 inches w.c. (2. 7 kPa). A typical single-stage regulator is shown in
Figure 1-11.
Travel stop on closing
cap opens internal relief
valve in emergency
ι
Large 3/4 inch NPT
drip-lid reduces
chance of blockage
by freezing rain
Internal relief valve
keeps downstream
pressure below 2 psig
Diaphragm
c=>
Orifice tube with
straight-through
flow design
Copyright Fisher Controls International Inc.
Reprinted with permission
Figure 1-11 Single-stage regulator
Automatic changeover regulators
Automatic changeover regulators are two stage regulators that are suitable
for homes, mobile homes and portable two cylinder installations. They
automatically change the supply over from the “service” to 由e “reserve”
cylinder when the “ service” cylinder is empty. This happens without an
interruption to the flow. These regulators also allow 也e empty cylinders to
be refilled or replaced without an interruption of the supply to the system.
Gas Technician 2 Training- Module 15
© Canadian Standards Association
27
UNIT 1
PRESSURE REGULATORS
Typical installation of two-stage regulator
system
Figure 1-12 shows a typical two-stage regulator installation. The first stage
of the system supplies a nearly constant inlet pressure of 8 to 10 psig (55 to ·
70 kPa) to a second-stage regulator.η1is means 出at the second副stage
regulator does not have to compensate for as much variance in inlet
pressures. Any pressure loss through the pipe or tubing can be corrected
by the second-stage regulator at the building being served. Smaller piping
can be used between the first- and second-stage units because of the higher
pressure.
First-stage
regulator
Second-stage
regulator
Figure 1-12 Two-stage regulator installation
28
Gas Technician 2 Training - Module 15
©Canadian S饱ndards Association
TOPIC
5
Selection
γequiγements
Selecting the correct gas regulator depends upon a number of factors. The
main factors are related to the rate of flow, type of gas, inlet and outlet gas
pressure and pipe or tubing size. These factors need to be taken into
account before choosing a regulator.
Selection
factors
Before a regulator can be selected for a particular application, the
following factors relating to the piping system must be taken into account.
First complete and size a sketch of the piping system, then get the
following information:
Rate offlow
The rate of flow through the regulator is determined by the number of
appliances connected to the downstream piping system. This flow rate
is usually expressed in standard cubic feet per hour or standard cubic
metres per hour.
•
The type ofg，αs
Ensure that the regulator is designed for use with the intended fuel gas
(natural gas or propane).
Inlet gαs pressure
Regulators are manufactured with a maximum inlet and outlet pressure
rating. Select the regulator that is designed to handle the maximum
possible system pressures. The inlet pressure is also a determining
factor in the rate of flow.
•
Outlet gas pressure
ηie
outlet gas pressure is the downstream system-operating pressure.
This press田e is usually fixed, but there may be situations where a
range ofa司justment is required. Outlet pressure is also a factor that will
determine the flow rate through the regulator.
•
Pipingor 阳rbing
size
The inlet and outlet pipe or tube size is a factor in determining how to
select the regulator body size.
Gas Technician 2 Training- Module 15
© Canadian Standards A弱。ciation
29
PRESSURE REGULATORS
UNIT1
Sizing factors
The following are general guidelines for sizing regulators. When sizing any
regulator always consult experienced personnel or the manufacturer.
•
Bo吵 size
The regulator body size should never be larger than the pipe size.
However, a properly sized regulator can be one or two sizes smaller
than the pipe.
•
Construction
The regulator should be constructed from materials compatible with the
nature of the gas, the gas flow and the temperature used. Also ensure
that the regulator is available with the desired end connections.
•
Pressure ratings
Pressure-reducing regulators are sized by using minimum inlet pressure
to ensure that they can provide 如II capacity under all conditions. It is
also very important to take note of the maximum inlet and outlet
ratings. Downstream pressures significantly higher than the regulator
pressure setting may damage soft seats and other internal regulator
parts.
•
Spring pressure range
If two or more springs have published pressure ranges 也at include the
desired pressure setting, for more
lower range.
acc田acy use 也e
spring with the
·年ringpe价rmance
The full published range of a s？由i~ can generally be used without
sacrificing performance or spring life.
•
Orifice diameter
The recommended orifice size is the smallest diameter 也at will handle
the flow.ηiis benefits operation:
by avoiding instability and premat町e wear
by allowing for smaller relief valves
by reducing lockup pressures.
Wide-open flow rate
刀ie
capacity of a regulator when it has failed wide open is usually
greater than the regulating capacity. Use the regulating capacities when
sizing regulators, and the wide-open flow rates only when sizing relief
valves.
30
Gas TE比如nician 2 Training - Module 15
«:>Canadian S阳ndardsAs部ciation
PRESSURE REGULATORS
UNIT 1
•
Accurαcy
Evaluate the need for accuracy with each installed regulator. This is
expressed as droop, which was discussed in the previous topic.
Inlet pressure losses
The regulator inlet pressure used for sizing should be measured directly
at the regulator inlet. Measurements at any distance upstream from the
regulator are suspect because line loss can significantly reduce the
actual inlet pressure to the regulator.
Turn-down ratio
Within reasonable limits, most so白，seated regulators can maintain
pressure down to zero flow. Therefore, a regulator sized for a high flow
rate will usually have a tum-down ratio sufficient to handle pilot-light
loads during periods of low demand.
•
Speed of response
Direct-operated regulators generally have faster response to quick flow
changes than pilot-operated regulators.
•
Overpressure protection
Evaluations for ove甲ressure protection should also be made at the time
of regulator selection.
Typical
selection
guides
Additional
issues for
propane
regulators
Typical tables used to select a regulator are in Appendix 1 at the end of this
unit. These tables are specific to Fisher Controls regulators, but the
selection procedure is similar for all manufacturers.
A systematic approach must be 岛llowed when sizing propane regulator
systems. First determine the lowest operating temperature for the storage
containers serving the installation. Table 1-2 lists the approximate vapour
pressures corresponding to a range of temperatures.
Gas Technician 2 Training - Module 15
© Canadian
Standa『dsAssoc阳lion
31
PRεSSURE
υNIT
REGULATORS
1
Table 1-2 Approximate vapour pressures of propane
。F
Temperature
(°C)
Approximate pressure
psig (kPa)
-40 (-40)
1.3 (9)
-30 (“34)
5.5 (38)
-20 (-29)
10.7 (73.8)
-10 (-23)
16.7 (115)
。（－ 18)
23.5 (162)
10 (-12)
31.3 (216)
20 (-7)
40.8 (282)
30 (-1)
51.6 (356)
40 (4)
63.3 (437)
50 (10)
77.1 (532)
60 (16)
92.5 (638)
70 (21)
109.3 (754)
80 (27)
128.1 (884)
90 (32)
149.3 (1030)
100 (38)
172.3 (1189)
110 (43)
197.3 (1361)
If using propane for space heating, select the lowest temperatures the
storage containers are likely to see over a 24 hour period. Consult with
the local propane distributor for a reasonable design temperat旧e which
reflects past experience.
It is also important to check the maximum temperature so that 由e 臼11
range of storage container vapour pressure is known.
Next, determine the maximum load in B阳岛（or kW). To do 由is, add all
the inputs from all of the appliance rating plates connected 坦白e system.
Seasonal demands should also be taken into account. Always u四 the
peak demand.
Now use a regulator manufacturer ’s performance curves to select the
appropriate first- and second-stage, or integral twin-stage regulators.
Figure 1-13 shows a typical performance curve 岛r an integral twin-stage
regulator.
32
Gas Technician 2 T1『aining - Module 15
© canadian Standards As叙犯ia自m
PRESSURE REGULA TORS
UNIT 1
CE20Q」SC〉〉右的
φζQC一
〉
ω」2的的。』也ω
之』
一。。
14
13
9
8
400
口
cu fUh
450
1000
MBtu/h
，、
nb
-
1250
hMb e
PH
怒吼
nn
0sto
EW4
Ua ，
户
a 民
-
9 咆
「F 」u
创
hd
n
500
@
Figure 1-13 Performance curve for a twin-stage regulator
There are three steps to using the performance curve:
Start at the bottom of the chart using the maximum connected load
appliances and equipment. In the above chart a maximum load
of 700 000 Btu/h has been assumed (point 1 on the graph).
仕om
2. Draw a line straight up that intersects the lowest expected vapour inlet
pressure. In this case，由e 75 psig inlet pressure c町ve was used (point
2).
3. Draw a horizontal line from this intersection point to the delivery
pressure scale at the left side of the chart (point 3). In this case, a
delivery pressure of 10.5 inches w.c. results, which is within the
acceptable range of 8 to 11 inches of w.c.
The process is similar when a first- and second-stage regulator are being
sized. The first-stage regulator is sized the same way as the twin-stage
regulator. The second-stage regulator is sized using the delivery pressure
仕om the first-stage regulator as its inlet pressure.
Once again, always make use of the manufacturer ’s literature.
」
Gas Technician 2 Training- Module 15
© Canadian Standards Association
33
TOPIC
6
Location and piping pγαctice
Make sure that the regulator is properly installed the first time. To ensure
that the regulator is installed properly, the installation process must be
properly planned. If all the steps are planned properly, the installation
process will usually proceed smoothly.
Preliminary
planning
First, make sure that the correct regulator has been chosen for the system. It
must have the correct orifice and control spring. Read the manufacturer ’s
guidelines for installing the type of regulator chosen. As part of the process
of choosing the correct regulator use a sketch of the piping system. This
sketch will also help to determine what supplies, equipment and tools are
required to complete the job.
。n-site
considerations
When arriving 低 the site, check the sketch to ensure that the intended
location of the regulator is suitable.
Regulator location
Place the regulator so that it can be easily serviced. There must also be
enough room above the regulator to allow for the removal of the actuator or
the spring casing from the body. Finally, ensure that there is enough room
to install a vent and sensing line if they are required. Details on the location
of the pressure regulator are in the Code.
Piping, tubing and hose systems
The piping, tubing and hose systems provide the link between the gas
supply, the regulator and the appliances. Check the following items to
ensure that the basic requirements for the piping have been met:
approved materials have been used for the piping
the piping is in an appropriate location
the sizing is adequate for present and future appliances.
Ex阳tsive 曲创ls on 叩proved piping，协1ingandho回 sys饱:ms are in the C优．
Gas Technician 2 T1『aining - Module 15
© Canadian Standards Association
35
PRESSURE REGULATORS
υNIT
1
Piping connections
First check that there are no misaligned piping connections that produce
strain on the body of the regulator. This could crack or warp the body of the
regulator and prevent it 仕om operating correctly or cause it to leak gas. The
piping should be properly supported so that it is properly aligned and does
not put stress on the regulator.
If the piping uses flanged connections, first assemble the flanges and
gaskets with the bolts tightened only by hand. Tighten the bolts using a
crossover pa忧em as shown in Figure 1-14. This is to prevent uneven
stress on the flange faces and cracked flanges.
Threaded fittings are used on pipe sizes up to
2 inches to connect a regulator to the piping.
On larger pipe sizes, flanged connections are
used. Butt weld connections are used on some
larger regulators.
6
8/
If using threaded joints, clean the pipe
threads and appl~ pipe lubricant sparingly to
male 也reads, being careful to start a few
threads from the end of the pipe. Do not tighten
the piping into the regulator body so 白at it
causes stress on the regulato卫 Do not
overtighten the pipe threads into the regulator
as this can damage the regulator body.
0 0 、
0 刀之＇＼ 0 、
3\0 、工／
‘
0 0
5
017
”
－一← 2
Figure 1-14
Tightening sequence for
a regulator flange
Direction of gas fl.ow
Be absolutely certain that you install the regulator so the flow arrow points
in the direction of flow. Most regulators convert an inlet pressure to a much
lower outlet pressure. Also, most regulators have outlet ratings below 也e让
inlet ratings. If a regulator is installed backwards，如11 inlet pressure will
enter the diaphragm casing. If this pressure is high enough the diaphragm
casing may rupt町、 causing regulator failure, damage to downstream
equipment and possibly a fire and explosion.
Service valve and pressure regulator leakage·
For information on service valve and pressure regulator leakage, refer to
Module 8, Unit 3.
36
Gas TE民如nician 2 Training- Module 15
。 Canadian Standards Association
TOPIC 7
Tγoubleshooting of γegulαtoγs
Most trouble shooting depends on the type of regulator, and it is normally
covered in the manu臼ctur町’s literature. If unsure about the regulator,
obtain the manufactur町’s guide.
Before beginning any tests, check
that the regulator is installed in the
line properly and that the pressure
conditions and flow rates are within
the design limitations of the
regulator. Many problems may also
be caused by misalignment of parts
due to the rough handling of the
regulator.
If the regulator has a bottom plug
(Figure 1-1 匀， remove it and work
the valve mechanism up and down
with your finger. The valve should
move 企eely.
Some common problems and their
solutions are listed below:
Figure 1-15 Regulator with
b。“om plug
Problem
Obstructed vents
Solution
Foreign material lodged between the
seat and disk
Remove the material and clean
Wrong regulator installed for the
Replace the regulator
Clear 。bstructions
appli臼tion
Failure of mechanical parts due t。
corrosion
Liquid propane in the regulator
Replace the parts
Clean the regulator. Check that the
regulator is not mounted bel。w the
tank where propane liquid may
accumulate
Other symptoms, toge出er with the potential causes and solutions are listed
in Table 1-3.
Gas Technician 2 Training - Module 15
Standards Association
© Canadian
37
Table 1-3 Troubleshooting pressure
lncorr＇部t
Outlet pressure too high
2.
In order to check outlet pressure
the appliance must be operating.
Under conditions of no flow,
pressure on the outlet side of the
straight-through-flow models, will
be equal to the pressure on the
inlet side.
Test
Possible causes
Symptom
Remedy
Remove seal cap.
spring adjustment.
Ruptured diaphragm.
regulato 『3
2. Apply soap solution to vent
Adjust for proper tension.
2.
Replace diaphragm.
3.
Replace regulator with one of
smaller size.
刀m 刀mQCF
〉→O 刀ω
℃刀mωωC
~
outlet-bubbles indicate leaky
diaphragm.
3.
4.
3. Check orifice size to
Gas is turned on upstream
with control valve open.
4.
Close control valve before
opening manual valve
upstream. Wait 30 s then
open control valve.
4.
This is a temporary condition
and will rectify itself in less
than 30 s.
5.
Manually tum o行 gas. Remove
seal 四p and adjusting screw.
If spacings between spring
turns are not uniform, spring
has probably been stretched
5.
Replace with new spring.
6.
Remove seal cap.
6.
Adjust spring to proper
tension.
sp付ng. Hold
diaphragm down with
screwd 『iver. If there is no rise
in the outlet pressure the inlet
pressure is too low.
7.
Check for obstructions in
system upstream of regulator.
8.
See that the arrow on the
bo忧om of the regulator points
in the direction of the gas flow.
8.
If incorrect, install regulator
properly.
9.
Remove spring. Hold
9.
问eplace
Use a manometer downstream of
the regulator to measure the
pressure. A manometer gives a
very accurate reading.
5. Stretched spring
Outlet pressure too low
6.
Incorrect spring adjustment.
7. Inlet pressure too low.
8.
问egulator
9.
Wrong spring.
improperly installed.
determine flow. Should not be
less than 5% minimum main
burner regulation capacity.
7. Remove
with correct spring.
l
CZ ｝『斗
。曲”→究
d比
ang3→
M
azg白tgoacsdu
口中E
国OD
。 OSEEMEZ 曲『一缸E”
M〉
Flow rate too low on main
burner regulators.
CZ一→4
EM →EzalgaEtu
2口
＠ OBD国as＝gB3
也由a
『
”二
〉”只
XUSE02
0840♀
S~m~tom
Possible causes
Ciiaphra~m down wlt'ii
screwdriver. Rise to correct
outlet pressure indicates
stronger spring is required.
10. Inlet pressure too high.
10. Regulators for domestic
service are not expected to
pe 付。rm accurately if inlet
pressure is greater than 28
inches w.c. (7 kPa).
Regulator responds but action
sluggish
sl。w 。r
11. Obstruction in vent causing
limited diaphragm movement.
12. Regulator equipped with surge
arrester for purposes of
improving combustion
characteristics.
13. Sensing hole at base of
Regulator formerly operating
satisfactorily, will no longer
maintain outlet pre辅ure
14. Change inlet pressure
conditions.
15. Loss of flexibility of
ω
旦旦坠巴
11. Inspect vent opening on top
cover of regulator. In the event
the regulator is vented to the
combustion chamber or some
other remote location, be sure
that the venting tube is free of
di 吭， ice or other obstructions.
12. Remove surge arrester from
vent to see if regulator
response is restored.
13. This condition occurs very
rarely but when it does exist
will always be detected at time
of original installation.
14. Check pressure as suggested
in points 7 and 10 above.
10. If inlet pressure is greater than
28 inches w.c. (7 kPa) consult
盯1anufacturer for special
applications.
11. Free vent hole with small wire.
Be careful not to puncture
diaphragm.
12. Check that orifices in surge
arrester are clean and not
blocked. Check with
manufacturer if the surge
arrester is properly sized for
the application.
13. Remove regulator from line,
clean sensing hole and reinstall.
14. Follow remedies in points 7
and 1O above.
15. 问eplace
diaphragm.
刀m 刀mQCF
℃响
NmωωC
〉叶。刀ω
threads on outlet side of valve
chamber blocked by excessive
pipe dope.
c.>
Remedy
Test
PRESSURE REGULATORS
UNIT 1
Assignment 1
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
孔That
2.
What are the three categories of gas pressure regulators?
3.
认That
4.
Where is the hydrostatic relief valve used?
5.
矶That
6.
What are the four elements of a direct operated regulator?
7.
When flow rate increases through a regulator, what happens to the downstream pressure?
8.
Of what materials are regulator bodies made?
9.
What controls the downstream pressure in a regulator?
are the two main purposes of gas pressure regulators?
is the pressure setting on a line relief device?
must the size of the vent piping from a relief device be?
Gas Technician 2 Training- Module 15
© Canadian Standards Association
41
PRESSURE REGULATORS
UNIT 1
10. What is a zero governor connected to?
11.
What 句rpe
of regulator arrangement is required in propane installations?
12. Will gas flow be interrupted by changing a propane cylinder if an automatic changeover
regulator is used on the installation?
13. What five factors need to be considered be岛re selecting a regulator?
14. Is operating temperat田e a factor when installing pressure regulators on a propane cylinder
system?
15. Should the arrow on a regulator body point upstream?
42
Gas Technician 2 Training 『 Module 15
。 Canadian Slanda叫s As锐地iation
APPENDIX A TO UNIT 1
Typicαlγegulator
selection
guide
The following tables are typical manufacturer ’s regulator selection guides.
They are provided here courtesy of Fisher Controls International Inc.
Gas Technician 2 Training - Module 15
©Canadian S恼ndardsAs部ciation
43
PRESSURE REGULATORS
UNIT 1
Bulletin
71:006
page 2
(FISHElr)
Selecting
Regulat，。r
ranged in horizontal rows by increasing capacities and
increasing body size.
Types
1. Use table 1 or 3 to determine which 。f the types
selected have inlet pressure capabilities that meet or
exceed those required by the application. Maximum
inlet pressures, arranged in ascending order are also
shown in tables 2 and 4.
Table 8 gives capaci创es in Scfh of 0.6 specific gravity
natural gas. Table 9 gives capacities in pounds of saturated steam per h以』r. Table 10 gives capacities in
gallons of water per minute. Tables 11 ~nd 12 give
capacities in Scfh of 0.97 specific gravity nitr吨en.
2. Re他r to tables 6 thru 10 to determine which Fisher
regulator type numbers are available in the body size
and flow capac忧ies required. Flow capacities are ar-
3. Always refer to the product bulletins to make your
final selection.
Tab知 1,
Table 2. Maximum R咱＇Ulator Inlet 伪，ssures in Ase，例ding Order
Mu/mum Regulator 仿他t Pressures by Type Number
PRESSURE
REDUCING
REGULATOR
TYPE
NUMBER
64
66
67
67H
75A
928
92C
92S
92W
95H
95L
99
133
166
翩翩翩U捕
MAXIMUM
’”LET
PRESSURE
Pala
250
5
250
400
200
250
刮目B
300
300
300
300
400(1)
60
60
SIZE,
INCHES
Bar
17.2
0.3
17.2
27.6
13.8
17.2
20.7
20.7
20.7
20.7
20.7
1/2
2, 3, 4
1/4
飞／4
1/2. 3/4, 1. 1-1/4,’ ·1/2. 2, 2-1/2
1-1/4, H/2, 2. 2·1/2. 3. 4, 6
1/2, 3(4, 1
1, 1·1/2, 2, 2-1/2. 3, 4
1, 1·’/2. 2. 2-1/2, 3, 4
1/4, 1/2, 3/4. 1,
1-1/2, 2
1/4, 1/2. 3/4, 1
27.6＜η2
4.1
4.1
17.2C11
主
1-1/2, 2
8
200(1) 13.8<η 10
6.9
12
100
144Q<1J 99.3<η 1, 1-112. 2, 2-112. 3, 4, e
298H-EK
310
1 o<’> ”剑” 1, 2, 3, 4
72.4
1, 2. 3. 4
10到
399A
55.2 6
3” A
”。
3/4, 1, 2
138
2000
627
17.2 3/4, 1, 2
250
627F
1, 2
103
1500
630, 631
1-1(2, 2
10.3
150
7306
17.2
1/4 x 1/8
250
912N
400(1) 27.&l ” 1,2,3.4,8
1创8·EGR
1. 2. 3, 4, 6
13.8
200
1190
414
1/4
1301
侃”。
17.2
1/2, 3/4
250
R522
8.6
3/4, 1. 1-1/4,’-1/2
125
S100
1-1/2. 2
125
5200. 52010
.6
3/4, 1
8.6
125
S250
3/4, 1
8.6
125
S251C
1-1/4, 1-1/2, 2
8.6
125
S300
3/4，飞 1-1/4, 1-1/2. 2
8.6
125
S301F
3/4, 1
8.6
$400
’ 25
10.3 3/4, 1, 1-1/4
$ω
Y600
10.3 3/4, 1. 1-1/4
150
Y690H
10.3 3/4, 1, 1-1/4
t伺
Y690
1-1/2, 2
10.3
150
Y倒2 Y693
， ι酬tlnl耐＂＇＂缸’e IOlh挡”“蛐目腼缸””翩翩，．幅幅唱.wt制晴..，幅幅W曹．
298C·KB &
298T-KB
25C目”
“
PRESSURE REDUCI” G
REGULATOR
TYPE NUMBER
’陆.ET
PRESSURE
Pl姐
5
60
100
125
150
200
250
”。
400
BOO
1050
1440
1500
2000
”0.3
4.1
6.9
8.6
10.3
13.8
17.2
20.7
27.6
55.2
72.4
99.3
103
138
414
86
133,
1f路
12－剖ch 29阪＞KB.
12-inch 298T-KB
8100, 5200, 5250, S251C. 5就泊. S301F. & 5400
73帽， Y600, Y890, Y692, Y69侧， Y6阔， Y695
75A, 10-inch ~陆C-KB＜”. 10-阳ch 298T-K811J, 11昏。
64. 67, 92日， 8-ineh 29以：；－KE酬，
8-inch 298T·KB!”, 912N, R522, 627F
” C, 92S ，能W,95”， 95L
67H. 99( ’ l, 109&-EGR（η
6-inch 399A
1 t＇。中阳ell 399A
298H-El((1l, 31Q<,)
630, 631
827
1301
ω∞
’ 」＂ ir蝠’回回剖’·阳帽’也翩翩悔。wnor 曲
，．”咽.wt自...，耐拖－··
’
44
Gas Technician 2 Training - Module 15
C Canadian Standards As四ciation
PRESSURE REGULA TORS
UNIT 1
Bulletin
71:006
page 3
Table 3. Inlet Pressure Ranges for
V匈'JOr
Recovery Regulators by Type Number
Nu町、ber
Regulator Type
M阳t
Pre91ure Ranae
1290
1 ／ιinch
wc to 7-inches psig (0.017 to 480 mbar
Y695
2斗nches
we to 7-inches psig (6. 7 to 480 mbar)
Y696
2-inches we
to 弘inches
psig (6.7
t。 480
笠!!tJ旦始皇
1, 2, 3, 4, 6
3/4, 1
mbar)
1-1/2, 2
Table 4. Inlet P附ssure Ranges for Vapor Recovery R吨ulators in Ascending Order
Inlet Pressure Range
Reaulator Type Number
1/4-inch we to 7-inct回S psig (0.017 to 480 mba叶
1290
2-inches we to 7-inches pslg (6.7 t。 480 mbar)
Y695, Y696
Table 5. Pressure Equivalents
Inches of
p。””ds per
Water C剖umn Square Inch
(Inches we)
(P 刷｝
3.5
7
10.5
14
21
28
Table 6. Flow Conversions
Ounces per
Inches 。f
Sq＂；~：；：nch
11！~＇饵
·cury” g)
0.12
0.25
0.38
0.5
0.75
0.25
2
4
6
8
12
16
口，51
0.76
1.02
1.53
2.04
”’lfibar
(n由ar)
8.62
17.24
25.86
34.48
51.71
68.95
to
T。 c。nve”
Standard Cubic Feet BTU per Hour<η
per Hour
Normal Cυbic Meters per H曲，r
(60"F and 14.7 psia) (O"C and 1.01325 bar, absolute)
BTU per Hour
Standard Cubic Feet per
(60°F and 14.7 ps阳｝
Multi副v
bv:
1()()()(1)
0.0268
H饵，而｝
Normal Cubic Meters Standard Cubic Feet per 抖。ur
per Hour
(6Cl°F and 14.7 psia)
kCl°C and 1.01325
bar, absolute)
’， Con咽rs阳、咽lid 四咐，。r natural gas ~0.6 s间αK gt8V<忖｝
。.001!1l
37.31
Table 7. Pressure Conversions
除这
Psi
lnct回S
WC
F’副N咱S
Inches of
per
W副町
Squa帽
(P嗣1
Column
(Inches
WC)
1
0.0361
Inch
Feet of
Water
Column
Inches
。f
Mercury
Ounces
P田 Sq1瞄啤
‘
K蝇。grams
Bar
Millibar
(mbar)
Kil。pncals
Incl
(k Pa)
”’ Squa”
Ce俯卧饵，．蝠，
＇~：~·
(lnct帽·
27.68
2.307
2.阅6
16
0.06895
68揭
6.895
0.0703
1
0.8333
0.07355
。.5776
。.002491
2491
0.2491
0.00254
”。1
｛臼I)
(kg/cm吨
Feet WC
。.4335
12
1
0.8826
6.936
0.02989
29.89
2.989
。.0305
Inches Hg
0.4911
13.60
1.133
1
7.858
0.03386
33.86
3.386
0.03453
Osi
。.0625
1.73
0.144
0.127
1
0.00431
4.309
。.4309
Bar
14.50
401.5
33.45
29.53
232
1
1000
o.。“‘
100
1倪。
mbar
0.0145
0.4015
0.0领45
o.o刽53
0.232
。.001
1
0.100
0.00102
Kilopascals
0.1450
4.015
0.3345
0.2953
2.32
。.01
10
1
0.0102
393.7
32.81
28.96
227.5
0.9807
980.7
98.07
kg/cm•
’4.22
Gas Technician 2 Training- Module 15
Standards Association
© Canadian
45
PRESSυRE
REGULATORS
Table
pe「at1ng
P「essure
8
UNIT 1
Regulator Capacities in Scfh of 0.6 Specific Gravity Natural Gas
I lnle升
I pressure
e「
l 「egulating
Number regulating
capacities
ca paαities
$402
265
S402
265
S102
410
S102
615
Y600
1,050
Y600
S252
280
S402
470
S402
470
S102
1,050
S102
640
Y600
1,200
Y600
1,050
1098EGR
6,600
S252
400
8402
840
S402
840
8102
1,400
8102
1,000
Y600
1,425
Y600
1098EGR
8252
400
S402
11,300
S252
1400
IS102
1,400
Y600
1,050
Y600
1,425
S102
1,150
S402
1,440
S402
1,440
1098EGR
21,000
只522
455
6102
1,400
Y600
1,050
Y600
1,425
S402
1,800
1098EGR
30,000
1::: J:::
46
Gas Technician 2 Training - Module 15
。 Canadian Standards Association
PRESSURE REGULATORS
UNIT 1
Regulating capacities
lncfi Bo~y
｜俨en
1171
S302
S102
S201
S202
7308
500
675
2,500
2,500
2,900
8301
S302
S201
S202
7308
1,400
1,400
3,600
3,600
6,000
S302
7308
8201
S202
99
66
133L
166
500
2,900
3,300
3,300
5,000
9,000
12,000
14,800
S302
7308
S201
S202
99
66
133L
1098EGR
1400
6,000
6,000
6,000
7,500
13,500
17,000
22,300
25,000
S302
7308
S201
S202
66
99
133L
166
1098EGR
3,200
丁 0 000
10 000
10,000
10,300
12,000
32,000
38 700
42,000
8302
7308
S201
S202
66
99
133L
166
3,500
，‘、，、，
3,500
7,000
7,000
7,750
1,400
l~lncFi 闷
!Maximum
Regulating
Capacities
I 1098EGR I 133,000
,
’‘’马d ‘圃，
S302
S201
S202
7308
S102
IM
'
才 66
S301
S302
S201
S202
7308
5oa
10，。∞
10,000
10,000
10,300
19,000
48,000
58,000
63,000
1098εGR
S302
S302
7308
S201
S202
S201
S202
99
133L
166
1098EGR
S301
S302
7308
S201
8202
S302
133L
7308
S201
8202
,
2,600
9,000
俑，000
10,000
’ 10,000
99
35,000
399A
92,000
1~到6
100,000
1098EGR
1.t2,000
Gas T~nician 2 Training -
~odule
© Canadian Standards Association
15
47
Unit2
Overpressure protection
Purpose
Anove叩ressure
condition occurs when the gas piping system pressure
exceeds the pressure regulator setpoint. If the pressure regulator
should happen to fail, components downstream that are not rated for
the pressure upstream could be damaged. Due to the importance of
protecting the system, ove叩ressure protection should be a prima可
consideration in the design of any piping system.
Learning
objectives
1. Describe overpressure protection.
2. Describe relief valves.
3. Describe security shutoff systems.
4. Describe the function and types of monitors.
Gas Technician 2 Training - Module 15
© Canadian Standards Association
49
Topics
1. lntroducti。 n ......................................…...............…................. 51
2. Relief valves ..................................….........….......................... 53
Pressure buildup . ...........…………….
