1. Copyright © 2010 Delmar, Cengage Learning. ALL RIGHTS RESERVED. Unit 34 Installing Branch Circuits

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

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

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

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

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

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

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

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