Trade of Plumbing – Phase 2
Module 3 – Unit 2
Module 3:
Domestic Heating/MMA Welding
Unit 2 – Domestic Heating Systems
Duration – 10 Hours
Trade of Plumbing – Phase 2
Module 3 – Unit 2
In unit 2 we learn how to:
Describe the working principles and types of domestic heating
systems.
List the basic components of domestic heating systems and
describe their function.
List common and alternative sources of heat energy.
Draw schematic representations of domestic heating systems.
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Key Learning Points
Rk
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D
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Sc
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P
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Principles of domestic heating systems.
Types of heating systems.
Components of heating systems.
Pipework layout.
Drawing of domestic heating systems.
Location and function of safety valves.
Location and function of vent pipe, cold feed pipe.
Primary flow and return pipework, cylinders.
Gravity circulation.
Fully pumped circulation.
Function, location, components of circulation pumps.
Types of radiators and radiator valves.
Heat transfer in heating systems.
Filling arrangement for sealed systems.
Function, location, size of expansion vessel in sealed
systems.
Sources of heat energy, solid fuel, gas, oil.
Alternative sources of energy
Communication.
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Wet Central Heating
Fire Extinguishers
Pipework Problems
Sealed Systems
Boiler Types
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Operator Protection
 No open-neck shirts;
Ultra-violet rays will burn the skin. It is most definitely not similar to
sun tanning.
 Regulation inflammable overalls only;
Arc-welding produces large amounts of hot sparks which will set
flammable clothing alight.
 No trainers/runners to be worn;
The steel metal plate used are heavy and sharp. Wear steel toe-cap
boots.
 Overalls not around waist;
Sparks will set casual tops alight
 Always wear protective clothing;
Arc-welding produces heat, glare, sparks, ultra-violet & infra-red rays
and harmful fumes. Welding gauntlets must be worn at all times. Face
masks are designed to deflect fumes and should therefore be held
close to the face. Gas welding goggles will not afford protection for
the face against the light intensity or the radiation and must not be
used. Shade 11 EW filters are required in the face mask for manual
metal arc welding. Always wear protective goggles when chipping
slag.
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Basic Pipework Layouts
Gravity Circuit
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Gravity Hot Water and Pumped Central Heating
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Module 3 – Unit 2
Fully Pumped DHW and CH System
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Module 3 – Unit 2
Cow Feed and Open Vent Positions
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Cold Feed and Open Vent
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Feed and Vent Pipes as Part of the Heating Circuit
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Module 3 – Unit 2
Close Coupled Systems
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Module 3 – Unit 2
Position of the Pump - Negative, Positive, Neutral
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Module 3 – Unit 2
Pump on Return
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Module 3 – Unit 2
Pump on Return/Cold Feed on Pump Inlet
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Module 3 – Unit 2
Fully Pumped System
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Open Vent as Part of the System
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Module 3 – Unit 2
High Resistance Boiler
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Module 3 – Unit 2
Close Coupled System
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Removal of Air from the System
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Single Pipe Heating Circuits
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Two Pipe Heating Circuits
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Minibore or Microbore System
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Heat Emitters
Radiators
Convectors
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Radiator Controls
 Lockshield
 Customer Control
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Module 3 – Unit 2
Thermostatic Radiator Valve (TRV)
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Module 3 – Unit 2
Possible Radiator Problems
 Reverse Circulation
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Possible Radiator Problems..continued
 Commoned Returns
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Sealed Or Pressurised Systems
 Typical Sealed System
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Module 3 – Unit 2
Expansion of Heated Water
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Module 3 – Unit 2
Interlinking of Solid Fuel to Automatic Boiler
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Pressure and Temperature Safeguards
 Pressure Release Valve & Discharge Pipe
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Filling and Maintaining the System Water
 Temporary Filling Loop
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Module 3 – Unit 2
Maintaining the Water Level
 Automatic Top Up Bottle
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Module 3 – Unit 2
Common Problems
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Temporary Filling Loop
Checking and Recharging Expansion Vessels
Overfilling a System
Defective Expansion Vessel
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Domestic Central Heating Main Equipment
The main equipment required in a domestic heating system consists of:
 A Boiler
 An Indirect Cylinder
 A Feed and Expansion Cistern or Expansion Vessel
 A Circulating Pump
 Radiators
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Domestic Central Heating Systems
The are two main types of domestic central heating systems:
 The Open Vent System - This system incorporates a feed and
expansion cistern, vent pipe, and cold feed.
 The Sealed System - In this system the expansion of water is taken
up by an expansion vessel.
