How to wire a light switch in the USA

4 way light switch with power feed via the light

This circuit diagram shows wiring for a 4 way circuit with the power source at the light fixture and the switches following.

A two-wire cable (C2) is run from the light to the first switch (SW1) and a 3-wire cable runs between all the switches. The hot source is connected to the common terminal on the first switch (SW1) and the hot terminal on the light fixture is spliced through all the light fixture to the common terminal of the last switch (SW3).

The travelers run from the first switch (SW1) to one set of terminals on the 4 way (SW2) and from the second set to the travelers on the last 3 way (SW3). The hot to the light is from the common terminal of SW3 (spliced through each switch box).
4 way switch with the the power source via the light


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Two lights between 3 way switches (power via a light)

The power for the circuit joins the light fixture F1 via the cable C5. The neutral connects to the light (LT1) and is spliced through to LT2 via the cable C4. The hot from the power source is spliced through to the common terminal of the switch (SW1) via cable C1.

The travelers from the switches, via C1 and C2, are spliced through the fixtures,and joined by cable C3.

The hot to the lights comes from the common terminal of SW2 via cable C2 where it is spliced to the hot of of LT1 via cable C4.
Two lights between 3 way switches with the power feed via one of the lights


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3 way light switch with power feed via the light (two lights)

The power, cable C1, joins the circuit at the light fixture F1. Here the neutral connects to the light F1 and is spliced through to light F2. The hot from the power source is spliced through both fixtures and terminates at the common terminal of SW1 via cable C3.

The travelers of each switch are connect together using cable C4 (taped white and red wires).

The taped white wire of cable C3 is the hot to the light LT2 (where the red wire of cable C2 is used to splice the hot to the next light, LT1).
Circuit diagram for 3 way switches controlling two lights with the power feed via the light


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Single light between 3 way switches (power via light)

The power source in this circuit enters the light fixture where the neutral connects to the light and the hot is spliced through (via cable C2) to the common terminal of the 3-way switch (SW2). The travelers between the switches are also spliced together in the light fixture. The power to the light is via the common terminal of the 3-way switch SW1.

Single light between 3 way switches with the power supplied via the light


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Three way light switch with power feed via the light

In this light switch wiring diagram the power feed joins the circuit via the light fixture where a two wire cable (C2) runs from the light, to the first 3-way switch (SW1), and a 3 wire cable (C3) joins the two switches. The hot source is spliced to the white wire (which should be marked as being hot with black tap) and run through to the common terminal of SW1, and from here the hot from the light is spliced through to the common terminal of the second 3-way switch (SW2).

3 way switch with power feed via the light (single light)

 


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2 way light switch with power feed via light

The power source enters the light fixture where the neutral connects directly to the neutral terminal  of the light. The hot wire from the source is spliced through to the 2-way switch and via the switch to the hot terminal of the light.
2 way switch with power feed via switch


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