Electrical 101

How to Determine Dimmer Switch Wattage Rating

Common dimmer wattage ratings are 150 watts, 300 watts, 600 watts and 1000 watts. 150 watt rated dimmers are usually for a single bulb. Wattage rating is usually on a sticker on the light fixture.

Multiply the number of fixtures by the wattage rating of each fixture.
Multiply the result by 125 % (continuous load).
Round up to the next dimmer wattage rating.

Dimmer wattage calculation example:

5 light fixtures.
60 watt fixture rating.
Multiply result by 125% (1.25).

5 fixtures x 60 watts = 300 watts.
300 watts x 1.25 = 375 watts.
Next higher wattage dimmer rating = 375 watts or higher (600 watts).

Dimmer

Switch

Do Dimmers Save Energy?

While older rheostat type dimmers do not, modern dimmers do save energy when dimming lights. Dimming lights also extend the life of incandescent light bulbs.

Dimmer Feels Very Warm

It is normal for a dimmer to feel warm especially if the lighting load is close to the dimmer rating. A higher wattage dimmer may need to be installed if the following apply:

If the lighting load is higher that the dimmer rating.
The dimmer feels too hot.

How to Install a Dimmer Switch

Dimmer switches usually have two black wires protruding from the back of the switch. One wire connects to the light(s), the other connects to line. The green wire connects to ground. If a dimmer has one black wire and one red wire, usually the black wire connects to line and red wire to the load.

Dimmer Switch Wiring Diagram

Ground connection is not shown.

Dimmer with 3 and 4-Way Lighting

A 3-way dimmer can be used on 3 and 4-way lighting. One dimmer can replace one three way switch. The dimmer black wire connects to the line or load (below it is connected to the line). The two colored wires (usually red) are the travelers. The dimmer green wire connects to ground. Ground connection is not shown.

Dimmer with 3 and 4-Way Lighting Wiring Diagram

Dimmer switches are used to control lighting level and can save energy. Dimmers work by limiting the voltage that goes to a lighting load. Dimmers work very well with incandescent bulbs because of a wide dimming range.

For other types of bulbs including CFLs, halogen, and LEDs, check to see that they are “dimmable” on the bulb package. Dimmable CFLs are usually more expensive and have a limited dimming range, mostly at the dim end.

Dimmer Switch Usage

Dining areas
Turning on certain lights at night without being blinded (kitchen, bathrooms, and bedrooms)
A 3-way dimmer can replace one of two 3-way switches

Dimmer Switches

Dimmer Switches

Photocells and Timers

Ceiling Fan Switch Wiring

Switch and Outlet Combo

Motion Detectors and Occupancy Sensors