How to Wire a Dimmer on a Three-Way Circuit
In the past, a three-way switch circuit could only be controlled using two three-way switches. But these days, three-way dimmer switches allow you to customize the level of light put out by a fixture on a three-way circuit. Wiring a dimmer on a three-way circuit takes about 15 minutes, but the job demands your complete attention as the inclusion of an extra wire on the switch can be confusing to those who have never worked on such a circuit before. Does this Spark an idea?
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Things You'll Need
- Screwdrivers
- Voltage tester
- Notepad
- Pencil
- Wire stripper
- Three-way dimmer switch
- Electrical tape
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Instructions
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Turn off the power to the three-way circuit by toggling off the circuit breaker in the electrical panel. Because three-way circuits are controlled by two switches, it is extra-important to check both lines for voltage before you begin working on the circuit.
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Remove the existing switch plate and the two screws that secure the switch to the wall box.
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Carefully remove the three-way switch from the wall box by pulling on the top and bottom tabs. Do not touch the sides of the switch.
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Use the voltage tester to check all of the lines on the switch for voltage.
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Use the pencil and notepad to draw a schematic of how the existing switch is wired. This is critical because a three-way circuit can be wired in a wide range of different ways, depending on where the feed enters the circuit. Make the drawing as detailed as possible and be sure each wire is identified on the schematic.
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Loosen the screw terminals on the switch and remove the wires. Bend them away from the switch in the same direction as they were installed. For instance, if the wire was connected to the top right screw, bend the wire to the top right of the box. This, along with your schematic, will help make it easier to remember where the wires get connected on the new dimmer switch.
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Check the wires to make sure they are in good condition. If they are corroded or in poor shape, use the wire strippers to snip off the affected ends and strip 3/4-inch of insulation from the end of the cut wire.
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Connect the wires to the dimmer switch in the same manner as they were on the previous switch. Then wrap the terminals of the switch with electrical tape.
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Secure the dimmer switch to the wall box and install the cover plate. Turn the dimmer switch all the way off.
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Turn the circuit breaker back on, then turn on the dimmer switch to test your installation.
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Tips & Warnings
Never attempt to work on a three-way circuit with the power on. Wiring a dimmer while the circuit is on can damage the dimmer.
If you have any reservations about working on a three-way circuit, please call a licensed electrician to perform the job.
