Dimmable Fluorescents


Active Member
Feb 9, 2007
Dallas, Texas
All fluorescent fixtures, before dimming, should be burned in for at least 100 hours. If that is not done, it will dramatically shorten the life of your fluorescent lamps, as well as lead to other problems with the dimming curve. Turn on the lights, and leave them on for the 100 hours....

Dimmers usually have to have different settings (or a completely different module) to be able to dim fluorescent fixtures properly - depending upon the type of ballast. Even with the correct ballast fine tuning the dimmer curve is critical to proper function.

There are 3 main types of fluorescent dimming ballasts, that I know of.

2 Wire

This type of ballast is able to dim just like a regular incandescent lamp would - with a hot and a neutral running through a dimmer. (In ETC world a D20) The settings on the dimmer usually need to be different than they would be for an incandescent fixture, but it can be done nonetheless. The Advance Mark X (read Mark 10) ballast is one of this type.

3 Wire

This ballast takes a different type of dimmer module. (In ETC land, it would take a D20F) This ballast uses a dimmed hot, a constant hot and a neutral.

4 Wire ballasts

This ballast can use a standard dimmer module (in switched mode) or a relay module. There also needs to be a 0-10v analog source that works in conjunction with the dimmer or relay. The switched source provides constant power to the module with the 0-10v provides the control signal while the ballast does the actual dimming based upon that signal.

See this thread. Strand C21 dimmers seem to require "Advance Mark X" (Mark 10) ballasts.

A perfectly adjusted dimmed fluorescent fixture will never completely dim on and off like a incandescent lamp. When the fixture is dimmed off it will drop to a very low intensity then suddenly blink off. When turned on, they will blink on to a low level then dim up gradually. Also remember that fluorescent fixtures require a certain amount of warm up time depending on a variety of factors. Turning on fluorescent lights can take anywhere from a few seconds to 2 or 3 minutes to reach full intensity. While they are warming up, it is not uncommon for fluorescent lights to have a pink or purple appearance. For these reasons fluorescent house lights can be distracting, unpleasant in appearance, and make quickly turning on house lights impossible.
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