Trade of Plumbing – Phase 2
Module 3 – Unit 2
The Open Vent System
The basic equipment in an open vent system:
Feed & Expansion Cistern
Indirect Hot Water Storage Cylinder
Boiler
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Cold Feed to the
Heating System
Standard Gate Valve
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Module 3 – Unit 2
Primary Flow to the
Cylinder
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Module 3 – Unit 2
Open Vent or Expansion
Pipe
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Module 3 – Unit 2
Primary Return
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Module 3 – Unit 2
Radiators
Radiators
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Radiator Valves
Each radiator is fitted with two valves:
 A Handwheel valve on the flow
 A Lockshield valve on the return
Handwheel Radiator Valve (Flow)
Lockshield Radiator Valve (Return)
Trade of Plumbing – Phase 2
Module 3 – Unit 2
The One Pipe System of Central Heating
Ring Main Circuit
Flow
Return
Trade of Plumbing – Phase 2
Module 3 – Unit 2
The One Pipe System of Central Heating
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Pump, Safety Valve, and Drain Cock
Safety Valve
Drain
Pump
Trade of Plumbing – Phase 2
Module 3 – Unit 2
The Two Pipe Heating System of Central Heating
Flow
Trade of Plumbing – Phase 2
Module 3 – Unit 2
The Two Pipe Heating System of Central Heating
Return
Flow
Return
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Module 3 – Unit 2
The One Pipe System of Central Heating
Advantages:
 Only one pipe is necessary to convey hot water to the radiators
 Cheap to install
Disadvantages:
 Hot water passing through the first radiator is cooled and returns to
the main flow pipe
 This water then supplies the next radiator and has the effect of
producing a lower temperature
 Only suitable for small single storey buildings
Trade of Plumbing – Phase 2
Module 3 – Unit 2
The Two Pipe System of Central Heating
Advantages:
 Hot water from the boiler supplies each radiator and then returns via
the return pipe without passing through any more heat exchanges
 Ensures a quick heat up time and a more positive flow to the
radiators
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Radiators
There are three main types of radiator:
 Panel
 Column
 Hospital
Radiators can be manufactured from any of the following materials:
 Mild Steel
 Aluminium
 Cast Iron
 Copper
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Radiator Connections
All radiators are threaded with female B.S.P.T. (British Standard Pipe
Thread) connections.
The location of the connections are:
B.O.E. - Bottom Opposite End
T.B.S.E. - Top and Bottom Same End
T.B.O.E. - Top and Bottom Opposite End
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Radiator Valves
 The flow connection to a radiator should be fitted with a
manually operated HAND WHEEL control valve
 The return connection should be fitted with a LOCKSHIELD
radiator valve
 A Thermostatic Radiator Valve (TRV) is used to control the
temperature of a radiator
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Positioning of Radiators
 Whenever possible, the radiator should be installed under a
window
 If the radiator cannot be fitted under the window it should be on
an adjacent wall
 The worst position is opposite the window as the convection
currents will encourage the cold down flow of air
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Circulation Pumps
 These devices, sometimes known as accelerators, are fitted to
the pipework to assist water circulation
 The pump is a very important part of the modern central heating
system
 It enables the use of smaller diameter pipes and boilers than
would be the case if a conventional gravity system was used
 The pump provides pressure inside the system which in turn
forces water to circulate throughout the whole system of
pipework and heat emitters
 The location of the pump within the system can be on the FLOW
PIPE (now generally accepted as the best position) or on the
RETURN PIPE
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Safety Valves
 It is essential that a safety valve is fitted in all heating installations
 Safety valves should be fitted directly on top of the boiler in the
hottest part of the system with no intervening valve or restriction
Safety Valve
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Safety Valve and Flow Pipe
 In the case of solid fuel wrap around boilers the previous
arrangement may not be possible and the usual practise is to fit the
safety valve on the FLOW PIPE as near as is practical to the boiler
 The safety valve should always be accessible for testing
Safety Valve
Flow Pipe
Trade of Plumbing – Phase 2
Module 3 – Unit 2
The Sealed System of Central Heating
In the sealed system the water is supplied from either:
 The Incoming Water Main
 A Top Up Bottle
When filling the system from the incoming water main a “FILLER
LOOP” may be used. This is a device which incorporates:
 A Check Valve (Non-Return Valve)
 An Isolating Valve
 A Flexible Pipe For Disconnecting
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Expansion Vessel
 An expansion vessel is a gas/air filled vessel used to take up the
expansion of water in sealed central heating systems
 The gas or air is separated from the system water by a rubber
diaphragm or washer
 The vessel is charged with gas or air equal to the static head of the
