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I have a dual 1-way dimmer switch, 240V rated for 40W-400W, to which one of the dimmers has 5 x 60W dimmable bulbs (ceiling lights) and always works without any issue, and the other dimmer has 4 x 28W dimmable bulbs (wall sconces) with which we are regularly having trouble.

Every time a sconce bulb goes pop, the circuit breaker trips and the associated dimmer dies while the other dimmer on the switch continues to work. We've had this not just on this particular lightswitch installation but also on another in the same property where once again wall sconce bulbs popping kills the associated dimmer.

Is this a common issue? At first I wondered whether with bulbs pointing upwards maybe if the filament dropped into the base it would cause a short-circuit and these problems might result, however I get the same issue with Halogen eco bulbs aswell.

Having had to replace these switches around 6 times now its getting a little rediculous. Any ideas what would cause this? If I change the wall scones would that make a difference do you think? Could it just be poor quality switches (typically £15, tried 3 different brands so far).

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    \$\begingroup\$ Some bulbs do fail with a momentary short circuit, and that's apparently not good for your dimmer. I'd be looking for bulbs with a different failure mode ... dimmable LED bulbs maybe. \$\endgroup\$
    – user16324
    Sep 2, 2016 at 14:32
  • \$\begingroup\$ If the sconce bulbs are tripping the circuit breaker, then it isn't surprising that the dimmer also fails. It takes a hefty current surge to trip a breaker. That really shouldn't be happening. I wonder if the bulbs are arcing internally until the circuit breaker trips. If so, putting a large inductance (e.g., an old-fashioned magnetic fluorescent lamp ballast) in series with the fixture might mitigate that. \$\endgroup\$
    – Dave Tweed
    Sep 2, 2016 at 15:05

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Your problem is very strange. I wonder if the problem isn't that the dimmer failures are what's popping the circuit breaker, not the bulb failure per se. With 3 different brands of dimmer failing the same way I'd say it's pretty clearly not the dimmer fault, which suggests you need to look elsewhere. The only other candidate I see is the lamp wiring, and the fact that it's a string of sconces which fails while the ceiling lamps are OK supports this. I'd suggest you get an electrician to check it out. I don't see offhand how a wrong connection would do what you describe, but it seems the obvious suspect.

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  • \$\begingroup\$ Keep in mind that the dimmers are in series with the bulbs, so a dimmer failure by itself can't pop the breaker. \$\endgroup\$
    – Dave Tweed
    Sep 2, 2016 at 17:07
  • \$\begingroup\$ @DaveTweed - Ordinarily I'd agree with you, but a half-dozen 28-watt bulb failures that pop the circuit breaker? Something is fundamentally wrong here, and it's got be a combination of wiring and dimmer. The OP is apparently installing the dimmers himself, and I get a bad feeling about this. \$\endgroup\$ Sep 2, 2016 at 18:04
  • \$\begingroup\$ Registered electrician has checked the lamp and switch wiring (all wiring in the property) previously following this issue and certified it as safe, correct and compliant with BS7671, and yet the problem reoccurs when bulbs reach end-of-life. \$\endgroup\$ Sep 5, 2016 at 12:05

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