Course:
Unit 6:
01.422
Agriculture Mechanics Technology II
Electrical Wiring
Lesson 4: Electrical Wiring System
Objectives:
1. Install service entrance equipment.
2. Install branch circuits.
3. Install grounding materials.
Teaching Time:
10 hours
References:
Electrical Wiring. AAVIM. Winterville, GA.
Materials and Equipment:
See following laboratory exercises.
Handout 6.4.1 - 6.4.4
1
TEACHING PROCEDURE
Introduction and Mental Set
Have local EMC personnel present the high voltage demonstration in the
agricultural mechanics laboratory.
Discussion
1.
Remember the following:
A.
More receptacles are installed in a building than any other
device.
B.
Many types and sizes of receptacles are used for different
purposes in the circuits.
C.
Some circuits contain receptacles that are switch controlled.
Others are always hot (energized).
2.
Refer to Electrical Wiring,
3.
Review transparency 26.
4.
Answer questions in workbook.
5.
Explain equipment grounding.
a. Grounding is making a connection between an electrical circuit or
electrical equipment and the earth (or some conducting body that
serves
in the place of the earth). The connection may be
intentional or
accidental. An intentional connection is made for
safety reasons. An
accidental connection may be a hazard.
b. Two types of grounding in an electrical system are:
-System grounding: Connecting one of the current carrying wires
in the electrical system to ground. System grounding is covered
in the lesson installing the service entrance panel.
-Equipment grounding: Connecting the non-current carrying metal
parts of components used in the electrical system and
equipment connected to the system to ground.
System grounding and equipment grounding are both intentional
2
connections to the earth.
c. Reasons for grounding:
-System grounding is necessary for the operation of 120 volt
circuits.
-Equipment grounding protects person from shock.
-Grounding helps to facilitate the instantaneous operation of
overcurrent devices (circuit breakers or fuses).
d. A ground fault is a condition in which current flows to ground
through an unintended path because of defective equipment or
misuse of equipment. This unintended path could be through a
person if the electrical system and/or electrical equipment is not
properly installed and maintained. When installing and/or
maintaining equipment, it is very important to provide a safe path
to ground if a ground fault occurs.
e. A safe path to ground can be provided by grounding the noncurrent carrying metal parts of equipment with the equipment
grounding conductor. When properly installed, the following may
be used for the equipment grounding conductor:
-Copper or other corrosion resistant conductor. The conductor
may be the bare or green insulated wire in the cable used to
furnish power to the equipment or may be a separate wire run in
the conduit with the supply wires to the equipment.
-Rigid metal conduit
-Electrical metallic tubing (EMT)
-Flexible metal conduit (in dry locations) if properly installed
-Liquid-tight flexible metal conduit if properly installed
f. Connecting the equipment grounding conductor in the service
panel:
-Service entrance panel: connect the equipment grounding
conductors to the neutral bar.
3
-Feeder panel: Feeder panels must have an equipment grounding
bar separate from the neutral bar. Connect the equipment
grounding conductors to the equipment grounding bar.
g. Grounding plug connected equipment:
-When installing receptacles, the equipment grounding conductor
is connected to the green grounding terminal on the receptacles.
The receptacles are then properly grounded.
-If the equipment has an equipment grounding conductor in the
supply cord, and if the equipment is connected with a grounding
plug into a grounded receptacle, the equipment will be
grounded.
-If the grounding prong on the plug for the equipment has been cut
off, or if an adapter is used to allow plugging a grounding type
plug into a non grounded receptalce, the equipment will not be
grounded.
h. Grounding permanently installed equipment:
-To ground permanently installed equipment, the equipment
grounding conductor must be run from the neutral bar in the
service entrance (or the grounding bar in a feeder panel) to the
grounding terminal on the equipment.
-If no terminal is designated as a grounding terminal, the
equipment grounding conductor is connected to some screw on
the frame of the equipment that is non current carrying.
i. Metal parts of the components used in the wiring system must also
be grounded.
-Metal cabinet of the service entrance panel. Use grounding screw
or strap to ground cabinet with the neutral bar.