...................... ········· ... 53
Pop-type relief valves ....‘….............…………….......……·…................ 54
Direct－。perated relief valves .. .. ....... ... . . . .......... . .....................……... 55
Internal relief valves............. . . ........…...…………............…........... 57
Sizing relief valves ....…·…........….......…….........…..........…….. ········· 59
Venting relief valves.. . . ........... .. .. ...........…. ················· ................. 59
3. Security ......................…..........…............……........................... 61
Shutoff systems ............……………·……………………………·… 61
4. Monit。rs ....”…·····································…...............…............... 63
Upstream wide-open monitors .............…………............. ········· .. 63
Downstream wide-open m。nitors .................…............…………………...... 64
Working monitors ......................……………………........….. ·········· ...... 64
Assignment 2............................................................................... 67
50
Gas Technician 2 Training - Module 15
。 Canadian Standards Association
TOPIC 1
Intγo duction
Overpressure occurs when the pressure of a system is above the setpoint of
the device controlling its pressure. It shows that there is some failure in the
system, and ifthere is no protection against this, it can cause the whole
system to fail. Thus overpressure protection is a primary consideration in
the design of any gas piping.
The objective in providing overpressure protection is to maintain the
pressure downstream of the regulator at a safe maximum value. This means
identifying the weakest part in the pressure system, then limiting
overpressure to that component ’s maximum pressure rating.
To identify the most vulnerable components, examine:
•
the maximum pressure rating of downstream equipment
•
the low pressure side rating of the main regulator
•
the piping.
The lowest maximum pressure rating of any of these components is the
maximum allowable pressure.
The worst-case conditions of regulator failure are those in which the
regulator fails in either a fully closed or wide open position.
•
A 如•lly
•
A fully open regulαtor
A fully open regulator causes excessive pressure conditions that are
damaging to equipment and create a potentially dangerous situation.
These conditions can be controlled by using some form of overpressure
protection.
closed regulator
A fully closed regulator produces an underpressure condition. This is
not damaging to equipment, but may create dangerous conditions in the
combustion chamber. This condition can be detected with pressure
switches which will shut the equipment down until gas pressure is
restored.
Types of overpressure protection include:
•
pressure relief using relief valves
•
momtors
•
automatic shutoff.
Gas Technician 2 Training - Module 15
© Canadian Standards Association
51
OVERPRESSURE PROTECTION
UNIT2
There are three selection criteria to evaluate the various methods of
overpressure protect10n:
•
Continuity
How important is uninterrupted downstream flow?
Where the
excess卢ow
is directed
Is the excess flow directed to the atmosphere, or is it contained in the
system?
•
System failure warning
How to indicate that the system has failed and is operating on the safety
system?
With this in mind briefly examine the advantages and disadvantages of the
three methods of overpressure protection as shown in Table 2-1.
Table 2-1 Advantages and disadvantages of different methods of overpressure protection
Relief valve
Monitor
Automatic shutoff
Continuity
Provides continuity of
service.
Provides continuity of
service as one regulator
takes over when another
fails.
Does not provide
continuity.
Ex臼ss
Normally released to the
atmosphere. Depending
on the nature of the gas
and the location of the
valve this can be
danger。us. It 明n also be
noisy and create
unpleasant odours.
No gas is vented to the
Any excess gas pressure
is contained in the
system.
0钝en
Not very clear as the
monitor may maintain
system pressure so no
effects are sensed
downstream. Visual
inspection and slightly
『ising pressure are
possible indi臼tions.
flow
Failure warning
52
given by the n。ise
and odours as the gas
vents to atmosphere. This
may go unnoticed in
is。lated areas.
atm。sphere.
Very clear since the
system shuts down.
Gas Technician 2 Training - Module 15
© Canadian Standards Association
TOPIC
2
Relief valves
Relief valves maintain the pressure downstream of a regulator at a safe
maximum value using any device that vents fluid to a lower pressure
system (often the atmosphere). They are considered to be one of the most
reliable types of overpressure protection available and are popular for
several reasons:
.
.
.
Pressure
buildup
they do not block the normal flow through a line
they do not decrease the capacities of regulators they protect
the noise and the odour act as an alarm if they vent to atmosphere.
A relief valve has a setpoint at which it begins to open. For the valve to
如lly open the pressure must build up to some level above the setpoint of
the relief valve.η1is is known as pressure buildup over se伊oint, or more
simply, buildup (Figure 2-1 ).
、、、卢
Pressure
buildup
。』3的的。』内地
Flow
Figure 2-1 Pressure buildup
Relief valves are generally available
.
.
.
.
in 岛田 types:
pop句pe
direct-operated
pilot-operated
internal relief valves.
Gas T~nician 2 Training - M<x.iule 15
© Canadian Standards Association
53
OVERPRESSURE PROTECTION
Pop-type
relief valves
UNIT2
Pop-type relief valves are essentially on-off devices. They generally
operate in either the closed or wide-open position as shown in Figure 2-2.
Loading
spring
Poppet
Wide-open
position
Closed
p。sition
Figure 2-2 Pop-type relief valve
Operation
Pop-type designs register pressure directly on a spring-opposed poppet, as
shown in Figure 2-2. The poppet assembly includes a soft disk for tight
shutoff against 由e seat ring.
When the inlet pressure increases above the relief valve ’s set pressure, the
poppet assembly is pushed away 丘om the metal seat. As the poppet rises,
pressure registers against a greater sur也ce 缸ea of 也e poppet. This
dramatically increases the force on the poppet. So the poppet tends to travel
to 由e 缸Uy open position until the ove甲ressure condition is reduced.
This style of relief valve does not throttle the flow over a pressure range
· and, because of its on-off nature，挝 may create press山e surges in the
downstream system.
If the relief valve capacity is significantly l缸ger 也相也e failed regulator's
capacity, the relief valve may overcompensate each time it opens and
closes, causing downstream pressure to become unstable and to cycle.
54
Gas Technician 2 Training -
Modu怡 15
。 Canadian Standa 『dsAssocia髓。n
UNIT2
OVERPRESSURE PROTECTION
Setpoint
The setpoint of a pop-type valve cannot be adjusted by the user. This is a
safety measure that prevents tampering with the relief valve setpoint. A
pinned spring retainer, initially loaded by the manu也cturer, keeps the
spring in position.
Application
This type of relief valve may be used where venting to the atmosphere is
acceptable and where relief pressure variations are allowable. It is low in
cost and its small size allows installation where space is limited.
Directoperated
relief valves
Direct帽operated relief valves provide throttling action, and require less
pressure buildup to open 出e relief valve. This relief valve looks like
an ordinary direct-operated regulator except that it senses u~stream
pressure rather than downstream pressure. It also uses a spring-close
action and contains the same essential elements as a direct” operated
regulator (Figure 2-3):
•
A diaphragm measures the system pressure.
The loading spring provides the initial load to the diaphragm and is
used to establish relief setpoint.
The restricting element throttles the flow.
口
nb
{}
m
Figure 2-3
Gas Technician 2 Training - M创ule 15
© Canadian Standards Association
Lower-pressure area
(usually atmosphere)
Direct－。perated
relief valve
55
OVERPRESSURE PROTECTION
UNIT2
Pitot-tube relief valve
While some direct-operated relief valves require s由iificant pressure
buildup to achieve maximum capacity, others with the Pitot tube can often
pass high flow rates with minimum pressure buildup.
The Pitot tube can decrease pressure buildup over setpoint. When the valve
is opening, high fluid velocity through the seat ring creates an area of
relatively low pressure. Since the low pressure area is located near the end
of the Pitot tube, fluid will be drawn out of the volume above the
diaphragm which helps to open the valve. The result is increased relief
valve capacity and reduced pressure buildup.
mg
-
BLeu
4aAUnH
nunV
nu
-
.
nH
Pitot
tube
Valve
disk
Figure 2-4
Pitot-tube田operated
relief valve
Adjusting the setpoint
白ie
setpoint of the direct-operated valve can be adjusted by removing the
cap and turning the adjusting nut clockwise to increase, and
counterclockwise to decrease, the relief pressure.
Application
Direct-operated relief valves are commonly used in natural gas systems
supplying commercial enterprises like res阳山ants and laundries, and in
industrial furnaces.
56
Gas Technician 2 Training - Module 15
© Canadian Standards Assoc陆目on
OVERPRESSURE PROTECTION
UNIT2
Internal relief
valves
Regulators 由at
include internal relief valves may eliminate the
requirement for external ove甲ressure protection.
An internal relief valve contains:
a loading element (its own light-loading spring)
a measuring element (it shares the main measuring diaphragm)
•
a restricting element (located in the centre of the main measuring
diaphragm). The restricting element is composed of the main
diaphragm and the relief valve seat which are pressed together by the
relief valve loading spring.
Operation
When no gas is flowing and the downstream pressure is normal, bo白白e
internal relief valve and the valve disk are closed (Figure 2-5a).
During normal operation of the regulator, downs位earn pressure is sensed
by 也e underside of the main diaphragm while a loading force is applied by
the main loading spring to the top side. The small loading spring of the
relief valve has no effect on normal regulator operation.
Changes in downstream pressure alter the force applied to the underside of
the main diaphragm. This produces movement in the position of the
diaphragm and a corresponding change in the position of the disk and seat
in the restricting element.
Overpressure conditions develop when the downstream pressure increases
above the setpoint of the regulator. This is usually caused by dirt lodging
between the disk and seat, or by internal component failure. When an
ove甲ressure condition develops, the downstream pressure lifts the main
diaphragm until the relief valve seat comes in contact with the pusher post
(Figure 2-5b). At this point, any increase in downstream pressure
compresses both the main and reliefloading springs. When sufficient 岛r臼
is applied, the main diaphragm and the relief valve seat will separate and
allow gas flow to pass through the centre opening in 由e diaphragm to 也e
relief vaive opening.
The amount of pressure buildup over setpoint will depend on the spring
rate of the relief valve spring and the size of the main regulator orifice.
Remember, to keep pressure build叩 to a minimum, the main regulator
qrifice should be the smallest size that will maintain the maximum required
flow rate.
、、白卢
Gas Technician 2 Training - Module 15
© Canadian Standards Association
57
OVERPRESSURE PROTECTION
UNIT 2
Internal relief
valve
Seat ring
台
(a) With gas not flowing and d。wnstream
pressure n 。rmal
¢=
台
(b) Internal relief in operation due t。
d。wnstream
high
pressure
Copyright Fisher Contr>ls International Incorporated
Reprinted with permission
Figure 2-5 Internal relief valve
Adjusting the setpoint
τ'he
loading force of the relief valve loading spring is not adjustable. The
relief valve setpoint is determined by the combined spring rates of the
relief valve and regulator springs. 卫iis design generally requires
significant pressure buildup to reach its maximum relief flow rate.
58
Gas Technician 2 Training - Module 15
© Canadian Standards Assoc国ion
OVERPRESSURE PROTECTION
UNIT 2
Application
Internal relief valves are used in house service regulators, line pressure
regulators, and appliance regulators for industrial equipment.
Sizing relief
valves
The size of the relief valve depends on the system. Relief valves are made
for different applications and operate in different ways; they also handle
different pressure ranges. Once the type of system is established, and the
pressure ranges that the system can safely handle, consult manufacturers'
tables before choosing a relief valve.
Note that you should be able to set the pressure on a pressure relief valve at
a higher value than the pressure on the regulator, but it should still be in the
range of downstream pressure limitations.
Venting relief
valves
Some aspects of venting gas pressure systems were discussed in Unit 1.
Venting of relief valves is also covered extensively in the Code. Check the
Code for all the relevant regulations before planning a venting system for a
pressure relief valve.
In particular, sizing relief valve vents is covered in Clause 5.5 of the
B149.1 Code. The manuf机turers ’ rule of thumb for sizing relief valve
vents is that it must be the size of the outlet if the termination point is less
than 10 ft (3 m) away from the relief valve. For eveηr additional 10 ft (3 m)
further away it is, the vent outlet must increase one size. A 90。 elbow has
an equivalent length of 3 ft (1 m). For long lengths, contact the
manufacturer or the authority having jurisdiction.
、、』卢
Gas Technician 2 Training- Module 15
Standards Association
© Canadian
59
TOPIC
3
Se cuγity
Shutoff is one of the simplest regulation systems for provid面g
ove叩ressure protection by containment. It uses one main regulator and a
manual reset shutoff valve, sometimes called a security system.
Shutoff
systems
Automatic shutoff systems are generally used by the utility company for
single-user applications. They provide containment of the process gas
during a failure, but interrupt the service. They must be manually reset.
Operation
The pressure in 由e system is controlled by the main regulator and
monitored by the shutoff valve.ηie shutoff valve is constructed with a
main diaphragm, a loading spring, and a valve disk and seat. The valve disk
is latched 扭曲e open position. The bottom of the diaphragm is exposed to
the regulated downstream pressure either directly or through a sense line,
both types shown in Figure 2-6.
<=
Outlet
(a) Direct sensing shuto何
Figure 2-6
、、－，
Gas Technician 2 Training 由 Module
©Canad阳n S恼ndards Assoc阔前on
15
叫
（
γ
<=
<=
(b) Shut。，ff with separate sense line
Shuto何 valves
61
OVERPRESSURE PROTECTION
UNIT2
If the regulated pressure exceeds the setpoint of the shutoff valve, the
pressure increase against the bottom of the main diaphragm unlatches the
valve disk, which swings closed against the seat to block off the flow of
gas. The high-pressure condition must be corrected before the shutoff valve
can be manually reset. With some models, a bypass must be installed
around the valve to balance pressure on each side of the disk before it can
be reset.
Adjusting the setpoint
Shutoff valves are designed for low- and high-pressure applications, with
several pressure ranges for each. The setpoint can be adjusted by turning
the adjusting nut to alter the compression of the loading spring.
Application
Many gas distribution companies provide an extra measure of protection to
places of public assembly. In these cases, the shutoff valve is often th已
extra overpressure protection device installed. Shutoff valves are also
commonly used by boiler manufacturers in combustion systems.
62
Gas Technician 2 Training - M创ule 15
。 Canadian Standards Association
TOPIC 4
Mo nitoγs
Several different types of monitoring systems are available. They can be
divided into two broad classifications:
•
wide-open monitors-upstream and downstream types
•
working monitors.
The monitor system makes use of two regulators that sense downstream
pressure. One of the regulators is known as the monitor and the other as the
worker. Under normal operating conditions the monitor regulator will
always be wide open because the monitor regulator setpoint is slightly
higher than the worker regulator setpoint.
A disadvantage of wide-open monitoring systems is that the monitor is
rarely exercised. As a result, it may become bound or sluggish, or damaged
in such a manner that it cannot provide tiβt shutoff when required.
Working monitors minimize 也ese problems by taking the pressure
reduction in two cuts and allowing both regulators to operate.
、、、－
Upstream
wide-open
monitors
The term upstream wide-open monitor refers to the location of the monitor
regulator in reference to the worker regulator. The monitor regulator is
located upstream of the worker regulator.
Operation
Figure 2-7 shows the operation of an upstream wide-open monitor
system where upstream regulator A monitors the pressure established by
regulator B.
A
Monitor
regulator
B
Worker
regulator
Figure 2-7 Upstream monitor wide-open
Gas Technician 2 Training- Module 15
© Canadian Standards Association
63
OVERPRESSURE PROTECTION
Downstream
wide-open
monitors
UNIT2
The only difference between upstream and downstream wide-open monitor
systems is that the function of the two regulators is reversed, as shown in
Figure 2-8. This time the monitor (standby) regulator is downstream of the
worker (operator). Systems can be changed 丘。m upstream to downstream
monitors and vice versa, simply by reversing the setpoints of the two
regulators.
A
B
Worker
regulator
Monitor
regulator
Figure 2-8 Downstream
Working
monitors
m。nitor
wide-open
Working monitors use design elements from both series regulation and
wide-open monitors. In a working monitor installation, the two regulators
work continuously as series regulators to take two pressure cuts
(Figure 2-9). Because both regulators are working, both are less likely to
become clogged, sluggish, or stuck.
Figure 2-9
叭forking
monitor
The worker pilot is connected as in series regulation and controls the
intermediate pressure Pintennediate· Its setpoint is at some intermediate
value that allows the system to take two pressure drops.
64
Gas Technician 2 Training - Module 15
© Canadian Standards Association
OVERPRESSURE PROTECTION
UNIT 2
The monitor pilot is in series ahead of the worker pilot αnd is connected so
that it senses downstream pressure. Its se伊oint is set slightly higher than
the required pressure.
When both regulators are performing properly, downstream pressure is
below the setting of the monitor pilot, so it is fully open, trying to raise
system pressure. Standing wide open, the monitor pilot allows the worker
pilot to control the intermediate pressure. As demand changes, the
downstream regulator adjusts flow and causes some change in the
intermediate pressure. The worker pilot on the upstream regulator senses
the change in the intermediate pressure and causes a repositioning of the
upstream regulator. In this way both regulators are allowed to work in
response to changes h 由e pressure demand.
Gas Technician 2 Training - Module 15
©Canadian S恼ndards Associa苗。n
65
UNIT2
OVERPRESSυRE PROTECTION
Assignment 2
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
What is the maximum allowable pressure downstream of a pressure controlling device?
2.
What are the most commonly used ove甲rotection devices?
3.
Does a relief valve decrease a regulator ’ s capacity?
4.
What measures 也e system pressure when using a direct-operated relief valve?
5.
What types of overpressure protection incorporate a restricting element?
6.
If 也e type
7.
Does an automatic shutoff automatically reset?
8.
Which press田e applications 缸e automatic shutoff valves designed for?
9.
Which type of monitor, wide-open or working, is less likely to have operating problems?
Why?
of system and the pressure ranges safely handled by the system are known, how
should a relief valve be chosen?
、、－
Gas Technician 2 T1『·ai『1ing - Module 15
C Canadian Standards Associa目on
67
Unit 3
岛f eters
Purpose
A gas technician routinely measures gas flow rates to determine
inputs. Calculating flow rates accurately requires a thorough knowledge of gas meter types, their operation, gas measurement standards,
and correction factors.
Learning
objectives
1. Describe types of meters.
2. Describe the care and handling of meters.
3. Describe installation procedures.
4. Determine gas flow rates.
＼、一
Gas Technician 2 Training- Module 15
©Canadian S幅ndards Association
69
Topics
1. Types of meters ..........................................…......................... 71
Displacement meters .................................…..........………......…...............71
Rate of flow meters .........….........…............................................................76
2. Care and handling of meters ....................”··”..........”........... 79
3. Installation procedures ....…”......................”··”··”··”··”··”.... 81
Placing of the meter ..…且.......………···············…….......…................................ 81
Meter bypass ..............................…·····································…·….......…........82
Leak testing the meter .......................……….....................…....................82
4.
De幅rmining flow rates …...........“......................................” 83
Characteristics of gas ........…………·········…··················….........…..................83
Absolute units of measurement ...….........................……………..................83
Standard units 。f measurement ......…...........…............................................85
Gas Law relationships .....................................….................…...................86
Calculating flow rates through meters ...........….....................….................... 89
Reading the meter ................................…....................……·······…...............89
H
Assignment 3 ”··”….........….........……..............….........….......…·… 93
70
Gas Technician 2 Training - Module 15
C Canadian Standards Association
TOPIC
1
Types of meters
Each piece of gas equipment is designed to produce a specific amount of
heat in the combustion chamber. This amount of heat is called the firing
rate or burner input. Gas regulations require that the burner input be
checked to ensure that it conforms to the equipment manufactur町、
specifications. These are found on the rating plate attached to the
appliance.
The common meters used in gas measurement may be grouped into two
categories:
•
displacement meters
•
rate-of-flow meters.
Displacement meters-measure the total quantity, or volume, of gas that
has passed through the meter at the time of the reading. These. types can be
adapted to provide rate of flow.
Rate-of-flow meters-measure the instantaneous gas flow rate. These
meters can have totalizers to provide total volume flow.
。 is placement
meters
Displacement meters operate on the principle of positive volumetric
displacement. A precise volume of gas passing through the meter is
measured.
Two common types are used in the residential and commercial markets:
diaphragm (bellows) meter
•
rotary (geared or lobed impeller) meter.
＼」－－
Gas Technician 2 Training- Module 15
© Canadian Standards Association
71
METERS
UNIT3
Diaphragm gas meter
The diaphragm gas meter (Figure 3-1) is 也e most 仕equently used gas
meter. It provides highly accurate readings over most of its range. It is used
mainly for residential and small commercial applications.
The drop in pressure when
the gas flows between the
meter ’ s inlet and outlet forces
the bellows action of this
meter. The greater the
pressure drop, the greater
the volume of gas flow
through the meter.
The diaphragm meter ’s
capacity is specified to reflect
a given pressure drop, called
the differential. Differentials
町e usually 0.5 inches w.c.
(125 Pa) and 2 inches w.c.
(500 Pa). Diaphragm meters
have capacities of up to
10 500 cu ft/h (300 m3届）
when the piping system
operates at less than 10
inches w.c. (2.5 kPa).
Figure 3-1 Diaphragm meter
The gas utility company uses many complex instruments to measure actual
flow rate. They then convert it into standard cubic measure for billing
purposes. When the flow rate is recorded under higher pressures, a
correction factor needs to be calculated for pressure.
ηie following 由ree
high pressure metering s~stems 缸e commonly used by
company; the location of the test dials on each instrument varies
with each one:
由e 回ility
Pressure factor measurement (PFM)
72
•
Base pressure index {BPI)
•
Base volume index (BVI)
Gas Technician 2 Ti『百i『1ing - Module 15
。 Canadian Standards Association
METERS
UNIT3
Pressure factor measurement (PFM)
The PFM system consists of a standard gas meter with a special regulator
that very accurately controls the gas pressure. It is normally used when the
gas pressures are either 2 or 5 psig (14 or 35 kPa) and the load is under
4000 cu ft/h (113 m3届）．
When reading the meter ’ s test dial, use a correction factor to calculate the
flow rate in Std cu ft岛 or Std m3 /h. The utility company arrives at a
predetermined correction factor by dividing local atmospheric pressure
plus working pressure by the required selling pressure. (This is covered in
Topic 4 of this Unit.)
The PFM correction factor is usually printed on a brass tag attached to the
meter inlet piping. An example of such a tag is shown in Figure 3-2.
Brass
meter tag
Figure 3-2 Brass meter tag
、、、‘－
Note
B吃fore
determining the flow rate to an appliance, clock the PFM meter test
dial, then use the correction/actor to calculate the flow rate in Std cu卢＇／h
or Std m3lh. Clocking the meter test dial is covered in Topic 4 of this Unit.
Base pre.臼ure index (BPI)
The BPI instrument is installed on meter sets where delivery pressures are
5 or 10 psig (35 or 70 kPa). As with the PFM instrument, it constantly
monitors meter gas pressure. It also has two additional feat山es:
It records the uncorrected volume of gas consumption at meter pressure
on a counter attached to the rear of the 坦白ument.
•
It constantly recalculates and corrects the volume to selling pressure on
a counter displayed at the front of 由e instrument.
The BPI test dial, shown in Figure 3-3 is located in the centre of the
instrument base, below the selling pressure consumption dial, and is
uncorrected.
、、白白d
Gas Technician 2 Tr百ining - Module 15
© Canadian Standards Association
73
METERS
UNIT 3
飞
Ci)
、
BASIC
PRESSURE INDEX
j
Consumption dial
Pressure indicator
Test dial at base
(through window)
Figure 3-3 Base pressure index
Determine the meter gas pressure by observing the indicator on the 仕untof
the BPI instrument. Use this pressure indicator to calculate the correction
factor (to be used in con unction with the test dial only).
Base volume index (BVI)
The BVI instniment (Figure 3-4苟且mctions like the BPI except 由at it
corrects to a selling temperature as well as to a selling pressure. Corrected
pressure and temperature selling indicators are on the 企ont of the
instrume时， with uncorrected consumption dials at 由e rear.
ηie
device in Figure 3-4b is replacing the BVI. It electronically calculates
corrected volume and pressure.
74
Gas Technician 2 Training - Module 15
© Canadian standards Ass<回ation
UNIT3
METERS
(a)
(b)
Figure 3-4 (a) Base volume index and (b) electronic c。rrector
The test dial is uncorrected, so after clocking the flow rate, use a correction
factor for temperat町e and press田e to determine the flow rate in standard
cubic measure. Note 由at the temperat田e correction factor is usually quite
small and may be.ignored for most clocking calculations.
Ro姐ry
gas meter
η1is
displacement type of meter, shown in Figure 3-5, is mainly used by
commercial or industrial customers. Rotary meters 缸e available with
pressure m由1gs of up to 1450 psig (10 000 kPa) and volume ratings of
175 to 105 000 cu Mi (50 to 3000 m3届）．
Figure 3-S
Ro饱ry
Gas Technician 2 Training - M。dule 15
。 Canad幅n
Standards As叙回ation
meter
75
METERS
UNIT3
Figure 3-6 shows the cross section of a rota可 meter at two stages of
impeller movement. The two impellers are synchronized to rotate within a
close-fitting housing. As the impellers 阳m they displace a fixed volume of
gas with each revolution, causing a slight differential pressure across the
rotor. This allows a measured volume of gas to be discharged through the
bottom of the meter.
A gear train transmits the number of rotations to a dial which displays the
gas volume discharged.
Inlet
Inlet
(a)
(b)
~abed
impeller
丁iming
gears
Figure 3-6 Cross-section 。f rotary meter shows tw。 stages 。f impeller movement
Rotary meters are oil filled, and the oil must be changed at least every two
years.
Rate of flow
meters
Rate of flow meters are referred to as “ inferential” meters because the
quantity of flow is determined by inference 齿。m interaction of the flowing
stream and a primary element, such as an orifice plate, inserted in the
stream.
。rifice
meters
Orifice meters are used 岛r measuring air and gas flows on combustion
systems. They allow the adj邵阳tents on nozzle mixing burners to be
simplified.
76
Gas T献：lmician 2 Training-Module 15
@Canadian S阳ndards Association
MεTERS
UNIT 3
The primary element in these meters is an orifice plate in the pipeline
which creates a differential pressure 由at varies in relation to the rate of
flow.
To obtain an accurate reading there should be a suitable straightening of the
gas flow upstream of the orifice.
Turbine meters
Turbine meters are used primarily by industrial customers and at city gate
stations where the flow of gas is large.
In a turbine meter a turbine wheel is kept in continuous rotation by the gas
stream. A secondary element, usually a revolution counter, measures 由e
total distance of travel of the gas past 也e primary device. Knowing the
cross-section of flow, the distance can be converted to units of total volume
passed. The rotor speed can also be converted into a flow rate reading.
In low gas flow situations, this meter loses its accuracy.
＼』卢
Gas Technician 2 Training - Module 15
@Canadian S阳nda『dsAssoci陆tion
77
TOPIC
2
Cajγeandhα·ndling
、、－
of meters
As with any sensitive measuring device, take care when handling the gas
meter-it may malfunction with· misuse and accuracy is imperative with all
meter work.
Note 由at
under the Federal Weights and Measures Act there are special
requirements with regards to the training of people who work with meters.
There are a number of basic points to caring for a meter.
•
It should always be kept in an upright position.
•
It should be properly secured when being transported.
•
When the meter is not in use 也e inlet and outlet connections should be
capped.
•
Meters should not be subjected to excessive pressures.
•
The meter must not be subjected to a vacuum.
•
No electrical grounds are to be connected to the meter.
Do not use an open flame to thaw or do other work on a meter.
、、－－
If a meter has been severely jarred, dropped, turned upside down or
otherwise damaged, re阳m it to the manufacturer.
＼、－
Gas Technician 2 Training - Module 15
standards Association
。 Canadian
79
TOPIC
3
Instαllαtion procedures
Gas meters are usually installed by the gas utility and so are not normally
responsibility of the gas technician. However, the location of meters
can affect the difficulty or e臼e of an installation. The gas technician will
also have to clock the meter to determine burner input rates (covered in the
next topic), and so the placing of the meter needs to be care臼Uy planned.
也e
Placing of the
meter
The location of gas meters is governed by the Gas Code. Refer to the
relevant sections to see 由e exact requirements. The gas utility normally
determines its exact location, but there is some flexibility in this matter,
and the meter may often be located to the satisfaction of the owne卫咀ie
difference between several alternative gas meter locations can be
significant, a证ecting piping and the venting of appliances.
There are three factors to consider when placing a gas meter:
accessibili可 to
the meter
compliance with Code, regulations and Utility requirements
•
protection 企om
passing traffic.
Meters may not be installed under combustible stairways, or in
unventilated places. They must also not be placed closer than 3 ft (900 mm)
to any source of ignition. The meter must be placed so 由at it is protected
from substances that may cause corrosion.
When connected ω 也e piping, the meter may not place any undue strain on
the piping. It must be properly supported.
A back-pressure re事ilator must be installed downstream of a meter if the
appliances connected to 也e piping from 由e meter may induce a vacuum in
也e met町. A check valve must be installed downstream of the met町 ifthe
appliances connected to the piping 仕om 由e meter may induce a back
pressure 扭曲e meter; or if the appliances 町e connected to a source of
oxygen or compres回d air; or if another 可pe of gas is used as a
supplementary gas, and may flow back into 也e mete汇
Always consult 由e local gas utility when planning a new in剑allation or
making a major alteration to an existing installation.
Gas Technician 2 Training- Module 15
ccanadian S恒ndardsAs回ciation
81
UNIT3
METERS
Meter bypass
A meter bypass is installed so that the meter can be serviced. In some larger
installations, the utilities supply a bypass around the meter. This can be
installed using rigid piping and fittings. In other instances, the utility will
have tees installed, and then use a portable bypass, consisting of a hose,
fittings and regulator. This portable bypass can then be temporarily
installed while the meter is being serviced.
Leak testing
the meter
Meters are leak tested by t~e utility prior to them being installed.
｛气
82
Gas Technician 2 Traiili咱－ Module 15
© Canadian Standards A辅∞幅画m
TOPIC4
Determining flow γαtes
Meters are used to determine flow rates, and so it is important to know how
to read and correct the readings from the meters in order to check the gas
input. The Code requires that each piece of equipment be checked and
a司justed to the correct firing rate. For this reason, apply the correction
factors for pressure and tempera阳re to determine the actual flow rates at
standard conditions.
Gas meters are usually rated in metric or imperial units, and a gas
technician should be able to convert between the two. Being able to read
and understand the reading on the meter will give 由e technician an
indication as to whether the appliance is operating properly.
Understanding how the Gas Laws apply to meas田ement of gas flow and
burner input allows for accurate calculations of flow rates 由rough gas
meters. Knowledge of the standards for gas measurement and how
pressur temperature relationships affect gas flow and burner input are
equally important.
•
、、－，
Characteristics
。f gas
Gas is an elastic substance. A volume of gas is veηsensitive to changes in
pressure or temperature.
The force of air particles continually striking each square inch of surface is
called atmospheric pressure. The mass of these p缸ticles gives them
weight. Gravity pulls them earthward, preventing their escape into space.
