Many homeowners take for granted that they can easily control their lighting with the flip of a switch. A standard single-pole switch is a light switch that controls a single light fixture, but a three-way light switch allows you to turn a light on and off in two separate positions.
Three-way switches are most commonly used at the top and bottom of stairs, or to operate switches at separate ends of a hallway. In rooms with separate entrances, it makes sense to use a three-way switch so you don’t have to navigate a dark room.
How to Wire a 3 Way Light Switch?
Please turn off the breaker
- Test your non-contact voltage tester on a known live circuit to see if it works.
- Find the breaker that controls the light or existing switch and turn it off.
- Use a tester to make sure the power is off.
Connect cables to box and light
- Connect a 14-2 NM-B cable (white, black, copper) from the power supply to the first switch position.
- If you are adding a 3-way setup to an existing situation, you should already have this cable.
- Connect 14-3 NM-B cables (white, black, red, copper) from the first switch to the second switch.
- Connect a 14-2 NM-B cable from the second switch to the light fixture.
This project assumes you will use a 15A breaker on your lighting circuit. If your breaker is 20 amps, you will need to use 12-2 and 12-3 NM-B cables.
Get your wires ready and Switch wiring
- Using a utility knife, carefully cut off a few inches of cable sheathing.
- Insulate each conductor with 3/4-inch strip stripper.
- Cut off a few 6-inch pieces. A length of exposed copper wire for use as a grounding pigtail.
- Prepare the wires for the 3-way switch. One has the cap on and the other has the insulation stripped.
- Connect the two grounds of the cable to the 6-inch cable. Copper pigtail.
- Make a loop at the end of the pigtail and wrap the green screw clockwise. tighten.
- Connect the two neutral wires (white wires) together. Do not attach to switch.
- 14-2 Secure the black wire of the power supply cable to the three-way black (common) screw. (Make a loop as before.) Newer 3-way switches are marked ‘Common’ next to the Common terminal screw on the back of the switch.
- 14-3 Secure the traveler wires (black and red) of the cable to the brass screws. It doesn’t matter which one goes where.
- Wrap electrical tape around the switch to cover the exposed terminals and secure the switch to the box.
Second switch wiring
- Join two bare pieces of land at 6 inches. Connect the copper pigtail and attach it to the green screw.
- Connect the two neutral wires together. Do not attach to switch.
- Secure the black wire of the 14-2 cable to the light to the black (common) screw.
14-3 Secure the cable’s black and red traveler wires to one of the brass traveler screws. (Again, it doesn’t matter which one.) - Wrap the switch with tape and attach it to the box.
Wire the light
- Start with the exposed copper ground wire and connect it to the light fixture.
- Connect the exposed copper wire to the green ground screw on the light fixture.
- Connect the white neutral wire of the cable to the white neutral wire of the light fixture.
- Connect the black wire of the cable to the black wire of the lamp fixture.
- Attach the light fixture to the box.
You are done: Make sure the light switch is secure in the box and add the faceplate. Turn on the breaker. Test the lighting by turning it on and off at each location. If something doesn’t work, turn off the breaker before checking! Double check that the brass screw has a traveler and power on the black/common. Turn on the circuit breaker and turn on the lights.
How do you know which direction the current flows?
If current enters the switch before it reaches the light, the neutral white wire from the electrical panel and the white wire leading to the light will connect together and become clogged. The black live wire from the power goes through the switch to the light. Flipping the switch interrupts the flow of electricity to the light, turning it on and off.
The circuit is wired so that when a wire carrying active current first enters the fixture’s electrical box, a switch interrupts the current. The white wire from the electrical panel is wired to one side of the light. The live black wire is connected to the switch, the white wire is also connected to the switch, but is connected back to the electrical box.
The easiest way for homeowners to test the actual direction of current is to use a non-contact voltage tester to trace the flow. Follow the steps provided by your tester that best fit the way your circuit is currently set up.
