Which is the coolest lamp?

I imagine that the LED downlighters which are a direct replacement for GU10s would be the coolest option, but you need more of them to get the same amount of light.

Anything with a dichroic (selective) reflector attempts to throw visible light forward whilst letting infrared pass though it and out the back.

One property of dichroic reflectors is they appear "colourful" if you look at them, with little patches of colour depending on how you look at them.

I've mostly seen dichroic used on LV halogen (where the reflector is part of the bulb assembly)

Timbo

The reason for the fireproof box is not the lamp itself, but due to you punching a hole through a fire barrier (the ceiling). Of course, mounting a cheap crappy incendiary device in the hole is not the brightest of ideas either, but secondary to the main issue.

None. There are some more expensive commercial recessed fittings with integral fire barrier.

larva lamps from the 60's, by the way the word is kewl bob

A further comment: This is from the building regs perspective.

If you are talking from the perspective of the lamp starting a fire, then a fully aluminised reflector rather than a dichroic reflector lamp would be better, but they've become very hard to find nowadays.

There are several issues here...

there is the issue of how much heat is generated by the fitting/bulb. This tends to be more of a problem with reducing the life of the bulb and transformer rather than being a direct fire risk IIUC.

(You are correct that the bulbs with aluminium reflectors tend to project more IR forward. The dichroic ones will let more reach the fitting (hence the fitting has to be designed to be able to take it). You can get dichroic bulbs in both 240V and 12V).

The more significant fire issue in many cases, is that fitting down lighters requires a large(ish) hole be cut in the ceiling. This in many cases breaching a fire resistant layer (i.e. the skim/plasterboard) between habitable rooms. In these cases an intumescent hood can be fitted to restore the integrity of the fire block.

Hard to choose on safety grounds... with a downlighter of any sort you need enough space behind it. Given that the bezel of a non dichroic bulb may get hotter, and hence be more of a touch hazard (if the ceiling is low enough), I would lean toward the dichroic bulb. On aesthetic grounds the dichroic bulb wins on several counts.

wrote | I heard that GU10 230v lamps throw the heat forwards and other types, | including LV, throw the heat backwards. The forward throwing type is | better for fire safety in ceilings. | Building inspectors are getting shirty about downlighters in ceilings, | wanting fireproof boxes around them. If a lamp throws heat forwards | then the fire aspect should not be an issue.

The issue is not so much the heat generated by the lamp. A fireproof box is going to concentrate that heat in a particular area, rather than letting it dissipate through the void. The problem is the fact that the ceiling is being pierced allowing the spread of smoke and fire from the room below into the ceiling void. The plasterboard ceiling is an important part of maintaining the fire integrity of the whole floor structure. These fire domes also have to be used for ceiling speakers, which do not generate any heat.

The use of ceramic flowerpots, while useful for keeping loft insulation away from the luminaire, does not preserve the fire integrity of the ceiling.

Owain

Yup agreed. I would have thought the prospect of the lamp itself being responsible for a fire is limited, since although they get hot, they don't typically get _that_ hot... (250 deg C tops as a guess, which is going to be below the flash point of most building materials).

Having said that, if your transformer melts and goes low resistance that might do it ;-)

I though that most GU10s were typically ali, and GZ10s the dichroic versions?

There have been cases. Two I know of were both due to bad lampholder connections -- in one case the lampholder started a fire and in the other case it shorted out and the transformer then started the fire.

Yes, you're right (although I can never remember which way round they are without looking it up). I was thinking of the 12V lamps, where fully aluminised reflectors used to be available, but have vanished now.

ceilings,

respect?

No-ones really answered the question, least not the way I read it... my answer is CFLs. You could also say LEDs, but theyre not a serious contender practically.

NT

I think the asnwer is there is not much to choose between them. It is the cutting of the hole that posses more risk than the choice of lamp.

An upturned ceramic pot with notch out of the rim for the cable and sealed with silicon to the plasterboard with preserve fire integrity.

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You'll have to get the silicon VERY hot to melt it enough to make it nice and sticky ;-)

and to remain on topic, I recenly tried out the little 7W GU10-compatible fluorescents to replace 5xmains 50W downlighters in the kitchen.

VERY disappointing - the halogens are back in and the mini fluorescents are doing a great job in my study.

Regards, Simon.

Multiply 7W by 4 to get equivalent, and in this case knock a bit off due to reflector losses and comparison with 12V rather than

Has anyone ever used these? Any reports? Light? Type of light? etc?

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