A Little Learning Takes the Mystery Out of the Four-Way Electrical Switch

Q: DEAR TIM: I am pulling my hair out trying to wire a four-way switch. What is the secret? Do you need a special four-way electrical switch or a four-way light switch? At this point, my new wife thinks she married a dunce. If you can't help, I will be forced to admit defeat and will call an electrician. -- Robert M., Fort Collins, Colo.

A: DEAR ROBERT: Don't beat yourself up too badly. A lot of people are flummoxed by the mysterious four-way switch. I liken the four-way switch, and its cousin the three-way switch, to the Wizard of Oz. If you pull back the curtain, you will see that the wizard is just a person. When you take away the plaster and drywall, you will see these switches are simple.

The first thing you need to know is that the four-way switch is special. If you look at a regular single-pole switch that controls a light or series of lights from one location, you will see it has two screws on it, plus the green ground screw. A three-way switch has one additional screw, and a four-way switch has four screws, plus the green grounding screw.

You use four-way switches in situations in which you want to control a light or other fixture from more than two locations. For example, the second-floor hallway lights in my house are controlled from four places. To accomplish this, you have to have two three-way switches and two four-way switches.

The placement of the four-way switches in the circuit is important. A four-way switch must always be between two three-way switches. I know this sounds confusing, but try to imagine how it would be done if you were to remove the drywall or plaster from your walls and ceilings.

I will describe in the simplest way I know how to wire a circuit with a four-way switch. I would start the job by nailing three electrical boxes to the wall studs. This circuit will have the mandatory three-way switches and the single four-way switch. Let's number the electrical boxes 1, 2 and 3, and let's assume they would be in a line as if the switches were in a long hallway.

The No. 1 box would be at one end of the hallway, and into it would feed the power from a cable that contains a white neutral wire, a black continuous-hot wire and the bare ground wire. The continuous-hot wire is controlled by a circuit breaker or fuse.

A second cable leaves the No. 1 box and proceeds to the No. 2 box in the middle of the hallway. This cable has four wires -- white, black, red and bare copper. A cable that contains the same four wires leaves the No. 2 box and goes to the No. 3 box at the far end of the hallway. A final cable leaves the No. 3 box and goes to the light fixture we are trying to control. This final cable is like the first one we installed in the No. 1 box: It has just white, black and bare copper wire.

In all three boxes, you connect the white wires to each other with a wire nut. You do the same with the bare copper wires and create a tail piece of bare copper that connects to the green grounding screw on each switch. In each box, you are left with black and red wires. These connect to the terminal screws on the switches.

Because you are concerned just with the four-way switch, look at the actual switch. Hold it up as if it were in the switch box. You will see that two screws are on the bottom and two on the top. In my example, you take the black and red wires from one of the cables and attach them to the bottom screws. It doesn't matter which ones. Then you take the red and black wires from the other cable and attach them to the top screws. Once again, it doesn't matter which color wire goes on which screw. Assuming you did not take apart the three-way switches in your circuit, your four-way switch will now work perfectly.

Tim Carter can be contacted via his Web site,http://www.askthebuilder.com/printer_Submit_Question.shtml.

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