-Metal cabinet of feeder panel. The cabinet must be grounded
through the equipment grounding bar.
-All metal boxes must be grounded. Use a grounding screw or
grounding clip to install the equipment grounding conductor to the
box.
4
6.
Complete laboratory exercises 1, 2, 3, and 4.
7.
Have instructor complete evaluation chart in the appendix of your
student workbook.
8.
Answer study guide questions #1.
9.
Find the required clearance for fixtures in closets, restrictions on
recessed fixtures, and spacing and thermal insulation.
10.
Refer to AAVIM Electrical Wiring
11.
Answer questions in workbook.
12.
Complete laboratory exercise #5.
13.
Have instructor complete evaluation chart in the appendix of your
student workbook.
14.
Answer study guide questions #2.
15.
Read Electrical Wiring.
16.
Observe transparency 27-42
17.
Observe questions in notebook.
18.
Complete laboratory exercises 6, 7, and 8.
19.
Have instructor complete evaluation chart in the appendix of your
student workbook.
20.
Answer study guide questions #3
SUMMARY
5
Have a service entrance panel wired with the weatherhead and branch
circuits. Ask the class to grade the installation. Have students to
explain the problem they have found with installation and what should
be done to correct the problems.
Evaluation
Laboratory exercise
Written exam
6
7
8
9
10
11
12
13
14
15
16
6.4.1
Study Guide Questions #1
1.
The most common type of receptacle is:
A.
single receptacle type.
B.
single receptacle with a switch.
C.
duplex receptacle with weatherproof cover.
D.
standard grounding duplex receptacle.
2.
Self-contained kitchen ranges normally require a heavy duty _____
ampere 125/250- volt receptacle.
3.
Match the following:
_____ connect brass receptacle terminal screw to:
_____ connect silver receptacle terminal screw to:
_____ connect green receptacle terminal screw to:
1. bare wire
2. black wire
3. white wire
4.
The grounding wire must always be connected to every metal box.
A.
true
B.
false
5.
Those receptacles in which are inserted into holes in the back of the
receptacle rather than being looped around screws on the sides are
called __________ receptacles.
A.
black hole
B.
alternate
C.
back wired
D.
easy wire
6.
By removing the break-off connection tab between the brass terminals
of receptacle, you:
A.
create a short circuit
B.
make it possible to connect a separate
C.
have a reduced utility bill
D.
make it a fire hazard
17
6.4.1
Study Guide Questions #1
7.
Match the following appliances according to their classification by
placing the appropriate letter code by each appliance:
A = portable
_____ built-in oven
B = stationary
_____ self-contained range
C = fixed
_____ coffee maker
_____ mixer
_____blender
_____clothes dryer _____window air conditioner
_____ water heater _____ garbage disposal
8.
Stationary and ____________ appliances are generally wired on
separate circuits.
9.
Most dryers are wired with No. 8 wire in a 60- amp circuit.
A.
true
B.
false
10.
A junction box is used only for:
A.
installing lighting fixtures overhead
B.
making wiring connections
C.
temporary connections
D.
electrical loads in excess of 30 amperes
11.
When connecting water heaters, you usually make the connections
directly to the conductors in the water heater and connect the
grounding wire to the metal case.
A.
true
B.
false
12.
The purpose of the switching device which controls the time-of-day
operation of heaters and other heavy demand appliances is to:
A.
spread energy distribution among the various circuits of the box.
B.
allow the appliance to operate during the periods when demand
on the power company lines are lower.
C.
enable the use of smaller wires.
D.
maintain a more uniform voltage.
6.4.1
18
Study Guide Questions #1
13.
Most clothes dryers can be plugged into a 120- volt receptacle and do
not require a separate circuit.
A.
true
B.
false
14.
In most central heating installations, the responsibility of the electrician
is to:
A.
perform the complete wiring and installation job
B.
perform the rough-in wiring
C.
wire up to the sep only
D.
recommend gas heat
19
6.4.2
Study Guide Questions #2
1.
The four mounting methods which cover the installation of most
lighting fixtures are:
A.
mounting direct to ______________
B.
mounting________________to box
C.
mounting fixtures to ____________
D.
mounting_______________fixtures
2.
