How to wire a 4 way switch. Wiring a 4-way switch is simply adding a switch to an already existing 3-way switch circuit. This allows you to control a load from other locations in addition to the (2) locations that a 3-way circuit provides. First of all we need to go over a little basic terminology on switches.
Go to my Switch Terminology Page where I discuss the terms used for the different types of home electrical switches. It should also help in understanding the functions of each type of switch.
When wiring a 4-way switch circuit, What were doing is simply controlling the power flow (Switching off/on) to the load (a light, lamp, outlet, ceiling fan etc..) from more than 2 different locations. a couple examples would be:
At each end of a hallway and a switch halfway down the hallway. or at the top & bottom of a stairway and a switch by the front door.
We will assume that the circuit in these examples are controlling the power source to the same load. (a Single Light)
Before going any further with the 4-way switch instructions, I would recommend you go to my Wiring a 3-way switch page and first become familiar with that circuit and how it functions.
OK, assuming you are all caught up on the 3-way concept, we will continue by making a 3-way circuit into a 4-way circuit. All that is required is wiring a 4-way switch between the (2) 3-way switches. Now don't let this be confused with where the switches are physically located in your home. This is how the circuit is structured. The switches can be physically located to your liking but you must keep in mind the ease of routing the wiring from point to point. Also, this example is just adding a single 4-way switch which will give you 3 locations to control your light. To add more locations to this circuit you just simply add additional 4-way switches in series with the existing 4-way switch.
The diagram below will give you a good understanding how this circuit is wired.