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Installing a Dimmer Switch

Installing a Dimmer Switch
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  Installing a dimmer switch is one of the easiest ways to transform a room. This single addition upgrades room lighting from two moods—on and off—to a range of subtle variations. Most dimmers are designed to fit a standard wall box opening, which makes it easy to replace the switch for any incandescent or halogen light with a dimmer.

Dimmers come in two basic wiring configurations: standard single-pole dimmers and three-way dimmers. With a standard single pole dimmer, a single switch controls a light. With a three-way dimmer, you can control a light with two switches. You’ll need one three-way dimmer and one three-way switch. This lets you dim from one location and turn the lights on and off from another.

While working with wiring may feel intimidating, installing a dimmer switch is a project many homeowners familiar with a few common tools can easily do themselves. But before beginning any project, review the manufacturer’s instructions and safety precautions carefully. If any doubts remain, consult an electrician.
 
     
 

Follow These Steps

Step One
Turn off the power to the switch
Turn Off the Power
1. Turn off the power to your switch at the breaker.
2. Confirm power is off by flipping the switch on and off.

Step Two
In a three-way switch configuration, mark the common wire with electrical tape before disconnecting the old switch
Remove the Old Switch
1. Remove your existing wall plate and the screws mounting the switch to the wall box.
2. Carefully 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. You won’t be using them.
3. Be careful not to 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.
4. If you’re 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.
5. Disconnect all wires from the old switch. If you’re replacing an existing dimmer, you’ll need to unscrew the wire nuts around the switch wires and house wires.

Step Three
In a three-way configuration, connect the dimmer switch common wire to the house common wire
Connect the New Dimmer Switch
Standard Single Pole Dimmer
1. If the house wires are bent, use a wire stripper to cut off the twisted ends. Remove ¾” of insulation from the end of the house wires and the dimmer switch wires, if needed.
2. 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.
3. 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
1. If the house wires are bent, use a wire stripper to cut off the twisted ends. Remove ¾” of insulation from the end of the house wires and the dimmer switch wires, if needed.
2. 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.
3. Connect the black dimmer wire to your tagged common wire and remove the electrical tape.
4. Connect the two remaining dimmer wires, called traveler wires, separately to each remaining wire in your wall box.
5. Use a screwdriver to mount your dimmer to the wall with the provided screws.

Step Four
Tighten the mounting screws on the wall plate and replace the dial knob
Replace the Wall Plate
1. Carefully tuck the wires back into the electrical box.
2. Tighten the screws holding the dimmer to the electrical box.
3. 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.
4. If the dimmer has a separate wall plate, tighten the mounting screws that hold the wall plate to the switch. If you’re 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.
5. If the dimmer has a separate knob, push it on.
6. You can now turn the power back on at the breaker and test the dimmer.

Difficulty and Time
 
Before You Go to the Store
Determine the total wattage of the lighting you will connect to the dimmer switch. Select a model rated for this wattage or greater. For example, if you have a chandelier with five 100-watt bulbs, select a dimmer with at least a 500-Watt capacity.
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