Closet fixtures must have at least:
A.
6 inches clearance where combustible materials may be stored.
B.
12 inches clearance where combustible materials may be
stored.
C.
18 inches clearance where combustible materials may be
stored.
D.
24 inches clearance where combustible materials may be
stored.
3.
Lighting fixtures should utilize the fixture to stud mounting when:
A.
the fixtures are heavy.
B.
the fixtures are at the end of a long wirerun.
C.
the fixtures have heavy ampere demand.
D.
the fixtures are light.
4.
A code provision requires that no thermal insulation may be installed
within _____ inches of a recessed fixture enclosure, wiring
compartment or ballast.
5.
To allow free circulation of air the recessed fixture must have at least
_____ inch clearance from combustible material.
A.
1
B.
2
C.
12
D.
2
20
6.4.3
Study Guide Questions #3
1.
Most switches used in lighting circuits are one of the following types:
toggle type, rocker type, push button type.
A.
true
B.
false
2.
Two additional types of switches for special purposes of effect are
the_______________ switch and the ______________ switch.
3.
Three-way switches are so called because:
A.
they control lights from three locations.
B.
they have three terminals on the switch.
C.
they can be used on only three circuits per building.
D.
they are operated with a rotary button with three positions for
different levels of lighting intensity.
4.
Four-way switches are operated from four locations.
A.
true
B.
false
5.
Unlike receptacles, the pigtail grounding wire is not normally required
to be connected from box to switch.
A.
true
B.
false
6.
If an outlet is at the end of a circuit the bare wire connects to:
A.
the outlet terminal
B.
the white wire
C.
the grounding screw in the outlet box
D.
no connection is necessary, just tape and push in the box
7.
The white wire in a cable may be connected to a switch without
identification only when it is used for the ___________ switch.
21
6.4.3
Study Guide Questions #3
8.
In connecting, a single pole switch with an incoming and an outgoing
cable in the box, you would connect:
A.
a black and white wire to the two terminals, the remaining two
wire (black and white) are connected with a wire nut.
B.
the two white wires to the two terminals on the switch, the two
black wires together.
C.
the two black wires to the two terminals, and the two white wires
are connected with a wire nut
D.
none of the above
9.
A switch loop is required when:
A.
one switch is used in a circuit
B.
the power source enters the lighting outlet box first
C.
the power enters the switch box first
D.
none of the above
10.
A white wire connected to a black wire or to a switch is considered to
be hot.
A.
true
B.
false
11.
Three-way switches are used only in pairs.
A.
true
B.
false
12.
You can identify the common or pivot terminal on a three-way switch
because:
A.
it has a reverse thread
B.
it has a hex-type head
C.
it is always at the back of the switch, by itself
D.
it is usually alone and a different color from the other two
terminals or it is labeled
13.
For wiring between three-way switches, you must use:
A.
three wire cable with ground
B.
two wire cable with ground
C.
four wire cable with ground
D.
the same as from the source to the first three-way switch
22
6.4.3
Study Guide Questions #3
14.
Traveler, or switching wires in three way switch installations connect:
A.
the switches to the light fixture
B.
the switches to the source
C.
the switches to each other only
D.
one switch to the light fixture, the other to the source
15.
A good way to identify the two terminals for traveler wires is:
A.
they will normally be a different color than the common terminal.
B.
they are larger in size than the common terminal.
C.
they are smaller than the common terminal.
D.
they are always silver.
16.
Four way switches are used only in combination with two three-way
switches.
A.
true
B.
false
23
6.4.4
Laboratory Exercise # 1
Your instructor will provide the following:
No. 12 three-wire cable with ground
No. 8 three-wire with ground
receptacles
switch boxes
wire nuts
wire cutters
screwdrivers
cable ripper
hammers
The procedure is as follows:
Properly connect 120- volt duplex receptacles, split-duplex receptacles
and heavy duty appliance circuits. Work to be neat and codeconforming.
