3 Way Switch Wiring / How to Wire 3-Way switches

You may be new to electrical work but wish to wire a 3-way switch.

3 way switch wiring is harder than a single pole. It is the interconnection of two or more switches.

3-way light control helps in hallways and large rooms to turn the lights from two locations.

But it’s harder to install than a single-pole switch

Read this article to learn how to wire a 3-way switch

Components of a three-way switch

  • The common
  • Two traveller terminals
  • Ground or Earth terminal.

How the 3-way switch works

A three-way switch allows you to control a light fixture like other switches, but they do this from two ends.

When the toggles from both switches are up or down, the circuit is complete and the light will be ON. When they are opposite, the circuit opens and there will be no light. This allows any of the switches to turn on or off the light.

Tools and materials required to wire a 3-way switch.  

They include:

  • Four in one screwdriver
  • Wire stripper
  • Plier
  • Voltage tester
  • Electrical tape
  • Utility knife

Materials required

  • Two 3-way switches
  • 14-3 or 12-3 Romex cable.
  • Electrical boxes.

Note: Before any electrical installation, ensure that you power off the circuit breaker and also wear your protective glove to prevent electric shock and other hazards.

Steps to Wire 3-Way switches

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 procedures.

Turn off your circuit breaker

Locate the circuit breaker that controls the branch circuit and turn off the circuit’s power.

This is to prevent electrocution and other hazards during the installation.

Mount two electrical boxes

Locate the two places you want to mount the switches and install the metal boxes.

This may be at the entrance and inside of your room, ends of the hallway, staircase, or any place of your choice.

Feed the box with cables.

Feed in a lengthy 14-3 NM Romex cable, or 12-3h if you are connecting to a 12-gauge wire. The 14-3 cable is a 14 gauge Romex cable with three insulated conductors, plus a ground wire.

The three insulated conductors are black, red, white, plus the earth wire.

Connect the wires from the source to the first switch

The 3-way switch comes with 4 terminals, the black or common terminal, two brass colour or traveler terminals, and the green screw “earth terminal”.

  • Connect the black (hot) cable coming from the power source to the black terminal of the switch
  • Join the neutral or white wire from the power to the white wire from the NM cable, using a wire nut
  • Also join the two brown wires together
  • Fix the bare copper or green earth cable to the metal box and connect it to the green terminal
  • Connect the black and red traveler wires from the NM cable to the brass terminals on the switch.

Install and connect the second switch box,

  • Join the white wire from the first switch to the white wire from the lamp holder.
  • Join the two brown wires too.
  • Connect the black wire from the lamp holder to the black terminal of the switch
  • Fix the earth wire on the body of the switch box and connect it to the green terminal
  • Connect the black and red travelers from the first switch to the traveler screws or terminals of the second switch to complete the installation.

Install the lamp holder

Connect the black or hot wire from the second switch to one of the screw terminals, and the white or neutral wire to the second terminal, fix your bulb and test-run your project.

Three-Way Switch Wire Diagrams

In this section, you will see different ways you can wire a 3-way switch

3-way wiring diagram: Power to Light Fixture.

This 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.

Three-way switch wire diagram: power to the switch

This 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.

3-way wiring diagram: Power to the junction box.

From the above wiring, 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 for 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.

Frequently Asked Questions

Does it matter which wire goes where on a 3-way light switch?

Yes, the black “hot wire” from the power source must connect to each switch’s common screw terminal, to enable it to carry the current from the source to the switches and then to the light fixture.

How many wires are hot in a 3-way switch?

Two hot or black wires. The one from the source which connects to the first switch common terminal, and the second one that runs from the 2nd switch common terminal to the light fixture.

What happens if you wire a light switch the wrong way?

if you wire a light switch the wrong way, the switch will not work properly, and may even lead to electrical hazards.

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About mariaelectricals

Hi, I am Emmanuel Nwankwo, a commercial electrician and the founder of mariaelectricals.com. I established this blog to share my decades of work experience in electrical installations and repairs.