Electricity: Wiring Variations



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Scores of wiring variations exist for any combination of switches, fixtures and receptacles. These basic diagrams can help you get started. The nonmetallic boxes and fixtures shown aren't grounded. Metal boxes and metal fixtures must always be grounded.

White wires in cables are normally used only as the neutral wires. However, in a two-wire switch-loop circuit, the white wire is used as the hot wire to supply power to the switch, so it must be re-identified with tape or similar marking. E.g., the black wire in the switch-loop circuit, shown below, is the switched hot wire that completes the circuit to the fixture. This pre vents having both a white neutral wire and a white hot wire at the fixture. This rule also applies to three-way and four-way switch circuits.

Caution: Always turn off power and use a voltage tester to make sure the circuit you’re working on is off.


Switch controlling a ceiling fixture. Power from the source feeds the switch box first. The hot wire connects to the switch. The switched hot wire completes the circuit to the fixture.

Switch controlling two or more fixtures. Power from the source feeds the switch box first. The switched hot wire, neutral and ground wires continue to two or more fixtures.


Switch loop. Power from the source enters fixture box first White hot wire, re-identified with black tape, supplies power to switch. Black switched wire completes the circuit to the fixture.


Switch loop with receptacle added after fixture. In this configuration, the switch loop controls the fixture only. The unswitched receptacle is hot all the time.

Switch loop with receptacle in the same box. The switch loop controls the fixture only. The unswitched receptacle is hot all the time.

Two fixtures with two switches, power entering switch. The circuit that supplies power to the switch box is used for two switches and two separate switched circuits.

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Receptacles wired in tandem. Power passes through one (or more) middle-of-circuit receptacles to end-of-circuit receptacle.

Split receptacles. The top half of split receptacles are always hot. The bottom half are switch-controlled. To split a receptacle, break off the tab between the hot brass terminals.
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Two fixtures with two switches, power entering one fixture. The black wire supplies power to both switches. The red wire is a switched hot wire back to fixture.

Wiring a 20-amp, 240-volt receptacle. Two-wire with ground cable for 240-volt receptacle for window air conditioner. No neutral wire required. Hot white wire in cable is reidentified with tape at all terminations.

Three-wire with ground cable for power supply to a 50-amp, 125/250-volt receptacle for electric range. Two hot wires, a neutral wire and a grounding wire are required.

Three-way switches, fixture after switches. The incoming hot wire attaches to the first switch’s common dark-colored terminal. The two hot wires of three-wire cable connect to a pair of brass-colored traveler terminals on each switch. The fixture’s hot wire connects to the second switch’s common terminal. (Three-way switch, Traveler terminals, Power source (two wire with ground), Three-wire with ground)

Three-way switches, fixture before switches. Power enters the fixture box. The reidentified white hot wire connects to the first switch’s common terminal. Red and reidentified white wires link traveler terminals of both switches. Black wire, which is connected to the second switch’s common terminal, leads back to the fixture. (Power source (two-wire with ground), Black tape)

Three-way switches, fixture between switches. Power enters the fixture box. The incoming hot wire is connected to the right switch’s common terminal. Two lengths of three-wire with ground cable, joined at the fixture box, link the right and left switches to each other and to the fixture. Reidentify white traveler wires as shown.


Controlling a light from three places using a four-way switch and two three-way switches. The incoming hot wire is routed through the fixture box to common terminal of the left three-way switch. Three-wire with ground cable connects all three switches. Black wire from the common terminal of the right three-way switch leads back to fixture.

Last modified: Friday, 2008-09-12 12:20 PST