Dimmer switch no longer dims

JBR

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We have a dimmer switch powering four GU10 halogen bulbs.
The other day, the lighting RCD tripped and I bulb had blown. No problem when I re-set the RCD except that, whilst the switch still turns the (remaining) bulbs on/off, it no longer dims them.

Is there some obvious reason for the loss of the dimming facility?
 
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The failure caused a temporary short circuit inside the bulb (lamp), and the high current has destroyed one or more components inside the dimmer.
Thanks, I'm sure you're right.
We have two choices then: keep things as they are and use the switch as on/off only, or buy a new dimmer switch (it wasn't expensive - Screwfix). I'll consult Marge for a decision.
 
We have two choices then: keep things as they are and use the switch as on/off only, or buy a new dimmer switch (it wasn't expensive - Screwfix).
If, as seems very probable, electronic components within the dimmer have been destroyed, it would not really be advisable to leave it in service, even if it still functions satisfactorily as an on/off switch - there's no telling what's happened inside it, so it could lurk as a potential fire hazard in the future if you leave it there.

Kind Regards, John
 
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If, as seems very probable, electronic components within the dimmer have been destroyed, it would not really be advisable to leave it in service, even if it still functions satisfactorily as an on/off switch - there's no telling what's happened inside it, so it could lurk as a potential fire hazard in the future if you leave it there.

Kind Regards, John
True.
The next question is whether to replace it with another dimmer. If another lamp blows, the same might well happen again. I would have thought that a good quality dimmer switch might have the necessary protection for surges in the power.
I wonder whether it is advisable to look for a more expensive and reliable dimmer or lamp.
 
There is a third choice. Repair the one you have. Most likely the triac is shorted. Triacs are cheap.
 
True. The next question is whether to replace it with another dimmer. If another lamp blows, the same might well happen again. I would have thought that a good quality dimmer switch might have the necessary protection for surges in the power.
I wonder whether it is advisable to look for a more expensive and reliable dimmer or lamp.
I don't think that any dimmer, no matter how expensive, could be guaranteed to survive the enormous currents that can flow (very briefly) when an incandescent bulb dies - since the electronics would be dead long before any 'protective device' (like a fuse) operated.

It's really an inescapable risk of incandescent bulbs. After all, you said that an RCD (did you mean that, rather than MCB?) tripped, and that will have happened as quickly as any 'protection' in the dimmer could have achieved.

Kind Regards, John
 
There is a third choice. Repair the one you have. Most likely the triac is shorted. Triacs are cheap.
True, and I might well consider doing that myself. However, it's not something I would suggest/advise to someone who 'needed to ask about it'.

Apart from anything else, it can be a challenge (sometimes a near-impossibility) to get (non-destructively) at the works of a dimmer module.
 
I don't think that any dimmer, no matter how expensive, could be guaranteed to survive the enormous currents that can flow (very briefly) when an incandescent bulb dies - since the electronics would be dead long before any 'protective device' (like a fuse) operated.

It's really an inescapable risk of incandescent bulbs.

Halogen lamps seem particularly prone to enormous currents on death. But halogen lamps are not supposed to be dimmed although many people do so.

It would make sense for the OP to replace his lamps with LED and the correct LED dimmer.
 
Halogen lamps seem particularly prone to enormous currents on death. But halogen lamps are not supposed to be dimmed although many people do so.
On the basis of research I've done in the past (and reported here) it seems that there may be some mythology around as regards halogens ...

In general, dimming an incandescent bulb increases its life, by reducing filament temperature. However, halogens rely on a very high envelope temperature, so reducing it is not such a good idea. Nevertheless, it appears that dimming even a halogen will result in an increase in life expectancy, albeit not as much of an increase as would be the case with a non-halogen incandescent.
It would make sense for the OP to replace his lamps with LED and the correct LED dimmer.
Agreed.
 
I don't think that any dimmer, no matter how expensive, could be guaranteed to survive the enormous currents that can flow (very briefly) when an incandescent bulb dies - since the electronics would be dead long before any 'protective device' (like a fuse) operated.

It's really an inescapable risk of incandescent bulbs. After all, you said that an RCD (did you mean that, rather than MCB?) tripped, and that will have happened as quickly as any 'protection' in the dimmer could have achieved.

Kind Regards, John
Sorry, of course I meant the circuit breaker!
 
There is a third choice. Repair the one you have. Most likely the triac is shorted. Triacs are cheap.
The dimmer unit is also quite cheap, so I wouldn't mess about with trying to do that!
 
Halogen lamps seem particularly prone to enormous currents on death. But halogen lamps are not supposed to be dimmed although many people do so.

It would make sense for the OP to replace his lamps with LED and the correct LED dimmer.
Yes, I think that is probably the best course of action.
The dimmer I have is not suitable for LEDs, but I agree that they are the future for a number of reasons and I think I shall buy four replacement LED lamps and a new, suitable, dimmer or perhaps just a simple switch. Personally, I don't really use the dimmer anyway, but I'll ask Marge if she'd be happy with a simple switch.
 
Sorry, of course I meant the circuit breaker!
That's what I imagined. When, many moons ago, I changed from fuses to MCBs, still in the days of incandescent bulbs, it was almost the rule rather than the exception that an MCB would trip whenever a bulb died - and, as I said, that should curtail the 'potentially damaging' current at least as quickly as any protection within a dimmer ever could - hence my previous comments.

Kind Regards, John
 
I've sent for a simple light switch and a pack of LED GU10s.
I was under the impression that LEDs are much more expensive than incandescent lamps. Imagine my surprise when I found 10 LED GU10s for £15. I thought they must be crap, but 4 1/2 stars on Amazon.
 

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