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Can a Dimmer Switch Be Used on a Three-Way Switch?

Last Updated Mar 30, 2022
grey room with dimmer switch
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Dimmer switches are a great quality-of-life improvement for your indoor lighting. However, there can be a little confusion about how to wire these switches into your pre-existing electrical grid. You’ll need certain switches, terminals, and wiring to install a dimmer switch correctly.

Dimmer switches can be installed on a three-way switch. This allows two controls to turn the light on and off, with a third switch left for the dimming function. Three-way switches can be used with single-pole applications when installing a dimmer switch.

Installing a dimmer switch on a there-way switch might seem complicated if you’ve never done it before, but as long as you keep some safety considerations in mind it isn’t a difficult home improvement project. Read on to learn more about dimmer switches and what you need to install one on a three-way switch.

How Does a Three-Way Dimmer Switch Work?

A three-way switch is the best option for installing a dimmer switch. This switch can turn the light ON/OFF in a standard switching operation and switch the control over to the dimmer switch.

In three-way switches without a dimmer function, the three-way switch allows the lighting control to be accessed through multiple switches on the circuit. (Source: Bob Vila)

If you tried to install a single-pole dimmer switch on a three-way switch, it would only turn the current on and off, but wouldn’t have a separate control to swap it over to the dimmer control switch.

How to Install a Three-Way Switch for a Dimmer

Planning on installing a three-way switch for a dimmer switch yourself? Before you get started, you’ll need the right tools and supplies. Here’s a list of what you need to get together.

Supplies

  • Dimmer switch: A dimmer switch can be set up for installation on a wall switch, but it requires a three-way switch rather than a single-pole switch. Since single-pole switches are the standard switch found in most residences, you’ll need to install a three-way switch before installing a dimmer switch for full functionality.

  • Voltmeter: A voltmeter is used to measure voltage and electrical potential. Voltmeters measure the amount of voltage passing between two points in an electrical circuit.
  • Screwdrivers (Phillips head and flathead): You probably won’t know whether your switch installation requires flathead or Phillips until you get into it, so have both screwdriver types available to avoid any hold-ups during installation.
  • Wire stripper: Wire strippers are used during switch installation to splice wiring together within an electrical circuit.
  • Measuring tape: A measuring tape is needed during electrical switch installation to measure the wiring used.
  • Needle nose pliers: Needle nose pliers are used during electrical switch installation to manipulate and cut wiring.

Once you have the above supplies gathered together, you’re ready to shut off electricity to the switch and get to work.

Note: Be sure that you turn off all electrical power to the switch you’re installing. Touching hot wires in a live electrical switch can lead to serious injury or electrocution. The switch should be tested with a voltmeter to ensure that there is no live voltage during installation. (Source: The Local Electrician)

Remove The Pre-Existing Switch

To put a dimmer switch on a wall switch, you’ll need to remove the pre-existing wall switch. Most standard switches will be a simple single-pole ON/OFF switch. To remove the old switch, perform the following:

  • Unscrew and remove the switch plate. In most cases, the new dimmer switch will come with a new switch plate that reflects the control scheme of the dimmer function.
  • Strip the insulation from the dimmer switch wires. Open the dimmer switch and strip 1-2 inches of rubber coating off the ends of the wiring to make a connection. Stripping the wiring needs to be done carefully to avoid cutting or damaging the metal part of the wire. (Source: AdaFruit)
  • Remove the old switch. Disengage the old switch from the wiring in the wall carefully. Use the voltmeter to double-check voltage before touching any wiring in the wall which might be live.

Wire the Dimmer Switch into the Three-Way Switch

Once the old switch is removed from the wall and the dimmer switch wiring is prepared through stripping the insulation, the dimmer switch is ready to be installed. (Source: House Beautiful)

  • Connect the outlet ground wire to your dimmer ground wire. Look for a wire that is green or copper. This wire should connect into the central bottom wire on the dimmer switch layout. Wrap the wires together and secure them with a plastic wire cap.
  • Connect the red wire in the dimmer switch to the hot wire in the outlet. The live wire in the wall is typically red but can also be black in some cases.
  • Connect the two black wires on the dimmer switch to the traveler wires in the wall outlet. These wires are usually marked with white or black rubber coating. Note: One of the two black traveler wires on the dimmer switch may be red with a white strip rather than black. 
  • Finish securing the wiring with plastic wire caps and place the dimmer switch in the wall. After testing the connection, replace the switch plate and screw it back into the wall.

After you re-secure the switch plate, the dimmer switch should be functional. If you have any questions about the electrical wiring or the electrical wiring does not match the descriptions above, consult a professional electrician.

Three-Way Switches Are Better for Dimmer Switches

A dimmer switch can be successfully installed on a single-pole switch as long as the circuit on the switch can be turned on and off from another switch on the circuit. However, three-way switches are a better option for installing dimmer switches in your smart home. This makes the process of installing the switch and the final control scheme much less complicated.

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