The weight of gas particles exerts a press山e. This weight presses with
equal force in all directions. Average a位nospheric pressure (or barometric
pressure) varies at different elevations above sea level, but 伽oughout
North America a fairly s切n也rd measure is set at 14. 73 psia ( 101.560 kPa).
ηus is at sea level.
Absolute
units of
町leasurement
For the purpose of this unit~ we will take the pressure exerted by 也e
.particles of air on a square inch of surface at sea level to be 14.73 psia
(101.560 kPa). This creates a density of air 副 0.0807 lb/cu ft (1.293 kg/m3)
at sea level. The densi可 is lower at higher elevations.
\-
Gas Technician 2 Training - Module 15
ccanad恼n
Standards Assc回捕。n
83
METERS
UNIT3
In setting standards for gas measurement, with atmospheric pressure
measured at 14.73 psia (101.560 陋的， the units of measurement for
pressure and temperature must also be expressed in absolute terms.
On the absolute pressure scale, zero is the point at which there is no
molecular movement to create pressure---in other words, a perfect vacuum.
On the absolute temperature scales, zero is the point at which there is no
molecular movement and therefore no heat.
Absolute pressure
All Gas Law pressure calculations must use absolute pressure
measurement. This means that all pressures measured in psig must be
converted to psia; and press田es in kPa (gauge) must be converted to kPa
(absolute).
For atmospheric pressure measured in imperial units, psig can be converted
to psia by adding 14.73.
Example
(imperial)
25 psig = 25 + 14. 73 = 39. 73 psia
345 psig
=
345 + 14. 73
=
359. 73 psia
For atmospheric pressure measured in metric units,
kPa (gauge) can be converted to kPa (absolute) by
adding 101.560.
Exαmple
(me衍ic)
35 kPa (gauge) = 35 + 101.560 = 136.560 kPa
(absolute)
70kPα （gauge)=
70 + 101.560
=
171.560 kPα
（α！bsolute)
(
84
Gas Tee却nician 2 Training-MOdule 15
。 Canadian Standards Association
、
METERS
UNIT3
Absolute temperature
All Gas Law tempera阳re calculations must be made using absolute
temperature. Rankine and Kelvin are the imperial and metric temperature
scales for measuring absolute temperature.
So temperatures measured in degrees Fahrenheit （。F) must be converted to
absolute temperature in degrees Rankine （。R). Temperatures measured in
degrees Celsius （。C) must be converted to absolute temperature in degrees
Kelvin (K).
To
convert 。F to 。R,
To
convert 。C
add 460.
to K, add 273.
Example
100。F
=100+460=560。R
225 。c
= 225 + 273 = 498。K
(imperi.α／）
Example
(me衍ic)
S阳ndard
..,
、』』
units of
measurement
When it comes to selling g邸， and thus using meters to clock 也e input on
.gas appliances, a standard gas pressure and temperature are used. They are
slightly different in the imperial and metric scale, so take care.
Imperial
Metric
Pressure
14.73 psia
101.325 kPa
Temperature
60。F
15°C
A gas utility sells gas measured at a standard pressure of 14. 73 psia at 60。F
in imperial measure,.or at 101.325 kPa at 15 。C in metric me邵阳e.
、、』－
Gas Tee茸mician 2 Traini『lQ-Mα拍脑
C Canadian Standards Association
15
85
UNIT3
METERS
Gas Law
relationships
Gases are generally invisible and tend to expand to occupy all available
space. There are also relationships between their pressure, temperature and
volume.
Pressure-volume
If a gas is compressed to a smaller volume, the pressure of the gas on the
container walls is increased if the temperature is held constant. We say that
pressure and volume are inversely proportional to each other when the
temperature of a gas is held constant. That is, at the same temperature, the
absolute pressure of a gas will double if 也e volume is compressed to
one-half, and vice versa. Using symbols we can write this as:
Example
Yi -
｝飞
v2
乓
Given 也at
V 1 is the original volume, P1 the original
V2 the final volume and P2 the final pressure,
solve the following problem.
press田e,
η1e pressure on 300 cu ft of air is increased 丘om50
psig to 100 psig. Calculate the air volume after
compression takes place.
Solution
瓦＝只×主
P2
& ’
v1 ＝ βOOcu 戎j
×
(50psig+14. 73) psia
+ 14. 73) psia
4ρ 00 psig
F二 ＝ 169.26 cu卢
86
Gas Technician 2 Training - Module 15
© Canadian Standards Association
UNIT3
METERS
Pressure-temperature
A change in pressure of a gas can be determined by its change in
temperature when the volume is kept constant. The higher the temperature
of the gas, the greater the velocity of each of its molecules, since its energy
level has been increased. This increase in molecular velocity, or speed,
increases the force the molecules exert on the container walls. This force
registers as a higher gas pressure if the volume is kept constant. The
pressure of a gas varies directly with the temperature of the gas ifthe
volume of the gas is kept constant. In symbols we can write this as:
Pi - Ti
P;
Example
Given 由at
T2
P1 is the original pressure, P2 也e new
pressure, T 1 the original temperature and T 2 the new
temp町at町、 solve the following problem.
If a piping system pressure tests at 50 psig and the
tempera阳re of the gas and piping is 70。F, calculate 由e
pressure in the piping system if the tempera饥.rre of the
gas and pipe 岛11to35 。F overnight.
Solution
P2 ＝旦旦2
飞
卫＝
(50psig+14. 73) psiα （35。F斗460)0R
e
。oop斗 460)0R
p、＝
64.73 psiax495。R
530°R
P2 =60. 46 psia-14. 73 psi，α
~
皂 ＝ 45.73 psig
、、－·
Gas Technician 2 Training - Module 15
@Canadian Standards Assoc国ion
87
UNIT3
METERS
Vol um e…temperature
If a gas is heated and allowed to expand at constant pressure, there will be
an increase in the volume of the gas relative to its temperature increase.
The volume of the gas varies directly with the temperature, provided that
the pressure of the gas remains constant. In symbols we can write this as:
问－vv
－T勺
za
Example
=
Given that T 1 is the original temperature, T 2 the new
temperature, V 1 the original volume and V 2 the new
volume, solve the following problem.
If the volume of a gas is calculated to be 500 cu ft at
70°C, calculate the new volume of this gas if the
temperature is raised to 300°C and the pressure is to
be kept constant.
Solution
V, _ !j_乏主
4
-
乓
V，－ β00 cuft） β00°C+27习。K
•-
(70。C+273）。K
V, _ 500 cu ft × 573。K
•343。K
v2 =853.3 cu卢
88
Gas T假如nician 2 Training - Module 15
© Canadian Standards Assc翩翩。n
UNIT 3
Calculating
flow rates
through
meters
METERS
When using a meter to clock a gas appliance input do the following:
•
Make s田e that the appliance being clocked is the only appliance in
operation. If necessary, shut off the gas flow to all other appliances.
•
Make sure 由at 也e appliance is firing continuously throughout the
clocking period. Avoid taking measurements immediately after startup.
Take readings after about 10 minutes of continuous operation.
Check the units of measurement of the meter.
•
Reading the
meter
Clock the meter two or three times and use 也e average.
There are tw。可pes of meter reading displays:
•
Dial type
The dial type are read according to 由e manufactur町、 design of the
display.
Direct reading type
Direct type of meters are easier to read than dial types because the
actual reading is displayed as a number indicating cubic metres or
cubic feet of gas.
Information on reading 也e meters is available 丘。m the local gas utility.
Dial type meter
There are two types of dials on a dial type gas meter:
•
Consumption dials
Consumption dials indicate the amount of gas which has been
consumed and provides information to the gas utility for billing
purposes.
•
Test dials
Test dials 缸e used to determine 由e input to appliances, and to indicate
if 也ere are any downstream leaks 坦白e gas line.
Figure 3-7 shows a typical dial type gas meter, and how 由e dials are read.
figure shows a meter that measures in cubic feet. Meters may
also me臼ure in cubic metres.
Note 也at this
、、－，，
Gas Technician 2 Training - Modu悔
Cl Canadian S阳市dardsAs割:>elation
15
89
METERS
UNIT3
③
③
Uζ￥λCUBIC
队把t))
FE盯
飞也二~
TEMPERATURE
、民、
COMPENSATED
＼」一 Test
dials
Figure 3-7 A dial type gas meter
On the meter shown in Figure 3- 7, every complete revolution that the test
dial on the left makes represents half a cubic 岛ot of gas. The dial on 也e
right measures two cubic feet of gas with every revolution. Once again,
check the meter to see the units of measurement.
Actual flow rates
When gas pressures 町e below 0.5 psig (3.5 kPa), no compensation is
needed for 也e e他cts of temperature and pressure. The following formula
is used to calculate the flow rate.
y 一
2J 一
οvE
KU
nuAU×-
= -- fs
Where:
QMV
Flow rate in cu 武岛 orm3届
AUAU
Seconds per hour (constant)
Volume of test dial in cu ft or m3
t
Example
Solution
90
Time per revolution of test dial in seconds
Determine 由e flow of natural gas 白rough a gas meter
where the test dial is 0.5 cu ft and the time for 1
revolution of the test dial is 36 seconds.
Q-3600 × 0.5
一一
36 s
=50cuft/h
Gas Technician 2 Training - Module 15
。 Canadian Standa叫s A捕。ciation
METERS
UNIT3
Flow rates with pressure (volume)
compensation
When gas pressures exceed 0.5 psig (3.5 kPa), the flow rates indicated by
the meter ’ s test dials must be corrected for pressure to show the true flow
rate.η1en use the following 岛rmula to calculate the flow rate.
Q＝［呼吁［主~］
Where:
、、－
Q
Flow rate (cu 企h orm3岛）
3600
Seconds per hour (constant)
V
Volume oftest dial (cu ft or m3)
t
Time per revolution oftest dial (in seconds)
Pa
Local a阳1ospheric pressure (psia or kPa)
pw
Working pressure of gas in meter (psia or kPa)
ps
Standard pressure (14.73 psia or 101.325 kPa)
Example
ηie
Solution
Q=[36~二~］［14.记江：产）
2 cu ft test dial takes 18 seconds to complete one
revolution. Calculate the flow rate to a burner in
standard cubic feet if the working pressure in the
meter is 5 psig and the local atmospheric pressure is
14.35 psia.
=400cuft/h × 1.313
=525.44 cuftlh
＼』－’
Gas Technician 2 Training - Module 15
Standards A揭∞刷m
。 Canadian
91
UNIT3
METERS
Flow rates with pressure (volume) and
temperature compensation
When temperature is a factor in measuring flow rate with gas pressures
over 0.5 psig, use the following formula to calculate the flow rate.
Q＝［年！［平］［1]
Where:
飞
Base
temperature ( 60。F or
T
Temperature of gas at meter in absolute units
Example
15 。C
in absolute units)
A 5 cu ft test dial takes 20 seconds to complete one
revolution. The local atmospheric pressure is 14.55
psia and the pressure of the gas 面 the gas meter is 10
psig. 咀1e temperature of the gas in the meter is 45 。F.
Calculate the rate of flow to the burner in standard
cubic feet.
Solution
Q=[3气ζ严l [145~~；；二叫［~］
=900 cuftlh × 1.66 × 1.02
= 1544.49
Std cu ft/h
The local weather bureaus generally repo此 barometric pressures that are
corrected to sea level. In 也e above equation the actual barometric pressure
must be used. This can be obtained from the weather bureau.
92
Gas Technician 2 Training - Modu幅 15
@ Canadian Standards Association
METERS
UNIT3
Assignment 3
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
Name two types of displacement meters.
2.
Which meter corrects for temperature and pressure?
3.
Which meter displays the correction factor .on a brass tag?
4.
Does the Base Pressure Index (BPI) correct the test dials? Do the Pressure Factor
Measurement (PFM) or Base Volume Index (BVI) correct test dials?
5.
If the pressure of a gas increases, what happens to 由e volume?
6.
If 也e tempera阳re
7.
If 由e
8.
Whatare 由e
9.
At what pressure are correction factors used when clocking 由emeter?
of a gas is increased what happens to the pressure?
temperature of a gas increases what happens to the volume?
test dials on a meter used for?
、、－
Gas Technician 2 Training - Module 15
Standards Assoc恼Ilion
@Canad幅n
93
METERS
UNIT3
10. Write the standard clocking formula for determining flow rate through a meter for gas pressure
less than 0.5 psig.
11. 认Trite
94
the clocking formula used for gas pressures greater than 0.5 psig.
Gas Technici~n 2 Training - Mod~le 15
© Canadian Standards Association
Unit4
Fuel containers
Purpose
Propane gas equipment is normally supplied 丘om either a cylinder or a
tank. To ensure a steady supply of gas, the container and accessories
must be sized and installed to meet the appliance needs under all ternperat町e and weather conditions.
Learning
objectives
1. Describe cylinders, tanks and accessories.
2. Describe how to size and install cylinders and tanks.
飞、‘－
Gas Technician 2 Training - Module 15
C Canadian Standards A揭ociation
95
Topics
1. Cylinders, tanks and accessories .................…........…......... 97
Cyhnders ............………………………………...................... 97
Tanks .......................…...………………...………··阳........................... 102
2.
Sizing and installing cylinders and tanks. …...................... 105
Pr。pane vaporization. ………...巫…··－·．．．．．，．．．．．．．．．．··…········……. 105
Sizing a container ............‘……………-…··-,.................,.….............. 107
Liquid withdrawal connections .......... ...............….........…….................. 113
Installation clearances ........………....……. ·····…·-……………·“.. . .. 114
Testing propane systems .....………......…………….. ...…........... 115
Assignment 4 .........................................................…................’ 117
Appendix A to Unit 4 ............”.........….......….........…................. 119
Vaporization rates for tanks and cylinders
Appendix B t。 Unit4 .......…....................................................... 121
Installation clearances for tanks and cylinders
96
Gas Technician 2 Training - Module 15
© Canadian Standards Association
TOPIC
1
CylindeγS, tα·nks α＇ nd
。ccessories
A major difference between natural gas and propane is how the fuel is
supplied. Natural gas is normally supplied 企om a natural well. It travels
企om the well through a large pipeline to a city or town gate station
operated by local utility. From here it is distributed to each building via
service piping. It passes through a meter set be岛re it reaches the consume汇
A steady supply of natural gas is assured if the piping and tubing systems,
as well as the required pressure regulators are operating correctly.
For propane, sufficient storage capacity is required to meet the total
demand of installed appliances and equipment, especially during cold
weather. It is 也us extremely important to select the coηect propane
contamer.
Propane comp缸lies normally lease propane tanks and cylinders to
customers, and then provide a filling service on the tank and an exchange
service on the cylinder.
Due to the need for safety, ~ number of standards and regulations are in
place which govern the ty肘， location and size of propane storage
containers. Refer to the Bl 49.2 Propane Storage and Handling Code for
these requirements.
Propane cylinders are intended for transportation both empty arid filled,
and tanks 缸e intended to remain stationary once 也ey are placed in service
and filled.
Cylinders
The B149.2 Code states 由at all cylinders must be fabricated, tested,
inspected and legibly marked in accordance wi由 CSA Standard B339 and
the Transportation of Dangerous Goods Regulations of Transport Canada.
Refillable cylinders may only be re-used without re-examination .and
testing within 10 years of the time of manufacture. After 由is time,
cylinders must be reconditioned and properly purged before being filled for
use.
Gas Technician 2 Training- Module 15
@ Canadian Standards Association
97
FUEL CONTAINERS
UNIT4
Cylinders come in a variety of sizes. The most common cylinder used on
outdoor appliances such as barbecues is the 20 lb cylinder. For most other
applications the most common cylinder size is 100 lb. Figure 4-1 shows the
components of a typical propane cylinder.
／ζNeck ring
Se『vice valve
- with integral
pressure relief
device
Cylinder
Figure 4斗
Sizes
of propane cylinders
A independent service valve controls the flow of gas out of the container.
This 句rpe of valve is found on both a propane cylinder and a propane tank.
The outlet of the service valve 1s called a servi臼 connection.
m1＼＼句
Sh川
hmmAU
itnnE
／阳附
件σ
Value outlet
Hex nut
Figure 今·2
POL thread for vapour servi臼
Vapour service connections usually have a POL (Prestolite) threaded
connection (Figure 4-2). The POL fitting is unique to vapo田 service and
cannot accidentally be connected to a liquid line.
In addition, vapour service connections used for outdoor cooking
appliances utilize features 出现 include:
•
means 岛r obtaining a leak tight connection without the use of tools
before gas flow is permitted,
98
Gas T民hnician 2 Training - Module 15
@
Canadian Standards Association
UNIT 4
FUEL CONTAINERS
automatic shutoff of the fuel when the cylinder connection device is
disconnected,
automatic temperature activated shutoff, and
•
excess-flow limiting.
Liquid se凹ice connections usually have a special thread (Figure 4-3)
designed by the Compressed Gas Association (CGA). This unique fitting
prevents the valve from being accidentally connected to a vapour service
valve.
Nipple
Left hand thread
Hex nut ＿＿；卢
越
Figure 4-3 CGA thread for liquid service
Cylinders and tanks may also have changeover manifold assemblies
attached to them. These devices are used in installations where there are
two cylinders or tanks in use. It allows the propane supply to be switched
from the supply tank to a reserve tank when the propane pressure in the
supply tank drops below a certain point. This changeover is done without
disrupting the supply. The main supply tank can then be refilled while the
reserve tank continues to supply propane to the attached systems. The
manifold assembly has a method of indicating 出at it has switched the
supply from one tank to another.
There are many di任erent types of changeover manifold assemblies, but
all perform 也e same operation. For in岛rmation on specific manifold
assemblies, consult the manufacturer ’s instructions.
由ey
Each cylinder has a number of markings on it to identify its characteristics.
Figure 4-4 shows the typical markings on a propane cylinder, and gives an
explanation for each of these markings.
Gas Technician 2 Training- Module 15
© Canadian Standards Association
99
FUEL CONTAINERS
UNIT4
A
B
C
D
了C -4BAM 17
f立与
U "SJN - 1
！＼注＇＇，，ii
F
I
G
H
34
ACME CO.
21.6 L
TB.40 KG
·~
E
04094
REγEST
REQUIRED PROPANE CYLINDER MARKINGS
A. Cylinder has been designed to
Transport Canada (TC) specifications
B. Transport Canada speci币cations for the design
of the propane cylinder
C: Working pressure of the cylinder in bars (17 bars = 1.7 MPa)
D. Water capacity, in litres
E. The letter ‘T ’ followed by the tare weight, in kilograms
(the tare weight is the weight of the empty cylinder with valve)
Note: Older cylinders may be marked in pounds (LBS)(1 lb= 0.45 kg)
F. Manufacturer’ s serial number
G. Manufacturer’ s name or symbol
H. Test month and year seperated by inspector's registered mark
I.
Space to show retest date
Figure 4-4 Typical propane cylinder markings.
100
Gas T副市nician 2 Training - Module 15
。 canadian Standards As回ciation
FUEL CONTAINERS
UNIT 4
Table 4-1 lists some of the common propane cylinders, together with their
applications and characteristics.
Table 4-1 Common propane cylinders, applications and characteristics
Type of
service
Typical use
Propane capacity
Water capacity
lb (kg)
US gal
I (litres)
US gal
Common DOT
and TC* codes
Stationary
Homes,
business
420(191)
99
1000 (454)
119
础， 4BA,
4BW
Stationary
Homes,
business
300 (136)
71
715 (324)
86
袍， 4BA,
4BW
Stationary
Homes,
business
200 (91)
47
477 (216)
57
徊， 4BA,
4BW
Stationary
Homes,
business
150 (68)
35
357 (162)
43
48
Exchange
Homes,
business
100 (45)
24
239(108)
29
48, 4BA, 4BW
Exchange
Homes,
business
60 (27)
14
144 (65)
17
箱， 4BA,4BW
Motor fuel
Tractor
100 (45)
24
239 (108)
29
48, 4BA, 4BW
Motor fuel
Tractor
60 (27)
14
144 (65)
17
咽， 4BA,
Motor fuel
Forklift
43.5 (19.7)
10
104 (47)
12
48, 4BA, 4BW,
4E
Motor fuel
Forklift
33.5 (15.2)
8
80 (36)
9.6
48, 4BA, 4BW,
4E
Motor fuel
Forklift
20 (9)
4.7
48 (22)
5.7
48, 4BA, 4BW,
4E
Motor fuel
Forklift
14 (6.4)
3.3
34 (15.4)
4.1
础， 4BA,4BW,
4BW
4E
Portable
Rec. vehicles
40(18)
9.5
95 (43)
11
46, 4BA, 4BW,
4E
p。rtable
Rec. vehicles
30 (13.6)
7.1
72 (32.7)
8.6
46, 4BA, 4BW,
4E
Portable
R~.
25 (11.3)
5.9
59.5 (27)
7.1
袍， 4BA,4BW
Portable
Rec. vehicles
20 (9)
4.7
48 (22)
5.7
46, 4BA, 4BW,
4E
p。rtable
Rec. vehicles
10 (4.5)
2.4
23.8 (10.8)
2.8
捕， 4BA,4BW,
vehicles
4E
Po『table
Portable
Indoors,
trailers
5 (2.3)
Torches,
.93 (.42)
1.2
12 (5.4)
1.4
咽， 4BA,4BW,
4E
0.2
2.2 (1)
0.3
39 (disposable)
臼mping
48240 (refillable)
叮C
codes include M to designate metric specifications
Gas Technician 2 T1『aining-Module 15
© Canadian Standards Association
101
FUEL CONTAINERS
UNIT 4
Tanks
When a larger installation is planned, propane storage tanks are often
required to deliver a sufficient flow of propane to meet the demand of
connected appliances. Tanks may also be preferred when the number of
cylinders required is inconvenient to handle, or when the delivery schedule
is not frequent enough to ensure a continuous supply. Figure 钊 shows a
typical storage tank and accessories.
Multi-valve (service valve,
vapour equalizing valve,
with excess flow, and fixed
liquid level gauge)
Filler valve
Liquid withdraw,
check valve
（。但enbo忱。m­
mounted)
Tank
~Tank
data
Figure 4-5 Typical propane st。rage tank and accessories
102
2 Training-Module 15
Canadian Standards Assoc掘tion
GasTecl可nician
@
FUEL CONTAINERS
UNIT 4
A common type of connection on a propane tank is a pigtail (Figure 4-6)
on a propane ta时c This type of tubing forms part of the vapour withdrawal
system. It allows for flexibility in movement of the rest of the piping in the
system.
Figure 4-6 A pigtail
As with propane cylinders, propane storage tanks have a label attached to
them to identi母 their characteristics. A typical ASME propane storage ta他
nameplate is shown in Figure 4-7.
． αR丁IF ANYTOWN, ONTARIO, CANADA
r·MAWP _
lw
PSI
AT ＿一＿ °F
AT
CAP. 一一一－一一
PSI YEAR
;;JA~一一一一一一一一一一一一一-i=t回国
………..:e•HI
• •自~. .
SH. THK. 一一一一一＿ HD. THK. 一一一一一＿ D. RAD. 一一一一一－
ABOV 仨 GROυND SERVICE. THIS CONTAINER SHALL NOT
CONTAIN APRODUCT HAVING A VAPOUR PRESSURE IN
EXCESS OF _PSI
AT ATEMPERATURE OF
飞F
OUTSIDE AREA
Figure 4-7 Typical ASME propane storage tank nameplate
The 岛1AWP gives the maximum allowable working pressure. The
minimum is 250 psig. The CAP gives the tank capacity in US W剖.er
gallons.ηie CRN is the Canadian registration number, and it indicates
compliance with the Code and the regulations. In Ontario the 0.1.N.
Gas Technician 2 Training - Module 15
Standards Association
。 Canadian
103
FUEL CONTAINERS
UNIT 4
indicates compliance with Ontario regulations for pressure vessels. The
label will also state whether it is for aboveground or underground service.
The style of the nameplate varies between manufacturers, and between the
US and Canada, but all approved tanks will have a CRN on the label.
Table 4-2 lists the applications and characteristics of some common AS岛E
propane storage tanks.
Table 4-2 Common ASME propane storage tanks types and characteristics
Type of Service
Water capacity
US gal (litres)
Pr。pane capacity
gal* (litres)
Propane
capacity (lb)
Domestic
100 (379)
80 (301)
338
Domestic
125 (473)
100 (379)
423
Domestic
150 (568)
120 (454)
508
Domestic
250 (946)
200 (757)
848
Domestic
325 (1230)
260 (984)
Domestic
500 (1893)
400 (1514)
Domestic
1000 (3.8 m3)
800 (3 m3)
Industrial/agricultural
1000-5000 (3.8-19 m3)
800-4500 (3-17 m3)
Service stations
1000-6500 (3.8-24.6 m3)
800-5850 (3-22 m3)
Bulk plant or st。rage
12 000斗 8 000 (45.4-68 m3)
10 800-16 200
(41-61 m3)
Bulk plant or storage
20 000-30 000 (76-114 m3)
18 000-27 000
(45.4-102 m3)
Bul_k plant or storage
30000毛0 000 (114-227 m3)
27 000-54 000
(102-204 m3)
Bulk plant 。r storage
60 000-120 000 (227-454 m3)
48 000-96 000
(182-364 m3)
*Based on propane specific gravity of 0.508 at 60。F (15.6。C). Actual quantity depends on actual specific
gravity.
104
Gas Technician 2 Training - Module 15
。 Canadian Standards Association
一一－
TOPIC
一一一一」一二二一
2
Sizing αnd installing
cylinde.γsαnd tanks
When sizing a propane container the most important consideration is the
vapour or liquid withdrawal capacity of the container. The container must
always have a propane withdrawal capacity that is high enough for the
application. If the container ’s propane capacity is too low (undersized tank
or cylinder), the appliances may not operate properly.
We will briefly review the propane vaporization process before discussing
the procedures for sizing propane containers. Knowing how propane reacts
under temperature and pressure changes will increase your understanding
of the factors which influence container sizing.
Propane
vaporization
Propane is made up of hydrogen and carbon atoms. Under normal
atmospheric pressure, propane is a vapour. To store propane, the vapour is
pressurized and stored as a liquid. Although it is stored as a liquid, when
filled to capacity, only 80% of the container is filled with liquid, the rest of
the container is filled with vaporized gas. Overfilling the storage container
reduces the volume available for vaporization, and may result in liquid
w诅1drawalα:cur由毡， orahy1命。创atic pressure b山ldup.
The relationship between the propane liquid and vapour is constant unless
the temperature of the propane changes, or 也e pressure inside the container
changes.
When the temperature of propane liquid inside a pressurized container
increases, the liquid boils and vaporizes. This vaporization increases the
pressure in the container. Since there is a relationship between temperature
and pressure, this boiling continues until the temperature and pressure
reach equilibrium at a new point.
Another way to make the liquid boil is to release some pressure. When
the supply valve opens and discharges vapo町， a drop in pressure occurs.
As a result, the liquid immediately boils off, trying to re-establish the
same pressure that was in the container before the valve was opened.
When the valve closes, the liquid continues to boil off until 由e cylinder is
re-pressurized.
Training 『 Module
Standa『ds Association
Gas Technician 2
© Canadian
15
105
FUEL CONTAINERS
UNIT 4
Vaporization rate
The vaporization rate of a container is the volume of propane that can be
boiled off inside the container, during a period of time. The vaporization
rate is expressed in cubic feet of vapour per hour. When sizing a container
for vapour se凹ice, always ensure that the container ’s vaporization rate is
equal to, or greater than, the demand for propane. If it is smaller, the
appliances will not operate at their rated inputs due to low pressure.
There are six basic factors that affect the vaporization rate of a propane
container. These factors either slow down the boiling rate, or speed it up.
As a result, the vaporization rate either increases or decreases due to these
factors.
Surface α阳o
106
of tank
Heat is transferred through the walls of the
container. The specific area of the tank that
comes in contact with the propane liquid is
called the wetted surf注ce area. In effect, the
larger the wetted surface area, the higher the
vaponzatton rate.
Ambient temperature
If the ambient temperature (temperature around
the wetted surf注ce area) is high, as in
summertime, more heat is transferred to the
liquid. As a result, the vaporization rate is high.
In winter, when the outside temperatures are
lower, the vapour pressure is reduced. When the
vapour pressure is reduced, the vaporization rate
is also reduced. Temperature directly affects the
vaponzation rate.
Temperature ofgas
The temperature of the liquid in the container
determines how much extra heat is needed for a
specific vaporization rate. If the liquid
temperature is low, more heat is required from
也e wetted surface area to bring the propane
liquid to its boiling point.
Level of liquid
As propane vapour is withdrawn, the liquid
level in the tank drops. This also means that the
wetted surface area decreases. Because of this,
heat transfer to the liquid decreases, and the
vaporization rate decreases.
Gas Technician 2 Training-Module 15
© Canadian Standards As四ciation
FUEL CONTAINERS
UNIT 4
Relαtive
humidity
Location
As the demand for propane vapour increases,
additional heat must be transferred to the liquid.
In transferring heat to the liquid, the air
surrounding the wetted surf出e may cool. If the
air is very moist (high humidity), the cool air
may reach its “ dew point” temperature and
condense on the wetted surface of the container.
If a high demand for vapour continues after the
moisture has condensed on the wetted surface
area, the dew or moisture will continue to cool
down rapidly. When the temperature reaches
32。F (0。C), the moisture will freeze. The
resulting “台ost line” on the wetted surface acts
as an insulator, drastically reducing the
vaporization rate of the container. Conversely, if
the air is very dry (low humidity), the
temperature surrounding the container can drop
a great deal be岛re any moisture or dew
condenses.
Containers can be installed above or
underground. Containers that are installed
aboveground benefit 企om high summer
temperatures as well as direct sunlight.
However, the vaporization rate of an aboveground tank or cylinder in the winter drops
because of the low outside temperatures.
Underground containers usually have constant
vaporization rates all year-round. This is due to
the relatively constant temperatures
underground.
Sizin~ a
container
When sizing containers, there are five important steps to ensure the factors
the vaporization rate are taken into account. Each step is
extremely important in properly sizing the tank or cylinder:
也就 affect
1.
Determine the total demand of all present and future appliances.
2.
Determine the total effective load on the container.
3.
Determine the most severe weather conditions under which the
container must operate.
4.
Determine the correct sizing table to use.
5.
Select the proper size and number of propane containers for the
application.
Gas Technician 2 Training - Module 15
© Canadian Standards 缸”ciation
107
FUEL CONTAINERS
UNIT4
Step
1 『Determine
total demand
Size the container so that it can handle the maximum possible load that will
be placed on it. Check the demand of all existing appliances and ask the
customer if any appliances will be installed in the near 如ture.
Locate the data or rating plate on each appliance in the system. Record the
input rating (Btu/h) of each appliance. Be sure to include the input ratings
of appliances which may be installed later.
If the data plate is missing, get this information by:
1.
Checking with the manufacturer or distributor of the appliance for the
appliance's exact rating in Btu/h, or
2.
