McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Electricity Principles & Applications Seventh Edition Richard J. Fowler Chapter 16 Residential Wiring Concepts (student version) McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. INTRODUCTION Equipment-grounding conductor Ground-Fault Circuit Interrupter Arc-Fault Circuit Interrupter Three-Way Lighting Circuit Four-Way Lighting Circuit Lighted-Handle Switches Wiring Lighting Circuits Low-Voltage Control Circuit

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Dear Student: This presentation is arranged in segments. Each segment is preceded by a Concept Preview slide and is followed by a Concept Review slide. When you reach a Concept Review slide, you can return to the beginning of that segment by clicking on the Repeat Segment button. This will allow you to view that segment again, if you want to.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Concept Preview Ground-fault currents less than the circuit- breaker rating won’t trip the breaker. Ground-fault current doesn’t present a shock hazard with grounded equipment. A GFCI removes the shock hazard when ungrounded equipment shorts out. An AFCI trips the circuit breaker before arcing in a circuit can start a fire.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. 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. White conductors may be used as hot conductors. A GFCI protects people from ground-fault currents. Equipment-grounding conductors are never fused. An AFCI reduces the risk of electrical fires.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. The motor develops a partial short. The branch circuit breaker doesn’t trip. No shock is received because the motor frame is grounded. 7.0 A 0.0 A 7.0 A Ungrounded table Grounded floor Motor standard receptacle 7.5 A 0.5 A Short There is no circuit fault. The motor is operating normally. The motor continues to operate with some ground-fault current. Equipment-Grounding Conductor

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Equipment-Grounding Conductor The partially shorted motor continues to run. It doesn’t trip the branch circuit breaker. A severe, or fatal, shock is received because the motor frame is not grounded. Then the equipment-grounding conductor develops a broken or corroded connection. ?.? A Motor Short standard receptacle 7.5 A 7.0 A Ungrounded table Grounded floor 0.5A 7.0 A

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Motor GFCI receptacle 7.0 A 0.0 A Ungrounded table Grounded floor Ground-Fault-Circuit Interrupter With no ground, a partial short in the motor doesn’t trip the GFCI either. No severe shock is received because the GFCI trips at about 5 mA. Short A faulty equipment-grounding conductor doesn’t trip the GFCI. 0.0 A

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Loose screw Neutral bus Hot bus Arc-Fault-Circuit-Interrupter Circuit Breaker This circuit breaker will open when an arc occurs. Click the mouse to try it. OFFON

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Ground-Fault Quiz Is an equipment-grounding conductor ever fused or switched? Is a green conductor ever used for a neutral conductor? Can a neutral-gray conductor be used for a neutral conductor? Will a ground-fault current greater than 10 mA trip a circuit breaker? Will a ground-fault current greater than 10 mA trip a GFCI? Will a load current of 25 A trip a GFCI receptacle rated at 20 A? no yes no yes no Will a 10-A ground-fault current cause an AFCI circuit breaker to trip? no

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Concept Review Repeat Segment Ground-fault currents less than the circuit- breaker rating won’t trip the breaker. Ground-fault current doesn’t present a shock hazard with grounded equipment. A GFCI removes the shock hazard when ungrounded equipment shorts out. An AFCI trips the circuit breaker before arcing in a circuit can start a fire.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Concept Preview Two 3-way switches provide 2-point control of a light circuit. Two 3-way switches and one 4-way switch provide 3-point control of a light circuit. Lighted-handle switches are lit when off. Momentary rocker switches are used to control the latching relay in a low-voltage- controlled lighting circuit.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Wiring A Three-Way Lighting Circuit Connect a hot conductor to the pole (dark-colored screw). 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. Ground the metal box. Connect the throws together. Light fixture 14-2/G 14-3/G 14-2/G

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. A Four-Way Lighting Circuit N H 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.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. When the light is off (switch open), the switch handle is lit. N H Switch 120-V lamp When the light is on (switch closed), the switch handle is not lit. Lighted-Handle Switch

