copyright © 2010 delmar, cengage learning. all rights reserved. unit 34 installing branch circuits

Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED.

Unit 34

Installing Branch Circuits


The Entrance Panel

• Electricity enters a building through the entrance panel

• Panels come in different sizes depending on the amount of current that will be leaving from the panel

• Panel consists of– large main breaker(s)– metal bars called busses– grounded strips


Wiring Boxes

• Available in rectangular or octagonal shapes in various depths

• Functions– Hold cable or conduit so that stress cannot be placed on

the wire connections– Nailed, screwed, or clamped to the building to support

switches, outlets, and fixtures– Contain all electrical connections made outside of

fixtures– Prevent mice or other vermin from nesting around

electrical connections


Electrical Code Requirements• All boxes must be fastened securely to building• All cables clamped securely to box• Cables running from box to box must run through the

interior of the building’s walls, floors, and ceilings• Cables must be secured by staples or clamps as needed to

prevent the cable from being caught and pulled• Metal boxes must be grounded• Wires in boxes must be connected to each other by wire

nuts


Code Requirements (continued)• Ground wires must be held together by a metal clamp or

solderless connector• Wires must be attached to the terminals of switches and

receptacles by tightening no more than one wire under one screw or spring-clamp

• Hot wires are attached to brass-colored screws• Neutral wires are attached to aluminum-colored screws• Ground wires are attached to green screws• When white wire is used as a hot wire, it must have the

insulation showing in the box painted black or marked with black tape


Testing a Circuit

• After wiring all lights and switches, the circuit should be tested before turning on the circuit breaker or inserting the fuse

• Use a continuity tester to be sure the circuit is not open

• Check for shorts by looking for places where current can get from black wires directly to the ground or neutral wires

• Test all boxes to be sure they are properly grounded


Important Terms• New work: installation of cable and conduit through

floors, ceilings, and partitions of new buildings• Fixture: base or housing for electrical devices• Receptacle: device for receiving electric plugs• Switch: device used to stop the flow of electricity• Duplex (double) receptacle: the most common type of

receptacle; wired so that both outlets are on the same circuit


Important Terms (continued)

• Splitting the receptacle: removing the metal strap between the two screws to wire each outlet to two different circuits

• Wire nuts: insulated solderless connectors• Single-pole switch: designed to be the only switch in a

circuit• Knockout: partially punched impression• Continuity tester: device used to determine if

electricity can flow between two points


Important Terms (continued)

• Continuity: connectedness

• Three-way switch: used in a pair to permit a light or receptacle to be controlled from two different locations

• Switching (traveler) wires: two wires attached to the light-colored screws on a three-way switch

copyright © 2010 delmar, cengage learning. all rights reserved. unit 34 installing branch circuits

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