Of all the electrical components in a home, none are more hated, and none cause more headaches, than the 3- or 4-way switch. Many homeowners have cursed the creation of these multi-wired monstrosities, yet, when they are working properly, they're the bee's knees.
Three and four-way switches work by opening and closing the circuit by numerous variations. We hope to have you in a more enlightened place by the end of this article. Just read it slowly, take a few breaths if you have to, and everything will be fine. For this lesson, we'll explain how to wire up a light using two 3-way switches and one 4-way switch. Keep in mind, this tutorial is more for wiring purposes than the actual installation of wall boxes and running wires. Once you know how to wire these switches up, the rest is easy.
We are going to simulate a hallway environment, with the locations for the switches already cut out and the hole in the ceiling for the light already there. There will be a 3-way switch at each end of the hall and the 4-way switch will be at the midway point of the hall. At one end of the hall, the wires are already fed. There is a black, a white, and a ground wire coming from the panel. The electricity is OFF, of course.
With us so far? Good, because it may get bumpy.
You will need both 2 wire and 3 wire Romex. The 3 wire Romex has a red wire along with the black, white, and ground.
1. At the first 3-way switch, where the wires are coming from the panel, run a length of the 3-wire Romex to the 4-way switch location. Now run another length of 3 wire Romex from the 4-way switch location to the second 3-way switch location. Lastly, run a length of 2 wire Romex from the second 3-way switch to the ceiling light.
2. Back at the first 3-way switch, wire nut the two white wires together. The black wire from the panel gets connected to the side of the switch with ONE screw. The black traveler wire gets connected to the top screw on the other side and the red traveler gets connected to the bottom screw. Wire nut the ground wires together along with a 6" piece of additional ground as the "pigtail." Connect the pigtail ground to the ground screw.
3. At the 4-way switch, wire nut the two white wires together. The black wire from the first 3-way switch gets connected to the top screw and the red wire gets connected to the bottom screw on the same side. The black wire heading to the second 3-way switch gets connected to the top screw and the red wire gets connected to the bottom screw of the other side. So you have a black and red coming in on one side and a black and red one leaving on the other. Follow the earlier instructions for the ground wires.
4. At the second 3-way switch, wire nut the two white wires together. The black wire coming from the 4-way switch gets connected to the top screw on the side with TWO screws. The red wire coming from the 4-way gets connected to the bottom screw of the same side. The black wire heading to the light gets connected to the side with ONE screw. Do the pigtail trick one more time for the ground wires here. At the light, wire nut the black wires together, then the white wires together, and then the ground wires together.
5. Wrap electrical tape around all of the switches and all of the wire nuts and screw everything into place. Install all covers and secure the ceiling light fixture. Install light bulbs in the fixture and turn the power back on.
6. Test your wiring by turning the light on at one 3-way switch, and flip the switch at the second one to turn it off. Flipping the 4-way in the middle should turn it off or on as well.
That wasn't so bad now, was it? At least now you have a general idea of how 3 and 4-way switches are wired, should you want to install or troubleshoot them in the future.