Measuring the size of the burner orifices and determining the rating
from an orifice sizing guide.
If you still cannot determine the input rating of the appliances, use
Table 4-3 as a guide to various input ratings. This table shows common
domestic, commercial, industrial and agricultural appliances and their
respective input ratings. However, try to determine the exact rating
before referring to Table 4-3.
Table 4-3 Average applian臼 input ratings and load factors
Appliance
Average input rating (Btu/h)
Average i。ad factor
Domestic
Range (with oven)
45 000 - 65 000
0.03
Dryer
20 000 - 25 000
0.15
Floor furnace
35 000 - 50 000
0.60
Recessed wall furnace
35 000 - 60 000
0.50
Central heating furnace
70 000- 125 000
0.50
Radiant heater
20 000 - 25 000
0.40
w.旨ter
35 000 - 50 000
0.16
heater
100 000 - 500 000
0.50
Range (with oven)
45 000 - 65 000
0.30
Griddle
35 000 - 40 000
0.30
Oven
50000 呻 75000
0.30
Fryer
100 000 -150 000
0.50
30 000-105 000
0.60
heater
Commercial
叭later
Clothes dryer
108
Gas Technicia『1 2 Training - Module 15
。 Canadian Standards Association
UNIT 4
FUEL CONTAINERS
Table 4-3 (Concluded) Average appliance input ratings and load factors
Industrial
Plumber’s pot
16 000 - 25 000
Tar kettle
1.00
500 000 - 2 000 000
1.00
6000-50 000
1.00
Grain/corn dryers
500 000 - 1 000 000
1.00
Peanut dryers
100 000 - 500 000
1.00
Tobacco curers
500 000 - 1 000 000
0.75
Construction heater
Agricultural
Poultry brooders
35 000 - 75 000
0.75
Livestock heaters
50 000- 100 000
0.75
Step
2－心
The appliance input ratings shown in Table 4-3 are based on continuous
operation for one 如11 hour (Btu/h). However, in many cases, an appliance
burner is controlled by a thermostat. As a result, the burner does not
operate for a full hour. Instead, it cycles on and off to satis命 the
temperature setting on the thermostat.
For example, an 80 000 Btu furnace requires 32 cu ft of propane every hour
to operate continuously. However, a properly sized furnace that is installed
in a well-insulated home will normally cycle on and off five or six times
each hour. As a result, the main burner operates for approximately 30
minutes out of each hour.
This on and off cycling means that the supply withdrawn 丘。m the propane
container is not continuous. In order to proper忖 size a container, you need
to know what gas supply is actually required.
Formula to calculate effective load
In order to determine the e能ctive (actual) load on a propane container,
perform the following calculation:
Input rαtingxLoαd factor= Effective load
Where:
Input rating
Gas Technician 2 Training - Module 15
Canadian Standards Association
©
is that shown on the appliance rating plate.
109
FUEL CONTAINERS
UNIT 4
Load factor
is the actual amount of gas used, divided by the maximum
amount of propane that the appliance would use if it
operated continuously. The right hand column of Table 4-3
contains the average load factors for various appliances.
If the load factor for a particular application cannot be
determined, use an average load 也ctor for the relevant type
of appliance or equipment. The following load factors are
“ safe” average load factors for individual appliances:
• Domestic0.5
• Commercial0.5
•Industrial 0.75
• Agricultural 1，。
In the 80 000 Btu/h furnace example, the propane container
only boils off half (30 minutes) of the vapour that it requires
to operate continuously. The load factor is therefore 0.5.
Multiple appliances
Since the propane container may be supplying gas to many appliances, all
loads must be added together to find the effective load on the container.
Use the following procedure:
1.
Determine the input rating for each appliance or piece of equipment.
2.
Multiply the input rating of each appliance by its proper load factor
(Table 4-3).
3.
Add the effective loads of each of the appliances together to determine
the total e旺ective load on the container.
For example, determine the total effective load of three domestic
appliances:
•
domestic water heater (35 000 Btu/h)
•
gas range (45 000 Btu/h)
•
central heating system (80 000 Btu/h).
Input rating × Load factor=Ejfective load
35 000 Btu/h × 0.16=5600 Btu/h
45 000 Btu/h × 0.03 =350Btu/h
80 000 Btu/h × 0.50 =40 OOOBtulh
= 46 950 Btulh
110
Gas Technician 2 Training - Module 15
© Canadian Standards Association
FUEL CONTAINERS
UNIT 4
Step 3-Determine weather conditions
町 vm
--KULU
圳的，
m
呻．
As stated earlier, several factors affect the vaporization rate inside the
propane container. During vapour withdrawal, the 队-vo most important
factors are:
c
ra
To properly size a container for vapour withdrawal, always size the
container so that it provides propane under the most di旺icult weather
conditions.
1.
Determine the times that the container normally provides propane
vapour to appliances (i.e. morning only, summer only).
2.
Determine the lowest outside temperature that occurs during a
normal operating period.
Step 4-Determine sizing table
The tables for sizing containers are organized according to the type and
size of container (AS如ffi tanks, stationary DOT厅C cylinders, portable
DOT/TC cylinders, etc.). For 出is reason, first determine the type of
container to be used before selecting one of the tables.
There are three tables for sizing containers, all located in Appendix 2 at the
end of this unit:
•
Table 仙” 1
is for AS1伍 aboveground tanks.
•
Table 4A-2 is for AS1在E underground tanks.
•
Table 4A-3 is for DOT厅C portable cylinders, exchange cylinders and
stationary cylinders.
Step 5-Select propane gas containers
Now that 由e effective load, operating conditions, and sizing table have
been determined, select the proper size and number of container(s) from
the tables. To make the tables easier to use, the vaporization rates are not
expressed in cubic feet per hour, instead the ratings have been converted to
Btu per hour (Btu/h).
Additionally, the ratings indicate the vaporization rate when the container
is ready to be refilled. As a consequence, all ratings in the tables are based
on a container that is a quarter full (25% of the container ’s water capacity).
Gas Technician 2 Training- Module 15
©Canadian S姐ndards Association
111
FUEL CONTAINERS
UNIT 4
This is because as long as the container is at least 25% full, an adequate
supply of gas is ensured.
Aboveground ASME tanks
To properly size an aboveground AS！＼.伍 tank, follow the steps using Table
4A-1 in Appendix 2.
Based on the relative humidity in the area, select the applicable table:
1.
•
•
•
Table 4A-la (50-60% humidity)
Table 4A-lb (60-70% humidity
Table 4A-lc (70-80% humidity)
2.
Based on the lowest temperature for the operating season of the tank,
select the appropriate temperature column in the table.
3.
Read down the temperature column until you locate a Btu rating that
is equal 旬， or greater than, the effective load of the application.
4.
Read across to the Tank capacity (gallons w.c.) column and locate the
required tank size.
Underground ASME tanks
Table 4A-2 in Appendix 2 lists the vaporization rate of various AS如E
tanks when they are installed underground. Note that temperature column
only lists 50°F. Regardless of the time of year, the earth surrounding an
underground tank usually remains around 50。E Note also that the
moisture content of the soil has been averaged out.
To select the proper size of an underground tank, merely read down the
50。F column until you find a ratmg 由at is equal to, or greater than, the
effective load of 也e application. Then, read across to the left to determine
也e proper size tank capacity (gallons w.c. ).
If the tank is undersized, a 仕ost line could develop on the tank and the
vaporization rate will drop off to zero. If this occurs, the tank must be dug
up and a larger tank set in, resulting in a waste of time and money.
Note
Never undersize an underground tank.
112
Gas Technician 2 Training - Module 15
@Canadian S恼nda『ds Association
UNIT 4
FUEL CONTAINERS
DOT,厅C
Cylinders (Portable, Replaceable, Stationary)
Table 4A-3 in Appendix 2 lists the capacities of common DOT/TC
cylinders. This table is different from the others because each cylinder has
four different vaporization rates: two ratings for winter and two ratings for
summer. Furthermore, the summer and winter ratings are divided into low
and high humidity. The average high humidity is 70% and the average low
humidity is 30%. Because of the low capacities of cylinders, a 10%
difference in humidity or temperature does not greatly change the
vaporization rate of the cylinder.
To select a DOT/TC cylinder for an application use the following
procedure:
Liquid
withdrawal
connections
1.
Select the column in Table 4A-3 由at represents the most severe
weather conditions for the area (winter and high humidity; summer
and low humidity, etc.)
2.
Determine the type of cylinder needed (portable, replaceable or
stationary).
3.
Read down the column until you. locate a Btu rating 出at is equal to, or
greater than, the effective load of the application.
4.
Read straight across to the extreme left column Cylinder Capacity and
select the cylinder required.
A liquid withdrawal connection is shown previously in Figure 今3.A
combination valve used for liquid withdrawal is shown in Figure 4-8. It is
designed for liquid service since it is equipped with a CGA 555 connection.
Gas Technician 2 Training - Module 15
©Canadian S恼ndardsAs回ciation
113
FUEL CONTAINERS
UNIT4
Liquid service
outlet (CGA 555)
Vapour
(to relief
valve only)
Liquid withdrawal
dip tube
Figure 4-8 Combination valve for liquid service
The excess-flow valve protects the container against uncontrolled
discharge of LP-gas in case the gas line breaks. The excess-flow valve is
installed in the liquid dip tube. The dip tube completely isolates LP-gas
liquid 丘。m the inlet to the relief valve. But vapour is free to flow around
the dip tube to the inlet of the safety relief valve.
Ins恒 l lation
clearances
Before planning the location of a propane container, check all code
requirements for clearance information. The diagrams and tables in
Appendix 3 serve only as a guide for approximate clearance information.
The key thing to remember is that propane is flammable. Sparks 仕om
electric motors and switches, for example, can transfer enough heat to
cause combustion. Even the heat 企om a lit cigarette or a vehicle exhaust
pipe can ignite a flammable mixt田e of propane and air.
A
114
Caution!
Never smoke around propαne installations!
Gas Technician 2 T『aining - Module 15
© canadian Standards Association
FUEL CONTAINERS
UNIT 4
Testing
propane
systems
For information on testing propane systems, refer to Module 8, Unit 3
where this topic is described in detail.
、、．，
Gas Technician 2 Training - Module 15
Standards Association
©Canad泪n
115
FUEL CONTAINERS
UNIT4
Assignment 4
When you have completed the following questions, ask your instructor for the
Answer Key.
、
I.
How long may a cylinder be in use before it must be reconditioned?
2.
List the factors that affect the vaporization rate of propane in a propane cylinder
3.
List the five steps used when sizing containers
4.
If an appliance rating plate is missing, how can the input be determined?
5.
What is the formula for determining e他ctive load?
6.
When is a vaporizer usually installed?
7.
What units of measurement are used to rate propane-fired stationary engines?
8.
Where is the information on installation clearances for tanks and cylinders?
Gas Tee茸mician 2 Training - Module 15
@Canadian S恒ndardsAs回ciation
117
APPENDIX A TO UNIT 4
Vaporization γαtesfoγ tanks
αnd cylindeγs
Table 4A-1 Vaporization rate of aboveground ASME tanks (Btu/h)
Vaporization Rates of Aboveground ASME TANKS (Btu/h.) - See Note 1
Humidity
Tank Capacity
(Gallons W.C.)
20°F
10'F
a-60%
50°F
46,326
57,424
76,937
127,919
227,834
750,944
30。F
120
150
250
500
1,000
6,000
39,651
49,145
65,842
109,472
194,975
642,661
35,745
44,299
59,358
98,694
175,787
579,380
31,970
39,629
53,096
88,279
157,232
518,240
29,951
37,123
49,729
82,697
147,276
485,432
b 一 70%
120
150
250
500
1,000
6,000
30,475
37,775
50,612
84,150
149,878
494,002
29,951
37,060
49,670
82,550
147,040
485,545
26,187
32,400
43.420
72,170
128,550
424,497
22,503
27,890
37,380
62,130
110,670
364,772
20,586
25,520
34,200
56,840
101,250
333,716
120
150
250
500
1,000
6,000
27,199
33,714
45,171
75,103
133,764
440,822
40 。F
。。 F
-10°F
-20'F
-30。 F
27,920
34,616
46,376
77,102
137,319
452,623
27,920
34,089
45,699
75,927
135,227
445,727
25,570
31,688
42,460
70,600
125,748
414,451
18,706
23,230
18,416
22,830
30,580
50,820
90,580
298,530
15,130
18,760
25,140
41,780
245,266
23,470
29,431
39,440
65,567
116,782
384,909
14,900
18,470
24,750
41,140
73,280
241,536
9,235
11,460
15,360
25,530
45,480
149,785
9,123
11,290
15,130
25,150
44,800
147,970
7,476
9,270
12,420
20,640
36,770
121,197
3 丁， 130
51,740
92,160
303,225
25,536
16,433
12,923
12,706
12,507
33,000
20,360
15,760
16,020
15,510
44,230
21,120
27,290
21,480
20,790
73,510
45,360
35,700
35,100
34,550
130,940
80,790
63,580
62,530
61,540
431,369
266,379
209,554
226,005
202,779
Note 1:All ratings based on tanks being 1/4 full. If tanks are 1/2 full, multiply 日tu's by 1.41
Note 2:At temperatures b副ow 20'F』 the vapour pressure may not be high enough for proper regutator operation. ti 国 nks are
c-80%
74 号420
1/3 full, multiply Stu's by 1.144
Table 4A-2 Vaporization rate of underground ASME tanks (Btu/h)
Vaporization Rate (Btu/h)
。f
Underground
ASME
Tanks
Underground Temperature 50°F (See Note 1)
Tank Capacity
50 。F Outside
(Gallons W.C.)
120
Temperatui:e
150
250
35,391
43,879
500
58,777
97,727
1.000
6,000
174,061
573,723
Note 1: All ratings based on tanks being }4 full.
For tanks
For tanks
Gas Technician 2 Training - Module 恼
。 Canadian Standards Association
1A full, multiply Btu ’ s by 1.144.
% full, multiply Btu's by 1.41.
119
FUEL CONTAINERS
UNIT4
Table 4A-3
Vap。rization
rate of common
Vaporizati。n
。f
cylinders (Btu/h)
Rate (Btu/h)
o。T厅C
Cylinders
Cylinder Capacity
Winter
(Lbs. of LP-gas)
Temperature= 0°F
5 ＃一 Portable
Is…
70。 F
Low
Humidity
High
Humidity
Low
Humidity
High
Humidity
30%
70%
30%
70%
7,000
4,280
13,370
8,182
20 ＃一
Portable
12,000
7,650
23,870
14,600
40 ＃一
Portable
16,600
10,160
31,710
19,080
20,700
12,660
39,540
24,200
100 ＃一 Exchange
25,000
15,300
47,750
29,220
200 ＃一
Stationary
31,000
20,200
59,210
36,240
300 ＃一
Stationary
39,000
25,090
74,490
45,590
420 # -
Stationary
45,000
29,980
86,000
52,630
60 ＃一 Port厄xch.
120
Common
DOT汀C
Note 1:
Ratings based on cylinders being '14 full.
Note 2:
The values for exchange (60 # and 100 的 cylinders 町e
for the supply cylinders only. When the supply cylinders are
connected to an automatic changeover regulator or mani岛Id,
one reverse cylinder should be added for each supply cylinder
that is used (i.e., 2 supply cylinders require 2 rese凹e
cylinders or a total of 4 cylinders for the installation).
Tee如nician 2 Training - Module 15
。 Canadian Standards Ass<冗iation
Gas
APPENDIXB TO UNIT 4
Installαtion
tanks
clearances Joγ
α：nd cylinders
For exceptions, see
Location of Consumer
Tanks in the
Propane Code
*Building openings
include windows,
doors, combustion
and fresh air intakes
ιJ哎亨
」~－－－，，.－－’
｜飞！豆.!t
--’/
～丁’~
队主~
，三”
Over 10,000 USWG
at the discretion of the
authority having jurisdiction
,/’
”’
,,,
T
l
Prop~rty line or 叫acent concrete
or masonry building with no openings
or source of ignition within the clearances
specified in Table 10.10.2
Figure 4A-1 Installation clearances for aboveground ASME tanks
Gas Technician 2 Training- Module 15
@Canadian S恒ndardsAs部:iciation
121
FUEL CONTAINERS
UNIT4
~（ note1)
2,000 gal w.c. to
30,000 gal w.c.
Adjoining property line
Note 1: Minimum dis恒nces for underground conshall be measured from the relief valve and
filling or liquid level gauge vent connection at the
container, except that no part of an underground
con幅iner shall be less than 10 ft from a building or
line of adjoining property which may be built upon.
恒iners
Figure 4A-2 Installation clearar:ices for underground ASME tanks
122
Gas Technician 2 Training - Module 15
© Canadian Standards Association
FUEL CONTAINERS
UNIT 4
Table 4A-4 Minimum distance requirements of ASME tanks
Minimum Distance R饲uiraments f1创
S钮咀onary ASME
Distance to •••
Tank
阳”。” and
Minimum Required Distance
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Gas Technician 2 Training - Module 15
。 Canad姐n Standards As回elation
123
FUEL CONTAINERS
UNIT4
Minimu~· 10 ft from
any air intake or
source of ignition
(air conditioner)
Firm, level, weatherproof
base located on consolidated
ground at grade level
For full 『equirements, se·
Installation of Cylinders
in Propane Code
Minimum 3 ft from
any building opening
be!ow the level of the
relief valve discharge
Figure 4A-3 Installation clearances for DOT.汀C cylinders
－飞
124
Gas Technician 2 Training- Module 15
。 Canadian Standards A瓢妇ciation
Module 16
Domestic Gas-Fired
Refrigerators
Because recreational vehicles are often without access to the
120 V electrical power needed to run 由e compressors found in
standard mechanical refrigerators, they have traditionally used
propane refrigerators. In recent years, however, with the search
for alternatives to electrically powered refrigeration, gas-fired
units are gaining popularity in homes because of:
•
the increased cost of electricity
•
the amount of power used by compressors
•
environmental considerations, since most compressor
refrigerants are destructive to the atmosphere.
Gas-fired refrigerators operate on an absorption principle whereby
refrigerant is circulated through three circuits where it absorbs heat
from the refrigerator and 企eezer compartments and cools the
evaporator fins. This system has no moving parts, is noiseless and
continuous. A number of models can operate on a single propane
flame, 12 V or 120 V circuits.
At the end of this module y。u will be able to:
•
•
Describe the
refrigerator
operation 。f a d。mestic gas悔自red
Describe the installation procedures for a domestic
refrigerator
gas－白red
•
Describe the service and maintenance procedures for a
gas-fired re肯igerat。r
d。mestic
Gas Technician 2 Training- Module 16
© Canadian Sta『idards Association
iii
Ken Bales, Manager, Gas Information Products, CSA, wishes to acknowledge the following individuals
who contributed as members of a Review Panel during the develbpment of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology (BCIT} is
acknowledged for its work in the technical development and editing of the original edition.
c。ntribut。rs and members 。f the Review Panel
John Cotter
Canadore College
Gas Limited
Eric Grigg
Canadore College
Warren Hayes
Superior Propane Inc.
Darrel Hilman
Southern Alberta Institute of Technology
Ken Kell
Centra Gas Manitoba
W. John Lampey Alberta Advanced Education & Career Development
Lorne Lowry
Algonquin College
Jim Noseworthy Durham College
Gary Prentice
Environmental Energy Consultants
Nick Reggi
Humber College
Rick Rogozinski Union Gas
Ron Royal
Fanshawe College
John Semeniuk Northern Alberta Institute of Technology
Allen Sidock
Cambrian College
John Simmons Loyalist College
David Stainrod D.J. Stainrod & Associates Ltd.
Terry Waters
Enbridge Consumers Gas
Bill
iv
Daviesυnion
Gas Technician 2 Traini咱－ Module 16
© Canadian Standards A豁出酬。n
岛1odule
16
Table of Contents
Unit 1
。 peration
Basic operating principles .......................……...... 3
Generator comp。nents ........…............................ 9
Types of systems and safety c。nsiderati。ns .... 15
Assignment 1 ....................…….......................... 19
Unit 2
Installation procedures
Venting requirements ..............…·胃..................... 23
Installing the
refrigerat。r
................................... 29
Assignment 2 .................................................... 33
Unit 3
Maintenance and servicing
Cleaning and bi-annual servicing ........…........... 37
Troubleshooting procedures ...........…............... 43
Assignment 3 .................................................... 45
、、－－
Gas Technician 2 Training - Module 16
© canadian Standards A钩。ciation
v
~
Unit 1
Operation
Purpose
Absorption re企igerators have no moving parts, are noiseless and
require only a small flame to operate. There are four basic components
to an absorption refrigerator: generator (boiler), condenser, evaporator
and absorber. Sealed under pressure, the refrigerant travels through the
system absorbing and releasing heat at key areas. 咀iis action serves to
cool the re企igerator and freezer compartments.
Learning
objectives
1. Describe the basic operating principles.
2. Describe the generator components of the gas-fired re企igerator.
3. Describe the types of systems and the safety considerations 岛r
each.
飞、‘－
Gas Technician 2
Training 』 Moclu悔 16
© Canadian Standards Associa剖on
1
Topics
1.
Basic 。perating principles .•.•••.................•...•..•...•..•..••........•..• 3
Basic components . . .. . ...........…. ... .. . . .………··‘…...... 3
Flow of refrigerant. . .. . . . .. ... ... .... . . ..... . ..…·-…. . ......... . ...... 5
2.
Generator components ...............….........….......….................... 9
Thermostatic valve. ….....….....................…………….....……... 10
Orifice and orifice housing ...…--……. .......... ...圃，................….... 12
Burner .........…….........……………...………··……··…....................... 13
P1ezo igniter .................………...............’‘.......………….............. 13
Thermostat bulb ..……··-....,.................…............................. 14
Carbon monoxide sensor ...……..,...‘……. ········· ..................... 14
Manual gas valve .. . ... . . ..........…...……·－…………….......……国.. 14
3.
Types of systems and safety considerations. ……............... 15
L1th1um-bromide systems ....……·····…·‘·-··-…… ….......… …......... 15
Ammonia absorption ....………...............…........….. ················. 16
Three-way refrigerators ．．．．．．．．．．．．．．．．．．．．…·町，........….. ·······………圄….. 16
E
Assignment
2
a
1 .................….......…..................................….........._•• 19
Gas Technician 2 Training - Module 16
。 Canadian Standards As回ciation
TOPIC
1
Basic opeγαting pγinciples
An absorption-refriger回ion system uses refrigerant, adsorbent, and heat to
create a cooling effect. Unlike the compression refrigeration system, the
basic absorption cycle uses no moving parts; the cycle depends on the
action and reaction between the re仕igerant and the adsorbent under various
pressure and temperature conditions in a vacuum. The system makes use of
the cooling effect that results when liquids flash to a gaseous state and the
condensing effect (changing the gas into a liquid) that results when heat is
removed.
Basic
components
Figure 1-1 shows a cutaway view of the four main components of a
propane refrigerator二
•
Generator
The operation of an absorption system is thermodynamic: it demands
thermal energy (heat) to make the refrigeration solution flow. The
generator is the heat energy source that begins and maintains the
operating cycle. The energy source may be steam, gas (natural gas or
propane) or hot water. In general, gas is used for a system having a
small capacity; steam and hot water may be used for systems having
large capacities.
The generator heats the refrigerant, turning it into a vapour so 由at it
will separate from the water solution and travel up to the condenser.
•
Condenser
The condenser removes heat 仕om 也e vapourized refrigerant causing it
to condense into a liquid. Condenser fins, located 扭曲e refrigeration
compartment, serve to transfer the heat from the fridge to the condenser
coils.
•
Evaporator
In the evaporator the liquid refrigerant encounters a pressurized
hydrogen atmosphere and evaporates. This heat transfer makes the
tubes of the evaporator cold. (This action is similar to blowing onto 由e
back of your hand when there is water on it. The blowing causes the
water to evapor础， and yo町 hand feels slightly cold.)
Thermal mastic is a heat transfer compound applied to the outside of
也e evaporator coils of the cooling unit at points where they make
Gas Technician 2 Training - Module 16
© Canadian Standards Association
3
OPERATION
UNIT1
metal-to-metal contact with the freezer plate and fins of the refrigerator.
Thermal mastic greatly enhances the cooling ability of the unit and
failure to use it will result in poor cooling.
•
Absorber
The absorber consists of a coil and a tank. The function of the liquid
inside the absorber is to attract-and absorb-一the refrigerant from the
evaporator. It is then stored in its tank until the generator begins the
cycle again.
Condenser
Evaporator
Copper capillary
tube
Absorber
Absorber
tank
Insulation
Baffle
Manual shutoff
valve
/
,, ,
/
I
I
飞
、
\!
Figure 1-1 Cutaway view of propane refrigerator
4
Gas Technician 2 Training - Module 16
© Canadian Standards Association
OP巨 RATION
UNIT 1
Flow of
refrigerant
Figure 1-2 shows the basic refrigerant flow through the three main circuits
of an ammonia absorbent refrigerator: the solution circuit, the condensing
circuit and the hydrogen circuit. The following explanation of the flow
describes how refrigeration occurs through the shedding or absorbing of
heat as the ammonia solution changes 企om liquid to vapour and back to
liquid again.
\ \ fI
circuit
ISolution
ammonia
Weak solution (ammonia
St叫蚓uti
+ wat
+ wate 「)
Condenser circuit
言 Vap
Liquid ammonia
Ammonia and hydrogen
Hydrogen circuit
Q Hydrogen
Absorber fins
Generator (boiler)
Figure 1-2 Basic operation of an ammonia absorption refrigerator
\
}
Gas Technician 2 Training - Module 16
©Canadian S姐ndards Association
5
OPERATION
UNIT 1
I. Strong solution is heαted by 立enerαtor
The perk tube is provided with a strong ammonia solution (a high
percentage of ammonia to water) from the absorber tank. When heated,
the ammonia in the strong solution begins to vaporize creating bubbles
and a percolating effect. The ammonia vapour pushes the now”
weakened solution up and out of the perk tube.
2. Ammonia vapour travels to condenser
The ammonia vapour (gas) leaving the perk tube goes upward towards
the top of the cooling unit. Little of the water vapour travels upwards
because ammonia vapourizes at a lower temperature than water, thus
causing the two to separate. (Any little water that does vapourize is
caught by a rectifier and sometimes a water separator.) At this point,
pure ammonia vapour is delivered to the condenser.
3. Meanwhile, weak solution travels back to absm加r
Meanwhile, while the rich vapourized ammonia is traveling to the
condenser, the now-weakened still-warm solution flows downward to
the top of the absorber coils and enters the absorber tank at a cooler
temperature. In its flow downward through the coil, the weak solution
picks up evaporated ammonia from the evaporator. This absorption
process generates heat which is dissipated through the absorber fins.
4. Ammonia vapour cools in condenser
Ammonia vapour enters the condenser where it is cooled by air passing
through the condenser metal fins at the rear of the refrigerator.
The cooling effect of the condenser, coupled with a series of step
downs in pipe size forces the ammonia vapour into a liquid state, where
it enters the evaporator section.
5. Liquid ammonia evaporates when it contacts pressurized hydrogen
Liquid ammonia coming in contact with pressurized hydrogen will
absorb heat and evaporate. This principle is used to absorb the heat
仕om both the freezer and re丘igerator boxes; as such there are two
stages to the evaporator.
Liquid ammonia enters the low temperature evaporator (freezer) and
trickles down the pipe, wetting the walls. Hydrogen, supplied through
the evaporator, passes over the wetted walls, causing the liquid
ammonia to evaporate into the hydrogen atmosphere at an initial
temperature of around-20。F (-29。C). Ninety percent of the ammonia
evaporates into this side of the evaporator (freezer compartment). As
the ammonia evaporates and continues to trickle down the tube, its
press田e and evaporation temperature rises.
The remaining 10% of the liquid ammonia enters the re仕igerator
portion of the evaporator and continues to evaporate (but at a higher
6
Gas Technician 2 Training - Module 16
©Canadian S组ndards Association
UNIT 1
OPERATION
temperature and pressure). Heat is removed from the refrigerator box
through the fins attached to the high temperature evaporato卫
6. The ammonia vapour and hydrogen drop to the absorber tank
The ammonia vapour, created by the evaporation, mixes with the
already present hydrogen vapour, making it heavier. Since the ammonia
and hydrogen vapour mixture is heavier than the purer hydrogen, it
drops down through the return tube to the absorber tank.
7. Ammonia vapour gets absorbed by strong solution and hydrogen
returns to evaporator
When the ammonia and hydrogen vapour mixture enters the absorber
tank through the return tube, much of the ammonia vapour is absorbed
into the surface of the strong solution, which occupies the lower half of
the tank.
Now lighter, the ammonia and hydrogen mixture (now with less
ammonia) begins to rise up the absorber coil. The weak ammonia
solution trickling down the absorber coil from the top is “hung巧f” for
the ammonia vapour that is rising up the absorber coil with the
hydrogen. This weak ammonia solution eventually absorbs all the
ammonia 企om the ammonia and hydrogen mixture as it rises, allowing
pure hydrogen to rise up the inner pipe of the evaporator section.
、、 F
Gas Technician 2 Training - Module 16
Standards Association
© Canadian
7
TOPIC
2
Generαtoγ components
Although various brands and models use different components and place
them in vastly different ways, the drawing in Figure 1-3 represents a
standard re仕igerator propane generator system.
Burner
Thermocouple
l时ector
housing
Orifice
(injector)
Combination
thermostat
and safety
)
shuto仔 valve
Piezo
igniter
Thermostat
__...capillary
Bulb temperature
sensing device
Figure 1-3 Standard generator system
Gas Technician 2 Training - Module 16
Canadian Standards Ass<回ation
C
9
OPERATION
UNIT 1
Thermostatic
valve
The amount of cooling depends on the amount of heat produced by the
flame. The higher the flame, the faster the cooling, and vice versa. The
operation is made automatic by the use of a thermostatic valve
(Figures 1-4 and 1-5) which senses the temperature of the evaporator
(through the thermostat capillary) and varies the heat input (by modulating
the gas pressure delivered to the burner) so that the correct temperature is
maintained in the refrigerator.
Gas
outlet ¢:i
<,,_,
Gas
T一 inlet
Temperature
control
Pressure
tap
Figure 1-4 Thermostatic valve-一-top view
Thermostat
(temperature control)
Bypass screw
~＼
\
＼、
尚且二司
Filter
口＞
Gas outlet
二2
Bypass circuit
Gas inlet¢
Spring mechanism
Thermostat operating
『nechanism
Spring mechanism
丁hermocouple
connection
Thermostat 臼 pillary
Figure 1-5 Thermostatic valve-cutaway view
10
Gas Technician 2 Ti『aining - Module 16
© Canadian Standards Association
OPERATION
UNIT 1
The thermostatic valve contains the following components:
•Mαnual
selector for electrical or gas operation
Most absorption re仕iger就ors can operate either on propane gas or
electricity. Some units have automatic energy selectors that
automatically choose the most appropriate source of power.
