Project Guide

How to Install a Dimmer Switch

1
CHOOSING A REPLACEMENT SWITCH
  • Turn off the power to your switch at the breaker.
  • Confirm power is off by flipping the switch on and off.
2
REMOVE THE OLD SWITCH
  • Remove your existing wall plate and the screws mounting the switch to the wall box.
  • Gently pull the switch away from the wall. If you see a bundle of white wires in the back of the wall box, you can leave them in place.
  • Do not touch any of the wires until you’ve confirmed they aren’t carrying electrical current. Test the circuit with a known working voltage tester, to ensure power isn’t reaching the circuit. If the tester detects voltage, switch off the appropriate circuit breaker or remove the appropriate fuse and test the circuit again.
  • If you are replacing a three-way switch, one wire will be connected to a screw that is colored differently or labeled “COMMON.” Note that this is different from the wire connected to the green screw, which is the ground wire. Tag the common wire with a piece of electrical tape to identify it when wiring the new dimmer.
  • Disconnect all wires from the old switch. If you are replacing an existing dimmer, you would need to unscrew the wire nuts around the switch wires and house wires.
3
CONNECT THE NEW DIMMER SWITCH

Standard Single-Pole Dimmer

  • If the house wires are bent, use a wire stripper to cut off the twisted ends. Remove ¾ inch of casing from the end of the house wires if needed.
  • Connect the ground wire from your dimmer to a green or bare copper wire in the wall box. Twist the ends together clockwise and cap them using a wire connector nut.
  • Connect each dimmer wire to a house wire by gripping the wire ends with a pair of pliers and twisting them together. The wires from the dimmer will typically be black. The two house wires may be black, red, or white with black marking. Tighten a wire nut over each pair of wire ends. If there is bare wire exposed, unscrew the wire connector, remove the wires, trim the ends of the wires with a wire cutter, and then re-cap the wires.


Three-Way Switch

  • If the house wires are bent, use a wire stripper to cut off the twisted ends. Remove ¾ inch of casing from the end of the house wires and the dimmer switch wires, if needed.
  • Connect the ground wire from your dimmer to a green or bare copper wire in the wall box. Twist the ends together clockwise and cap them using a wire connector nut.
  • Connect the black dimmer wire to your tagged common wire and remove the electrical tape.
  • Connect the two remaining dimmer wires, called traveler wires, separately to each remaining wire in your wall box.
  • Use a screwdriver to mount your dimmer to the wall with the provided screws.
4
REPLACE THE WALL PLATE
  • Carefully tuck the wires back into the electrical box.
  • Tighten the screws holding the dimmer to the electrical box.
  • If you are installing a dimmer that has a removable knob, remove the knob from the dimmer by gently pulling outward before attaching the wall plate.
  • If the dimmer has a separate wall plate, tighten the mounting screws that hold the wall plate to the switch. If you are using a wall plate with a “screwless” design, screw the wall plate adapter to the dimmer, and carefully snap the wall plate onto the adapter.
  • If the dimmer has a separate knob, push it on. You can now turn the power back on at the breaker and test the dimmer.