What is a Three-Way Switch?
A three-way switch is a type of electrical switch that makes it possible to control a light or other electrical load from two different locations, like the top and bottom of a staircase.
To wire a three-way switch circuit, three-way switches have three terminals:
- The common terminal
- The traveler terminals (2)
Three-way switches get the name because they have three possible positions: on, on via the other switch, and off.
How Do Three-Way Switches Work?
Three-way switches work by toggling between providing a power path between the common terminal and one of the traveler terminals.
When the light or other load needs to be turned on or off from two locations, cables called 'travelers' connect the two three-way switches. The travelers carry the switching signal between the switches.
One of the switches has an additional 'hot' wire connecting to the common terminal to provide supply power to the circuit. The other switch's common terminal connects to the load you want to control.
Flipping either three-way switch reconnects the travelers and common terminal to change the power flow in the circuit. This lets you turn the light on and off from either location.
Wiring a Three-Way Switch
Follow these steps to wire a three-way switch circuit:
1. Connect the Power Source
- Connect the hot wire from the power source to the common terminal on one three-way switch.
- This could be coming from a circuit breaker panel or another switch.
2. Connect the Light or Load
- Connect the load wire to the common terminal on the other three-way switch.
- The load is whatever you want to control like a light or outlet.
3. Connect the Traveler Wires Between Switches
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Connect the traveler wires between the traveler terminals on each three-way switch.
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There should be one traveler wire connecting the same traveler terminal on both switches.
4. Connect the Neutral and Ground Wires
- Connect the neutral wires from the power source, switches, and light together with a wire nut.
- Connect the ground wires from the power source, switches, and light together as well.
5. Mount the Switches and Test the Circuit
- Mount the wired switches into electrical boxes.
- Turn the power back on and test that the light can be controlled from both switch locations.
Helpful Tips
Here are some helpful tips when wiring a three-way switch circuit:
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Label the wires to avoid confusion. 'Power in,' 'Light,' and 'Traveler 1/Traveler 2' works well.
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Break the circuit tabs on the traveler terminals so each traveler wire gets its own terminal.
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Double check the wiring before turning the power back on. Make sure the traveler wires go to the same terminal on both switches.
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Use the right wire gauge for the circuit amperage to avoid hazards.
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Phase tape can help identify the traveler wires for easier troubleshooting later.
Safety Precautions
Take these safety precautions when working on home electrical wiring:
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Turn off the power at the circuit breaker before doing any work.
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Verify the power is off by testing wires with a non-contact voltage tester.
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Follow local electrical codes and get any required permits.
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Use a cable ripper to strip wires properly without nicking the copper.
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Wear electrical gloves and safety goggles in case of shorts.
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Double check connections are tight and correct before restoring power.
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Never work on wiring alone, have someone there to assist if needed.
Conclusion
The basic process to follow when wiring a three-way switch is:
- Connect power at one switch.
- Connect the load at the other switch.
- Install traveler wires between the same terminals on both switches.
- Complete neutral and ground wiring.
Key tips are labeling wires, breaking off switch tabs, and taking safety precautions.
With good wiring practices and by following code, a three-way switch circuit can provide safe and convenient control over lights and outlets from two locations.