Understanding 3-Way and 4-Way Switches

Do you have a room that has two or more entrances and you would like to have a switch at each entrance to control a light? Or more commonly, did your electrician set one up for you and now you have replaced a broken switch but can’t get it to work right? Fear not, some simple diagrams should help sort it out.

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First of all, there are 2-way, 3-way, and 4-way switches; each with a different purpose. Two-way switches are most common and only have two terminals in addition to the ground screw. These are very simple in nature and simply either break or complete the circuit to turn a light on or off.

If you have two switches that control a light, you must use 3-way switches (more on 4-ways later if you have more than 2 switches). Usually we see people get in trouble when they want to replace one switch with a dimmer. The dimmer in this situation must be a three way and the three wires must go to the correct terminals. (at the end of this article we explain how to look at a switch and most of the time get the hook-up correct. When all else fails, use a continuity tester.) Three-way switches will have 3 terminals in addition to the ground screw Wire Pull Tester. One hot(usually black) wire either comes from the power panel into the switch or one hot wire exits the switch and goes to the light. In between the switches are two wires called travelers. These are considered switched hot wires and can be typically black, red, or sometimes a white wire has black tape wrapped around it at each end to designate it as a hot and not a neutral wire.

Four way switches are used when you have 3 or more switches to control a light. As can be seen in the diagrams below, there is always a 3-way switch at the start and end of the circuit, with 1 or more 4-ways in between. The 4-way switches simply have the two travelers coming in and then going out to the next switch down the line.

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