Wiring a 3 Way Dimmer Switch

If you are replacing an existing 3-way switch: When replacing an existing 3-way switch take note of how the existing switch is wired BEFORE you remove the wiring, then refer to your notes to help you wire the new 3-way dimmer switch.

Many manufacturers are now producing dimmer switches that can be used for either Single Pole or 3-Way Switches. For the Single Pole application the instruction sheet will have you cap off one of the wires which will not be used.

Care should be taken in selecting your dimmer switch.
Most dimmers are rated for 600 watts of power consumption, so if you have several light fixtures which will be controlled by the 3-way dimmer switch you will need to count the number of fixtures, the number of lamps per fixture and the watts per lamp. Calculate the total watts which will be controlled by your 3-way dimmer switch. A good rule of thumb with any electrical load calculation is to never exceed 80% of the rated load for any electrical component or device.

NOTE:
Never wire a regular dimmer to an older fluorescent light fixture that is not rated for dimming or a fixture which has CFL - Compact Fluorescent Lamp adapters.

Dimming non-compatible fixtures or lamps will cause the fluorescent lamps to over heat and burn out prematurely.

Newer specially designed fluorescent fixtures and dimmers are available which are are compatible and work well together.

Dimmer Switch Basics

Dimmer Switch Watt Ratings

Residential dimmer switches are available for several load requirements including 600, 800 and 1000 watts. If you do not size your dimmer properly the dimmer could overheat and cause internal damage. Regular 3-way dimmer switches are designed for incandescent lamps unless otherwise stated.

Dimming Low Voltage Lighting fixtures

Consult the instruction sheet that accompanies the low voltage lighting fixture for the correct dimmer to use. Some fixtures allow you to use regular dimmers, however some do not.

Wiring a Standard 3-Way Dimmer Switch

3-Way Dimmer Switches typically come with the following pre-wired leads

Green wire: Attach to the bonded ground wire(s) in the switch box.

Two Red wires: These wires attach to the "travelers" which are the pair of wires attached to the two screws at one end of the regular 3-way-switch.

One Black wire: Attach to the wire commonly found on the screw by itself on the regular 3-way switch, typically the Power or the Switch Leg leaving to the fixture(s).

2 times longer
4 times longer
20 times longer
More than 20 times longer

STEP 1
The typical 3-Way switch wiring has two screw terminals at one end of the switch. This is where the "travelers" are connected.
The opposite end of the switch has one screw terminal which may be a different color as seen here in this photo. Depending on your wiring configuration, this single terminal will have attached either the Power Line or the Switched Leg that leads to the fixture.

STEP 2
This wired 3-Way dimmer switch has the Red and White "travelers" attached to the set of screw terminals at one end of the switch. The screw at the other end of the switch has either the Power or Switch Leg wire attached to it.

STEP 3
Here a 600 watt Knob Style 3-way dimmer switch has pre-wired leads: Green, two Red and a Black Lead ready for installation.

STEP 4
This 3-Way Dimmer Switch is wired as follows:
The Green Ground Lead attaches to the switch box ground wire, the Red and White "travelers" are attached to the pair of Red Leads and the Black Lead is connected to the Power or Switch Leg connected at the fixture(s).