Downlights burning plasterboard

mk2phil · 27 Jan 2010

Hi there,

I've installed some Low Voltage downlighters in my ceiling, using MR8 35w bulbs. The fittings themselves are a satin nickel finish, and after you've had them running for about 30 secs you cant touch the fitting becuase it's so hot.

I assume that its normal for them to run this hot, but now I've noticed that there are burn marks around the fitting. Its a white ceiling so its quite obvious. Is there anything I can do to stop this from happening - for example fit 20w bulbs instead?

Or could I use LED bulbs (0.3w) to solve the problem? I'm worried that 0.3w bulbs wont be anywhere near as bright as the existing 35w ones.

If I did change to LED bulbs I realise that you must use a constant voltage transformer. The ones I've seen reckon you can use 50+ bulbs on one transformer..?!! If so, how do you wire them up? When I fitted the 35w bulbs I was told that you can suffer voltage drop towards the end of the run if you use a few fittings per transformer. Does this not apply with LED lights?

Many thanks for your help

electronicsuk · 27 Jan 2010

This only normally happens if the fittings are covered in insulation or airflow is in some other way restricted such that the heat can't escape. Is this the case?

GaryMo · 27 Jan 2010

Do the lamps have a dichroic reflector (heat back into the luminaire) or a aluminium reflector (heat away from luminaire)?

mk2phil · 27 Jan 2010

Not sure what type of reflector they are as I've thrown the boxes out now.

Yes they are in an enclosed space so that might be the problem I suppose. They're being used to highlight a wall feature, and as such there isn't much room above/around the light for heat to escape.

So I have to figure a way to allow the heat to escape or perhaps use LED's.

Will LED's be a suitable replacement? They're being used to highlight a specific area of the room and not being used to light the whole room.

electronicsuk · 27 Jan 2010

mk2phil said:
Not sure what type of reflector they are as I've thrown the boxes out now.

They'll almost certainly be dichroic, it'd be very rare for an aluminised reflector to be included.

mk2phil said:
Yes they are in an enclosed space so that might be the problem I suppose. They're being used to highlight a wall feature, and as such there isn't much room above/around the light for heat to escape.

So I have to figure a way to allow the heat to escape or perhaps use LED's.

If the fittings are capable of taking a standard 50w halogen lamp then really they should be installed properly, otherwise there is the risk of someone replacing whatever low power lamps you fit back with 50w models again in the future.

Nontheless, without changing the fitting, you have the options of LED or an aluminised reflector lamp that will reflect the heat out into the room rather than the ceiling void. Whether or not reflecting the heat outwards is a suitable proposition depends on what you're trying to light, and how close it is to the light source.

mk2phil said:
Will LED's be a suitable replacement? They're being used to highlight a specific area of the room and not being used to light the whole room.

Yes, if you buy good quality ones such as these. Stay away from anything with tens of standard 5mm LEDs in one lamp, look for something with one or three powerful luxeon-style emitters.

Taylortwocities · 28 Jan 2010

This is from Australian wiring regs but IMO is a reasonable guide - in the absence of the maker's instructions

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Taylortwocities
28 Jan 2010
1

ban-all-sheds · 28 Jan 2010

Can you get non-incandescent halogen lamps in Australia, then?

Taylortwocities · 28 Jan 2010

Very clever them Aussies

TicklyT · 28 Jan 2010

ban-all-sheds said:
Can you get non-incandescent halogen lamps in Australia, then?

Probably not, but you can get non-halogen incandescent lamps there, just as you can here.

ban-all-sheds · 28 Jan 2010

That's not how they've worded those instructions...

electronicsuk · 28 Jan 2010

Taylortwocities said:
This is from Australian wiring regs but IMO is a reasonable guide - in the absence of the maker's instructions

Untitled

Taylortwocities

28 Jan 2010

1

Is that image upside-down?

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Downlights burning plasterboard

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