How to Select the right Lighting Dimmer

When lighting, selecting a dimmer you must first determine where you want to place it. It is important to select a dimmer specifically designed to control the source. You need to know if the fixture is an incandescent, flourescent or low voltage. Is it a string of fixtures or one single light that has multi purposes.

Incandescent dimmers cannot be used with a flourescent or low voltage transformers. Dimmers designed for magnetic low voltage maybe used with an incandescent loads. Also a dimmer should never control a receptacle because a motor load could be plugged into it.

If you are using standard A medium based bulb or reflector bulb the dimmer might have a tendency to make them hum. Change the bulb if that doesn't help change the style of bulb you are using.

Calculate the total load being used for a fixture or run of fixtures. If the bulbs are incandescent the wattage ratings are usually marked on the bulbs. Add the wattages of all the bulbs that are being used for this location then select a dimmer that is rated above or equal to your total wattage. You will have to know if the location is single pull (one Location) or a 3-way (multi locations).

If you are installing multiple dimmers side-by side or gang control they must be derated to prevent heat build-up. Multi location dimmers allows full-range dimming from two to ten locations. By using smart dimmers you can use up to nine accessory dimmers that work together with a smart dimmer, so you can use more than one control to dim a light fixture.

Its normal for dimmers to feel warm to the touch. Both low and high wattage dimmers are engineered to minimize heat build up. High wattage dimmers, 800 watts, are constructed with metallic fins to help cool and dissipate heat from within the device. Smaller dimmers use the metal mounting strap for the same purpose. Mounting wall controls vertically will help to diffuse the heat and protect the components.

The average dimmer operates at approximately 14o degrees, UL allows a maximum temperature of 195 degrees. When dimmers are ganged together, each dimmer's load must be derated to offset the resulting heat build-up if several units are used in the same wall box.

Ganging is a practice where two or more lighting controls are mounted side by side using required number of connected wall boxes. Because ganging may require the removal of part of the fins or mounting strap that helps dissipate heat from within the device, removing a portion of theses will require derating (reducing the capacity of a control when side sections are removed) the dimmers to prevent over heating.

Power switching circuits that seperate dimmers are capable of generating electrical noise called radio frequency interference. It can radiate or conduct directly from a dimmer through an AC powerline. AM radios are the most susceptible to noise, yet sensitive audio equipment, microphone cable, intercoms may also be affected.

Many dimmers feature built-in radio frequency interference filters with a choke coil and capacitor filtering network that eliminate most of the noise. Dimmers rated 600 watts or lower uses a bar coil filter that is more effective with higher power loads.

Much of the data presented here is found in manufacturers catalogs and informational booklets. _______ Here are some of their do's and don'ts

1) Do not place sensitive equipment directly near dimmer installation.

2) Do not run microphone and audio cables parallel to dimmer wiring.

3) Place dimmer on a seperate circuit from audio equipment.

4) Use low-impedance microphone cables and shielded audio cables.

5) Buy an in-line filter for your audio equipment

6) Properly ground all equipment.

7) For incandescent loads, use an electronic low-voltage dimmer.

Most of household electrical projects are simple, but caution and good judgement are essential when working with electricity. Common sense can prevent accidents. Always turn off power to area before you begin. Restore power only when repair or replacement is complete. Don't attempt an electrical project beyond you capablility and skills.

return to Lighting with Dimmer Switches

return to Home Lighting Design