Electricity

1
Electricity Principles Applications Sixth
Edition
Richard J. Fowler
Chapter 16 Residential Wiring Concepts
2
INTRODUCTION

• Equipment-grounding Conductor
• Ground-Fault Circuit Interrupter
• Arc-Fault Circuit Interrupter
• Three-Way Lighting Circuit
• Four-Way Lighting Circuit
• Lighted-Handle Switches
• Low-Voltage Control Circuit

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Facts about Residential Wiring

• A residence uses a 120-V/240-V single-phase
  system.

• Hot conductors are 120 V with respect to neutral.

• Hot conductors are 240 V with respect to each
  other.

• Neutral conductors are either white or neutral
  gray.

4
More Facts About Residential Wiring

• White conductors may be used as hot conductors.

• An AFCI reduces the risk of electrical fires.

• A GFCI protects people from ground-fault currents.

• Equipment-grounding conductors are never fused.

5
Equipment-Grounding Conductor
7.5 A
0.5 A
There is no circuit fault. The motor is
operating normally.
The motor develops a partial short. The branch
circuit breaker doesnt trip.
The motor continues to operate with some
ground-fault current.
No shock is received because the motor frame is
grounded.
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Equipment-Grounding Conductor
?.? A
7.0 A
The partially shorted motor continues to run. It
doesnt trip the branch circuit breaker.
Then the equipment-grounding conductor develops a
broken or corroded connection.
A severe, or fatal, shock is received because
the motor frame is not grounded.
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Ground-Fault-Circuit Interrupter
0.0 A
0.0 A
A faulty equipment-grounding conductor doesnt
trip the GFCI.
With no ground, a partial short in the motor
doesnt trip the GFCI either.
No severe shock is received because the GFCI
trips at about 5 mA.
8
Arc-Fault-Circuit-Interrupter Circuit Breaker
Loose screw
OFF
ON
Hot bus
Neutral bus
This circuit breaker will open when an arc occurs.
Click the mouse to try it.
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Ground-Fault Quiz
Is an equipment-grounding conductor ever fused or
switched?
No
Is a green conductor ever used for a neutral
conductor?
No
Can a neutral-gray conductor be used for a
neutral conductor?
Yes
Will a ground-fault current greater than 10 mA
trip a circuit breaker?
No
Will a ground-fault current greater than 10 mA
trip a GFCI?
Yes
Will a load current of 25 A trip a GFCI
receptacle rated at 20 A?
No
Will a 10-A ground-fault current cause an AFCI
circuit breaker to trip?
No
10
Wiring a Three-Way Lighting Circuit
14-2/G
14-3/G
Connect a hot conductor to the pole (dark-colored
screw).
Ground the metal box.
Connect the throws together.
Continue the neutral and equipment-grounding
conductors.
Connect a hot conductor to the remaining pole.
Again continue the neutral and equipment-grounding
conductors.
Finally, connect the light fixture to the
appropriate conductors.
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A Four-Way Lighting Circuit
The circuit is in the off position. Equipment
grounding is not shown.
Flipping the 4-way switch turns the circuit on.
Flipping either 3-way switch turns the light back
off.
Flipping the 4-way switch again turns the circuit
back on.
Flipping the other 3-way switch turns the circuit
off again.
In summary, flipping any switch at any time will
reverse the condition of the circuit.
12
Lighted-Handle Switch
When the light is off (switch open), the switch
handle is lit.
When the light is on (switch closed), the switch
handle is not lit.
13
Lighted-Handle 3-Way Switches
B2
B1
H
The light is on and the handles are not lit.
When either switch is toggled, the light goes out
and both handles are lit.
14
Low-Voltage-Controlled Light Circuit
Click the mouse and watch.
A switch is rocked to off.
The relay opens.
The light goes out.
And, the switch returns to its open position.
Another switch is rocked to off.
Nothing happens.
Again, the switch returns to its open position.
Now, a switch is rocked on.
The relay closes.
The light goes on.
Again, the switch returns to its open position.
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Switching-Circuit Quiz
A 3-way lighting circuit requires _____
insulated conductors between switches.
three
A 4-way lighting circuit requires _____
insulated conductors between switches.
three
A _____ colored conductor should not be used in
the return leg of a switch.
white
A 4-way lighting circuit provides control of a
light from _____ locations.
three
The handle of a lighted-handle 3-way switch is
lit when the light is _____ .
off
A three-terminal relay stays in the on position
until the _____ is pulsed.
off coil
16
REVIEW

• Equipment-Grounding Conductor
• Ground-Fault Circuit Interrupter
• Arc-Fault Circuit Interrupter
• Three-Way Lighting Circuit
• Four-Way Lighting Circuit
• Lighted-Handle Switches
• Low-Voltage Control Circuit