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Question DetailsAsked on 6/1/2016

Dimmer getting hot with two cluster pendants

My electrical guy installs two cluster pendants (24 G50 bulbs, 25 watt) with a dimmer. Sounds safe enough right? but the dimmer is getting hot. what is the next plan of action. The new switch was installed next to an existing one. Help :)

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1 Answer


Dimmers have different wattage ratings - and commonly about 1/4 as high for LED and CFL as for incandescent lights, so if you have 600W of LED or CFL lights on one dimmer I would expect it to be almost glowing.

However - the residential dimmer switches I am used to run from 150W to 600W ratings depending on manufacturer and model - so even if you have one rated at 600W, that would most likely be an intermittent rating, not constant-on rating - commonly you derate electrical componets by 20% for long-running applications, so even a 600W dimmer should probably not exceed about 480W if these lights are commonly on for say an hour or more at a time. Switch, or the box it came in (if saved) should say on it what the applicable ratings are.

Even if rated for 600W maximum, never a good idea to run at rated capacity for a long time. And if installed in a box with another switch the proximity of that switch (and any heat from it) reduces the rating of the dimmer. Even more so if he had to clip the cooling fins to fit it in a box with another switch, as they are generally designed to go in a single gang metal box, so sharing a box or boing in a plastic box is commonly a sub-standard or derating situation. The fins are commonly made to be able to clip them for narrower installations, but that requires derating per the manufacturer's ratings sheet.

Therefore - this switch is probably running at maximum rated capacity at best, and might be well over rated capacity. Of course, you don't know for sure till you find the box or the pullthe switch out of the wall and read the ratings, but if it is too hot to reasonably hold your hand on it indefinitely (i.e. maybe fairly warm but not HOT) then it is a safety hazard and should be replaced with a higher rated switch, moved to its own box if proximity is the problem, etc. as applicable.

In my mind, using one dimmer for 600W of lights in 2 clusters is just bad practice - too much load in one switch, plus general practice would be for each pendant to have its own switch to allow for individual control.

Answered 3 years ago by LCD

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