Laboratory Exercise # 2
Installing a duplex receptacle outlet and cover plate
Your instructor will provide the following:
wiring demonstration panel C
duplex receptacles
needle-nose pliers
screwdriver
wire stripper
cover plate for duplex receptacle
solderless connector
knife
one 6- inch piece of grounding wire
Procedures are as follows:
1.
In the plastic receptacle box installed on the panel, pull the wires out of
the box and separate them. Remove 1 inch of insulation from the end
of each wire.
24
6.4.4
Laboratory Exercise # 2
2.
Obtain one 6- inch piece of grounding wire. Connect this wire to the
green or bare grounding wire in the cable with a solderless connector
with needle-nose pliers.
3.
Bend a hood on the end of the white wire, black wire, and the one
grounding wire.
4.
Connect the 6- inch wire to the green terminal located on the bottom of
the duplex receptacle.
5.
Connect the black wire to one of the bronze screws on the receptacle.
6.
Connect the white wire to one of the silver screws on the receptacle.
7.
Fasten the receptacle to the box using the two furnished screws.
8.
Place the cover plate over the duplex, receptacle and tighten the
attachment screw.
Laboratory Exercise # 3
Your instructor will provide the following:
wiring demonstration panel C
two duplex receptacle outlets with ground
No. 14 two-wire cable with ground
grounding clip
two cover plates for duplex receptacles
one solderless connector
two 6- inch No. 14 green wires
rule
needle-nose pliers
screwdriver
wire stripper
25
6.4.4
Laboratory Exercise # 3
Procedures are as follows:
1.
On panel C of the student demonstration board, locate the switch box
on stud No. 3. Assume the box contains two No. 14 two-wire cables
with ground. Pull the wires out of the box and separate them
according to the wires entering and leaving the box. (Wires entering
the box are those coming from the junction box on panel D. Those
wires leaving go to the second receptacle)
2.
Strip 1 inch of insulation from each wire.
3.
With needle nose pliers, bend hooks in the end of the two black and
two white wires.
4.
Take the two existing grounding wires and connect them to two 6- inch
green wires with a solderless connector.
5.
At the other end of one of the 6- inch green wires, make a hook using
the need-nose pliers.
6.
Connect this wire under the green terminal located on the bottom of
the receptacle. Be sure the hook is placed clockwise around the
screw so is will be drawn smaller not larger.
7.
Take the loose end of the other 6- inch green wire and slip a ground
clip over it and then install the ground clip over the edge of the box. In
some installations a grounding screw may be used to connect the
ground wire to the box.
8.
Connect one set of black and white wires to opposite terminals on one
end of the receptacle and connect the other set to the other end of the
receptacle. The black wire is always fastened to the bronze screw and
the white wire is fastened to the silver screws.
9.
Fasten the receptacle to the box using two furnished screws.
10.
Place the cover over the box and tighten.
26
6.4.4
Laboratory Exercise # 3
11.
Wire the second receptacle located on stud No. 2. Connect the black
wires to the bronze screws on the receptacle.
Laboratory Exercise # 4
Wiring an octagonal box
Your instructor will provide the following:
wiring demonstration panel C
No. 14 two-wire cable with ground
rule
wire stripper
three-prong plug
blank octagon over plate
three solderless connectors
grounding clip
green grounding wire, 6 inches long
screwdriver
cable ripper
cable cutter
Procedures are as follows:
1.
Locate the outlet box previously installed on stud No. 4 of panel C.
Remove a knockout from bottom of this box.
2.
Install No. 14 two-wire cable with ground. Six inches of cable should
extend into the box with the sheathing removed. Tighten box
connector.
3.
Measure the cable four feet from the outlet box and cut.
4.
Install a three-prong 120 volt plug on this end of the cable.
5.
Remove one inch of insulation from all wires in the outlet box.
6.
In the outlet, join the two black wires together with a solderless
connector.
27
6.4.4
Laboratory Exercise # 4
7.
Join the two white wires together with a solderless connector.
8.
Obtain a 6- inch piece of green grounding wire and join it to the two
copper wires in the box with a solderless connector.
9.
Place a ground clip on the other end of the 6- inch piece of green wire
and attach the clip to the box.
10.
Push all the wires and solderless connectors into the box and fasten a
cover plate over the box.