Thermost，αt control
When the thermostat calls for cooling, the maximum pressure of
propane is allowed through to 由e orifice of the burner. The thermostat
control adjusts the amount of pressure admitted and thus controls the
size of the flame and the amount of heat generated. Manufactur＇町、
specifications will indicate the maximum and minimum pressures
allowed for their make and model.
•
Bypass screw
When the desired temperature is reached, the thermostat blocks the
“ open” pathway and routes 也e propane through the bypass circuit. The
bypass section only allows a very small amount of gas through, just
enough to keep the thermocouple and the re仕igeration system heated.
Generally, the bypass screw is factory-a司justed and should not be
modified.
•
Pressure tap
For most propane-fired re世igerators, the correct gas inlet pressure is 11
inches w儿， however manufactur町、 specifications will speci命 exact
pressure. This appliance is probably the most sensitive when it comes
to gas pressure; there is very little tolerance in the gas pressure before
problems begin.
•
Thermostatic control
The thermostatic control mechanism operates in relation to 也e
temperature of the evaporator fins.
、、－
With 由e safety device open, the gas flows normally 加OU辟出e
main passage up to the thermostat operating mechanism.
2. By increasing the temperature at 也e evaporator.，也e gas inside the
thermostat capillary increases in pressure, causing the set and pin to
rise.ηiis results in less obstruction to gas flow and the burner fires
at a relatively high rate.
1.
Gas Technician 2 Training- Module 16
©Canad阳n
Standards Association
11
OPERATION
UNIT 1
3. As the temperature in the evaporator becomes cooler, the gas
pressure inside the capillaηdecreases, and the pin and set lower
due to the action of the spring. This results in more obstruction to
the gas flow and the burner fires at a lesser rate.
If the temperature in the evaporator becomes very cold, the
obstruction completely blocks the flow of gas. Gas is provided to
the burner exclusively through the bypass circuit.
Orifice and
Orifice housing The orifice controls the amount of gas injected into the burner. The main
在mction of the orifice housing is to provide a correct air-gas ratio. As the
diameters of the air and gas passages are preset, this component does not
require adjusting.
The size of the flame is set by the orifice and the gas pressure. If one or the
other is incorrect, then the flame will not be co汀ect. Often microscopic
debris accumulates around the orifice hole, making it smaller. Also, oil
仕om the propane tank and other propane components can be deposited on
the orifice, making it easier for debris to stick to it.
Note
Do not use sharp tools to clean the orifice. To clean it, soak it in non-oily
solvents and then blow air through it.
Older models have a hole drilled through them and sharp tools may
increase the size of the orifice, which will increase the heat output of the
flame and foul up the combustion or ruin the cooling unit. Modem orifices
are a thin ruby cylinder, perforated with a laser ray which ensures high
precision and absence of burrs in the hole. A modem orifice is therefore
more difficult to accidentally enlarge. The cleaning rules, however, still
apply.
Dust or lint present in the air is sucked in through the primary air openings
and collects at the openings, slowly changing the character of the flame
仕om blue, hard and low, to yellow, soft and elongated. A growing yellow
flame is your first warning that the housing must be cleaned.
If the flame pa位em (small and lean) indicates that the orifice is too small
and cleaning does not change the flame, replace 也e orifice. The same
applies if the flame p甜em (large and rich) indicates that 也e orifice is too
big.
Note
Make sure to clean the burner when changing the orifice.
12
1总chnician 2 Training- Module 16
。 Canadian Standards A路。ciation
Gas
OPERATION
UNIT 1
Burner
The burner must be clean and undamaged. The mesh or screen has to be in
place at the top of the burner (Figure 1-6). The screen protects the burner
from debris falling down into it and also helps form the flame.
Burners should be cleaned yearly with a stiff brass bristle brush to
eliminate dirt in each opening in the burner mesh. The burner venturi
should also be cleaned with pipe cleaners or with a venturi brush.
Thermocouple
Prima 叩 air
Mesh
openings~
Electrode
Orifice housing
(side view)
。时fice
(front view)
Figure 1-6 Typical refrigerator burner assembly
Piezo igniter
The igniter is typically the piezoelectric type which contains a springloaded striking plate that, when pushed, strikes a quartz crystal.ηie crystal
generates an electrical charge which is transferred down the wire to the
electrode. When properly installed and working, the high voltage between
the electrodes and the burner will create a spark at the burner, igniting any
unburned gas. If it fails to operate, the fault may be due to too much
distance between the electrode and the burner (ideal is 2-3 mm dis阳nc吟，
or to creepage or poor electrical contact.
Note
Wire leading to the electrodes should not contact any metal parts.
Gas Technician 2 Training- Module 16
© Canadian Standards Association
13
OPERATION
Thermostat
bulb
UNIT1
The bulb of the thermostatic valve is in the shape of a wound capillarγtube
(Figure 1-3) that is positioned at a specific point on the evaporator (usually
the fins) of the re rigerator box.
Modem bulbs are designed so the last 4 inches (10 cm) of the capillary is
the sensing element.
Carbon
monoxide
sensor
Some refrigeration units include a carbon monoxide sensor that is
integrated into the millivolt safety valve (thermocouple-driven) safety
device. This device alerts the user that there are levels of carbon monoxide
above the allowable 50 ppm and shuts down the burner should dangerous
level of CO be present. These units operate from a battery and the testing
procedures include a battery check as well as the CO sensor check.
Check with the manufacturer ’ s instructions on how to test this sensor. Newer models feature a disconnect that allows the CO sensor unit to be
separated from the appliance should there be any need to service the
product.
Manual gas
valve
14
The manual gas valve is the main connection between the gas supply and
由e re台igerator. It consists of a main housing and a on/off valve, which is
manually activated.
Gas Technician 2 Training - Module 16
© Canadian Standa『ds Association
TOPIC
3
Types of systems and safety
considerαtions
A gas technician may be called upon to service the system that provides
heat to absorption refrigerators. The associated gas burner and its heat
exchanger are part of the gas technician ’s expertise. Note that a gas
technician is not a re仕igeration technician and so the re rigeration
components should be left up to that trade.
Lithiumbromide
systems
The water-lithium-bromide system is similar to the ammonia-water system
however, instead of cooling fins on the condenser and absorber, there are
circulation water tubes that caηy away the heat.
Additionally, it does not use hydrogen at high pressure to carry 趾
refrigerant vapour, instead it operates at very low pressures 也 order that the
temperatures in the evaporator and re仕igerator cabinet can get low enough
to reach the required degree of cold.
Safety
Lithium-bromide solution is non . .toxic, non-flammable, non-explosive and
chemically stable. However, it becomes corrosive when exposed to air and
may irritate skin, eyes, and mucous membranes.
Emergency first aid
扩you
come in contact with lithium-bromide solution, flush the contacted
area with lukewarm water for at least 15 minutes. Remove contaminated
clothing, taking care not to spread the chemical. 扩contamination is exten”
sive, remove clothing under running water. Seek medical attention if irritation persists.
Gas Technician 2 Training - Module 16
©Canadian S恼ndards Association
15
OPERATION
Ammonia
absorption
UNIT1
The ammonia absorption cooling unit has been described in this Unit and is
a sealed unit that is not meant to be tampered with in any way. The cooling
unit contains ammonia, sodium chromate and hydrogen at a pressure of
300 to 350 psi (2067 to 2412 kPa).
Safety
Do not drill, weld or cut on the cooling unit. Rupturing the cooling unit will
immediately engulf the area in ammonia and hydrogen, displacing air.
Hydrogen is flammable, and ammonia is an intensely irritating gas that can
render one unconscious.
Emergency first aid
The key words for first aid involving ammonia are air and water. If you
inhale ammonia or get the liquid ammonia on you, immediately get to 企esh
air and flush any affected area of your body or clothing with plenty of
water. Sodium chromate is a carcinogen. It you get sodium chromate on
you, wash thoroughly with soap and water. If you have any lingering
eff与cts 齿。m, or any doubts about an encounter with the ingredients of a
cooling unit, see a physician.
When working with or changing a cooling unit, never allow yourself to be
cornered in a small area. Always have a means of exit. Al由ough cooling
units 町e very 剖out, all it takes is one weak point (a deteriorated pipe, for
example) to create a problem.
Note
If a cooling unit does rupture,
ammonia to dissipate.
Three-way
refrigerators
st，啡。way from
the area and wait for the
ηlT臼－way re企igerators
re企igerators
are combination gas-electrical absorption
that operate on:
•
120 V heater receives its current from a 120 V AC power supply
•
12 V heater receives its current 仕om a battery
•
gas burner 由at receives gas from a propane tank or a natural gas supply
line.
咀ie automatic energy selector (AES) system lets the circuit board in the
re企igerator select the most appropriate available heat so山ce. If 120 Vis
16
Gas Technician 2 Training - Module 16
。 Canadian Standards A弱。ciation
－蝇、飞
υNIT
OPERATION
1
available、 the refrigerator will always select it for the power source. If 120
V is unavailable, the next power source in order is 12 V, but only under
certain conditions. The refrigerator is designed to use 12 V power only
when the vehicle is running and the batteries are being charged. If 120 Vis
unavailable and the conditions for 12 V operation are not met, the
refrigerator will operate on propane.
Safety
For three-way refrigerators, you will have to adhere to safety requirements
for both electricity and gas.
Wiring and schematic diagrams
Manufacturer ’ s literature for three-way refrigerators will often include
wiring diagrams and schematics for installation and troubleshooting
purposes. An example is shown in Figure 1-7.
12 VOLTS DC
12 VOLTS pc
12 VOLTS DC
+
b」f -1－ 一｜
o- +
写忏
(}
。l
12VOLTS DC
120 VOLTS AC
(
SWITCH
THERMOSTAT
。 JUNCTION BOX
q) HEATER
TERMINAL BLOCK
( RELAY
HEATER
£> FUSE2A
( SWITCH
®LAMP
®
I L
I
I
: @i_ -- .i
(
(
(
(
WHITE
BLACK
GREEN
GREEN/YELLOW
3 - way
已妇i
e
G
without igniter
Courtesy ofDometic Corporation
Figure 1-7 Example of manufacturer’s wiring diagram for three-way refrigerator
Gas Technician 2 Training - Module 16
Canadian Standards Association
©
17
OPERATION
UNIT 1
Assignment 1
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
2.
List the four basic components of an absorption
re企igeration
system.
What percentage ofliquid ammonia evaporates into the freezer compartment side of the
evaporator?
3.
What mixture drops down the return tube to the absorber tank?
4.
On what does the amount of cooling depend?
5.
How is a burner orifice cleaned?
6.
What is the main function of the orifice housing?
7.
认That
8.
What three energy sources do three-way refrigerators operate on?
should you do if a cooling unit ruptures and liquid ammonia is splashed on you?
Gas Technician 2 Training- Module 16
© Canadian Standards AS!.妇ciation
19
Unit2
Installation procedures
Purpose
Domestic gas-fired refrigerators are commonly found in recreational
vehicles、 but many are also installed in homes. One of the most
important factors for trouble-free operation is the proper venting
behind the refrigerator. Since the re仕igerator works on the principle
of absorbin~ and releasing heat, it is of utmost importance to have
proper air circulation.
e均
LOwe
nge
nd
-
ws
1. Describe the venting requirements for domestic gas-fired
refrigerators.
2. Describe the procedure for installing a domestic gas-fired
refrigerator.
Gas Technician 2 Training - Module 16
© Canadian Standards Association
21
Topics
1. Venting requirements ...........................….......….................... 23
Venting suggest1。ns . . . . ......苟，．…………·…．，．．．．，…................”’..... 23
Sealed combustion vent in RVs. ......... .......…………-…...... 25
Roof vent ..........................................…. . . .. .. .. . . . ...,… .27
2. Installing the refrigerat。r ................................….................... 29
Gas connections . ....…….......…..............…….....……................ 29
Flue system ..........................……................................... 30
Controls ...........................……..........................………·-……… 30
Installation procedure .……··町……….......... .. . ..... . ............ 30
Instructions to customer .....................，…………·”…………·”町............. 31
Defrosting ..…..………·-……····· ..............….............. 32
Assignment 2 .........................................................…................... 33
22
Gas Technician 2 Training - Module 16
© Canadian Standards Association
TOPIC
1
Venting γequiγements
The evaporator in an absorption refrigerator needs to dissipate the heat it
absorbs from the refrigerant; it is therefore essential 由at proper venting
occur behind the refrigerator. If the heat is not dissipated away 丘。m the
condenser, the ammonia will not be able to liquefy, thus no cooling will
take place.
When the cooling unit gives off heat, it causes air around it to warm. Warm
air rises causing cooling air from the lower vent to enter the area and to
extract more heat from the cooling unit and also rise. The greater the
difference in temperature between the warmer air and the cooler air, the
faster the air will rise. Narrowing the path of the air flow forces the cooler
air through the cooling unit coils as it rises.
Theoretically, perfect venting will create a draft that will remove heat from
the cooling unit in even the warmest conditions. However, perfect venting
is not always that easy to achieve. The purchase of an add-on fan can solve
a lot of problems in borderline venting, but is not a c田e all for terrible
venting. The important thing to remember is 白at the fan should be installed
above the cooling unit, preferably right at the roof vent. The purpose of this
fan is to improve the dra丘， not to blow air onto the cooling unit.
Venting
suggestions
The list below suggests ways to improve the venting, however always
follow the manufacturer ’s certified installation instructions:
Make s田e there is zero clearance on the sides and top of the 仕idge,and
only 1 inch (25 mm) clearance between 也e back of the 仕idge and the
wall (Figure 2-1).
If there is any space left on the sides or top of the fridge dead air
space or cavities will form causes warm air to accumulate,
drastically reducing air flow. If the sides or top areas have any
clearance, use pieces of fibreglass insulation to block the spaces.
Any more than 1 inch (25 mm) clearance means 由e draft may bypass the condenser fins.
Gas Technician 2 Training- Module 16
Standards Association
© Canadian
23
INSTALLATION PROCEDURES
UNIT2
Roof vent
1 inch (25 mm) max.
clearance
。
Lower vent
Figure 2-1 Proper clearances for venting
If there is more than 1 inch clearance at 由e rear of the fridge, install
baftles between 出e two vents, directing air coming into the bottom
vent over against the condenser fins to within a 0.25 inches (6 mm).
Refer to Figure 2-2.
Baffle to within
0.25 inches (6 mm)
Lower vent
Figure 2-2
•
of baffles to reduce clearance
Sometimes circumstances prevent the use of a top-mounted vent, and
anupp配 side vent is the only solution. An upper side vent will work if
done properly and only with small re企igerators. If installed with a side
vent, the bottom of the upper side vent should be at the same level as
由e top of the re岳igerator.
．
24
Lo臼tion
αi many installations there is not enough height for this
requirement. A deflector should then be made from 由e top of the
refrigerator to 白e top of the upper side vent (Figure 2-3）.ηiis will
help to channel the air to the outside.
Gas Technician 2 Training - Module 16
©Canadian S恒ndards A岱ociation
UNIT 2
INSTALLATION PROCEDURES
Sheet metal
deflector
Baffle to within
0.25 inches (6 mm)
Lower vent
Figure 2-3 Location of deflector if n。t enough room for installation requirements
Sealed
combustion
vent in RVs
The sealed combustion vent design, commonly used in recreational
vehicles, consists of two parts (Figure 2-4):
1. Upper and lower vents
These vents, as in other designs, exhausts the heat away 企om 也e
condenser (using the internal air from 也e vehicle). If either of these
two vents are obstructed, or 由e interior of the vehicle is extremely hot,
the cooling unit will not perform efficiently since the condenser will
not be allowed to cool sufficiently.
2. Sealed combustion section
The sealed combustion section consists of two flex tubes which link the
burner assembly to the outside vent housing. The larger flex tube is a
fresh air intake which feeds outside air directly to the burner. The
smaller flex tube is 由e e对1aust 阳be which is used to dissipate the
products of combustion 仕om the boiler tube.
Gas T~nician 2 T1『aining - Modu悔
©canadian S恼ndardsAs职x:ialion
16
25
INSTALLATION PROCEDURES
UNIT2
It is important to note the contour of
these two tubes as well as the outside
vent housing. If the tubes are not
installed as per Figure 2-5, it will be
veηdifficult to keep the burner lit.
Upper vent
!!
Without a trap in the tubes, there will
be a back draft into the burner box
causing the flame to blow out.
i
「li
－－！
Sealed
combustion
section
‘-
Lower vent
In the case of the exhaust tube, there
could be a build up of condensation
within the tube. If it is not bent
properly, this condensation will
drain backwards, drip onto the
burner and extinguish the flame.
Figure 2-4 Sealed combustion vent requirements
Vent tolerance
Wedge
Filing plate
Outside
Vent casting
“ P”
Wind screen
trap
Separating plate
Figure 2-5 Installation of vent h。using and tubes
26
Gas Technician 2 Training - Module 16
。 Canadian Standards Association
INSTALLATION PROCEDURES
UNIT2
Vent housing
The vent housing for a sealed combustion vent must not follow 也e contour
of the van; it must be less than 90。 to the ground (Figure 2-5）.而is angling
allows the condensation to flow out of the housing.
Some manufacturers design vent housings to include a separator plate.
This plate serves to prevent e也aust air from being channeled back into the
企esh-air intake.
Roof vent
The roof vent, which caps off the venting also allows for good air flow.η1e
roof vent is centered over the cooling unit (Figure 2-1 and 2-2) and is at
least as long as the cooling unit is wide.
Gas Technician 2 Training- Module 16
© Canadian
Stan曲rds A部ociation
27
TOPIC
2
Installing the r价igerator
A refrigerator installed in a mobile home or recreational vehicle must
comply with CSA Z40 and should be installed in accordance with the
manufacturer ’ s instructions. For installations in other types of dwellings,
the refrigerator must be installed according to the Propane Storage and
Handling Code, CSA Bl 49.2 and the manufacturer ’s certified installation
instructions.
In all cases, the re仕igerator must be installed on a flat and level floor, away
from direct sunlight and 企om any o均ect that may radiate heat. Other
considerations include:
The location of the re企igerator (whether in a house, recreational
vehicle or trailer) should be well ventilated but not dra~.
Because this type of re仕igerator operates on gravity and without
mechanical means, it is extremely important 也at it be installed level.
If the unit is to be built-in, refer to the manufacturer ’s specifications 岛r
clearances.
•
Gas
connections
Keep appliance 企ee from combustible materials, gasoline and other
flammable vapours and liquids.
Propane“ fired re仕igerators are usually made to be connected with a 3/8
inch (10 mm) copper tube 也就 is free 丘。m sharp comers and curves. It is to
be mounted on the conical coupling connected to the manual shutoff valve.
This feed pipe must be placed so as to avoid damage when the re丘igerator
is removed from its compartment.
When connecting the refrigerator to 也e gas supply, check the required
as marked on 也e appliance rating plate. Never connect a propane
gas cylinder directly to 由e re企igerator without a regulator.
press田e
Note
Check the sealing ofall joints, from bottle to r价'igerator, with soapy
solution.
Gas Technician 2 Training - Module 16
©Canadian S恒ndardsAss<冗阳tion
29
INSTALLATION PROCEDURES
UNIT2
Flue system
The flue directs hot gases around and away from the generating unit.
Occasionally, these flues may be restricted by placing the refrigerator too
close to the wall, by placing objects over the opening, or by having some
obstruction fall into it. The flue must be kept clean to ensure proper
functioning of the refrigerator. The procedure for cleaning the flue is
covered in the “ Cleaning and Bi-Annual Servicing" topic, Unit 3 of this
module.
Controls
Most refrigerators have their controls located on a console at the base of
出e re仕igerator and are connected to the control devices in the rear of the
unit.
Installation
procedure
币ie
following procedure is typical of a manufacturer ’ s installation
mstructions.
1. If refrigerator is to be installed over ca叩et or uneven flooring, install a
24 x 24 inches (600 x 600 mm) metal panel.
2. Disassemble the burner box.
3. Clean the burner orifice with solvent or with a special tool provided by
the manufacturer to ensure it is free from dirt.
4. Place the re仕igerator in its definite position. Turn the levelling bolts
under the unit until the re仕igerator is level. Remove it from its location.
5. Connect the gas supply to the manual shutoff valve. Use a certified
flexible type metal connector of sufficient length.
6. Connect a pressure gauge at the pressure tap of the thermostatic valve.
Now check the operation:
1. Operate the re企igerator according to the instructions and allow it to
work for at least 30 minutes.
2. During this 30 minute period, check the connections for leaks using a
detergent and water solution. Check from the gas inlet to the orifice
spud.
3. Check the reading on the pressure gauge. If the appliance is operating
singly on the line, the operating pressure should not be higher than 11
inches w.c. (2.75 kPa) With other appliances on the same line, the
pressure should not fall below 10 inches w.c. (2.5 kPa)
30
Gas Technician 2 Training - Module 16
© Canadian Standards Association
INSTALLATION PROCEDURES
UNIT2
4. With a mirror beneath the flame tube, make sure that the flame colour
is blue. It should not reach the tip of the baffie, which will be slightly
aglow.
5. Check the operation of the flame-failure device as follows:
i.
With the re仕igerator running, set the thermostat to the coldest
se忱ing.
n. Close and then immediately open the selector valve. The flame will
go out but the gas supply will continue to flow.
iii. Listen carefully. In about 30 to 40 seconds you will hear a slight but
ve可 distinct “ click” to signify that the valve has closed.
6. Tum off the gas at 出e control leaving the manual shutoff valve open.
Replace the plug on the thermostatic valve.
7. Replace the burner box.
You can now install the re企igerator in the selected location making sure
the flexible connector does not kink.
由at
Instructions
to customer
、、』卢
The following points should be covered with the customer after installation
to ensure they understand the operation and can pinpoint potential
problems:
•
Noti龟ring
the customer 由at, unlike the compressor re仕igerator, the
operation of an absorption re企igerator is noiseless and, therefore，出ey
will not be able to tell whether it is working by simply listening.
Also instruct them on the warranty and cleaning procedures.
Advise them to keep the owner ’ s manual close by 岛r handy reference.
Instruct them on how and when to de企ost 由e re企igerator and freezer
compartments (see next page).
•
The efficiency of the unit will be reduced if the customer crams the
refrigerator with too much food.
The unit should be left empty to operate for about 6 - 8 hours d町 light
up for it to come down to temperature.
Gas Technician 2 Training - Module 16
© Canadian Standards A”。c阳tion
31
INSTALLATION PROCEDURES
UNIT2
Defrosting
After a time ice will begin to collect on the fins of the evaporator to a point
where it will reduce the efficiency of the refrigerator. It is recommended
that defrosting be done when 50% of the space between the fins is taken up
by ice. The interval between defrosting can vary considerably, depending
on the climate and the extent of use.
Some designs incorporate an automatic defrost option, whereby the
refrigerator will periodically run through the defrost cycle. The following
procedure is typical of manufacturer ’s instruction for manually defrosting
the evaporator fins in the re企igerator. In either case, refer to the
manufacturer's instructions on the defrosting procedure.
1. Remove food from the main compartment or from the freezer.
2. Set the th~rmostat knob to the defrost position.
3. Leave the unit for approximately 2 hours.
4. The refrigerator will continue to work on a low flame to provide
re丘igeration for the freezer.
5. The ice on the fins will melt and run through a drain to the rear of the
refrigerator and into a number of small containers where it will
evaporate.
6. Check the fins to make sure they are free of ice.
7.
A司just
the thermostat to its usual setting.
The 仕eezer
needs defrosting less frequently (every two months or so).
When there is a large build up of ice in the freezer compartment:
1. Tum off the gas at the selector and remove all the food.
2. Remove all the loose components from the refrigerator (such as racks,
drawers, etc., including the batteries for lights).
3. Tum the drip pan around so that the drain hole is towards the front and
place a suitable container under it, to catch the runoff of melting ice.
4. Use the plastic scraper to remove ice as it melts.
5. Leave the doors open until all the ice has melted down and then remove
the container.
6. Return the drip tray to its normal position.
32
Gas Technician 2 Training- Module 16
© Canadian Standards Association
INSTALlATI。N PROCEDURES
UNIT2
Assignment 2
When you have completed the following questions, ask your instructor for the
Answer Key.
re食igerator?
1.
What are the clearances for the top, sides and rear of a gas” fired
2.
On small refrigerators, what are your options if a top-mounted vent is not possible?
3.
Name the two parts of the vent system commonly used in recreational vehicles.
4.
What will happen if the e对iaust tube is not installed properly?
5.
Why does a gas-fired re仕igerator have to be installed level?
6.
How long does the refrigerator need to be operating before you can check whether it is
operating properly?
7.
After the installation checks are complete, how long should the re仕igerator run before the
customer places any food in it?
8.
What is a sign 也at 也e re企igerator should be defrosted?
、、－
Gas Technician 2 Training - Module 16
© Canadian Standards Association
33
Unit 3
Maintenance and servicing
Purpose
The three key factors for ensuring domestic gas-fired refrigerators
operate properly are: the re企igerator is level, it has the correct input,
and it has proper air circulation to dissipate the heat generated. If these
three conditions are met, the re仕igerator should operate successfully.
LO
nd
ebi
a·j
re
nge
-
ws
1. Describe the bi-annual cleaning and servicing procedures.
2. Describe the troubleshooting procedures.
Gas Technician 2 Training - M创ule 16
©Canadian Standa『'ds Association
35
Topics
1. Cleaning and bi-annual servicing. …..................................... 37
Condenser fins and absorber ..........--………·…“...,.-…... 37
Flue system ... ... . .... ........ .... ........ . . ..…………................... 37
SeN1cing basics. …….........…......……...…··萨……. ············ ..... 38
Testing components ......…········· ............................…................. 39
Replacing Components .....………........……-………. ..
............ .40
Additional components .......…．．．．．．．．．…...………………·句，.......... .41
2. Troubleshooting procedures ........…........................….......... 43
Trouble-shooting tips ………. ········ ...,…… ……”’··-…....…-………… .43
a
Assignment 3 .........…...........…................…..............…..................... 45
36
Gas Technician 2 Training- Module 16
。 Canadian Standards Association
TOPIC
1
Cleaning αnd bi-annuαl
servicing
To maintain a safe and efficient operation, these re仕igerators should be
serviced and maintained twice a year, preferably before a season of
continued use and especially if the re仕igerator has been closed down for
some time.
When servicing gas-fired absorption refrigerators, check to be sure that the
gas supply is at 11 inches w.c. (2.75 kPa) pressure.
Condenser
fins and
absorber
Fins on the condenser must be cleaned periodically to make sure there is
good heat removal 企om these surfaces. To check and clean the condenser
fins and absorber, move the refrigerator away from its permanent location
making sure the flexible connector does not kink. Dust building up on the
absorber and condenser can lessen the heat transfer, impairing
performance. Therefore, as a first step, remove the dust 企om 由e
refriger回or and the enclosure. Use a paintbrush to clean the condenser.
Flue system
After a period of operation, the flue may need to be cleaned. Rapid heat
transfer from the gas flame to the generator body is reduced if the flue is
dirty and the flue should be cleaned periodically to:
ensure proper re企igeration
reduce gas consumption
•
prevent incomplete combustion and the generation of carbon
monoxide.
The following procedure 岛r cleaning 也e flue is typical of manu也cturers
instructions. In all cases, be sure to place papers or cloth under the
refrigerator to collect dirt or debris.
1. Cover the burner with a cloth. Loosen and remove the flue extension.
Gas Technician 2 Training - Module 16
© Canadian Standards Association
37
MAINTENANCE AND SERVICING
UNIT3
2. Remove the baffle assembly. Clean and inspect this assembly.
The baffle may contain burnt dust and light surface corrosion. The tip,
however, must be intact, not corroded. Soot must not be present, as this
is a sign of incomplete combustion. Should this soot occu飞 contact the
dealer or manufacturer.
3. Run the brush through the flame tube. Soot must not appea卫
4. Reassemble the baffle, if necessary checking its extension.
5. Assemble the flue extension, making sure the wire of the baffle fits into
the slot in same.
6. Remove the cloth from the burner and reinstall the burner box.
7. Now check the refrigerator operation.
Servicing
basics
In absorption refrigerator servicing there are three factors that must be kept
in balance:
•
heat input
•
air circulation
levelling.
Proper heat input
The manufacturer designs the refrigerator so 由at 由e maximum input
setting is high enough for the unit to respond ~uickly to added loads, but
not so high 也at the generator is scorched or blistered. The minimum input
setting is low enough to prevent over-cooling, but not so low as to allow
the flame to be blown out by drafts.
38
To
ens田e
proper heat input do the 岛llowing checks.
．
ηie
gas press田e can be checked with a manometer at the pressure tap
(on the thermostatic valve) and corrected by adjusting the regulator at
the cylinder.
•
If the orifice is partially blocked，由e orifice can be cleaned or replaced.
•
刀ie filter 怕也e
•
If the flame impinges on a surface, or is burning yellow, the gener创or
and flue passages will become coated wi由 soot, and have to be cleaned
for rapid heat transfer. Ensure you do not damage the generator
surfaces.
gas control inlet side should be cleaned or replaced.
Gas Technician 2 Training - Modu始 16
© Canadian Standards A”。elation
MAINTENANCE AND SERVICING
UNIT 3
Proper air circulation
To ensure proper air circulation, air flow to and from the unit must not be
restricted. Ensure the back of the refrigerator is the coηect distance from
the wall and 由at foreign objects have not fallen into the space.
The cooling fins of both the condenser and the absorber must be free of dirt
and lint which would hamper the flow of air and the release of heat to the
atmosphere.
Proper levelling
Keep the system .level during installation and maintenance, allowing
liquids to flow in the proper direction so that heat is absorbed and released
according to the system ’ s design. Mainly, it is important 也at 也e evaporator
be level so that the liquid ammonia is spread out over a large area.ηiis
allows the heat to be drawn efficiently 仕om 白e re仕igerator cabinet.
If a unit is temporarily unused, it may fail to start to cool on the first try.
The traps may empty ofliquid, with 由e ammonia vapo町 blocking the
tubes in the wrong places. To overcome this condition, some manufacturers
recommend one of the following methods:
Shut the unit off for several hours, allowing all the ammonia vapour to
condense and flow back to 由e generator and to fill the liquid traps.
•
Testing
components
After about 10 minutes of operation, tilt the unit to the left for 30
seconds，也en to 由e right for 30 seconds. Do this 也ree or 岛ur times,
then put 由e re企igerator in the upright, level position. If the unit is not
defective, it should begin 企eezing.
The following information on testing components is intended to give a
broad understanding of the basic process. Specific manufactur町、
instruction for component testing will be pro叫ded in the service manual.
