How to Wire a Switch Leg

Introduction

Wiring a switch leg allows you to control a light fixture from a switch that is not located directly next to the light. This guide will walk you step-by-step through how to wire a switch leg correctly and safely.

What is a Switch Leg?

A switch leg is a wiring method that allows you to control a light fixture from a remote location. It consists of a 3-wire cable that runs from the switch to the light fixture.

• The hot wire brings power from the panel to the switch.
• The switched hot wire carries power from the switch to the light fixture.
• The neutral wire completes the circuit back to the panel.

Wiring a switch leg allows you to put the switch in a more convenient location, like next to a room entrance, while having the light fixture somewhere else, like the middle of the ceiling.

Materials and Tools Needed

To complete this project, I will need:

• 3-wire NM cable - To run from the switch to the light fixture. The exact gauge will depend on the size of the circuit.
• Wire stripper - For stripping the cable and wires.
• Voltage tester - To make sure the power is off before working.
• Wire nuts - For connecting the wires.
• Electrical tape - For covering splices.
• Phillips screwdriver - For opening up the switch and light fixture boxes.

I will also need the appropriate switch and light fixture for the project.

Step-by-Step Installation

Follow these steps to correctly and safely install a switch leg:

1. Turn Off Power

The first step is to turn off power to the circuit I'll be working on at the main breaker panel. I will then verify it is off by using a non-contact voltage tester. Working on live circuits can result in a serious shock, so this step is critical.

2. Install Switch Box

I will install a plastic switch box at the location where I want the switch. The box should be secured in place with screws to a stud or joist in the wall.

3. Install Light Fixture Box

Next, I install the light fixture box directly above where I want the light. This box gets mounted directly to the ceiling joists. I will feed the NM cable from here to the switch.

4. Run Cable between Boxes

Now I can run the 3-wire NM cable between the light fixture box and the switch box. Leave a few extra feet of slack at both ends. The cable should be stapled every few feet for support.

5. Make Connections at Light

In the light fixture box, I will connect the wires:

• Hot (black) - Connect to the hot terminal on the light fixture.
• Switched Hot (red) - Cap this off with a wire nut, as it will not be used in the light box.
• Neutral (white) - Connect all the neutral wires together, including on the light.

6. Connect Wires at Switch

Inside the switch box, I will connect the wires:

• Hot (black) - Connect to one terminal on the switch.
• Switched Hot (red) - Connect to the other terminal on the switch.
• Neutral (white) - Cap this off with a wire nut, as it will not be used at the switch.

7. Mount the Devices

With the wiring complete, I can now mount the switch and light fixture into their boxes. Follow the manufacturer instructions to make the proper connections.

8. Test and Restore Power

Once everything is installed and connected properly, I can restore power. I will test the switch to make sure it functions correctly before completing the project.

Conclusion

When complete, the switch leg will allow the installed light fixture to be turned on and off from the remote wall switch. This provides a convenient way to control lights from a wall switch located away from the fixture. Following proper safety procedures like turning off power is critical. Once wired correctly, the switch leg provides an effective way to control lighting.