Anatomy of a Three-Way Switch

Introduction to Three-way Switches
Do-it-yourself electrical projects can be a handful unless you know the basics of what you’re working on. Many homeowners can change an outlet or a single-pole switch, but give them a couple of three-way switches and fear fills their eyes! By knowing what each part of the switch is, what wire to use, and how to connect it, the mystery of hooking up three-way switches disappears. Here is a step-by-step guide with pictures to walk you through this three-way mystery. Hopefully, it will help you in completing the project.

Parts of a Three-Way Switch
A three-way switch has four different screws on its body. The green screw is always for the ground wire (this is the bare copper wire). Now you’ll notice three other screws on the switch. The two brass colored screws across from each other are called the traveler screws. These carry the power from one switch to the other. The last screw will be a darker color, usually dark brass, copper or black. This is where you will connect the hot wire on one switch and the black wire to feed the light on the other switch.

Safety First
For safety purposes, be sure to always install a switch that has a ground screw. The ground should hook to the switch and also the box. For an added safety feature, try wrapping electrical tape around the switch, covering the entire area where the screws are exposed. Always turn off the power before working on a switch.

Making the Proper Connection
In this diagram, I’ve assembled a power source (12-2 NM Cable with a ground) feeding two different three-way switches. These would normally be on opposite sides of a room, staircase or hallway. The switches are shown controlling a light.

Notice how the black wire (hot wire) feeds one switch (connected to the dark screw), the neutral wire (white wire) splices and carries on, and the ground wire (bare copper wire) splices, connects and carries on. The switch then has a red and black wire (travelers) that continue to the second three-way switch (connects to the brass colored screws).

At this switch, the ground and neutral wires splice and carry on to the light. The black wire going to the light is connected to the darker colored screw on the switch. Finally at the light, the black wires tie together, the white wires tie together and the bare copper wire connects to the box and the light’s ground wire (if it has one).

By following these instructions and looking over the wiring picture diagram, installing three-ways should be a snap!

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