A 3-way switch wiring or multi-way switching allows you to control one ceiling light from two different locations. It is the interconnection of two or more switches.
Three-way switches are useful in hallways and large rooms as you can toggle ON/OFF the lights from both ends.
But unlike a single-pole dimmer, installing a multi-way light is harder. It has more screw terminals and thus requires more wires.
Parts of a three-way switch
- The common
- Two traveller terminals
- Grounding or Earthing terminal.
How a multiple or 3-way switch work
A three-way switch toggles ON and OFF the light fixture like other switches. But they do this from two ends.
When the toggles from both ends are up or down, the circuit is complete and the light will be ON. When the toggles are opposite, the circuit is open and there will be no light. This allows any of the regulators to power ON/OFF the light.
Tools required for three-way wiring
- Four in one screwdriver
- Wire stripper
- Voltage tester
- Electrical tape
- Utility knife
- Three-way switches (2)
- 14-3 or 12-3 Romex cable.
- Electrical boxes.
How to Wire a 3-Way Switch
There are three methods, but all depend on whether the hot wire goes to the switch first or the light fixture.
Whichever way you prefer, installing a 3-way light is easy when you follow our switch wiring diagrams.
- Turn off the branch circuit from your electrical panel and add all the electrical boxes required.
- Feed in a lengthy 14-3 NM Romex cable, or 12-3 if you are connecting to a 12 gauge wire. The 14-3 cable is a 14 gauge Romex wire with three insulated conductors, plus a ground wire. The three insulated conductors are black, red, and white plus the earth wire.
- Connect the wires to the right terminals on the switch. The green screw is for earth wires, the two brass coloured screws are for travelers while the dark screw is the common terminal.
- Ensure you wrap all the white wires used as travelers with black electrical tape for easy identification.
Three Way Switch Wire Diagram when Power goes to the Light Fixture First
This diagram shows how you can wire a three-way light when the power is coming from the light fixture.
- From the diagram, you can see that the power source enters the fixture box
- The hot or black wire connects to the common terminal of the second dimmer.
- Blue and red wires link the traveler terminals for both switches
We also connected the red wire to the common terminal of the first switch which moves back to the light.
3-way wiring diagram power at switch
This diagram shows a 3-way light control when the power enters from the switch.
- From the diagram, you can see that we connected the incoming live wire to the common terminal of the first switch.
- We then connected the traveling terminals of the two switches with black and red wires, before connecting the second common terminal to the bulb.
Note: The neutral (white) wire from the supply moved to the bulb without branching to any switch.
Three-way wiring diagram, light fixture at the middle
From the wiring diagram, the supply enters the junction box and connects to the common terminal of the right switch.
Two Romex cables with four wires and an earth cable joined at the junction box to connect the traveler terminal of the two switches and the bulb.
Difference between three-way switches and single poles
- A single pole light switch has two terminals and a ground screw while a three-way switch has 3, plus a ground screw.
- The toggle switch of a single-pole has ON and OFF while the 3-ways doesn’t have.
- A single-pole switch controls a ceiling light from one location while the three-way control light from two different locations.
- A single pole is good for small rooms with few light sources, while a multi-way switch is for large rooms and stairwells.