Laboratory Exercise # 5
Installing lighting fixtures
Instructor will provide the following:
wiring demonstration panel D
No. 14 two-wire cable with ground
wire stripper
knife
needle-nose pliers
switch box
one lampholder
single pole switch
two solderless connectors
two grounding clips
screwdriver
one 60- watt light bulb
switch cover plate
6 inch piece of green wire
1/4 inch electric drill
3/4 inch drill bit
28
6.4.4
Laboratory Exercise # 5
Procedures are as follows:
1.
Mount a switch box on the right side of stud No. 1, 40 inches above
the outside edge of the lower plate.
2.
Drill 3/4 inch holes in stud No. 2 and No. 3, five inches down from the
upper plate.
3.
Obtain a roll of No. 14 two-wire cable with ground. Run the cable from
the octagon box already installed between studs 2 and 3 to the switch
box on stud No. 1. Cut this cable, allowing 6 inches to extend into
each box. Run another No. 14 cable from other end of octagon box to
stud No. 4 (an imaginary source). Be sure to run both cable through
the holes drilled in step 2. Again, cut cable to allow 6 inches to extend
into octagon box.
4.
Strap the cables to the upper plate, and staple cable to stud No. 1
within 12 inches of the switch box.
5.
At the octagon box, fasten together the white wire which comes from
the switch box to the black wire which comes from the source (stud
No. 4) with a solderless connector.
6.
Connect the black wire which comes from the switch box to the brass
terminal on the lampholder.
7.
Connect the white wire from the source to the silver terminal on the
lampholder.
8.
Fasten the grounding wires from both cables and a 6 inch piece of
green wire together with a solderless connector. Fasten the other end
of the green wire to the junction box with a grounding clip.
9.
Push the wires and connectors up into the box and fasten the
lampholder into place by tightening the screws. Put a 60- watt light
bulb in the lampholder.
29
6.4.4
Laboratory Exercise # 5
10.
At the switch box, install a single-pole switch Y connecting the black
wire to the other switch terminal. Fasten the copper wire to the box
with a clip.
11.
Push the wires into the switch box and fasten switch to box. Put a
switch cover plate in place and tighten the screws.
Laboratory Exercise # 6
Connecting a switched split duplex receptacle
Your instructor will provide:
wiring demonstration panel B
two duplex receptacles and cover plates
single pole switch and cover plates
three grounding clips
screwdriver
five solderless connectors
needle-nose pliers
four 6- inch pieces of No. 12 green wire
three 6- inch pieces of No. 12 black wire
one roll of black tape
Procedures are as follows:
1.
At the switch box on stud 1, panel B, pull the wires out of the box.
There should be two black, two white, and two bare copper grounding
wires, and one red wire.
2.
Using a solderless connector and 6- inch piece of black wire, connect
the three wires together. Attach the other end of the short piece of
black wire to the bronze screw at the top of the receptacle. Break off
the metal strip between the two bronze screws.
3.
Attach the red wire to the other bronze screw.
30
6.4.4
Laboratory Exercise # 6
4.
Fasten the two copper grounding wires plus two 6 inch of green wires
with a solderless connector. Fasten one of the short pieces of green
wire to the box with a ground clip. Fasten the remaining green wire to
the green grounding screw on the receptacle.
5.
Attach the two white wires to the sliver screws on the receptacle. Do
not remove the metal strip between the screw.
6.
At the switch box on stud No.2, panel B, pull the wires from the box.
There should be two black wires, two white, two copper grounding
wires and one red.
7.
Join the black wire coming from the switch box on stud No. 1 and the
white wire coming from the box on stud No. 3 with a 6- inch piece of
black wire and secure with a solderless connector. Place black tape
on this white wire. Take the receptacle and remove the bronze link
with a pair of needle-nose pliers on the hot side of the receptacle.
Fasten the other end of the short piece of black wire to the bronze
screw at the bottom of the receptacle.
8.
Fasten the remaining white wire to the silver screw on the receptacle.
9.
