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kambites

Original Poster:

40,737 posts

106 months

[news] 
Wednesday 10th November 2010 quote quote all
We've got two 12v halogen light fittings in our living room, each with 6 bulbs.

When all the bulbs are working, they work fine for about twenty minutes and then start flashing on and off every 20 seconds or so. Once they are down to a single bulb (which doesn't take long, since they blow pretty damned fast when they're flashing on and off), it works fine.

According to my widget from Maplin, the mains voltage is hovering around 243v which is a tad high but well within the 230 +10%/-6% range.

Any ideas?

mk1fan

4,684 posts

110 months

[news] 
Wednesday 10th November 2010 quote quote all
How are they wired up? Series, parallel?

Also, do they each have a transformer or does one transformer serve them all?

Finally, are they wired through a dimmer?

The last time I had flickering/flashing lights - coincidentally LV - it was the dimmer at fault.

As a first step check all the wiring connections for a loose fitting.

Eggman

1,253 posts

96 months

[news] 
Wednesday 10th November 2010 quote quote all
I had a similar-ish problem with some halogen lights in a kitchen; they'd periodically go out for a few minutes and then come back on.

It turned out that the transformer supplied by the kitchen fitters wasn't up to the job, so I replaced it with a chunkier one and the problem went away.

mrsxllifts

2,501 posts

84 months

[news] 
Thursday 11th November 2010 quote quote all
^^yes

WE had same trouble, the transformer that came with the lights wasn't man enough for the job and lights would overheat, started by flashing then would go off completely, after 30-45mins they would have cooled enough and would come back on again.

V8A*ndy

2,162 posts

76 months

[news] 
Thursday 11th November 2010 quote quote all
How long have they been installed?

Our last lot had the ceramic fittings breaking up due to the heat. They would heat up, expand and break the electrical connection. Then cool again in a few seconds and come back on.

This was often the ceramic on the bulb as well ot just the fitting the two pins fitted into.

The newer connections that run to the transformers are much better.



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satans worm

1,590 posts

102 months

[news] 
Thursday 11th November 2010 quote quote all
Possibly overheating?

How much ventilation do they have behind them?

Ours do the same due and I plan on making some new, larger, fireproof boxes for them.

kambites

Original Poster:

40,737 posts

106 months

[news] 
Thursday 11th November 2010 quote quote all
The transformers are built into the light fittings. Each fitting is on a different light switch (within the same switch block). This is a simple on/off switch not a dimmer.

They sit proud on the surface of the ceiling and have vents in the sides of the unit. I installed them a few months ago and they have had the problem since new.

Edited by kambites on Thursday 11th November 09:37

Simpo Two

59,695 posts

150 months

[news] 
Thursday 11th November 2010 quote quote all
I'd put 50p on overheating too.

Do they have glass in front that you could remove to help cooling?

kambites

Original Poster:

40,737 posts

106 months

[news] 
Thursday 11th November 2010 quote quote all
Simpo Two said:
I'd put 50p on overheating too.

Do they have glass in front that you could remove to help cooling?
No, the transformer is in a metal cage at the top of the fitting, with the bulbs on stalks sticking out of it.

If they're overheating, why? Are they just badly designed or is something else likely to be wrong?

Eggman

1,253 posts

96 months

[news] 
Thursday 11th November 2010 quote quote all
Could be badly designed, or just built down to a price. It could also be something else - have you put brighter bulbs in, for example? Also, if your living room has a high ceiling it could be pretty warm up there by the time it's comfortable 'down below' - possibly rather warmer than the designer had in mind. Does it work any better when the room is cold?

Now I think of it, it's interesting that the fitting is only happy with one bulb going - makes me wonder if the thing has got a bit knackered and overheats more readily than it should.

What wattage bulbs are you using?

turbospud

182 posts

123 months

[news] 
Friday 12th November 2010 quote quote all
va rating of the transformer will be differant to the lamps being used,change the lamps

kambites

Original Poster:

40,737 posts

106 months

[news] 
Friday 12th November 2010 quote quote all
The bulbs are the ones that came with the fitting.

hairyben

3,448 posts

68 months

[news] 
Friday 12th November 2010 quote quote all
All the bulbs go off together right?

probably transformer then, I see you don't think it's overloading (common mistake, cheap nasty ikea etc lights rated to take 20w lamps, people then buy 50's) but factory fit transformers tend to be the cheapest nastiest items avaliable, on everything from argos £20'ers to several-hundred-pound items from big posh designer stores. I frequently change them for clients so the lights can be dimmable.

bullitinhead

203 posts

54 months

[news] 
Friday 12th November 2010 quote quote all
I would ask what is the wattage rating for the lamps and what is suppose to be in there, what is the rating of the transformer, I have a kitchen 12volt transformer and although the rating exceeds the lamp ratings it still cuts out and flashes as it overloads. taking only light out of the circuit fixes the problem.


bullit

hairyben

3,448 posts

68 months

[news] 
Saturday 13th November 2010 quote quote all
bullitinhead said:
I would ask what is the wattage rating for the lamps and what is suppose to be in there, what is the rating of the transformer, I have a kitchen 12volt transformer and although the rating exceeds the lamp ratings it still cuts out and flashes as it overloads. taking only light out of the circuit fixes the problem.


bullit
Could be thermal cut out (overheating). Removing a lamp will decrease work and hence heat. Is it tightly enclosed/ covered in thermal insulation etc? If so and if poss try moving it to where it has lots more air to see if this helps.

Large transformers running lots of lamps seem more prone to heat issues than individual 60VA trannys at each lamp.

hairyben

3,448 posts

68 months

[news] 
Saturday 13th November 2010 quote quote all
Another cheap fix if the tranny is overload/heating is to use lower wattage lamps or evan LED's in a couple of the lampholders. The mixture of LED/halogen lighting should still see you a decent overall light quality over pure LED.

Dimmable systems may have issues with LED's.

E36GUY

4,294 posts

103 months

[news] 
Tuesday 16th November 2010 quote quote all
hairyben said:
Another cheap fix if the tranny is overload/heating is to use lower wattage lamps or evan LED's in a couple of the lampholders. The mixture of LED/halogen lighting should still see you a decent overall light quality over pure LED.

Dimmable systems may have issues with LED's.
Or you could just get decent LEDs in the first place and ditch all the halogens. £24 each to PH'ers.
http://www.ecoledlight.co.uk/ShowDetails.asp?id=41...

kambites

Original Poster:

40,737 posts

106 months

[news] 
Monday 22nd November 2010 quote quote all
Unfortunately they're G4 bulbs and as far as I can see, you can't get particularly bright G4 LED bulbs.

It does seem odd that they would sell a fitting with a transformer not capable of supplying the bulbs included in the pack.



Sounds like it's probably time to throw out the light fittings at chalk the hundred odd quid that they cost up to experience.

Edited by kambites on Monday 22 November 11:26

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