Agricultural Mechanics Fundamentals & Applications Chapter 33Installing 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 breakers –Metal bars –Grounded strips

Wiring Boxes Available in rectangular or octagonal shapes in various depths. Functions: –Hold cable or conduit so 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 Box fastened securely to building. Cable clamped securely to box. Cables running from box to box must run through the interior of the buildings walls, floors and ceilings, be secured by staples or clamps, and secured as needed to prevent the cable from being caught and pulled. Metal boxes grounded. Wires in boxes connected to each other by wire nuts.

Requirements Cont. Ground wires held together by a metal clamp or solderless connector. Wires attached to terminals of switches and receptacles by tightening no more than one wire under one screw or spring-clamp. Hot wires attached to brass-colored screws. Neutral to aluminum and ground to green screws. White wire used as a positive wire 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, places where current can get from black wires to the ground wires or can bypass the bulb and flow directly to the neutral wires. Test all boxes to be sure they are properly grounded.

Important Terms New Workinstallation of cable and conduit through floors, ceilings, and partitions of new buildings. Fixturebase or housing for electrical devices. Receptacledevice for receiving electric plugs. Switchdevice used to stop the flow of electricity. Duplex (double) Receptaclemost common typewired so both outlets are on the same circuit.

Terms Cont. Splitting the Receptacleremoving the metal strap between the two screws to wire to two different circuits. Wire Nutsinsulated solderless connectors. Single-pole Switchdesigned to be the only switch in a circuit. Knockoutpartially punched impression. Continuity Testerdevice used to determine if electricity can flow between two points.

Terms Cont. Continuityconnectedness. Three-way Switchused in a pair and permits a light or receptacle to be controlled from two different locations. Switching (traveler) WiresTwo wires attached to the light-colored screws in a switch.