How to Wire a Two-Way Switch
Wiring a two-way switch, also known as a three-way switch, allows you to control a light fixture or other device from two different locations. For example, you may want to turn on a light from the top and bottom of a staircase. Wiring these switches properly is important for safety and functionality. In this guide, I will walk you through the complete process of wiring a two-way switch step-by-step.
Things You'll Need
Before getting started, make sure you have the following materials:
Two-way switches - You will need 2 switches to control the light from two locations. Choose switches rated for the voltage in your home (typically 120V).
Electrical wires - 14/2 or 12/2 NM electrical wire with ground. Choose the gauge based on the amperage rating of your circuit.
Wire strippers - For stripping the insulation off the wires.
Wire connectors - To join the wires together.
Voltage tester - To safely test the wires are dead before working on them.
Phillips screwdriver - For mounting the switches and connecting wires.
Turn Off Power
Safety should always be the number one priority when working with electrical wiring. Before doing any work, use a voltage tester to confirm the circuit is dead. Turn off the appropriate breaker in the service panel that controls the circuit you are working on.
Identify the Fixture Wires
At the light fixture, you will find the following wires:
Line or hot wire - Typically black insulation. Brings power from the service panel to the light.
Neutral wire - Usually white insulation. Completes the circuit back to the panel.
Ground wire - Bare copper or green insulation. Provides a safe path for electrical faults.
Load wire - Often black insulation. Carries power from the switch to the light fixture.
Identify each of these wires before proceeding.
Install the First Switch
- Mount the first two-way switch in the electrical box. Only remove knockouts where wires will enter.
- Connect the line (typically black) wire to the common terminal on the switch.
- Connect the neutral (typically white) wire to the neutral terminal on the switch.
- Connect the ground wire to the ground terminal on the switch.
- Connect a 14/2 wire between the light fixture and the second switch location. Connect to the traveler terminals on the first switch. This wire will carry the switched power to the second switch.
Install the Second Switch
- Mount the second two-way switch in the second electrical box near the other location.
- Connect one of the traveler wires to the common terminal on the second switch. It does not matter which traveler is used.
- Connect the other traveler wire to one of the traveler terminals on the second switch.
- Connect a 14/2 wire between the second switch and light fixture.
- At the light, connect the line or hot wire to one wire from the second switch.
- Connect the other wire from the second switch to the load wire on the light fixture.
- Connect all neutral and ground wires properly at the light fixture.
This completes the basic wiring. Turn the power back on and test that the switches work to control the light from both locations.
Three-Way Switch Wiring Diagram
Here is a wiring diagram depicting the wiring installation:
The line or hot wire brings power into the first switch. From there, the two traveler wires carry power between the two switches in a continuous loop. The second switch sends power via the load wire to the light fixture.
Tips for Wiring Two-Way Switches
Use the correct gauge wire for the amperage rating of the circuit. 14 gauge is sufficient for most basic lighting circuits up to 15 amps.
Match the colors of the wires to follow electrical code and conventions. For example, use black for hot wires, white for neutrals, and green or bare copper for ground wires.
Ensure electrical boxes are large enough to accommodate the number of wires. Use spacers if needed to avoid pinching wires.
When working with aluminum wiring, use special aluminum-rated switches and connectors. Apply antioxidant paste to reduce oxidation.
Label the wires to avoid confusion on three-way circuits. Tape or marker at both switches helps identify travelers.
Test the switches to confirm they work properly at both locations after wiring is complete.
Following basic wiring safety and taking care with the traveler wires are the keys to successfully installing and wiring two-way switches. With a little time and patience, you can wire these switches properly. The result is being able to conveniently control lights and devices from multiple locations in a home or building.