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6 low voltage downlights in a bedroom on a dimmer switch and 4 downlights in the bathroom all on one circuit with a 6A m.c.b. in the board and all lights with their own transformers.
At first the low voltage lights were not fire rated and were without hoods and insulation was covering them, bulbs kept blowing and transformers going.
So i have replaced all downlights for fire rated ones and replaced the transformers that were not working and put new bulbs in all lights.
A day later one of the lights in the bedroom wont come on, and this one had a new transformer and light and bulb.
What could be wrong?
Can anyone help?
Is there anything wrong with this setup?
Sensible answers would be much appreciated thank you.
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  • Thread Starter Thread Starter
  • #2
It could be as simple as a dicky new transformer, we have had loads mate, theres a lot of cheap **** tranys from china out there, may be or may be not.


  • Thread Starter Thread Starter
  • #3

Could be faulty transformer, faulty lamp.

Maybe thermal cut-out on tranny has operated, fire rated downlights are more enclosed than non fire rated, heat builds up quicker.

Did you make sure that the insulation was well away from the new lights??

nothing wrong with 10 lights:) on 1 circ 10x50w is only a couple of amps.
if the lamp,transformer and fitting are all new then i suspect a loose connection at either the faulty point or the previous 1,
failing that lamps are notorious for being unreliable, by the way make sure the transformers are dimmable

Bright Sparks

  • Thread Starter Thread Starter
  • #5
There could be a number of issues;

Blown lamp
Faulty lamp holder
Failed transformer
Transformer thermal cutout ( but should re-start, if a good Quality transfomer used)
Insulation causing failure due to over heating (Working temp is about 45-50 Deg C max)
Loose cable

Hope that helps


  • Thread Starter Thread Starter
  • #6
sounds daft but whatsd the max voltage on the downlighters..!! me in my wisdom once upon a few month back natually just grabbed the first set of gu10 lamps and fitted !! lights were intermittent!! transforms were ok but holder was only rated to 35w and i wacked in 50w....!! :( simple mistake!!

but your case sounds like duff transformer!! try a different light in the fitting!!



  • Thread Starter Thread Starter
  • #7
I had a similar scenario.
Turns out it was the lamp holder. The pin holes somehow had got slightly warped and bigger, and the lamp was just not staying in. If i forced it in, it still was not working.
So check this out, before changing the transformer, much cheaper as well.
Hope this helps,



  • Thread Starter Thread Starter
  • #8
just a thought, but are the replacement lamps coolfit? If not 200oC goes back up behind the fitting.


  • Thread Starter Thread Starter
  • #9
hmmm 200 degrees...!! hatch a plan to capure the heat and re use it for heating of water!!


  • Thread Starter Thread Starter
  • #10
Are trannys compatable with dimmer? also Wheres the RCD? lol


  • Thread Starter Thread Starter
  • #12
what is the rating of the dimmer switch??

and by low voltage do you mean 230v mains, cause if so i thought you had to derate dimmer switches if this was the case.

Please correct if wrong :D



  • Thread Starter Thread Starter
  • #13
Brushed Chrome Dimmer Switches for low voltage lighting

take your pick from dimmers.... plenty to choose!!

not sure on derating factor!! just new to this game if im been truly honest! never heard of it before though!!

British Standard BS 7671:2008 defines low voltage (LV) as
50–1000 V AC or 120–1500 V ripple-free DC between conductors.
50–600 V AC or 120–900 V ripple-free DC between conductors and Earth.

any thing below is ELV any thing above is HV

Bright Sparks

  • Thread Starter Thread Starter
  • #14
Slightly off topic, but yes Halogen downlights get hot. All that Electricity pumping through the filament not only provides light but a lot of heat, in excess of 200 Deg C (This is for a standard Dichroic reflector lamp), an aluminium reflector lamp will help 'push' the heat forwards, but if covered with insulation it will quickly over heat the fitting, cause early lamp failure and / or discolouration/warping of the fitting.



  • Thread Starter Thread Starter
  • #15
Make sure your transformers are still above the insulation because they can still cut-out if not. Also as someone else said make sure you are using 'coolfit' lamps with the fire-rated fittings as they allow for less heat moving up the fitting. I've seen people put ordinary dichoric lamps in these fittings only for the lampholders to begin melting!


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