Using a solderless connector, fasten together the red wire, the
remaining black wire, and a 6- inch piece of black wire. Connect the
other end of the short piece of black wire to the bronze screw at the
top of the receptacle. Repeat step number 4 using the grounding
wires.
10.
At the switch box on stud No. 3, panel B, fasten the white wire to the
bronze screw on the switch. Fasten the black wire to the other bronze
screw on the switch. Fasten the bare copper wire to the switch box
with a ground clip.
11.
Push wires into each box and fasten switch and receptacles to the
boxes. Place covers over boxes.
31
6.4.4
Laboratory Exercise # 7
Running cable to ceiling outlet and two three-way switches
Your instructor will provide the following:
wiring demonstration panel C
No. 14 two wire cable with ground
No. 14 three wire cable with ground
claw hammer
rule
center punch
1/4 inch electric drill
3/4 drill bit
12 No. 6 round head wooden screws, 2
cable clamps (attached to boxes)
octagon junction box
two switch boxes
screw driver
8 cable staples
switch box extension
cable ripper
pencil
Procedures are as following (figure 19):
1.
Mount an octagon box on the middle of the upper plate on panel C
between stud No. 2 and No. 3. Allow a 2 inch space between the box
and the plywood.
2.
Mount a second octagon box on stud No. 4 twenty eight inches above
the lower plate.
3.
Mount two switch boxes 40 inches above lower plate studs 1 and 4.
Mount a switch box extension to the box on stud No. 4.
4.
Drill 3/4 inch holes in studs 2 and 3, 55 inches above the lower plate,
and drill another 3/4 inch hole in stud No. 3, 5 1/5 inches below the
outside edge of the upper plate.
5.
Run a No. 14 two wire cable with ground from the octagon box on the
upper plate through the hole in the top of stud 3, to the octagon box on
stud No. 4. The will be the Asource@cable.
32
6.4.4
Laboratory Exercise # 7
6.
Run another section of No.14 two-wire cable with ground from the
octagon box on the upper plate, through same upper hole, to the
switch box on stud No.4.
7.
Run the No. 14 three-wire cable with ground from the switch box on
stud 4 through the lower holes in studs 2 and 3, to the switch box on
stud No. 1.
8.
Staple all cable to the studs within 12 inches of box.
Laboratory Exercise # 8
Connecting a ceiling outlet with two three-way switches
Your instructor will provide the following:
wiring demonstration panel C
two three-way switches
four solderless
needle-nose pliers
screwdriver
three grounding clips
black tape
porcelain receptacle
two switch cover plates
Procedures are as follows:
1.
At the switch box stud No. panel C, strip wires one inch and form
hooks at the end of the black, white, and red wires.
2.
Connect the copper wire to the box with a grounding clip.
3.
Connect the black wire to the common terminal. It is usually on the
side of the switch where only one terminal is located.
4.
Connect the white wire to a terminal on the side of the switch where
two terminals are located, opposite the black wire.
33
6.4.4
Laboratory Exercise # 8
5.
Connect the red wire to the remaining terminal. Install the switch and
a switch cover plate.
6.
At the switch box on stud No. 4, Panel C, connect the two ground
wires (bare) to a 6- inch length of green wire with a solderless
connector and fasten to box with a grounding clip.
7.
Connect the black wire from the octagon box between stud No. 2 and
No. 3 to the common terminal (single terminal side) on the three-way
switch.
8.
Connect the white wire coming from the other switch to the terminal
screw opposite the black wire screw.
9.
Connect the red wire to the remaining terminal.
10.
With a solderless connector, join the remaining white wire (from the
octagon box) to the remaining black wire (from the other switch). Mark
this white wire with black tape. Install the switch, then install a switch
cover plate.
11.
At the octagon box between stud No. 2 and No. 3, join the white wire
from the switch to the black wire from the source with a solderless
connector and mark the white wire with black tape. Join two bare
copper ground wires and one 6- inch green wire with solderless
connector. Connect to other end of green wire to octagon box with
grounding clips.
12.
Connect remaining black wire from switch to the bronze screw on the
porcelain lampholder. Connect the remaining white wire from source
to silver screw on lampholder. Mount the lampholder to the octagonal
box.
34