bulb goes bad "burns"dimmer???

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ritelec

ritelec

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Jersey
I went to install a dimmer supplied by the home owner today. Lutron C-L decora type (cfl,led,incan) . It is a combo single pole 3 way type.
I turned the circuit off and replace the existing bad one with this new one. I wire it for 3 way and turned the circuit back on.

It controls a 3 bulb hanging fixture over a kitchen table. Check the switch, good, check the slide dimmer... dims but turns out there's two led bulbs and one incandescent a lamp in the fixture. The led's dimmed all the way but the incandescent lamp not all the way... I figure I'll play with the little fine adjustment on the dimmer, remove the cover and the dimmers smoking??? Turned off breaker, removed the dimmer, went through testing open bare travelers and point...
The incandescent was no longer working, swapped the working led to that socket, that socket is working.

Rehooked up the dimmer, It worked and dimmed (the two led's) but I didn't feel right leaving it, so I replaced it with a regular 3 way till I get a new dimmer.

Called lutron, I said what happened and asked if the dimmer might have burnt because the incandescent bulb went bad... they said yes that happens...... WHAT????

If a bulb burns out a dimmer starts to smoke and maybe catch on fire (would it catch on fire, or burn out internally and fail ??) Lutron is sending another dimmer out.

Has anyone experience dimmer failures because a bulb went bad???

Thanks
 
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One of the main reasons for a large spike in current when the bulb fails is the arc that forms starting at the break in the filament, and then it grows substantially:

http://www.sigcon.com/Pubs/edn/NotYourFault.htm

Better quality bulbs have a fuse in the bottom that limits the duration of the current spike but apparently many cheaper bulbs do not.
I suspect such a fuse might usually prevent a breaker from tripping, but it may not be quick enough to prevent many dimmers from being damaged.
 
It happens more often with heavy filament bulbs like PAR lamps or high power bulbs. They have enough metal that the burnout can create a momentary cloud of ionized metal that pulls a really big surge. You can tell that is happening when the bulb flashes really brightly as it burns out.
It is a common failure mode of motion detector units with PAR bulbs.

A lighter filament bulb may brighten a bit as the hot spot in the filament gets very efficient, but the actual lamp current does not go up like it does in a plasma event in a heavy bulb.
 
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