Carbon monoxide sensor
The following procedure is 可pical of a manufacturer ’s instruction on how
to test a carbon monoxide sensor:
1. Push and hold test button down until a “be叩” is heard, then release
button.
2. Unit will test measurement circuit for correct operation.
、、－，
Gas Technician 2 Training - Module 16
©Canadian S姐ndards Association
39
MAINTENANCE AND SERVICING
UNIT3
3. At the end of the test, the unit will sound a three-second test
confirmation beep and resume normal operation.
The test will shut down the gas supply to the appliance so it will need to be
re-lit to resume operation.
Flame-failure device
Check the operation of the
flame－也ilure
device as follows:
1. With the re丘igerator running, set the thermostat to the coldest setting.
2. Close and then immediately open the selector valve. The flame will go
out but the gas supply will continue to flow
3. Listen carefully. In about 30 to 40 seconds you will hear a slight but
very distinct “ click” to signi行 that the valve has closed.
Replacing
Components
白ie
following information on replacing components is intended to give a
broad understanding of the basic process. Specific manufacturer ’s
instruction for component replacement will be provided in the service
manual.
Orifice (injector) housing
The orifice (iniector) can be taken off by disassembling the nipple holder
with two open-end sp创mers.
1. Take off the injector piece and check whether it is obstructed.
2. Clean with alcohol and compressed air.
3. Before reassembling, tap gently a few times on 由e gas tube leading to
the burner to loosen any lint collected in the tube.
4. Reassemble, tightening carefully.
Burner
Depending on 也e 17pe of re企igerator, the burner assembly can be a gas
only or a combination gas-electric unit.
To replace a gas only burner:
1. Remove the cover by removing the screws.
2. Unscrew the burner jet.
40
Gas Technician 2 Traini咱－ Module 16
© Canadian Standa『'ds A岱∞抱回on
MAINTENANCEAND SERVICING
UNIT 3
3. Remove the burner by removing the mounting screw.
4. Insert replacement burner that is the same make and model.
5. Reassemble mounting screw and cover.
To replace a gas-electric burner:
1. Remove the covers by removing the screws.
2. Disconnect the heater cords at the terminal blocks (note the location for
later reassembly).
3. To avoid damaging the capillary tube, remove it carefully from the
evaporator.
4. Remove the screws.
5. Release the burner housing 企om the flue by turning the lever outwards
and to the right.
6. Pull the equipment out from the cabinet.
7. Replace burner with the same make and model.
Additional
components
The following components also affect the overall performance of the
refrigerator and should be tested and serviced during a call. Refer to
the manufacturer ’s service manual for cleaning, testing and servicing
mstructions:
•
cabinet and absorber fan motors
•
door switches
•
cabinet lights
•
heaters
defrost switch
•
door seal
•
refrigeration unit
•
de台ost
Gas Technician 2 Training - Module 16
©Canadian S恼ndards Association
heater and safety switch.
41
TOPIC
2
Fγoubleshooting proceduγes
The procedure for troubleshooting absorption refrigerators is similar to that
of other gas-fired appliances. When responding to a customer trouble call
you would:
1. Clarify customer complaint by asking questions to get as much
information as possible.
2. Interpret customer complaint using manuf民tur町、
service
manuals.
3. Identify potential faults that are causing the complaint, and test the
components believed to be at fault.
TroL』 ble-
Shooting tips
When troubleshooting gas-fired refrigerators, the following tips are
specific to this type of appliance.
•
Sodium chromate can be identified by its bright yellow colour. If this
shows up on the outside tubes it is a sign 出at there is a re丘igerant leak.
This chemical solidifies when exposed to air.
If a cooling unit is functioning properly, there will be even heat on both
the boiler section and the middle of the absorber coils.
If the boiler section is hot and the absorber section is warm it
indicates that the evaporator unit is blocked.
If the boiler section is warm and the absorber is hot, the hydrogen
circuit has lost its charge of hydrogen. The boiled ammonia is
circulating through the cooling unit because there is no hydrogen
present to cause it to evaporate.
If the inside of the 企id~e is warm, but there is frost on the
condenser fins, this indicates there is an internal leak in the
evaporator.
η1e
troubleshooting chart in Table 3-1 provides more detailed information
on the causes of some typical problems.
Gas Technician 2 Training - Module 16
© Canadian Standards Association
43
MAINTENANCE AND SERVICING
UNIT3
Table 3-1 Troubleshooting chart
No refrigeration
Refrigerator not cold enough
Refrigerator too cold
Burner flame goes 。ut
Odours inside refrigerat。r
Odours outside refrigerator
Frost forms rapidly
Yellow spots on tubing (s。dium chromate)
Manual defrosting impossible or incomplete
Automatic defrosting impossible or incomplete
Possible cause of malfunction
Gas leak
Refrigerator not level
·!·
Not enough air circulation
Faulty or clogged orifice (injector)
Flame contacts tube
e
I o
•
j.
Flue partially blocked
Defective thermostat (or set too low)
j.
Incomplete contact of thermostat 臼pillary
lnsu仔icient
I I
primary air
Room temperature too low
Drafts
Input too high
•I I
Poor burner flame (too low)
I J. l I. L
..
. ..
Defective safety system
By-pass incorrect
Bame· incorrectly set
Poor gasket sealing on door
•
.
I •
i饵 layertoo
thick
τhermocouple
tip not in position
Fo。d compartment needs cleaning/odorous food
'•
I
L
I
II Il
44
I
I
Unit stored with door closed
Failed refrigeration unit
Leakin absorption system
Gas Technician 2 Training - Module 16
© Canadian Standards Association
MAINTENANCE AND SERVICING
UNIT3
Assignment 3
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
认That
2.
What should you do if you notice soot buildup on the baffle?
3.
What happens if the generator flame goes out?
4.
矶That
5.
Why is it important to keep the flue clean?
6.
When adjusting the minimum heat input, what two things do you look for?
7.
What tool is used to clean the condenser?
8.
Why is it important to keep the condenser and absorber fins clean?
9.
How would you clean an orifice?
are the three factors that must be kept in balance in a gas-fired refrigerator?
is wrong if you notice a yellow substance on the tubes?
10. If the absorber is hot and the generator section is warm, what does 由is indicate?
Gas Technician 2 Training- Module 16
© Canadian Standards Association
45
Module 17
Conversion Burners
A conversion burner is one designed to fit an appliance 由at originally burned a fuel other than natural gas or propane. The most
common units burned oil, however, you may encounter some that at
one time burned solid fuel (sawdust, wood or coal).
Safe and satisfactory operation of a gas conversion burner depends
to a great extent upon proper preparation, selection, and installation. Conversion burners should be installed according to the Code
book, manufacturer ’ s instructions and local codes.
At the end
Gas Technician 2 Training - Module 17
©Canadian Standards Ass<沁iation
。f this m。dule.y。u
will be able t。：
•
Determine the guidelines f。r
conve此ing
•
Prepare appliances and venting systems for c。nversion
•
Select and install conversion burner
.
c。nduct flue
appliances
gas analysis and adjust c。nversion burner
based 。n the results
iii
Ken Bales, Manager, Gas Information Products, CSA, wishes to acknowledge the following individuals
who contributed as members of a Review Panel during the development of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology (BCIT) is
acknowledged for its work in the tech 『iical development and editing of the original edition.
Contributors and members 。f the Review Panel
John Cotter
Bill Davies
Eric Grigg
Wa 「ren Hayes
Darrel Hilman
Ken Kell
W. John Lampey
Lorne Lowry
Jim Noseworthy
Gary P「entice
Nick Reggi
Rick Rogozinski
Ron Royal
John Semeniuk
Allen Sidock
John Simmons
David Stainrod
Terry Waters
iv
Canadore College
Union Gas Limited
Canado「e College
Superio「 Propane Inc
Southern Alberta Institute of Technology
Centra Gas Manitoba
Alberta Advanced Education & Career Development
Algonquin College
Durham College
Environmental Energy Consultants
Humber College
Union Gas
Fanshawe College
Northern Alberta Institute of Technology
Cambrian College
Loyalist College
D.J. Stainrod & Associates Ltd.
Enbridge Consumers Gas
Gas Technician 2 Training - Mod~le 17
© Canadian. Standards Association
Module 17
Table of Contents
Unit 1
Guidelines for converting
appliances
Factors to consider ...........................……............ 3
Installer’s responsibilities .....................……......... 5
Code requirements ........……………………......….... 7
Assignment 1 .........….........................……......... 11
Unit 2
Preparation for conversion
Preparing a boiler for conversion ...................... 15
Preparing a furnace f。r conversi。n ................... 19
Preparing venting system
Cho。sing
for c。nversion ....... 23
a conversion burner ...........…............ 27
Assignment 2 ............…..................................... 35
Unit 3
Burner installation and flue gas
analysis
The。叩。f
combustion ........…...............….......... 39
Flue gas analysis ............……............................ 43
Burner installation and start-up checks ........... 55
Completing the installation ........…..................... 59
Assignment 3 ..............…................................... 61
Gas Technician 2 Training ” Module 17
Standards Association
。 Canadian
v
Unit 1
Guidelines for converting
appliances
Purpose
Not all appliances can be converted. The Code and manufacturer ’ s
specifications must be consulted while considering an appliance for
conversion. Factors such as availability of gas, design of the combustion chamber and appliance venting are some of the important considerations when converting from oil or solid 臼el to gas. The gas
technician will be responsible for determining the acceptability of an
appliance, choosing the correct burner, and doing the installation. The
technician ’s responsibilities are included in the Code.
e同
LOwe
nge
nd
-
ws
1. Determine suitability of appliance for conversion.
2. Describe the installer's responsibilities.
3. Outline applicable Code requirements.
Gas Technician 2 Training - Module 17
©Canadian S恼ndards Association
Topics
1. Factors to consider ..............…...........…................................... 3
2. lnstalle『·＇s responsibilities ....................................................... s
3. Code requirements ..........…........…..............................…......... 7
Conversi。ns ..................…........ ......... . ............ . ................ 7
Conversion burners ．．．．．．．．．．·－…..........…...……….............…·国.......... 7
Conversion of warm-air furnaces. …………··-………·……………. ······ .. 8
Vent connector ............…........……………............…·－………啕.....庐.. 9
Assignment 1 .................…........…................................................ 11
2
Gas Technician 2 Training - Module 17
© Canadian Standards Association
TOPIC 1
Factors to consider
Before proceeding with the removal of parts from the existing appliance, a
care臼l inspection as to the condition of the appliance must be carried out.
It is pointless to recommend that a unit be converted when its general
condition indicates that it is near the end of its useful life. Moreover, if the
heating system is improperly sized, or the unit cannot perform in extremely
cold weather, then the system itself requires improvements. A conversion
to gas will not improve poorly designed systems.
The four main factors to consider before conversion are described below;
unless all four factors are in place and workable, it is pointless to begin the
conversion.
1.
Avαiiability
of natural gαs/propαne
Check with the local gas company to ensure that a natural gas supply
line is available for the area or that a propane supply system can be
installed.
2. Design of combustion chamber
The most suitable combustion chamber design for conversion is the
updraft type shown in Figure 1-la. Appliances having a downdraft or
semi-revertible flue (Figure 1-1 b) are more difficult to convert
satisfactorily and burner selection is somewhat limited. Some
combustion chamber designs are not very suitable for conversion. For
example, when an oil furnace is a fully revertible type (Figure 1-lc),
having a large portion of the heat exchanger below the combustion
chamber and the flue outlet located just above floor level, code
restrictions apply.
一下
12inches
mm)
or higher
(b) Semi-revertible
(806
{a) Updraft
(c) Revertible conversion restricted
Figure 1-1 Combustion chamber designs
Gas Technician 2 Training - Module 17
Standards Association
© Canadian
3
GUIDELINES FOR CONVERTING APPLIANCES
UNIT 1
3. Efficiency of current appliance
Oil and solid－且iel appliances operate at higher temperatures than gas
burners and thus produce a larger amount of radiant heat transfer. To
get the maximum heat transfer 仕om a conversion, it is desirable to have
a maximum scrubbing of the flue gas against the heat exchanger areas.
Units with no secondary heat exchangers, no shelves on top of the unit,
or a pot belly design do not usually result in efficient conversions.
4. Appliance venting
Most oil and solid－也el appliances vent to a masonry chimney. Due to
the reduced heat emission of gas firing, condensation can develop in an
oversized and unlined chimney. If the chimney is in poor condition, or
it is not possible to install a liner, a new vent system must be installed
as part of the conversion.
Additionally, if soot has accumulated inside a chimney flue, further
aηangements will have to be made to have the chimney thoroughly
cleaned out. Unless this is done, there is danger that the soot will dry
out and 臼11 down in large quantities, blocking the vent connector.
Other factors to consider when determining the suitability of conversion
include:
•
Overall heating system
Questioning the owner on the efficiency of the appliance may point to
weak spots in the system that will not necessarily be improved with a
conversion. Some rooms may be poorly heated due to:
insufficient duct or register capacity
small radiators
incorrectly located thermostat.
•
Age ofαrppliance
Oil-fired furnaces that are more than 10 years old should not be
converted unless the manufacturer can recommend it.
•
Manufacturer s recommendations
Check with the manufacturer before conversion since some units may
specifically not be recommended for conversion.
4
Gas Technician 2 Training - Module 17
© Canadian Standards Association
TOPIC
2
Installers γesponsibilities
The success and continued safe operation of a conversion burner
installation depends a great deal on the quality of workmanship and the
care taken during the initial burner installation.
The responsibility for a safe and satisfactory installation rests with the
person who:
determines the acceptability of an appliance to be converted
specifies the burner which is best suited for the job
•
handles the installation.
These responsibilities in many cases are assumed by one perso~ or
organization, the installing contractor.
Code
requiremen怡
Section 4.3 of the CSA Bl49.1 Natural Gas and Propane Installation
Code clearly specifies the installer ’ s responsibilities during and after a
conversion.
4.3.1 Before leaving installations, installers shall ensure that the appliance, accessory,
component or equipment they installed complies with the Code requirements, and the
person initially activating the appliance shall ensure that the appliance is in safe working
order.
4.3.2 Installers shall instruct the user in the safe and correct operation of all appliances
or equipment 也at they install.
4.3.3ηm installer shall ensure that the manufacturer ’s instructions supplied with the
appliance are left with the user.
4.3.4 Before installing any replacement part of an appliance, the installer shall ensure
that the replacement p缸t provides operational characteristics at least equivalent to those of
the original part.
4.3.5 When the installation or conversion of an appliance constitutes a conversion from
another form of energy, the installer shall advise 也e user of the appliance, at 也e time of
installation or conversion, to have the former form of energy either removed or left safe
阻d sec田e from accidental activation; for example, the user shall be advised
Gas Technician 2 Training - Module 17
©Canadian S阳ndards Association
5
GUIDELINES FOR CONVERTING APPLIANCES
*
a)
UNIT 1
in the case of a fuel oil supply tank
to remove th巳自11 pipe, and cap or plug the exposed fill pipe opening to an inside
tank;
ii. to shut off the tank outlet valve, remove the filter, and plug or cap the valve
outlet; and
iii. where 吐ie tank is located outdoors, to disconnect all exposed piping or tubing and
cap or plug the piping or tubing as close as practicable to the tank;
i.
的
in
i.
ii.
c)
to shut off the fuel oil supply line valve located within the building; and
to disconnect the fuel oil supply line immediately downstream of the meter, and
cap or plug the outlet of the meter;
in the case of a propane system,
i.
ii.
d)
the case of a fuel oil central distribution system
to shut off the cylinder or tank valve; and
to disconnect and cap or plug the propane supply piping or tubing outdoors; and
in the case of an electrical appliance,
i.
ii.
to shut off the power supply to the electrical appliance at the switch, and
to ensure that the over-current protection，如se, or circuit breaker has been
removed or put in the off position.
4.3.6 The installer installing the installation or conversion, as specified in 4.3.5, shall
advise 由e user of the appliance in writing of the procedures to be followed in
disconnecting the supply of the former form of energy.
4.3. 7 It shall be the responsibility of the installer of a piping or tubing system, to
perform pressure tests in accordance with Clause 6.22.2, and
tubing system is gas-tight at the completion of the tests.
to ensure that the piping or
4.3.8 It shall be the responsibility of the installer of an appliance to perform tests in
accordance with Clause 6.22.3 and to ensure that the system is gas-tight at the completion
of the tests.
valve
*
Note: For Ontario 4.3.S(a) is revoked and the following substitued for it:
a)
in the case of a fuel oil tank,
i.
remove the fill pipe and cap or plug the exposed fill pipe opening to an inside
tank; however, do not remove the tank vent pipe;
ii. shut off the tank outlet valve, remove the filter, and plug or cap the valve outlet;
iii. where the tank is located outdoors, disconnect all exposed piping or tubing as
close as practicable to the tank; cap or plug the exposed fill pipe opening to the
tank; however, do not remove the t缸lk vent pipe; and
iv. advise the owner/operator of the tank in writing that the tank may be required to
be removed in accordance with the Fuel Oil Regulation and the oil shall be
removed by a certificate holder trained for the purpose.
6
Gas Technician 2 Training - Module 17
© Canadian Standards As驭沁iation
TOPIC
3
Code γequi；γements
The CSA B149.l Natural Gas and Propane Installation Code specifies
clearly the requirements for conversions. The intent of these sections is to
ensure safe operation of the appliance, compatibility of the burner, and
proper venting.
Conversions
7.6.1 The minimum clearances from combustible material for a boiler or a
converted to gas shall be
缸mace
a) for a boiler as specified in Clause 7.1.3;
b) for forced air furnace, (i）企om top (casing, bonnet or plenum),
I inch (25 mm); (ii) the jacket sides and rear, 6 inches (150 mm); (iii)
front 24 inches (600 mm); and
c) for a gravity furnace, (i) vertical, 6 inches (150 mm); (ii) sides and rear,
6 inches (150 mm); (iii）丘。时， 24 inches (600 mm), except as specified
in Clause 4.13.2.
7.6.2 An appliance to be converted shall be 也oroughly cleaned, leak
tested, and examined for serviceability. Any unserviceable parts shall be
repaired or replaced.
7.6.3 When an existing vented appliance is to be converted from a solid or
liquid a时，也e chimney shall be examined and shall meet the requirements
of Clauses 8.12.2 to Clause 8.12.11 inclusive.
Conversion
burners
7.7.1 A conversion burner designed by the manufacturer of 由e appliance
to be converted or a burner compatible with the appliance to be converted
shall be used.
7.7.2 When an oil-fired furnace in a mobile home is converted to gas，也e
conversion shall be by means of
a）血e
furnace manufacturer's certified burner conversion package; or
b) a certified conversion burner, provided that
i. it is compatible wi曲曲e furnace and its installation;
ii. the basic design of the furnace is not altered; and
Gas Technician 2 Training - Module 17
© Canadian Sta『ldards Assoc阁曲。n
7
GUIDELINES FOR CONVERTING APPLIANCES
iii. when
UNIT 1
a司justed,
manu臼cturer ’s
the burner firing rate does not exceed the furnace
specified firing rate.
Note
Combustion and ventilation air requirements for mobile homes are detailed
in CSA Standard Z240 Mobile Homes. The venting and clearances should
be designed and sized according to the manufacturers recommendαtions.
7.7.3. A conversion burner shall be correctly positioned and firmly secured
to eliminate direct flame impingement on any surface other than a flame
spreader.
Conversion of
warm-air
7.8.1 A revertible flue furnace shall not be converted by the installation of
furnaces
a) a natural draft burner, unless
the centreline of the flue collar is at least 12 inches (300 mm) above
the burner port (as shown in Figure 1-1 胁，
u. the flue outlet is extended to permit installation of the draft hood or
draft regulator so that 也e relief opening is at least 12 inches (300
mm) above the highest flue pass, and
iii. a bypass at least 1 inches (25 mm) in diameter is connected to the
top of the highest flue pass and extends through the outer casing,
terminating in 由e vent connector. A direct draft damper may be
used as an alternative to the bypass;
1.
b) a fan-assist burner, unless
i. there is compliance with the requirements of (a)(i) to (iii); or
ii. there is compliance with the requirements of (a)(i) and (ii), and the
burner incorporates spark ignition, a pre-pur肘， and an automatic
valve with an integral dual safety shut-off feature.
7.8.2 The bypass referred to in Item (a)(iii) of Clause 7.8.1 shall be gastight and shall be constructed of metal at least equivalent in strength and
corrosion resistance to the metal 仕om which it is extended.
7.8.3 A forced-air furnace with a secondary heating surface located on 也e
suction side of the circulating air blower shall not be ~onverted to gas
except where such a heating surface consists of a single cylindrical flue
pipe passing directly from the primary heat exchanger to the flue collar and
having a single continuously gas-tight welded joint.
8
Gas Technician 2 Training - Module 17
C Canadian Standards Association
GUIDELINES FOR CONVERTING APPLIANCES
UNIT 1
7.8.4 An easily readable caution sign or label of durable mater臼l having
black letters on a yellow background shall be either on or attached to each
side of the circulating air blower compartment access door of a fuel
converted forced-air furnace and shall be worded as follows:
Tl-IlS
“ WARNING:
COMPART~在ENT~机JST
EXCEPT 认呼IBN
“AVERTISSE丸1ENT:
BE CLOSED
SERVICING”
CE CO！－.在PART1'.IBNT DOIT RESTER FER岛伍，
SAUFPOUR L’ ENTRETIEN”
The words ” WARNING ” and ” AVERTISSE1'.IBNT” shall be in a minimum
of 3/8 inch (9.6 mm) in height and the remainder of the lettering shall be in
a minimum of 3/16 inch (4.8 mm) in height.
7.8.5 The flue outlet referred to in 7 .8.1 shall be made of a material at
least equivalent in strength and corrosion resistance to that of No. 24 GSG
(0.60 mm) galvanized steel.
7.8.6 An automatically controlled gr!lvity or forced-air furnace shall be
equipped with a high-temperature limit control, and the maximum setting
of the control shall be
a)
350。F (175 。C)
b) 250°F
Vent
connector
GasTechnic』an
© Canadian
(120。C)
for a gravity furnace; and
for a forced-air furnace.
8.18.18 A vent connector of either Type B or L vent material shall not be
used between the flue outlet and the draft-control device of either a
converted furnace or converted boiler.
2 Training 白 Module 17
Standards Association
9
UNIT 1
GUIDELINES FOR CONVERTING APPLIANCES
Assignment 1
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
Will a conversion to natural gas improve an improperly sized system?
2.
Are all combustion chambers suitable for conversion?
3.
The temperature of emissions from gas firing are (more/less)
temperature of emissions from oil or solid-fuel appliances.
4.
If a liner cannot be installed in a masonry chimney, what must be done to accommodate a gas
conversion?
5.
Who is responsible for a safe and efficient conversion?
6.
Must an appliance be thoroughly cleaned before conversion? What is the Code reference?
7.
What is the. maximum setting of a high-limit control on a forced-air 如mace?
Gas Technician 2 Training - M。dule 17
Standards Assoc幅画m
。 Canadian
than the
11
Unit2
Preparation for conversion
Purpose
As solid fuel and oil appliances do not normally bum as clean as gas,
and the burning temperatures are generally higher, the combustion
chamber must be thoroughly checked and cleaned before a conversion
burner is installed. Similarly the venting system must be checked to
ensure it is in acceptable condition. Once the appliance and venting
system have been checked and modified as required, the choice of
conversion burner is dependent on the combustion chamber geometry
and other selection criteria.
Learning
1. Explain how to prepare a boiler for conversion.
o均ectives
2. Explain how to prepare a furnace for conversion.
3. Explain how to prepare a venting system for conversion.
4. Describe the criteria used to choose a conversion burner.
Gas Technician 2 Training- Module 17
© Canadian Standards Association
13
Topics
1. Preparing a b。iler f。r conversion ......”.......…........…............. 15
Types of boilers …….....……··-…….... ............ .，町…........….... 15
Boiler inspection . .. . ........ . . .. . . ......…...….....…… …............ 16
Re-conditioning ..............................… …………..…... ..
. ............ 16
Combustion chamber lining …·‘·······………………......…................... 17
Other preparation ...…,..................….................…................…... 18
E
E
a
2. Preparing a furnace for conversion ..........…..............…....... 19
Furnace inspection .................……………….............……........... 19
Re-conditioning ….....………......…........……............,…-…-….. 20
Other preparation ...…….......…..................”…………………··....…...... 21
3. Preparing venting system for conversion .......…................. 23
Air requirements ...........…….......... ···········.…....... ·····‘.............. 23
Venting ..........………………················…圄··－…....………··….......... 23
4. Choosing a conversion burner .........................................….27
Types of conversion burners ................…··…················· ...曹................… 27
Burner selection criteria .,.........…....................……….........………......... 30
Assignment 2 .............….......…........ •••••••• ••••••••••••••••••••••••••••••••••••• 35
14
Gas Technician 2 Training - Module 17
© Canadian Standards Assoc阁tion
TOPIC 1
Pγepαγing
a
conversion
boileγfor
Before conversion, a boiler must be care且Illy inspected for cracks or loose
cement in the heating sections, warped doors and door frames, and any
other defects that might permit uncontrolled leakage of air into the
combustion chamber. All conditions of this type must be corrected before
installing a gas conversion burner.
Types of
boilers
When converting boilers, be aware that there are two basic types of boiler
construction that require different conversion treatment.
Wet-base boiler
In a wet-base boiler (Figure 2-1 时， the return lines
enter the boiler at its base. When converting this
type of boiler, there is usually no卢repot1 required
if proper burner is selected. Check with the
manufacturer.
Dη1-base
A dry-base boiler (Figure 2-lb) is one where the
boiler water connections enter at base of the
boiler sections which sit on top of a dry base.
boiler
(a) Wet-base
(b) Dry-base
Used by permission ofthe copyright
holder, the American GasAssociation
Figure 2-1 Types of boilers
1Boilers sometimes require a 币repot to protect against the conversion burner flame
impingingαl the combustion chamber’s metal sides, back or top. If you are unsure ab。ut
whether the unit requires a firepot, consult with experienced personnel
Gas Technician 2 Training - Module 17
© Canadian Standards Association
15
PRE PARA丁ION FOR CONVERSION
Boiler
inspection
UNIT2
The following inspection should determine that there are no conditions that
make the converted appliance uneconomical or unsafe.
1. Shut off the fuel.
2. Remove the burner.
3. Remove the flue pipe.
4. Remove the domestic hot water coils (if any) from the combustion
chamber.
5. Thoroughly clean all heating surfaces and flue passages with brushes or
scrapers to loosen scale and dirt.
6. Clean any residue from low-water cutoff.
7. Vacuum boiler. Take precautions to preserve the cleanliness and
neatness of the premises while removing soot and debris.
8. Examine firepot, if any, to determine condition. Carefully clean firepot
if it is to remain. (Be careful to not damage fibre-type pot.)
•
Resize, replace, reshape, or repair firepot as required
9. Visually inspect boiler for cracks in the seams and body. If you detect
cracks, first repair by re-cementing (or replacing) and then perform
leak test.
Cast-iron sectional boilers must be checked for sealing between the
boiler sections. If there are cracks, replace or repair with furnace
cement.
Steel boilers are examined for distortion of the side walls. Do not
convert if distortion is severe.
Reconditioning
When repairing cr ks with 且rrnace cemen
the label..
1. Re-cement joints around the boiler base to prevent air leakage into the
combustion chamber. (First loosen old joint compound.)
2. Cement all joints between boiler sections.
3. Seal the following areas with furnace cement:
•
16
grate openings
cracks around door frames.
Gas Technician 2 Training - Module 17
。 Canadian Standards Association
PREPARATION FOR CONVERSION
UNIT2
Leak test
Boilers require a leak test to ensure that the boiler is water tight.
1. Test the boiler with pressurized wate卫 If there is dampness at any of the
joints it is a sign that there is a crack.
2. Open drain at bottom of boiler and flush out chamber until water is
clear. Sediment on the bottom can hide a small crack.
3. Re-cement any cracks found during the leak test.
Combustion
Chamber lining Examine the combustion chamber lining for 仕actures or deterioration and
determine if repair is necessaη. If it is in good condition, the existing
chamber liner can be used. If you have to build up the current chamber, use
precast or field-built insulating firebrick rated for service exposure to
2300。F (674。C) combustion products (Figure 2-2). Make it of a thickness
necessary to maintain structural integrity during thermal expansion and
contraction caused by intermi阳nt burner operation.
The lining is required for three reasons:
to protect surf民es that do not transfer heat (e.g. the steel outer wall of a
boiler)
to provide a radiant bed for rapid heat transfer to the prima可
of the heat exchanger
surfaces
to prevent flame contact on the heat exchanger walls if the firing
chamber is unusually short.
The combustion chamber lining in some boilers (such as Type B) require
insulation all around to prevent excessive heat loss through the non-heated
exchanging surfaces. Insulation should be rated for service to at least
1800°F (528°C).
For more informαrtion on Type B combustion chαmbers, see
“ Combustion chamber geometry" in Topic 4: Choosing α Conversion
Burner.
Gas Technician 2 Training- Module 17
© Canadian Standards Assoαation
17
PREPARATION FOR CONVERSION
UNIT2
cement
Insulating
firebrick
y~~邵阳
Seal door
opening
surfaces
Common
brick
Figure 2-2 Combustion chamber lining
Other
preparation
Preparation for conversion may also include the following tasks:
1. File the firing door catches and install a spring-loaded door holder. This
provides a method of pressure relief for the combustion chamber. If the
firing door is so badly distorted that it cannot be tightly sealed closed,
then the door must be replaced.
2. Check location and condition of ductwork. Inspect the condition of
sealing and insulation (if required).
3. Verify that the heating unit conforms to Code requirements in terms of
clearance from combustibles.
18
Gas Technician 2 Training - Module 17
。 Canadian Standards Assoc陆目on
TOPIC
2
Pγepaγi吨 α furnαcefoγ
conversion
Before a gas conversion burner is installed in a 如mace it must 丑rst be put
in first-class condition. One of the first steps is to make sure that inner
radiator steel sections have not rusted through and that domes and radiators
have tightly cemented joints. Defects of this type are not readily seen by
eye so a smoke test is required to make sure products of combustion will
not escape 仕om the furnace into the house.
Furnace
inspection
The following inspection of the furnace should determine that there are no
conditions that make the converted appliance uneconomical or unsafe.
1. Shut off power to furnace (if electric).
2. Shut off fuel.
3. Remove burner.
4. Remove flue pipe.
5. Thoroughly clean all heating surfaces and flue passages with brushes or
scrapers to loosen scale and dirt.
6. Vacuum furnace. Take precautions to preserve the cleanliness and
neatness of the premises while removing soot and debris.
7. Check gaskets on joints between heat exchanger and combustion
chamber.
