How to Install a Single-Pole Dimmer Light Switch

  • 01 of 09

    Introduction

    Installing a light dimmer switch
    michellegibson / Getty Images

    Installing a dimmer switch helps you save energy and create a relaxing mood in a living room, dining room, or bedroom. For most do-it-yourselfers, it is a fairly simple task to install a single-pole dimmer switch.

    What is a Single-Pole Dimmer Switch?

    A dimmer switch is a light switch that, via a slider, dial, or some other method, regulates the flow of electricity to a light. The dimmer switch can turn off a light, turn it on at its brightest, or anything between. A single-pole dimmer switch is one that controls only one light.

    Troubleshooting and Additional Information

    Dimmer switches are larger than conventional light switches. Unless you have enough room in the receptacle (the electrical box containing the wires), you may not be able to install one.

    Dimmer switches are not universal. Be sure to purchase the right dimmer for your light.  

    Consult the dimmer instructions as your primary source, with this guide as a supplement. Because dimmer switches are sensitive devices, it is possible to damage them if they are not installed properly.

    Safety Considerations

    Whenever working with electricity, be sure that the circuit supplying the area where you will be working is shut off. Verify that the electricity has been shut off by testing with a voltage detector.

    Project Metrics

    • Working Time: 30 minutes
    • Total Time: 20 minutes
    • Skill Level: Beginner
    • Material Cost: $10 to $20

    What You Will Need

    Equipment/Tools

    • Voltage tester
    • Wire stripper
    • Wire ripper
    • Eye protection
    • Manual screwdriver (Phillips and flat-head)
    • Cordless drill with Phillips and flat-head bits

    Materials

    • Single-pole dimmer switch
    • Face plate (if not included in the switch kit)
    • Wire nuts
    • NM electrical cable (optional)

    When to Call a Professional

    If you feel uncomfortable installing a dimmer switch, call a licensed electrician for assistance.

    Continue to 2 of 9 below.
  • 02 of 09

    Turn Off the Circuit Breaker

    Turn off circuit breaker
    Lee Wallender

    Find the circuit breaker for the light and flip it off. Circuits are often labeled by builders, electricians, or previous homeowners. 

    Continue to 3 of 9 below.
  • 03 of 09

    Remove the Existing Light Switch Plate

    Removing light switch plate
    andrewginns / Getty Images

    With your manual flat-head screwdriver, carefully remove the two short machine screws holding the outer switch plate to the existing switch. 

    You will not be reusing this plate for the dimmer switch. In most cases, you will need to purchase a specialty plate or one may be included with the dimmer light switch kit.

    Continue to 4 of 9 below.
  • 04 of 09

    Remove the Screws Holding the Switch to the Box

    Remove screws holding old switch
    Lee Wallender

    Use your cordless drill with a driver bit to remove the existing switch from its box. You may need to press hard to turn out the machine screws holding the old light switch to the receptacle box. Without using enough force, you might strip the heads of the old machine screws, making it difficult to remove the switch.

    Continue to 5 of 9 below.
  • 05 of 09

    Confirm That Power to the Switch Is Off

    Confirm that power is off to old switch
    Lee Wallender

    It is best practice to always verify that the circuit has been turned off by scanning all wires inside the electrical box with a voltage detector.

    Holding your voltage tester with one hand, slowly pull out the existing light switch so that it is a few inches out and still attached to its wires.

    With the voltage tester on, touch the end of the tester to the black wire extending from the receptacle to the light switch. Your tester should indicate that this wire is not live.

    To be certain, touch the voltage tester to various other wires leading to the light switch.

    Continue to 6 of 9 below.
  • 06 of 09

    Remove Wires From the Old Light Switch

    Remove wires from old switch plate
    Lee Wallender

    Use either a manual screwdriver or a cordless drill to unscrew the light switch terminal screws holding the wires on. With these screws, you can use either a flat-head or a Phillips head bit. Either type of bit works suitably well.

    Continue to 7 of 9 below.
  • 07 of 09

    Attach the Wires to the Single-Pole Dimmer Switch

    Attach wires to dimmer switch
    Lee Wallender

    Attaching the dimmer switch to the wires extending from the box is fairly straight-forward since it is mostly a matter of matching colors.

    • A black wire on the dimmer attaches to a black wire in the box
    • A second black wire (sometimes red) on the dimmer attaches to a black wire in the box
    • A green is attached to the ground wire, which may be either a bare copper wire or a green wire.

    Twist a wire nut around each wire connection. No bare copper should be exposed beyond the wire nut. If so, remove the wire nut, snip a small portion of the twisted wires with the cutting end of your wire stripper, then turn on the wire nut again.

    Continue to 8 of 9 below.
  • 08 of 09

    Cap the Red/White Striped Wire

    Cap off the red/white-striped wire
    Lee Wallender

    As this is a single-pole installation, the red/white striped wire coming from the dimmer is not needed. Cap off this single wire with a wire nut.

    As wire nuts tend to come off of single wires, twist a short length of electrical tape around the wire nut and wire to keep them together.

    Continue to 9 of 9 below.
  • 09 of 09

    Replace and Screw in the Dimmer Switch

    Putting the dimmer switch back into the electrical box may be difficult, due to the mass of wires inside the box and the size of the dimmer switch's back.

    Make sure that you have properly folded over the wires and gently put them back into the box.

    Screw the dimmer switch onto the electrical box. The screws will help to nudge the dimmer switch deeper into the box. Make sure that the dimmer switch is completely flush with the outer edge of the box. With a screwdriver, replace the switch plate. 

    Go to the service panel and flip the circuit breaker back on. Return to the dimmer switch and turn it on for testing.