Dimmer went bang...

M

MrSafety

Guest
I have one of these infrared dimmers

http://www.tlc-direct.co.uk/Products/VLIQ1402.html

and have been using it for quite a while. Before Xmas I installed 2 sets of Ikea low-voltage lights

http://www.ikea.co.uk/webapp/wcs/st...uctId=15174&langId=-20&parentCats=10111*10448

and put 4 x 20w bulbs on each transformer. So, this gives me

gang1 - operates a single 60w bulb in a walk-in cupboatd
gang2 - operates 2 ikea transformers powering 4 x 20w bulbs each - a total of 160w.

The dimmer switch ran warm (but the dimmer switch instructions said it was normal so don't worry) and the switch buzzed when the lights were on or dim which was annoying but I lived with it.

Anyway, on Friday night while the lights were about half-dimmed for 10 minutes continuously, something went "crack", the lights were jacked up to full brightness and the dimmer control wouldn't turn the lights off. It also smelt of electrical burning so I turned off the circuit and took the switch off the wall.

The following day I refitted the switch to the wall but the other way around - I figured I had blown gang 2 but gang 1 was still working and only operating a walk-in cupboard so I swapped them over. The minute I turned on the power the wall switch started smoking and I ran downstairs and turned off the power.

I appear to have blown both gangs on the lightswitch and have reverted back to the normal (undimming) lightswitch.

So, did I overload the switch? It had worked for 1 month - was I lucky or was the switch dodgy?

If I am overloading it, can anyone recommend a suitable 2 gang replacement for my lights which won't cost the earth? Or do I just need to have, say, 3 bulbs on each light instead of 4?

[I assume it is clear from my predicament that I am not living up to my nom de plume when it comes to electricity :- !]
 
A

ancientgeek

Guest
I haven't figured out the details, but:

1. Low voltage and mains voltage halogens do put a bigger strain on dimmers than ordinary (sometimes called GLS) bulbs. You can't put so much total wattage through the dimmer.

2. "electronic" low voltage transformers can work in a similar way to the dimmer (chopping the mains on and off). You may need either to use a real transformer, or a dimmer/transformer pair that are compatible. It's something to do with leading edge and trailing edge switching.

3. Some dimmers don't like any halogen lamps. The manufacturers are tending not to make these any more because people take them back broken within warranty.

4. When halogen bulbs fail, the filament burns through. If the dangly ends touch together shortening the filament length, the current draw can increase enormously, blowing the dimmer. I don't know if this affects low voltage halogens, but name brand mains halogens incorporate a fuse in the bulb to protect dimmers and help prevent MCB's tripping. Some cheaper ones don't.

5. I have got this far the hard way.
 
F

fufna

Guest
These dimmers are known to blow on occasion (i have 3 2 gangs) It's a case of them being worth it for the money regardless IMO
 

ReTrO

Well-known Member
Something I learnt today:

Trailing Edge (TE) dimmers cannot sucessfully dim anything with an inductive load, which includes strip lighting (forget it's name) and some transformers.

It's quite likely that the dimmer wasn't very happy with your transformers and has gone bang as a result.

I'll check with my lighting engineer tomorow, see what he thinks.

We distribute Polaron lighting equipment at work and use a lot of TE bits in the new racks.
 
M

MrSafety

Guest
Hmmm. Thanks for the input but I'm not sure I'm really any wiser.
Is my dimmer trailing edge? Do I want to know what that means?

Taking fufna at his word, I guess my question becomes:

Do I (a) stick with the cheap TLC dimmers and expect them to go bang on occasion or (b) opt for a fancier, more expensive model? If (b), which model will SAFELY dim my lights?
 
M

MrSafety

Guest
Ok, just had it confirmed from the manufacturers of the TLC dimmer that my lights have wire-wound transformers with which the dimmer is incompatible. Hence, it blew up.

So, can anyone recommend an infra-red dimmer which will work my wire-wound transformer LV halogens?
 

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