8. Check for cracks in heat exchanger. Replace if cracks are discovered.
9. Visually inspect furnace for cracks. Some hairline cracks will open and
shut with the heat of the furnace. These cracks may not show during the
smoke test so do a very careful visual inspection.
If forced-air furnace:
Remove fan assembly from blower compartment.
• Remove draft regulator and plug outlet.
Gas Technician 2 Training - Module 17
© Canadian Standa『ds Association
19
PREPARATION FOR CONVERSION
υNIT2
Using light and mirror, check through fan compartment opening
for:
cracks on seams (or elsewhere)
wa甲ing
and distortion of heat exchanger.
In the event of a defective heat exchanger, consult the Code to
determine if it can be repaired or if it needs to be replaced
rust spots.
Inspect all other surfaces you could not see from below through the
fan compartment.
You can inspect through the humidifier opening (if any), make
an inspection opening in the warm air plenum, or, in extreme
cases, dismantle the 如mace.
If a gravity 臼mace:
• Examine the body with a flashlight.
• Check through the burner opening with a mirror.
Ifjoints seem ti酬， you can perform a smoke test. If you detect cracks, first
repair by re-cementing (or replace) and then perform smoke test.
Reconditioning
If cracks or 丘actures, especially above the gr耐 level, are found in any of
世1e casings, after they have been cleaned, the casings shall be replaced.
Repairable cracks or 企actures in other materials should be sealed with
furnace cement. Follow directions on label.
•
Cement all joints between sections.
•
Tightly grout ash pit to 也e floor.
•
Seal the following areas with furnace cement:
open面gs
-
20
for grate shaker bars
cracks around door frames
under clinker door.
Gas Technician 2 Training 唱 Module 17
。 Canadian Standards Association
UNIT 2
PREPARATION FOR CONVERSION
Smoke test
Test the air-tightness of the combustion chamber to ensure no unwanted air
leaks in.
1. Block furnace flue outlet.
2. Light smoke generator and place in fire chamber.
3. Quickly close feed door and observe whether any smoke or odour
escapes from the registers upstairs.
Other
preparation
Preparation for conversion may also include the following tasks:
1. File firing door catches and install a spring-loaded door holder. This
provides a method of pressure relief for the combustion chamber. If the
firing door is badly distorted so that it cannot be tightly sealed closed,
then the door must be replaced.
2. Check the location and condition.of ductwork. Inspect the condition of
sealing and insulation (if required).
3.
Veri命 the
heating unit conforms to Code requirements in terms of
clearance from combustibles.
Gas Technician 2 Training - Module 17
© Canadian Standards Association
21
TOPIC
3
Pγepa1切g
venting system
Joγ conve.γsion
Once the boiler or furnace has been checked and repaired as necessary, the
combustion air and venting system must be checked and prepared for the
conversion.
Air
requirements
If the automatic oil burner operated trouble-free, it is probable that the area
around the heating plant has enough air infiltration for combustion and for
diluting the flue gases.
However, you must make sure that the new installation conforms to the
local Codes and Regulations.
1. Check that combustion air ducts or openings are provided and that they
meet local Code requirements.
2. Check whether ventilation openings are required. If so, ensure they
meet local Code requirements.
Note
Make sure there are no return-air outlets in
the 卢rnace
area.
Venting
The venting system of the oil-fired appliance will already be installed. Your
task is to ensure that it meets the Code requirements.
Note
Moveable flue pipe dampers are not permitted on any gas conversion
installation.
1. Inspect the chimney for unsafe conditions such as deteriorated
masonry, excessive soot, or other blockage.
2. Inspect the vent connector for proper gauge, size and condition. Size
the vent connector based on the size of the draft hood or according to
the Code.
3. Ensure the clearance between the flue pipe and combustible material
strictly adheres to the Code.
Gas Technician 2 Training - Module 17
© Canadian Standards A岱ociation
23
PREPARATION FOR CONVERSION
UNIT2
4. Check whether an exhaust fan, kitchen ventilation system, clothes
dryer and/or fireplace is installed in the building. If so, ensure the
venting of these appliances does not interfere with the conversion
burner operation.
的 Turn
on all the exhaust fans of the appliances in the common vent.
b) Cycle the conversion burner.
c) Check the draft in the venting system with a
there is adequate vent velocity.
dra白 gauge
to ensure
Sizing a chimney
Most oil and solid-fuel appliances use a masonry chimney to exhaust the
flue products; however, since these chimneys were designed to e对1aust flue
products that were hotter than those of a gas burner, it may be too large and
not draft properly causing the flue products to condense. If a masonry
chimney is being used to vent a conversion burner, it must meet the code
requirements for construction standards and size.
I. Size the chimney or flue pipe using good engineering practice, or the
Code book.
2. If masonry chimney is the correct size and is lined with clay tile or
transite (which protects the mortar 仕om the flue gases），让 can be used
as is. Ensure there is a cleanout.
3. If the masonry chimney is too large, install an approved liner
(Figure 2-3).
(a) Rigid material
(b) Flexible material
Figure 2-3 Liner for large chimney
24
Gas 丁丽chnician 2 Training - Module 17
。 Canadian Standards Association
PREPARATION FOR CONVERSION
UNIT 2
Venting requirements for chimneys
The layout and configuration of the venting system should be determined
before proceeding with the gas conversion to ensure that it can be installed
according to the general venting requirements in Annex C of the CSA
B149.l Code.
An appliance can be individually vented into a chimney if equipped
with a draft hood and the chimney is sized and lined (Figure 2-4).
An appliance with fan-assist burner can be vented into chimney
provided there is a draft-hood appliance also vented into the same
chimney (Figure 2-5).
An appliance with fan-assist burner cannot be vented into a chimney.
This configuration is prohibited (Figure 2-6).
Tile-lined
masonry
chimney
Tile-lined
masonry
chimney
Vent
connector.
Figure 2-4 Ora食－hood apliance
vented to lined (tiled) chimney
Figure 2-5 Fan” assist appliance vented
with dra食－hood appliance
Tile-lined
masonry
chimney
Figure 2-6 Prohibited installation (single fan-assist applian臼
vented to chimney)
Gas Technician 2 Training- Module 17
© Canadian Standards Association
25
PREPARATION FOR CONVERSION
UNIT2
Draft control devices
The choice of draft control device is determined by the type of conversion
burner selected. Read the manufacturer ’ s instructions and the Code
reqmrements.
1. Determine (if any) which 可pe of draft control device is required:
Atmospheric conversion burner applications require draft hoods.
Power burner applications can use double-acting barometric draft
regulators if specified by the manufacturer. Single-acting
barometric dampers are not pe口nitted.
In semi-revertible appliances, install a double-acting barometric
damper so relief opening is 12 inches (30 cm) above highest
flue passage.
Figure 2-7 shows the correct and incorrect locations to place a
barometric damper in a power burner conversion.
2. Ensure the draft control device is installed in the same room as the
heating appliance. This ensures no pressure difference between the
relief opening and the combustion air supply.
Double swing
barometric damper
(preferred location)
'\
'-
Other correct ＂－＋~
locations for
,l
barometric damper
location of
barometric
damper
Figure 2-7 Correct and incorrect lo臼tion of barometric dampers
26
Gas Tee如nician 2 Training- Module 17
。 Canadian Standards Assc记iation
Ton℃ 4
Choosing a conversion
burner
There are numerous criteria to selecting the correct conversion burner: the
basic design of the appliance (combustion chamber size and shape) the
input requirement, the type of gas, etc. When selecting a specific type of
burner, investigate the capabilities of the burner since design variations
between manufacturers provide vaηring performance levels for the same
type of burner. Review the manufacturer ’s specifications and
recommendations before specifying any particular burner model.
Each conversion burner should bear the seal of appr ed testing body
certifying compliance with Standard for Domestic Gas Conversion
Burners.
Types of
conversion
burners
There are two main types of conversion burners, classified according to
how the combustion air is distributed:
•
natural draft (atmospheric) burners use the combustion air naturally
supplied to the combustion chamber
•
power burners use a mechanical device to supply combustion air at
varying pressures.
Natural draft (atmospheric) burners
Natural draft burners are those where the combustion air is brought to the
burner, and the products of combustion are vented, without the assistance
from a mechanical device. There are 饥No main 勾rpes of atmospheric
burners, designed to provide the required flame geometry: upshot and
in shot.
Upshot burner
The upshot burner (Figure 2-8) fires vertically with the flame being
diverted by a spreader. The flame 1s generally circular in shape and has a
uniform cross section.
Gas Technician 2 Training - Module
© Canadian Standards Association
17
27
PREPARATION FOR CONVERSION
UNIT2
This type of burner
is mainly used with
Runner tube
如maces or boilers
Stainless steel
igniter
that were originally
flame deflector
manufactured for
coal burning use. By
removing grates and
ashpit doors, the
conversion burner
can be installed in
\
the ashpit section
Adjustable legs
and the flame
spreader distributes
Secondary air
the heat from the
adjustment
firepot up to the
dome and heating
Figure 2-8 Upshot atmospheric burner
surfaces.
The atmospheric ported upshot burner design consists of a series of ports,
slots, or ribbons whereby the flames fire vertically-generally uniform in
height 一h the combustion chamber.
lnshot burner
An inshot burner
(Fi~ure 2-9) fires
horizontally into
the combustion
chamber. It may
have a spreader
or target plate
downstream of
the burner head
to direct the flame
Adjusting
mounting
flange
Stainless steel
flame spreader
Inshot conversion
burners 盯e mainly
intended to
Figure 2-9 lnshot atmospheric burner
replace oil burners.
Oil burners are generally flange-mounted and fire into a re仕actory or
stainless steel combustion chamber within a furnace body
28
Gas Tee却nician 2 Training - Module 17
© Canadian Standards Association
PREPARATION FOR CONVERSION
UNIT 2
Power burners
Power burners (Figure 2-10) are equipped with a mechanical device, such
as a fan or blower, to provide pressurized combustion air to the burner. This
allows better control of the combustion process and a high input for a given
volume of combustion space. The pressure at which the air is delivered, as
well as the burner design, provide the flame geomet可（ shape of the flame).
Electronic
control module
Combustion
air fan
Burner
nozzle
Figure 2-10 Typical fan-assist power burner
Low-pressure upshot
The low-pressure upshot burner fires vertically into the combustion zone.
The flame is generally round and symmetrical. Combustion air is supplied
at a pressure sufficient to overcome the resistance of the burner. This
burner is also called a fan-assist burner.
Low-pressure inshot
Low pressure inshot burner fires horizontally into the combustion zone.
Combustion air is supplied at a pressure sufficient to overcome 也e
resistance of the burner. 古1is burner is also called a fan-assist burner.
High-p网路sure
inshot
The high-pressure inshot power burner fires horizontally into the
combustion zone. Combustion air is supplied at a pressure sufficient to
overcome the resistance of the burner and the appliance. This burner is also
called a forced” draft burner.
Gas Technician 2 Training - Module 17
Standards Association
© Canadian
29
PREPARATION FOR CONVERSION
Burner
selection
criteria
UNIT2
Before reaching the final decision as to what burner is best suited for the
appliance, the following conditions must be considered to ensure proper
selection and application of the burner to the appliance:
•
firing rate (input range) of the burner
•
flue gas travel
combustion chamber geomet可·
Calculating firing rate
The firing rate of the burner must match the input of the appliance being
converted, and in no case shall a burner be set at a firing rate that exceeds
or is less than that specified by the manufacturer.
η1ere
are several methods to determine the firing rate.
1. Heat loss of the building
The heat loss of the building can be calculated using the principles and
guidelines established in the ASI亚AE Handbook Fundamentals or in
HRAI Guidelines.
When a proper building su凹ey has been made and the hourly heat loss
calculated, the conversion burner Btu input should be set at double the
estimated hourly Btu loss (Input = 2 x hourly Btu loss). This will allow
for the heat loss 企om flow and return lines or air ducts, also a margin
for pick up and burner efficiency.
2. Rating plate
Check the input and output ratings on the rating plate (if available), or
manufactur町’s recommendations. Do not exceed the marked input
rating.
3. Burner nozzle size
If the boiler is being converted from oil, the burner nozzle size can be
used to calculate the burner input.
Since:
• burner nozzles are rated in US gallons/h
one US gallon of oil equals 140 000 Btu
•
gas input is based on 80% of oil consumption,
you can calculate the required input using the following formula:
Input =Nozzle size x 140 000 Btu x 0.8
30
Gas Technician 2 Training - Module 17
。 Canadian Standards Association
PREPARATION FOR CONVERSION
UNIT2
4. Boiler horsepower rαting
If the boiler ’ s rating is written in boiler horsepower (BHP), the input
can be calculated based on the horsepower rating and projected
efficiency.
Since:
one BHP equals 33 4 75 Btu/h
•
gas efficiency is based on 75% of BHP,
you can calculate the required input using the following formula:
Input=
BHP
×
33 475 Btu/h
0.75
5. Area of grate
Coal-fired furnaces have a definite ratio of output to grate areapresumably as the grate area represents the capacity of coal that could
be burned in the unit. For conversion pu甲oses, the input of
atmospheric burners can be based on the area of the grate 司
(Table 2-1 ). Notice that round grates are measured by their diameter
while rectangular grates are measured by their area.
Table 2-1 Maximum permissible firing rates for atmospheric burners
Round grates (diameter)
Inches (mm)
14
16
18
20
22
24
26
28
(350)
(400)
(450)
(500)
(550)
(600)
(660)
(711)
Btu/h (kW)
75 000 (23)
100 000 (30)
丁 25 000 (37)
150000 (45)
丁 85 000 (54)
220 000 (64)
260 000 (76)
300000 (90)
Rectangular grates (area)
Inches (mm)
18 x 18
18 x 22
18 x 28
20 x 20
20 x 24
20 x 28
22 x 22
24 x 24
24 x 28
(450 x 450)
(450 x 559)
(450 x 711)
(500 x 500)
(500 x 600)
(500 x 700)
(550 x 550)
(600 x 600)
(600 x 700)
Btu/h
165 000
195 000
245 000
195 000
235 000
270 000
235 000
280 000
300 000
(k叭。
(48)
(57)
(72)
(57)
(69)
(79)
(69)
(82)
(90)
Once you have determined the input, the manifold pressure and orifice size
can be set according to manufacturer ’s input tables.
Gas Technician 2 T1『aining - Module 17
©Canadian S姐ndards A部ociation
31
PREPARATION FOR CONVERSION
UNIT2
Flue gas travel
As previously mentioned, oil and solid』iel appliances have three basic
modes of flue gas travel. These are shown in Figure 2-11.
I. Updr41声
Flue gas travel is constantly upward with flue products exiting at or
very near the highest point of the heat exchanger. All burner types may
be considered for this conversion.
2. Semi-revertible
Flue gas travel is upward initially, then downward to exit the appliance.
The flue outlet is 12 inches (30 cm) or more above the burner ent叩
level. Some atmospheric and all power burners may be considered for
由is conversion.
3. Revertible
Flue gas travel is upward initially,，也en downward to exit the appliance.
The flue outlet is located from below to 12 inches (30 cm) above burner
entry level. Revertible appliances are only to be converted according to
the CSA B149.1 Code restrictions.
一下
12inches
(806 mm)
(a) Updraft
or higher
(b) Semi-reve『tible
(c) Revertible conversion restricted
Figure 2-11 Three modes of flue-gas travel
Combustion chamber geometry
Certain types of burners are better adapted to one boiler than another. For
example, where short fireboxes are encountered, it is often better to use a
burnerwi由 a higher heat release and to avoid long flames 也就 impinge
upon me阳1 surfaces. Similarly, the geome町 of the burner flame should
match 由at of the combustion chamber whenever possible (i.e., a round
flame for a round chamber; an elongated flame for a rectangular chamb创．
32
Gas Technician 2 Training- Module 17
© Canadian Standards A揭ociation
PREPARATION FOR CONVERSION
UNIT2
There are two basic types of chamber geometry.
•
Type A designs include combustion chambers at the base of the heating
zone (Figure 2-12a). Heat transfer surfaces are located at, below and
above flame level.
•
Type B designs include combustion chambers and heat exchangers on a
supporting base (Figure 2-12b). Heat transfer surfaces are above flame
level only. Note that for Type B combustion chambers, inshot burners
are acceptable only if a combustion chamber liner and insulation are
installed.
Supporting
base
(a) Type A
(b) Type B
Used by permission of the copyright holder
the American Gas Association
Figure 2-12 Typical combustion chamber designs
、
」
Gas T臼:hnician 2 Training - Module 17
© Canadian Standards Association
33
PREPARATION FOR CONVERSION
UNIT2
Assignment 2
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
Be岛re
2.
Why is a smoke test performed?
3.
Is a water test required on the boiler?
4.
Does the flue outlet have to be plugged before a smoke test is performed?
5.
If cracks are discovered in the heat exchanger of a furnace, what must be done?
6.
After the appliance has been checked and repaired, what is done next?
7.
If a masonry chimney is too large, what must be done?
8.
Can an appliance with a fan-assist burner vent into a chimney?
9.
Is a draft control device required to be in 也e same room as the appliance?
a conversion is undertaken, what must be done to the boiler?
Gas Technician 2 Training - MOdule 17
©Canadian Standards A部盹iation
35
PREPARATION FOR CONVERSION
10. What are
the 队NO
UNIT 2
main types of conversion burners?
11. To ensure coηect application and selection of a conversion burner, what conditions must be
considered?
12. How many Btu are contained in one US gallon of fuel oil?
13. Gas efficiency is based on what percentage of boiler horsepower?
14. Are revertible appliances recommended for conversion?
15. Are inshot burners accepted for use on a Type B combustion chamber? If so, under what
conditions?
36
Gas Technician 2 Training - Module 17
©Canadian S恼nda『ds Association
Unit 3
Burner installation and flue
gas analysis
Purpose
Once the burner is installed, a gas technician must do the start up
checks and conduct a flue gas analysis for reasons of combustion efficiency and for the safety of the dwelling occupants. An accurate flue
gas analysis will determine the levels of carbon dioxide, excess air,
stack temperature and whether the combustion process is complete.
Learning
1. Describe the theory of combustion.
o均ectives
2. Describe flue gas analysis.
3. Describe the procedure to install a burner and perform start up
checks.
4. Describe how to complete an installation.
Gas Technician 2 Training - Module 17
© Canadian Standards Association
37
Topics
1. Theo叩。f combustion ........… ….......…·…............................ 39
H
Stoichiometric or perfect combusti。n .........................................,….............. 39
Complete combustion ......…-……........….. ..... ........ . . .... ········…. .... .40
2. Flue gas analysis ...............….............................................….43
About appliance efficiency ...............…………….......…町…………. 43
Analyzing for efficiency ………-………··…........…..........…·……........ .44
Plotting combustion efficiency .......................………...……··...”…..... .46
Reasons for poor efficiency .........…..……...............………··-……… 49
Analyzing for safety . . .....………··……......’....…...…···国…....... 51
3. Burner installation and start-up checks ........……….......... 55
Burner Installation...... . .‘……·-……….............................................. 55
Start-up and adjustments. ……………………………..........…................ 57
4. Completing the installation ................................................… 59
Removal of old fuel system .….........….......….......,....“……………...... 59
Protection of property .. .. .. ......…….. ·····…………………................ 59
Instructions to customer. …,..........………·‘…............... ···············…….. 60
’
Assignment 3 ..............….............................................”……......... 6
38
Gas Technician 2 Training- Module 17
。 Canadian Standards Association
TOPIC
1
Theory of combustion
Combustion is a chemical process in which the rapid oxidation of fuel
results in the production of energy (heat). To start and sustain combustion,
three ingredients must mix together in 由e correct proportions:
•
fuel, usually natural gas or propane
oxygen, obtained from the air
surrounding a burner
•
heat, enough to bring the fuel to
ignition pomt.
If any one of these elements is absent,
combustion will not begin nor will it
support itself if an element is removed.
Gas technicians refer to this three-way
relationship as the combustion triangle Figure 3斗
(Figure 3-1).
Stoichiometric
or perfect
combustion
The combustion trinagle
Stoichiometric or perfect combustion is the process of combining
chemically exact amounts of fuel and oxygen so that both components are
totally consumed, with no combustibles or uncombined oxygen remaining
in the flue gases.
The ratio of oxygen t。如el in perfect combustion is as follows:
2cu 盘。f oxygen
•
are required to burn 1 cu ft of natural gas (2: 1 ratio)
5 cu ft of oxygen are required to burn 1 cu ft of propane ( 5: 1 ratio).
Perfect combustion for natural gas and oxygen is expressed in the chemical
formula:
CH4+202
Gas Technician 2 Training - Module 17
© canadian Standards As曲ciation
• C02 + 2H20 + Heat
39
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
Perfect combustion for propane and oxygen is expressed as follows:
C3H8 +502
• 3C02 + 4H20 +Heat
Remember that because perfect mixing of gases is only theoretically
possible, perfect combustion cannot actually be maintained in a
combustion chamber.
Complete
combustion
Because air is 20% oxygen (02) and 80% nitrogen (N2), we need to supply
more air to the burner than perfect combustion with pure oxygen would
require. The air requirements for burning natural gas and propane can be
expressed in the following ratios:
10 cu ft of air is required to burn 1 cu ft of natural gas ( 10: 1 ratio)
25 cu ft of air is required to bum 1 cu ft of propane (25: 1 ratio).
In order to ens田e that these ratios are maintained, excess air is introduced
into the combustion chamber. (The quantity of excess air is often one and a
halftimes the air needed for stoichiometric combustion.)
When excess air is introduced, however, more gases must be heated by the
same amount of Btu. This decreases the initial temperature of the flue gas.
At the same time, a larger volume of flue gas is forced through the heat
exchanger in a shorter period of time, causing a decrease in heating
efficiency.
By analyzing the amount of carbon dioxide and oxygen in the flue gas, you
can a哗ust the amount of excess air to achieve complete combustion wi由
minimal loss of heating efficiency. Flue gas temperature is also an
indication of combustion efficiency.
Products of combustion
The products of complete combustion are produced in the 岛llowing ratios.
One cu ft of natural gas (CH4) produces the following products:
•
1 cu ft of carbon dioxide (C02)
•
2 cu 班。fwater vapour <H20)
8cu 企 of nitrogen
40
(N2).
Gas T由:hnician 2 Training - Module 17
© Canadian Standards Association
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT 3
These ratios are expressed in the chemical formula:
CH4 +202 + 8的＋
Excess
air
• C02 +
2H20 十 8N2+
Excess air+ Heat
One cu 虫。fpropane (C3H8)produces the following products:
•
3 cu ft of carbon dioxide
•
4 cu ft of water vapour
•
20 cu ft of nitrogen.
These ratios are expressed in the chemical formula:
C3Hs+502 +20N2+Excess air
• 3C02+4H20+20N2+Excess air+ Heat
For more informαtion on the theory of combusti。”’ refer to Module 3.
Gas Technician 2 Training - Module 17
©Canadian S剧，dardsAssoc阳lion
41
TOPIC 2
Flue gαs analysis
The combustion process forms products which are exhausted through the
flue or chimney stack. These are referred to as flue gas. Determining
whether the conversion burner is properly installed and is operating safely
can be achieved by analysing the contents of the flue gas.
There are two main reasons for analyzing the flue products: to determine
appliance 写fficiency and to ensure the burner is operating safely. Flue gas
measurement is always taken as close as possible to 也e flue collar and
before any draft control devices.
For more information on instruments for flue gas measurement,
Module 2.
About
appliance
efficiency
r，价r
to
An appliance is most efficient when the greatest amount of usable heat is
produced in its combustion chamber for a given amount of fuel being
burned. Essential坊， an appliance is most efficient when the amount of its
input is near to 由e amount of its output.
Appliance output
Combustion Z伊ciency =
Appliance input
η1e
relationship between input and output is also called stea，吵 state
笔庐ciency.
Seasonal efficiency and AFUE
To determine the overall efficiency of an appliance under actual usage
conditions, other ene电y loses must be considered: the offcycle losses such
as standby losses; room air escaping up the venting system; and the input
consumed by a standing pilot. The more standby losses 由at occur, the more
often the appliance has to cycle on and the longer it takes to reach the
四：tpomt temperature.
Overall annual efficiency is called the annual卢·el utilization 笔fficiency
(AFUE). Seasonal efficiency is 由e efficiency of the appliance based on one
season of usage, whereas AFUE is based on usage over a one-ye町 period.
Gas T创如nician 2 Training - Modu悔
©Canadian S伽ndards A鹅。ciation
17
43
BURNER INSTALLATION AND FLUE GAS ANALYSIS
Analyzing for
efficiency
UNIT3
Analyzing the flue gas is a way to determine the appliance efficiency. This
analysis comprises the measurement of two items from the same location at
the same time:
the percent of carbon dioxide (or the percent of oxygen)
the net stack temperature.
Wi由 these two measurements, the combustion efficiency of the appliance
can be obtained from a chart. Sophisticated flue-gas analyzers are capable
of continuously measuring 也e levels of C02 and/or 02 and the flue gas
temperature, and then calculating the appliance ’s efficiency.
Percent of C02
The percentage of carbon dioxide in the flue gas sample at perfect
combustion is known as the ultimate% C02. This percentage is based on
comparing the volume of C02 to the volume of remaining dry flue gases.
At perfect combustion and with no excess air, the theoretical percentage of
C02 will be at its highest possible level (Figure 3-2).
Ultimate% C02
12
10
'#.
4
2
－τ
Methane
(CH4)
。
60
%Aeration
80
。
20
40
60
80
100
% Excess Air
Figure 3-2 Chart showing relationship between %C02，。2and
excess air for natural gas
44
Gas Technician 2 Training - Modu悔 17
© Canadian Standards Assα革ation
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
(When calculating the percentage of C02 in the flue gas, the water vapour
is removed and the test made on a dη basis. ） ηie ultimate % C02 is the
number of parts of C02 divided by the total number of parts of dry gases in
the sample. This can be expressed as:
C02
Ultimate % C02
=
Total dry gases
Since the chemical make蝴up of each fuel gas is different, each fuel gas
produces different amounts of C02. For natural gas, the dry sample is one
part C02 to approximately eight parts N2. The % C02 is thus one part
divided by nine total parts:
% C02
=
1/9 x 100%
=
11.1 %
Table 3-1 compares the ultimate % C02 ratings between natural gas and
propane.
Table 3-1 Ultimate % C。2 of natural gas and propane
Gas
Natural gas
Ultimate%
C。2
11 -12%
depending on gas makeup
Propane
13.9%
。xygen （。2)
Another option 岛r measuring the combustion efficiency is to use 也e
percent of oxygen in the flue gas to evaluate the combustion process. Since
there is a direct relationship between amounts of C02 and 02 in the flue
gas either one can be used to determine the combustion efficiency.
During complete combustion as shown in Figure 3-2, as 02 goes higher,
C02 goes lower. Notice 由at at approximately 50% excess air, the
quantities of C02 and 02 are equal.
Flue gas te『nperature
The second reading required 如r an efficiency test is the flue gas
temperature.ηiis temperature indicates how much heat has been absorbed
Gas Technician 2 Training - Module 17
Standards Association
©Canad抱n
45
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
by the heat exchanger, which is in tum affected by how much air is passing
through the combustion chamber. By measuring flue gas temperature, you
can gauge how much energy is being lost to the atmosphere. The differ回ice
between the flue gas temperature and the ambient (room) temperature is
the net stack temperature.
Ideally, for an appliance or heating plant to be I 00% efficier此， the
temperature of the flue gas would have to be equal to room temperature. In
other words, all of the heat produced during combustion would have been
absorbed by the heat exchanger and transferred to its application.
For example, at pe价ct combustion, the temperature of the combustion
process involving natural gas and oxygen is around 5000。F (2760。C).
When air is introduced, the temper创ure is reduced to around 3550°F
(1950。C) because of the dilution e岱ct of the nitrogen passing through the
combustion process. As more excess air is added to ensure complete
combustion, the temperature is further reduced.
Pio忧ing
combustion
efficiency
Once you have the levels of C02 (or the levels of 02) and the net stack
temperature, you can use a combustion efficiency chart as shown in Figure
3-3 to determine the level of appliance efficiency. Note that due to
conversion burner design characteristics (such as fan-assist）由e
combustion efficiency ratings will be different for each make and model of
conversion burner. Check with the manufacturer to determine the ideal
level of efficiency.
Natural gas example
The chart in Figure 3-3 can be used to plot the combustion efficiency of a
boiler burning natural gas under the following conditions:
46
•
C02 is 9.5% (02 reading is 4%)
•
Flue gas temp町ature is 365°C
•
Room temperature is
15。c.
Gas Technician 2 T1『sining - Module 17
© Canadian Standards A踊ociation
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
Proced旧e:
Establish the net stack temperature (365 。 C-15 。C
= 350°C).
2. Draw a vertical line (do忧ed）丘om the 9.5% point on the C02 scale.
3. Draw a horizontal line (dotted) from the net flue gas temperature line at
350°C.
4. The two lines meet on the %combustion efficiency c田ve at 75.
Thus the combustion efficiency for this appliance is 75%.
% Combustion e仔iciency
600°
50
c
52
54
~
56
58
64
62
60
66
68 一一一～l
c
72 一一｝
400。 c
74
76
300°
c
78
200°
c
82
80 －一
气 Ucg曲u
C。
A
ε＝3
的DEOOJF
由Z忘 Z
23HEO旦
B的
ε 咽。2
500°
84 一一一
100。 c
%C02
4
5
6
7
8
9
nE5l14
10
11
%02
←卡一才
%Ex饵ss
air
-
nu
41·
Figure 3-3 Combustion e背iciency chart for natural gas
Gas Tee扣，ician 2 Traini吨－ Madu胎 17
©Canad阳n Stan曲时s Association
47
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
Propane example
The chart in Figure 3-4 can be used to plot the combustion efficiency of a
boiler burning propane under the following conditions:
.
C02 is 8% (02 reading is 6.8%)
.
.
flue gas temperature is 475°C
room temperature is 7 5 。c.
Procedure:
Establish the net stack temperature
(475 。C-75 。C=400。C).
2. Draw a vertical line (dotted) from the 8% point on the C02 scale.
3. Draw a horizontal line (dotted）台om the net flue gas temperature line at
400。c.
4. The two lines meet on the %combustion efficiency curve at 69.
Thus the combustion efficiency 岛r 由is appliance is 69%.
600。 C
70
72
c
AUtU
oE由 C。Z由32EOO萨
、
－
J
曲目
由Z
oogagωaε
g。由
3EV
500°
74
76
400。 c
78
300°
80
c
82
84
200。 c
86
100°
c
。
%C02%02
12
11
%Ex饵SS
120
100
air
8
7
6
10
8
9
90 80 70
10
9
60
6
7
50
40
12
11
5
30
4
14
。
2
3
20
13
15
10
5
。
Figure 3-4 Combustion efficiency chart for propane
48
Gas Technician 2 Training - Module 17
©Canadian S恼ndards Association
υNIT
3
Reasons for
poor efficiency
BURNER INSTALLATION AND FLUE GAS ANALYSIS
In general, the higher the flue gas temperature，也e lower the efficiency.
