I installed a dimmer switch for my new recessed lighting. I’m using flourescent flood lights (that are rated as not dimmable) in the fixtures.
There is a very low buzzing sound coming from the switch. I assume this isn’t normal. What’s causing the buzzing? The light bulbs? Is it a defective switch?
I’ll go home tonight and swap out the floods for standard incandescent to see if there isn’t a buzz.
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Replies
It could be a few things. How many lights are on this switch? The draw may be too much for that dimmer.
4 cans, 16 watts per flourescent bulb. It's a new 20 amp circuit. I currently have two banks of 4 cans on the circuit. Each set of 4 cans is on its own dimmer. The dimmers are rated at 600 watts.
Dimming fixtures often buzz at switch or bulb. Drives me batty. Changing the bulb or simply undoing and redoing, sometimes you get lucky and the harmonic frequency that creates the loudest buzz will happen at a light setting that isn't the setting you use most often.
I really hope someone chimes in here with 'brand X never buzzes.'
CFL's don't like to be on a dimmer. The incandescents should do better.
Incandescents that buzz on a dimmer do so because the filaments are coiled. They act as tiny solenoids or electromagnets, and they vibrate twice per AC cycle when the triac kicks in. Rough service incandescents do a lot better because the filaments are long loops rather than tight coils.
When the dimmer itself buzzes, it's the inductor in it acting as an electromagnet and putting out a strong magnetic pulse every time the triac fires. Tightening the mounting screws sometimes helps. Better more expensive dimmers with bigger inductors should buzz less. Going to a 600 Watt dimmer may help where a 300 Watt buzzes. Likewise from 600 to 1000, but those 1000's are pricey.
-- J.S.
It's definitely the dimmer that's buzzing. I can hear it clearly when standing next to the switch. Should a 600 watt dimmer buzz with only 64 watts of draw? And I'm not even using the dimming feature of it. The lights are on full power.
I recently looked at the guts of dead 1000W and 600W dimmers (tried to use them for something they weren't designed for). They are pretty minimal in terms of they way they're put together and the quality of the electronic components. In my testing I noticed that they don't have a pure AC signal on the output. There is a small DC offset that ranges from .5 to 6 volts depending on the load. This is no big deal to a regular incandescent bulb, but when DC is applied to the electronics in a CFL bulb or the coil of a low-voltage transformmer for halogens, it could cause overheating in the load or odd behavior like the humming you heard in the dimmer.
Its the flourescent bulbs. I had a client that had recessed cans and dimmers everywhere. When he got his first electric bill he decided to switch to flourescent bulbs. He did this before I changed out all the dimmers and they were making alot of noise. It stopped as soon as I got rid of the dimmers. I'm not sure why. The ballast? Strange frequency from the gas? Got me.
The dimmer "it's self" should not make any noise. But they often have a small coil with the leads wrapped around it. It is a coke to reduce RF noise.If the CFL's have switching (electronic) ballast they can act like a large capacitor and have a large surge current. That surge current could cause the coke to hum.BTW, you can get dimmable CFL's. http://www.efi.org has some.
Even low voltage lights will make a dimmer hum. This site has more information on dimmers.
http://www.pegasusassociates.com/products/Dimmers/Dimmers.htmlYou get out of life what you put into it......minus taxes.
Marv
Never heard of dimable CFL's, sounds good. I'm not sure what was making the switch hum, but I know it was the switch (or something inside it) and it wasnt doing it before the CFL's.
The buzzing is semi-normal for a cheap dimmer, but you shouldn't be using a dimmer on non-dimmable lights. This can lead to overheating and a fire.
I'll be picking up dimmable lights tonight. With just 4 out of 8 lights on, the room is too bright to not have a dimmer...and that's with 16 watt CFL floodlights. Sheesh. I can't imagine what it would be with the higher 30watt CFL's (125 watts of "normal" bulb output) that the fixture can take.
BTW, what would overheat? The dimmer or the bulb/fixture?
Yes.
Both can overheat. The choke coils and/or transformers in these devices expect to see AC voltage only. If a DC voltage is applied, the coils start to saturate and can overheat. The 600/1000W dimmers I tested all have some DC voltage at the output. Think about it, 6 volts at 5 amps is 30W of heat that has to be dissipated from the coils in these small boxes or bulbs - they will heat up quite a bit.
I now know what you mean. I changed the CFL's out last night for Phillips Halogena's. I was amazed at how warm the cfl's were for only being on (max) 5 minutes. My other cfl's in other non dimmed circuits can be on for hours and still only be warm to touch.
I tried the rough service bulb and it in fact stopped the buzzing entirely. However, that bulb for the same wattage is larger than the standard bulb and now sticks out below the bottom of the pendant fixture! Now I'll try to find a Rough Service bulb that is the same size.
(that are rated as not dimmable)
I hate to point out the obvious, but can't you just replace the dimmer with a standard switch? I mean, since you can't dim them anyway. Just a thought.
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Both Philips and TCP make dimmable CFLs. If your cans had R40 or Par38 bulbs in it, you can get a CFL in R30 or Par30 so that the bulb stays inside the can. I did this in an apartment last year and cut the power usage noticably and had more light to boot.
http://www.lighting.philips.com
http://www.tcpi.com
Thanks for the info. I'll relay it to my customers. =)See my work at TedsCarpentry.comBuy Cheap Tools! BuildersTools.net
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