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. H N R2R2 R1R1 B2B2 B1B1 3-way switch S2S2 S1S1 Lighted-Handle 3-Way Switches The light is on and the handles are not lit. When either switch is toggled, the light goes out and both handles are lit.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Wiring a lamp switching circuit when the lamp is in a “dead-end” outlet box The next slide shows the connections in the switch outlet box when the power cable also comes into the switch outlet box. The slide after that shows how a porcelain lamp holder is connected when the outlet box is plastic. Had the box been metal, then the grounding wire would have been connected to the box with a grounding screw.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Power cable from previous outlet box Cable to lamp outlet box Plastic outlet box Stud Two neutral (white) wires Three grounding (bare) wires Hot wire from previous outlet box Switched hot wire to lamp outlet box Mounting screw The snap switch receives power from the previous outlet box and sends it to the lamp outlet box

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Ceiling joist Unused grounding wire bent down to bottom of box White wire to the light screw Porcelain Lamp holder Black wire to the dark screw Cable from switch outlet box Lamp outlet box without a feed through to another outlet box.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Wiring a lamp switching circuit when the switch is in a “dead-end” outlet box The next slide shows the connections in the switch outlet box when the hot wire to be switched comes from the lamp outlet box. Notice that the hot wire is a white wire with black tape around it. The slide after that shows the connection used to feed the hot wire to the switch outlet box. It also shows how the porcelain lamp holder is powered. Had the box been metal, then a third grounding wire would have been connected to the box with a grounding screw.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Grounding wire Hot wire from lamp outlet box Switched hot wire to lamp in outlet box Grounding screw Mounting screw Plastic outlet box Cable from lamp outlet box An outlet box housing only one switch and one two- conductor/G cable does not require a neutral conductor Wall stud

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Ceiling joist Grounding wires bent down to bottom of box White wire to light screw Porcelain Lamp holder Switched black wire to the dark screw Cable to switch outlet box Lamp outlet box feeds power to the switch in the switch outlet box. Power from previous outlet box White wire with black tape feeds power to the switch outlet box

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Wiring a lamp switching circuit with a feed through in the lamp outlet box The next slide shows the connections in the switch outlet box when the power cable enters the switch outlet box and power must also be fed through the lamp outlet box. The slide after that shows the connections in the lamp outlet box required to pass power to the next outlet box as well as power the lamp holder. Had the box been metal, then a third grounding wire would have been connected to the box with a grounding screw.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Plastic outlet box Stud The 14-3/G cable provides a hot wire, a switched hot wire, a neutral wire, and a grounding wire for the lamp outlet box. Power cable from previous outlet box 14-3/G cable to Lamp outlet box Grounding-wire feed through and switch grounding wire Neutral-wire feed through Hot-wire feed through and hot wire to switch Switched red wire to the lamp oulet box Mounting screw

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Ceiling joist Porcelain Lamp holder 14-3/G cable from switch outlet box Lamp outlet box with a feed through to another outlet box. Power fed from switch outlet box. White wire to light screw Switched red wire to the dark screw Cable to next outlet box Neutral-wire feed through and neutral feed to lamp holder Hot-wire feed though Grounding-wire feed though

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. 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. N H Low-voltage supply Low-Voltage-Controlled Light Circuit

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Switching-Circuit Quiz A 3-way lighting circuit requires _____ insulated conductors between switches. A 4-way lighting circuit requires _____ insulated conductors between switches. A _____ colored conductor should not be used in the return leg of a switch. A 4-way lighting circuit provides control of a light from _____ locations. The handle of a lighted-handle 3-way switch is lit when the light is _____. A three-terminal relay stays in the on position until the _____ is pulsed. three white three off off coil When a white wire must be used as a hot wire it is covered with ____. black tape

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. Concept Review Repeat Segment Two 3-way switches provide 2-point control of a light circuit. Two 3-way switches and one 4-way switch provide 3-point control of a light circuit. Lighted-handle switches are lit when off. Momentary rocker switches are used to control the latching relay in a low-voltage- controlled lighting circuit.

McGraw-Hill © 2008 The McGraw-Hill Companies Inc. All rights reserved. REVIEW Equipment-grounding conductor Ground-Fault Circuit Interrupter Arc-Fault Circuit Interrupter Three-Way Lighting Circuit Four-Way Lighting Circuit Lighted-Handle Switches Wiring Lighting Circuits Low-Voltage Control Circuit