The following conditions reduce heat efficiency because they raise the
temperature of the flue gas.
Ove圳ring of
burner
A heating appliance is designed to produce a certain
amount of heat. Overtiring creates additional heat which
cannot be recovered, and hence escapes up the flue. This
causes a rise in the stack temperature because it is unable
to exchange the extra heat.
Insufficient air Insufficient air flow across the heat exchanger reduces
flow across
the heat transfer and increases the fuel consumption.
heat exchanger
Incorrect
excess α·1r
supply
The levels of excess air can be measured by the quantity
of oxygen 扭曲e flue gases. When there is insufficient
excess air supply, the following results:
lazy flame
incomplete combustion and sooting.
Too much excess air can cause the following:
raises the stack temperature by allowing flue gases to
escape too fast for heat exchanger to absorb the heat
can cause flame impingement
can cause noise in combustion process leading to
customer complaints.
Dr~斤
conditions
Draft conditions can result in high or low flue gas
temperatures，也e production of carbon monoxide and
aldehydes, and/or flue g部 sp迦age. 白ie air should be
adjusted with al:'proximately 0.02 inches w.c. (50 Pa)
overftre draft with neutral pressure point baffle if
necessary.
The main causes of incorrect draft are:
Gas Technician 2 Training- Module 17
© Canadian Standards Assoc剧。n
•
improper setting of the air shutter
•
wrong barometric setting
•
long horizontal vent connector.
49
UNIT3
BURNER INSTALLATION AND FLUE GAS ANALYSIS
Dirty heat
exchangers
A dirty heat exchanger surface will insulate the
equipment and prevent effective heat transfer. This
increases fuel consumption.
Incorrect
An incorrect draft control device, or an incorrectly
neutral pressure a司justed dra武 control device can lead to a neutral
pressure point se位ing that disturbs the draft and velocity
point setting
of the flue products. Figure 3-5 shows that with a coηect
neutral pressure point a match flame will blow out above
the latch and be drawn in below the latch.
Match flame
blows outward
above latch
吨··氢，也
问佣
..
OO,
AU
nHFU
nuahH
Mateh flame
pulls in
below latch
Figure 3-5 Testing for c。rrect neutral pressure point
Dirty filters
50
Di均r
filters on a 岛rced-air furnace reduce the air flow
across the heat exchanger, thus reducing the heat
exchange capabilities of the appliance.
Gas T创加1ician 2 Traini咱－ Modu悔 17
© Canadian Standards Association
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
Analyzing for
safety
The second reason for analyzing the flue products is for safety reasons. You
want to make s町e that there is complete combustion and there is no carbon
monoxide being emitted.
Even though the appliance is operating efficiently and there is enough
excess air being introduced, (i.e. the C02, 02 and stack temperatures are
within acceptable range) the burner can still be emitting carbon monoxide
and aldehydes. Generally speaking, as the appliance is adjusted to obtain
higher combustion efficiencies, there is a 也nger that CO levels will
increase. CO should be maintained at very low levels and should not
exceed 50 ppm (on an air－仕ee basis1).
A
Caution!
Carbon monoxide is toxic, odour free, and life threatening. It is veη
important to use the flue gas analyzer to check for levels of carbon
monoxide ifier installing a conversion burner.
Often when CO is produced, it is accompanied by aldehydes. Aldehydes
are a group of transparent, colourless gases wi由 a suffocating smell,
produced by the partial oxidation of fuel gas. Because of this, they are
easily detected. They are toxic and irritating to the eyes, throat and nose.
Percentage of C02 in complete combustion
Since excess air is required for complete combustion, there will be higher
levels of oxygen in the flue gas, and less C02，由an the ultimate %.
For example, if 50% excess air were introduced, there would be one extra
cu ft of oxygen and four extra cu ft of nitrogen in the flue gas.η1e total flue
gas would be as shown in the following formula:
CH4 + 202 + 8N2 + 02 + 4N2 → C02+2乌0 + 8N2 +02 + 4N2
1Sincethe 响ue
gas co时ains varying quan回ties of air (depending on peri但时 excess air)
on an air free basis. The air－伽·ee 阳ctor is the ratio of the
ultimate %C02 of 伽e gas being burned to the actual %C。2 in the 由uegas sam~胞 For
example, for natu『al gas at 11.1°.k ultimate C02 and a 加e gas sample with 8.8% C02,
a 臼rbon mα10xide concentration of 0.03% in the 甜阳al sample would 陪pr回ent0.04%
on an air－骨臼 basis. ［（刊. 7 + 8.8) x 0.03 = 0.04]
theCOlim民 is u副ally speci由ed
、、－一
Gas Technician 2 Training - Module 17
@Canadian S切ndards Association
51
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
The dry sample (without the water) would be one part C02 in 14 total
parts, and the percentage of C02 would only be 1/14, or just over 7%.
Note that the percent of C02 does not necessarily indicate complete
combustion. For example, in referring to Figure 3-2, a 10% C02 reading
can be an indication of either negative excess air (90%) or positive excess
air ( 110%). It is therefore necessa可 to also measure the CO content to
ensure complete combustion.
Reasons for incomplete combustion
Carbon monoxide (CO) and aldehydes are produced 仕om incomplete
combustion, under the following circumstances.
Lack of
excess air
．咱
T
川m
M
旷，。
Earι
αW
－
ru
Wrong burner selection can mean poor mixing of fuel
and air, causing incomplete combustion.
Flame
impmgement
CO can be produced when a flame is chilled below
ignition tempera阳re. This occurs when the flame
pa忧ems allow the flame to contact heating surfaces
before complete combustion has taken place.
Cracked heat
exchanger
Cracked heat exchangers can cause the heated supply
air to come in contact with the flue products and the
flame, interrupting the combustion process.
Significant gas
leak
A significant gas leak in the pilot line or in 由e vicinity
of the combustion chamber could result in incomplete
combustion.
Burner
A damaged or improperly positioned main burner
could result in flame impingement and poor mixing on
the burner.
ma拚mction
52
0n
Lack of excess air is the most common reason for the
production of CO. However, if you have analyzed the
flue gas for levels of C02 and 02 and have determined
that excess air is not 由e cause of the problem, poor
mixing on the burner, chilling of the flame, or a
cracked heat exchanger are possible causes.
Gas Technician 2 Training - Module 17
。 Canadian Standards Association
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
Flue gas analysis results
The following ideal natural gas combustion efficiency results are general
guidelines only; check with the manufacturer to ensure you are using the
figures designed for their conversion burners.
C02 for atmospheric burner
7.5 - 9%
02
5-8 %
C02 for power burner
9 - 10%
02
3-5 %
CO for atmospheric/power burner
0- under 50 ppm (air free)
Flue gas temperat町es
350-400。c
Modifications based on flue gas analysis
In summary:
too much excess air increases the amount of air required to be heated
which is then wasted as it vents up the chimney
too little excess air means there is a danger of incomplete combustion.
For atmospheric, fan-assist or power burners, the air supply openings are
adjustable and must be positioned to achieve the optimal amount of air
flow forene电y efficient combustion.
When excess air is added to ensure complete combustion the appliance
efficiency decreases because the excess air is absorbing heat and being
exhausted up the chimney.
If your analysis indicates incomplete combustion:
•
check appliance input
•
check excess air
•
check primary air (on atmospheric burners)
check burner design and location.
Gas Technician 2 Training - Module 17
@Canad阳n S幅ndards Association
53
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
If your analysis indicates poor efficiency:
•
check appliance input
•
decrease excess air
•
adjust dra企 control.
After the adjustments do another flue gas analysis to ensure you have
complete combustion and good combustion efficiency.
54
Gas Technician 2 Training- Module 17
© Canadian Standards Association
TOPIC
3
Buγneγ instαllation αnd
stαγt-up
checks
The proper installation of a conversion burner is critical to 由e safe and
efficient operation of the appliance. The installation must be carried out as
specified by the conversion burner manu臼ctur町、 installation instructions
and it must meet the Code requirements. Consequently, all checks and
adjustments must be done with safety and efficiency in mind.
Burner
Installation
Installation of a burner shall be so planned that it and all its controls will be
readily accessible for inspection, cleaning, a司justments and repairs.
Conversion burners come as a complete package, but you must choose the
correct orifice size to suit the input, position the sleeve and burner, and set
the air shutter if required. Details of various manufactur町、 burners differ.
Be sure to follow the installation instructions supplied by 也e manufacturer.
Burner sleeve location
Conversion burners may be mounted in a sleeve that is sealed to the
combustion chamber with refractory material.η1e burner can then be
removed 企om the sleeve for servicing or repair.
Position the burner sleeve and nozzle 1 inch (25 mm) short of the inside of
the combustion chamber (Figure 3-6). This protects the burner nozzle 齿。m
the hot combustion chamber tempera阳res.
Before permanently setting the burner in place:
1. Check 白at the burner nozzle and pilot are fr.臼 of 岛reign materials.
2.
Check 由at 由e
Gas Technician 2 Training '- Mod晦 17
e Canadian Standards As割沁ialion
spark igniter has not been damaged or displaced.
55
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
Combustion
chamber
由
nn Emmm
u
、
m
m
’ 1
-
Figure 3-6 Fan-assist conversion burner with spark igniter mounted in burner
sleeve in combustion chamber
Burner location
The burner must be solidly supported on fireproof material both front and
rear and be level in both directions. Table 3-2 gives typical burner location
guidelines.
Care should be exercised when installing the burner to avoid undue strain
on, or distortion of burner tube or other component which would impair its
且mctioning.
Table 3-2 Typical installation guidelines
Appliance
lnstallati。n
Boilers
Burner po此s set at least 1 inch (25
mm) above the grate level.
Single-port upsh。t
Boilers
Bo忱。m 。f flame spreader set at
least 1 inch (25 mm) above the
grate level
Drilled port or multi才et
upshot
warm-ai 『
furnace
Burner ports set above the grate
level, but not more than 1/3 the
distance between the grate and
the bo忱。m level of the firing door.
Burner type
Drilled port or
upshot
multi才et
Single-port upshot
叭角『m-air
furnace
56
location
8。tt。m of flame spreader set
above the grate level, but not
more than 1/3 the distance
between the grate and the b。忧。m
level of the firing door.
Gas Tee如nician 2 Training - Module 17
。 Canadian S姐ndards Association
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
Gas orifice
Many conversion burners come with orifices for both natural gas and
propane.
1. Install the appropriate gas orifice.
2. If the orifice is adjustable, follow the
a司just the orifice for correct input.
Start-up and
adjustments
manu岛ctur町、 instructions
and
After completing all the required pre-start checks (testing, purging) as
required by the Code, the conversion burner is ready to be started up and
adjusted. In some localities the authorities having jurisdiction may need to
be consulted regarding local start-up requirements (e.g., an inspector may
need to be on site during start-up).
Limits, controls and interlocks
Depending on the input, and the type of appliance, the start-up checks can
be very simple or very complex. The limits, controls and interlocks that
may require checking include:
•
fan switch
·•
flow switch
•
low-water cutoff
•
pressure gauges
•
water-fill controls
•
pressure controls
•
pressure-relief valve and drop tube
•
steam-pressure controls
•
compression tank
•
circulator and controls
•
limits
•
thermostat location and voltage
•
heat anticipator.
The Code requires you to leave the appliance in safe operating condition.
you must check all safeties and interlocks before leaving. Some
may be checked before start-up, others may need to be checked after
start-up.
τ'herefore,
Gas Technician 2 Training - Module 17
Standards Association
。 Canadian
57
BURNER INSTALLATION AND FLUE GAS ANALYSIS
UNIT3
Do the following checks after start-up. Make any necessary adjustments.
1. Check burner operation.
To light up the burner safe竹， follow the specific start-up directions
provided by the burner manufacturer. Cycle the burner on and off
several times with the thermostat or aquastat. Ensure sequence occurs
as designed.
2. Ensure any potable water connections meet the plumbing code for
required cross connection devices.
3. Check draft control device for proper operation.
If using a barometric draft control, use a draft gauge to measure and
adjust the draft as required by the appliance manufacturer.
4. Conduct flue gas analysis on power burners.
Adjust the air shutters as required.
5. Clock the meter to ensure burner input is correct.
6. Check the fan motor, blower speed, and pulley size (if applicable).
Oil motor if required.
58
Gas Techniαan 2 Training-Module 17
© Canadian Standards Assoαation
TOPIC 4
Completing the installation
In some jurisdictions, upon completing the installation, the installer must
immediately noti命 the serving gas supplier and the authority having
jurisdiction that the installation is complete.η1e CSA B149.1Code
clearly specifies the installer's responsibilities; it is advisable to review
these before, during and after the conversion.
Removal of
old fuel
system
The contract between the installer and the customer will detail the
installer ’s responsibilities with regard to disposing of the old fuel system.
Unless otherwise stated in the contract, all parts removed from the
appliance such as oil burner, oil lines and valves or grates and ash pit door,
shaker arm and handle, should be le~ on the premises for the customer to
dispose.
•
Check the Installer's Responsibilities section of the CSA B 149 .1 Code
to determine the tasks involved in removing the old fuel system.
Note that some tanks were installed before basement steps were
installed so the tank may need to be cut apart to get it out. At all
times have an adequate fire extinguisher (ABC type) handy as
blades can become hot and ignite vapours.
Protection of
property
At all times, protect the customer ’s prope吗r with an acceptable oilabsorbent material and carefully clean up all debris or spills created during
the installation.
If tank to be left on customer ’s property, plug all openings to avoid
spills.
•
Do a final clean up of basement before leaving the premises.
Gas Technician 2 Training- Module 17
© Canadian Standards Association
59
BURNER INSTALLATION AND FLUE GAS ANALYSIS
Instructions
to customer
UNIT 3
Inform the customer about the hazards of flammable liquids and vapours
and instruct them to keep flammable products away 仕om the vicinity of the
appliance.
Once the conversion is complete the installer is responsible for thoroughly
instructing the customer on how to properly and safely operate the
converted unit. The customer should also be informed about the periodic
maintenance required based on the conversion manufactur町、 instructions.
The manufacturer ’s instructions should be posted in a prominent location
near the appliance. A record of the installation a司justment data should be
affixed to the burner or the converted appliance and shall contain the
following data:
input in cu ft/hr (m3/s)
manifold pressure se忧ing
•
measured flue gas temperature
%C02or%02
•
60
date and installer's name.
Gas Technician 2 Training- Module 17
。 Canadian
Standards Ass<沁园ion
UNIT 3
BURNER INSTALLATION AND FLUE GAS ANALYSIS
Assignment 3
When you have completed the following questions, ask your instructor for the
Answer Key.
1.
Define “ combustion."
2.
Can perfect combustion be maintained in a combustion chamber?
3.
How does a gas technician determine how much excess air is being introduced into the
combustion chamber?
4.
What is the purpose of performing a flue gas analysis after setting up a conversion burner?
5.
Do…叫…m缸in in 由e 叫阳tion 咄en calcul低ing
th
gas?
6.
What would be the temperature of the flue gas if an appliance was 100% efficient?
7.
At what level must the level of carbon monoxide remain below (on an air－丘ee basis)?
8.
List the four main reasons 岛r the formation of carbon monoxide.
9.
List the seven main reasons for inefficient combustion.
Gas Technician 2 T1『aining - Module 17
© Canadian Standards Association
61
岛1odule
18
Water Heaters and
Combination Systems
Installation of new and replacement gas water heaters form a
normal part of your duties as a gas technician. The types of heater,
controls, components and piping systems vary greatly, as do the
installation requirements for each type. A th<?rough understanding
of gas-fired water heaters and combination system installation,
servicing and maintenance will ensure that the hot water
requirements are adequate for the building.
At the end of this module y。u will be able t。：
Identify and understand the operation of gas－币red water
heaters
Gas Technician 2 Traini『唱－ Module 18
e Canadian Standards A路。ciation
•
Identify and understand the 。peration of combination
systems
•
Size and install gas-fired
combinati。n systems
•
Service hot water heating and
h。t
water heating and
c。mbination
systems
iii
Ken Bales, Manager, Gas Information Products, CSA, wishes to acknowledge the following individuals
who contributed as members of a Review Panel during the development of the original edition of the
Gas Technician 2 Training Materials. In addition, British Columbia Institute of Technology {BCIT) is
acknowledged for its work in the technical development and editing of the original edition.
c。”tribut。rs and members 。f the Review Panel
John Cotter
Bill Davies
Eric Grigg
Warren Hayes
Darrel Hilman
Ken Kell
W. John Lampey
Lorne Lowry
Jim Noseworthy
Gary Prentice
Nick Reggi
Rick Rogozinski
Ron Royal
John Semeniuk
Allen Sidock
John Simmons
David Stainrod
Terry Waters
IV
Canadore College
Union Gas Limited
Canadore College
Superior Propane Inc.
Southern Alberta Institute of Technology
Centra Gas Manitoba
Alberta Advanced Education & Career Development
Algonquin College
Durham College
Environmental Energy Consul恼nts
Humber College
Union Gas
Fanshawe College
Northern Alberta Institute of Technology
Camb时an College
loyalist College
D.J. Stainrod & Associates Ltd.
Enbridge Consumers Gas
Gas Technician 2 Training - Module 18
@ canadian Standards Association
岛1odule
18
Table of Contents
Unit 1
Water heaters
Installation requirements ..................................... 3
Types
。f water
heaters …........…………................ 9
Controls and accessories. ………….......………..... 19
Piping layout ..................................................... 29
Storage systems .................………….......…........ 35
Rem。val
and
installati。n
procedures ................ 37
Assignment 1 ..............….........…....................... 43
Unit 2
Combination systems
lnstallati。n
requirements ..........……................... 49
Types of combination systems. …………….......... 53
System layout ....................……………................ 61
V\/iring procedures ..................………·………........ 63
Assignment 2 ........…......................................….. 65
Unit 3
System sizing
Water heater sizing ............………......…….......... 69
Space heating requirements ............................. 71
Pump sizing .................…........…·······…............. 77
Assignment 3 .................…................…............. 79
Unit4
Servicing systems
Electrical components ..............……................... 83
Non-electrical problems and servicing .............. 87
Analyzing malfunctions ..............….................... 99
Assignment 4 ................................……............ 103
Gas Technician 2 Training- Module 18
© Canadian Standards Association
v
Unit 1
Water heaters
Purpose
Installation of new and replacement gas water heaters is a normal part
of a gas technician ’s duties. The types of heaters, controls, components
and piping systems vary greatly, as do the installation requirements for
each type.
It is important for the gas technician to be able to
identi却 and
select
the proper water heater and related equipment required for an
application and perform the work in accordance with applicable Codes
and manufacturer ’s instructions.
Learning
1. Describe installation requirements for water heaters.
o时ectives
2. Describe types of water heaters.
3. Describe water heater controls and accessories.
4. Describe water heater piping layout.
5. Describe hot water storage systems.
6. Describe water heater removal and installation procedures.
Gas T创：lmiαan 2 Training-Module 18
© Canadian Standards Association
1
1. Installation requirements ........................................................ 3
Interpret codes .. . ......…. . .... ....... . . . . .... . .................. 3
Use installation inst 「uctions and trade manuals .--… ……..................... ?
a
2.
Types of water heaters ............................................................ 9
Water heaters . ...’·········…..........…·－…国..
. ..........’............. 9
Underlnsta 『itaneOL』s .............目．．．．．．．．．．．．．．．．－．．．．’．．－－．．．．··－··－…................... 12
Copper-fin-tube with storage tank ..…………………………................ 14
Direct-vent ．．萨.........…..........‘．．．．－．．－．．．’．．，．．．目..........................目.......... 14
p。wer·嗣
Condensing ..........’.............，墨．’．．．．．．．．．．．．．．．…町……...……··…确．．．．… 17
Combination units ......……·-·...,.…….....……...........……............. 18
3.
Controls and accessories ...................…............................... 19
Anti-scald device ..…........…..........................,……··-………................... 19
Unitrol ..... . ........................... . .. .. . ...…......................................…...... 19
Aquastat ..............................................……·-….........….. .. . .. . .… 21
Limit c。ntrols ..… ………………………·-……..........................21
Dip tube ．．．．啕….......... ······ ...........…….........……··········· ..................... 23
An。des ......................………··………….................……..............…........….24
Venting systems .........................…..................... ········….......…................. 25
Valves ．．．．．．…………….......…·．．．．．．．．．……..............啕................................... 25
Circulating pumps .............………………......…··..........…………........ 26
a
4.
Piping lay。ut. ..............…......................................................... 29
Water piping layout ...……...... .- .........……......….........…且..............……........ 29
Gas piping layout ..............................................………··…….........…….. 32
Piping drawings .........................................….....…...................... 32
5.
Storage systems ..............…................................................… 35
Large tank storage heaters. …...............……………-…·········……………………… 35
Two-tank systems ...........……······· ........…….......………..............…............ 35
Circulating water heaters ............................................................................36
Instantaneous water heaters ......................…………-…………..... 36
6.
Removal and installation procedures .................................. 37
Removal procedure .........……………….......…...............….........……........ 37
Installation procedure ....................………...............…….........…................. 38
Water piping installation ..........…·······….......…···············································拥
Gas piping installation .................…................………...............…··……...........40
Venting installation ..............….........…...............……….........….....................40
Filling the water heater .................................………......…··························….41
Installation checklist. ……··…..........................……. ··············………...............41
Lighting the pilot burner ...........….............................….........…….................42
Assignment
2
1 ............................................................................... 43
Gas Technician 2 Training- Module 18
© Canadian Standa『ds Association
TOPIC]
Installation requirements
The following Codes specify the requirements for installation of gas-fired
water heaters:
Interpret
codes
•
Natural Gas and Propane Installation Code, CSA B 149 .1
•
Canadian Plumbing Code.
The gas technician is responsible for correctly interpreting and following
the relevant Code requirements when installing gas-fired water heaters.
Natural Gas and Propane Installation Code
requirements
Two Parts of the CSA B149.l Code specifically address the requirements
for water heaters:
•
Part 7 - Installation of specific types of appliances
•
Part 8 - Venting systems and air supply for appliances
Part 7 - Installation of specific types of
appliances
7 .26 Water heaters
7.26.1 A water heater, unless of the direct-vent type, shall not be installed
in a bathroom, bedroom, or any enclosure where sleeping accommodation
is provided.
7.26.2 A water heater shall have a tempera阳re and pressure relief device
that has a discharge pipe of a size at least equal to the nominal size of the
device outlet. The discharge pipe shall terminate not more than 12 inches
(300 mm) above the floor.
7 .26.3 An instantaneous－可pe (tankless) water heater, unless certified for
installation on a combustible wall, shall be provided with appropriate
protection as specified in Table 4.1. Such protection shall extend the full
length and width of the heater and its draft hood.
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7.26.4 Except when permittjed by Clause 4.13.2, the minimum clearance
from combustible m创erial for an underfired storage-type water heater shall
be 2 inches (50 阳时， and e minimum clearance for any other type of
water heater shall be 6 inchl s (150 mm). See also Clause 4.14.2.
7.26.5 A direct-vent w创er lieater shall have a minimum access clearance of
3 ft (900 mm) on the bumet side.
7.26.6 Before installing an fnstantaneous type (tankless) water heater, the
installer shall ensure 也就白1~re is sufficient water supply for proper
operation of the heater.
Part 8 - Venting systems and air supply for
appliances
8.13 Vent and chimney ~izing
'
'
8.13.1 A V削 or a chimney I serving a single appliance shall provide
effective venting and shall be sized
(a) so that its effective arealis not less than that of the draft-control device
outlet or the flue outlet; or
(b) in accordance with goo4 engineering practice, such as by the use of
(i) Table C. l, C.2, C.5, vr C.6 of Annex C for a dra直…hood-equipped or
a fan-assisted Category II appliance; or
(ii) engineered venting 阳.bles acceptable to the authori句r having
j山isdiction.
8.13.2 A vent or chimney s~rving more than one appliance shall provide
effective venting and shall pe sized
(a) so 白at its e:ffective flue ~rea is not less than 由at of the largest dra也
control device outlet or the largest flue outlet, plus 50% of the sum of the
· outlet areas of the additional appliances; or
(b) in accordance with goo<ji engineering practice, such by use of
(i) Table C.3, C.4, C工 pr C.8 of Annex C for a draft-hood-equipped or
a fan-assisted Category II appliance; or
~ii) ~gineered venting tables acceptable to 也e au也ority having
jurisdiction.
8.13.3 A vent may be any $ape, provided its venting capacity is equal 阳
of round pipe for which it is substituted and its minimum
也e capacity
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internal dimension is not less than 2 inches (50 mm). In no case shall the
area be less than the area of a 3 inch (75 mm) inside diameter pipe. See
Table C.10 of Annex C.
8.14 Vent and chimney termination
8.14.1 A vent or chimney shall extend high enough above either a building
or a neighbouring obstruction so that wind from any direction will not
create a positive pressure in the vicinity of either the vent termination or
the chimney termination.
8.14.2 Except for a special venting system with positive vent pressure, a
vent shall extend not less than 2 ft (600 mm) above the highest point where
it passes through a flat roof of a building and not less than 2 白（600 mm)
higher than any portion of a building within a horizontal distance of 10 负
(3 m).
8.14.4 A chimney shall extend not less than 3 ft (900 mm) above the
highest point where it passes through the roof of a building and not less
than 2 ft (600 mm) higher than any portion of a building within a horizontal
distance of 10 ft (3 m).
8.23 Draft hoods
8.23.1 Except for an incinerator, a dual-oven type combination range, and a
direct-vent appliance, an appliance requiring zero over-fire draft for
operation shall be installed with a draft hood.
8.23.2 A draf王 hood shall not be used on an appliance with either positive
over-fire draft or an induced draft.
8.23.3 A draft hood either supplied with or forming part of an appliance
shall be installed without alteration.
8.23.4 When a draft hood is required and it is not supplied by the appliance
manu臼cturer, it shall be supplied by the installer and it shall be of an
approved design. See Annex F.
8.23.5 The draft-hood outlet shall be of the same size as the appliance flue
collar unless otherwise sized in the appliance manufacturer's installation
mstruct1ons.
8.23.6 A draft hood shall be in the same room as 由e combustion air
opening of the appliance. A draft hood shall not be installed in a 臼lse
ceiling space, in a room other than the one the appliance serves, or in any
manner that could permit a difference in pressure between the draft hood
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relief opening and the combustion air supply. The draft-hood supplied for a
conversion burner shall be located so that the burner is capable of safe and
efficient operation.
8.23. 7 A draft hood shall b中 installed in the position for which it was
designed with reference to the horizontal and vertical planes, and shall be
located so that the relief op ning is not obstructed by any part of the
appliance or adjacent construction. The appliance and its dra由 hood shall
be located so that the relief opening is accessible for checking vent
operat10n.
8.23.8 A draft regulator shall not be used as a substitute for a draft hood.
Canadian Plumbirg Code installation
requirements
Section 6 of the Canadian Plumbing Code specifies the requirements for
hot water tank installations. The two areas of most concern to gas
technicians are those dealing with shut-off valves and relief valves.
Requirements for shut-off valves include the provision that a pipe that
supplies water to a hot wat~r ta时t shall be provided with a shut-off valve
located close to the tank.
Provisions for relief valves µiciude requirements that a storage-type service
water heater be equipped \\jith a pressure relief valve designed to open
when the water pressure in the tank reaches the rated working pressure of
也e tank. Additionally it requires that storage-type service water heater be
equipped with a temperat田e relief valve with a temperature sensing
element located within the top 150 mm of the tank and designed to open
Indirect service water heaters are required be equipped with a press田e
relief valve, and a temperature relief valve on eveηstorage tank that forms
part of the system.
A shut-off valve is not penµi扰ed on the pipe between any t创业 and the
relief valves or on 由e discllarge lines 丘om such relief valves.
The plumbing code also re~uires that a vacu』um relief valve be installed
when anyt础 may be sub ect to back-siphonage.
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Use
i nsta Ilation
instructions
and trade
manuals
Additional requirements and recommendations for gas-fired water heater
installations can be found in various publications, and in manu臼cturer ’s
instructions, manuals, and service bulletins.
Manufacturer’s recommendations
Compliance with manufacturer ’s recommendations and instructions is
necessary for safe and efficient water heater installation and servicing.
The manufacturer ’s documentation typically includes information on the
following topics:
•
safety requirements and precautions
installer and owner responsibilities
•
location requirements
•
water piping installation instructions
•
gas piping and venting installation instructions
•
water heater start-up instructions
•
operating and troubleshooting instructions.
Gas Technician 2 Training - Module 18
Canadian Standards Association
©
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TOPIC
2
Types
ofwαteγ he ateγs
Water heaters
Water heaters form the largest class of gas appliances. Their popularity is
due to low initial cost, low operating cost, cleanliness and convenience.
Water heaters range in size 仕omve可 small recreational vehicle units, to
domestic sizes for residential use, to larger installations for commercial
buildings and manufacturing processes.
Direct-fired heaters
The most common type of water heater used for residential service and
low-demand commercial applications is the direct乒red storag巳 heater. In
the context of a water heater, the term direct-fired means that the heat from
the gas flame is in direct contact with a ta时t or pipe containing the water to
be heated. A direct-fired, residential storage-type water heater is shown in
Figure 1-1 on page 10.
Indirect heaters
In an indirect water heating system, the water is not heated directly by the
gas flame. The water is heated by a fluid that has been heated
directly.
heat 企om the
An indirect system typically consists of a hot-water storage tank connected
to a coil located in a steam or hot-water boiler (see Figure 1-2). In
Figure 1-2, the water in the heating coils is heated by the steam produced in
the boiler. The temperature of the water in the storage tank is maintained by
the circulating convection flow of water through the system.
In other indirect systems, the heating fluid flows into a coil installed in the
hot-water storage tank (see Figure 1-3).
、、、、『－
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HEATERS
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Di岱rer川ypes of gas-fi叫 water heater and combination systems that are
in common use include:
•
mstantaneous
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kgo
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川
时
泣·咀
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oj
cdpec
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出
under-fired storage
由
•
Vent
connector·
Hot water
outlet
Flue tube
(heat exchanger)
Flue
baffle
Anode rod
Dip tube
Insulation
Storage
tank
Combination
thermostat &
gas valve
Main
burner
Floor
shield
Figure 1-1 Direct布red, residential storage-type water heater
10
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UNIT 1
丁emperature
and pressure
「elief valve
台
飞
Thermometer
\
/
；国
lQ}- -
合
合
Cold
.
' －『白－ - - －一，明－ - - －明白、,
Steam
boiler
Figure 1-2 Indirect-fired system with heating coils in boiler
Hot
water
outlet
飞 Thermometer
合
Thermostat
飞
V
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