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CFL Bulbs and Dimmer Switches–Are They Compatible?

DIY Questions and Answer May 14, 2010 Chad



Q:  I’ve heard that the new CFL (compact fluorescent light) bulbs are incompatible with dimmer switches. Is that true?

 

 A:  The problem with most CFLs and dimmer switches is that dimmers work by breaking up the amount of electricity reaching the light fixture. This staggered electrical current is actually making the light flicker, which works fine for a traditional incandescent bulb because the dimming action simply reduces the amount of heat produced by the filament. CFLs, on the other hand, do not use heat to produce light. The new fluorescent bulbs contain a gas that produces invisible ultraviolet light when excited by electricity. When the light hits the white coating inside the CFL, the coating converts it into white light. During this process, fluorescent bulbs regulate power through the tube, which is not compatible with the dimmer’s intervals of electricity interruption. This means that when working with a standard CFL, a dimmer would cause the CFL to dim or flicker erratically and eventually go out altogether. It shortens the life of the CFL and, in some rare cases, a dimmer operating a standard CFL could result in a fire.

However, evolving technology is addressing the incompatibility issue, and currently there are Energy Star-qualified CFLs that are specially designed to work with dimmers and are labeled accordingly. These bulbs are more expensive than regular CFLs (about $12), but offer all the regular energy-saving benefits. Aside from price, dimmable CFLs do have some other shortcomings: They only dim to roughly 20 percent of the rated lumens and when turned down further they turn off completely. Furthermore, as traditional incandescent bulbs get dimmer, the light gets softer, but dimmable CFLs don’t share that characteristic. If you aren’t comfortable shelling out $12 for a dimmable CFL, you can simply dim an incandescent bulb, which is already saving energy and extending the life of the bulb. (Information courtesy of the American Lighting Association)