# lighting controls with fluorescents

**URL:** <https://boards.straightdope.com/t/lighting-controls-with-fluorescents/457501>\
**Category:** Factual Questions\
**Created:** [July 23, 2008, 4:43pm UTC](https://boards.straightdope.com/t/lighting-controls-with-fluorescents/457501 "2008-07-23T16:43:07Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![chronodisticha](https://avatars.discourse-cdn.com/v4/letter/c/e19adc/32.png) [@chronodisticha](https://boards.straightdope.com/u/chronodisticha)\
**Post date:** [July 23, 2008, 4:43pm UTC](https://boards.straightdope.com/t/lighting-controls-with-fluorescents/457501/1 "2008-07-23T16:43:07Z")

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Why can’t some lighting controls, like motion or light sensors, work with fluorescents? Is it because of noise on the line? A tendency to flutter on and off when changing modes? Or is it a RFI thing?

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**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\
**Post date:** [July 23, 2008, 6:06pm UTC](https://boards.straightdope.com/t/lighting-controls-with-fluorescents/457501/2 "2008-07-23T18:06:08Z")

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My understanding is that the controllers can’t handle the reactive load of a fluorescent fixture’s ballast, as opposed to an almost purely resistive load of an incandescent bulb’s filament.

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**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\
**Post date:** [July 23, 2008, 6:12pm UTC](https://boards.straightdope.com/t/lighting-controls-with-fluorescents/457501/3 "2008-07-23T18:12:08Z")

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Solid-state lighting controls use Triacs to switch the load. Triacs handle resistive loads just fine, but a cheap circuit design may be marginal with inductive loads, due to the current and the voltage not being in phase, which can cause turn-off problems. There are solutions to this problem, but it increases the cost a little, and the manufacturer might just not want to deal with all the potential problems.  
If you are truly interested in the nitty-gritty, here is a start: [http://www.eng.uwo.ca/electrical/information/courses/ece457a/Thyristors.pdf](http://www.eng.uwo.ca/electrical/information/courses/ece457a/Thyristors.pdf)

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**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\
**Post date:** [July 23, 2008, 7:53pm UTC](https://boards.straightdope.com/t/lighting-controls-with-fluorescents/457501/4 "2008-07-23T19:53:22Z")

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Many will work fine, if down-rated. Which is easy to do, since CFL bulbs are much lower wattage than the equivalent incandescent bulbs.

I have a motion detector light on my back door; the controller was designed to handle 150 watts (2 75-watt floodlights), but I have since replaced those with 2 CFL lights of 26 watts each. So the controller is handling only 1/3 of it’s capacity. That’s been working fine that way for several years.