Wiring a Light Switch

There are two methods for wiring a basic on/off (single-pole standard duty) switch to a light or a set of lights.

One method is to bring the power supply in to the light fixture outlet box, and then use what is called a “switch-leg drop” to the switch box, and the other way is to bring power in to the switch box, and then run the “switched” cable up to the light or lights.  The second method is by far the best way, especially if you are using the switch to control more than one light outlet.

Method #1 (The switch-leg drop)

Step #1

Run your 2-wire power feed cable to the outlet box for the light fixture.  Then run a 2-wire cable to the outlet box for the switch that will be used to control this light.

Step #2

Properly install the cables in the device boxes and terminate your ground wires as per code rules and accepted trade practices.

Step #3

In the light box, splice the black power wire in, to the white wire going to the switch.

*Note that this is one of the few times that it is acceptable to use a white wire as a hot conductor, providing that you identify this as a live wire by using a piece of black tape, or a permanent felt marker to color in a section of the wire close to the connection point so as to clearly identify that the wire is not a neutral conductor as one would normally expect!

The white neutral conductor from the source is connected to the white wire(s) or neutral terminal of the light fixture.  The remaining black wire returning from the switch will be connected to the black wire (s) or the hot or live terminal for the light fixture.

Step #4

In the switch box, the white wire (which is a hot wire as described above) is again identified as such, and is connected to one of the terminals of the single-pole switch (It doesn’t matter which of the 2 terminals, but  personally I always use the bottom terminal for hot, the top terminal for the switched wire).  The black wire is then connected to the other terminal to complete the circuit.

Method #2 (Power to switch, then to light or lights)

Step #1

Run your power feed cable in to the switch outlet box first, then run a cable from the switch box up to your light outlet box.

Step #2

Properly install the cables in the device boxes and terminate your ground wires as per code rules and accepted trade practices.

Step #3

At the switch box, splice the incoming neutral or white wire to the white wire going to the light box.

Connect the black live wire from the power cable in to one of the terminals on the single-pole switch (again, it doesn’t matter if you use the top or the bottom terminal of the switch, but I prefer to use the bottom terminal for the hot wire), and then connect the black wire from the cable going to the light fixture to the other terminal of the switch.

Step #4

At the light fixture, the white wire connects to the fixture neutral (white) wires or neutral terminal, and the black wire connects to the fixture live(black) wires, or hot terminal (terminals are found on basic fixtures such as keyless lampholders).  If you have more than one fixture to be controlled by the switch, then you would now run cable from this light fixture to other lights that you would like controlled by the switch.