system
 In a domestic situation this pressure should never exceed 1 bar
 In a domestic central heating system the water temperature should
never exceed 80ºC
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Sealed System of Central Heating with Top Up Bottle
Top Up Bottle
NRV
AAV
Safety Valve
Drain
Gauge
Sealed Expansion Vessel
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Sealed System of Central Heating with Filler Loop
AAV
Safety Valve
Drain
Gauge
Sealed Expansion Vessel
Double Check Valve and Temporary Connection
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Sizing of Expansion Vessels
System Load
Size of Vessel
Internal Gas Pressure
Safety Valve Pressure
(kW)
(Litres)
(Bar)
(Bar)
3
4
0.5 – 1.0
3
6
4
0.5 – 1.0
3
12
8
0.5 – 1.0
3
18
12
0.5 – 1.0
3
24
18
0.5 – 1.0
3
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Advantages of the Sealed System
 There is no loss of water through evaporation because there is no
F&E cistern, and therefore there is less risk of oxygen entering the
system
 The vessel can be located close to the boiler and therefore monitored
on a regular basis
 Pumping over or pitching into the F&E cistern is eliminated
 The boiler can be located anywhere in the installation
 In industrial situations the system can be operated at high
temperatures
 There is a cost saving in time and material due to the elimination of
pipework to the F&E cistern
 The danger of frozen pipework is greatly reduced because there may
be no pipes in the attic
Trade of Plumbing – Phase 2
Module 3 – Unit 2
The Sealed System in Industrial Installations
 In systems which need to be designed to operate at or over 100ºC,
the pressures must be higher than 1 bar
 In large installations where excessively long pipe runs are common,
and the criteria for domestic situations were applied (i.e. max. water
temperature of 80ºC), the temperature drop over the long run could
be such as to make it impossible to achieve the required heat output
 A “PRESSURISED” sealed system is used to overcome this difficulty
 The higher the internal pressure of the system the higher the
temperature of the circulating water
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Automatic Air Vents
An automatic air vent is a valve designed to release air automatically
from the high point of a central heating system
Automatic Air Vent
Return
Flow
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Commissioning of Wet Central Heating Systems
 The pump should be removed and replaced
with a suitable piece of pipe to bridge the
gap
 The system should then be drained down
and receive a flush through to remove any
wire wool, flax, PTFE tape, flux, solder, etc.
 At this stage the boiler can be commissioned for correct operation
 Close all lockshield valves and go round the system balancing the heat
emitters to each room
 Check the operation of the programmer, room thermostat, and cylinder
thermostats, etc.
 Recheck for leaks
 Refill and vent the system, adding an inhibitor, if applicable
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Handing Over
 The working of the system should be demonstrated to the user and
the best methods of economic and efficient usage explained
 All documentation supplied with equipment should be left with the
owner/occupier
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Identification of Circulating Pumps
Impeller
Stator
Rotor
Windings
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Assembling Oil Fired Boilers
Flue
Flow
1.
Adjustable boiler thermostat
2.
Oil pump
3.
Ignition transformer
4.
Solenoid valve
5.
Photo electric cell
6.
Boiler limit thermostat
7.
Temperature gauge
8.
Burner motor and fan
9.
Nozzle
10. Ignition electrodes
Cleaning Door 11. Burner control box
Waterways
Fire Brick
Return
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Assembling Oil Fired Boilers
1.
Reset button
2.
Control box
3.
Ignition transformer
4.
Ignition cables
5.
Nozzle assembly
6.
Nozzle
7.
Brake plates
8.
Blast tubes
9.
Ignition electrodes
10. Connecting pipe
11. Air damper
12. Solenoid valve
13. Pump
14. Drive coupling
15. Indication, air damper
16. Fan wheel
17. Adjustment, air damper
18. Photoresistor
19. Motor
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Radiator
Identification
B.O.E
T.B.O.E
IN
OUT
T.B.S.E
Double Panel
Single Panel
Treble Panel
High Output
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Types of Radiator
Wall Radiator
Classic Radiator
Classic Wall Radiator
Wall Radiator
Hospital Radiator
Royal Radiator
Narrow Pattern Hospital Radiator
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Fitting of Expansion Vessels
Water Connection
Air or Gas
When the heating is cold, the air or gas
charge completely fills the vessel
Air or Gas Valve
Water
When the system starts to heat up, the
expanding water begins to compress the
air or gas charge
Water
When the system is at full temperature, the
water has reached its maximum expansion
and the air or gas charge is fully
compressed
Trade of Plumbing – Phase 2
Module 3 – Unit 2
Expansion
Copper Cylinder
Identification
Hot water
supply
Expansion pipe leveled off to
prevent one pipe circulation
Expansion connection
Gate
valve
Drain
cock
Cold feed
connection
Copper cylinder heated by
immersion only
Indirect cylinder with
immersion heater
Copper cylinder with
immersion heater
Twin coil indirect
cylinder with
immersion heater