Halogen down lights

[Paul2886]

Your opinions would be much appreciated.
Imagine a flat roof conservatory approx. 20' x 12' with the conventional polycarbonate type roofing that has been fitted with a false ceiling about two below, constructed of tongue and groove knotty pine.
Within this timber false ceiling are fitted a number of halogen down lights but with no protective cowels fitted above. There is no detection in the conservatory and it has to be passed through to gain access to the main front door.
There is a door (FD30s) seperating it from the main entrance lobby of the home. It is used as a lounge in a care home for approximately 18 people.
Hope I've explained that ok and inviting your thoughts on the situation because as you'll know these lights radiate a tremendous heat in all directions and I have problems with the untreated timber ceiling. Thanks

[kurnal]

I dont suppose theres any other way out from the main entrance lobby?

Just out of interest how far is the timber ceiling below the polycarbonate roof? you say 2- is this cm or m ?

As you know if this is an escape route surface finishes should be class O. if it is the only escape route I would be a little concerned. Are there any furnishings in the conservatory?

Whilst I dont like these downlighters, I think the biggest problem is where they penetrate a fire resisting ceiling. The manufacturers usually recommend a clear space bre maintained above the fittings and different types of bulbs are available- some deflect heat downwards, others upward.

What are the properties of the polycarbonate in a fire ? Do we know?

[John Webb]

Ordinary 12 volt halogen bulbs (GX5.3) are either 'Dichroic' or not. It is the former that allow heat out of the back by having a reflector that does not reflect infra-red, only the visible light. Some downlight manufacturers in their instructions say these should not be used in their fittings, but dichroic bulbs are the more readily available and one should assume that they will end up in fittings regardless of the makers' instructions.

On the other hand some design their fittings and firehoods to work satisfactorily with dichroic lamps. See for example www.illuma.co.uk

I assume that there is a two-foot gap between ceiling and roof as the other dimensions are given in feet. Provided there is ventilation of this area so that the heat build-up is minimised, I would not be too worried about the heat heading towards the roof.

Neither would I be concerned about heating of the false wood ceiling. The radiated heat is mostly upward and to a limited extent downwards and does not actually fall on the wood. Most of the heat going in the direction of the wood will be the heat conducted from the fitting to where it passes through and is clamped to the ceiling. There will be some convected heat as well, but the ventilation mentioned above should deal with that.

I cannot recall how polycarbonate burns exactly, but I think it needs a reasonable heat source with flame for ignition, then it's a bit like wood but will drip burning droplets - these might be capable of igniting wood. Subject to high temperature it will become soft and sag and eventually fail, hence its use for skylights to give venting.

Hope this helps.

[Brian Catton]

I think that the protection required largely depends upon the use of the space between the ceiling and polycarbonate roof. does it have wiring passing through it, apart from that serving the halogen lights.

By the way youi havenet said whether the lights are 240 or LV through a transformer.
With the structural materials you have described I would prefer to see detection in the conservatory and, depending on the risk, also in the void between the pine ceiling and the roof.

Also were the lights installed in accordance with IEE rules and manufacturers instructions.

Most of these lights have to be fitted with an FR hood.

[Paul2886]

I dont suppose theres any other way out from the main entrance lobby?

Just out of interest how far is the timber ceiling below the polycarbonate roof? you say 2- is this cm or m ?

As you know if this is an escape route surface finishes should be class O. if it is the only escape route I would be a little concerned. Are there any furnishings in the conservatory?

Whilst I dont like these downlighters, I think the biggest problem is where they penetrate a fire resisting ceiling. The manufacturers usually recommend a clear space bre maintained above the fittings and different types of bulbs are available- some deflect heat downwards, others upward.

What are the properties of the polycarbonate in a fire ? Do we know?

Hi Kurnal, The timber ceiling is about 9 inches below at one end and 3 feet the other end owing to the polycarbonate roof having a slope. It is furnished as any typical lounge in a care home and there are alternative routes from the building but the new conservatory encompasses the original main front door

[kurnal]

With alternative means of escape available from the entrance lobby, which presumably are true alternatives and separated frome each other, and a fire door to the conservatory, I would not be too concerned about the lights, the conservatory should be fitted with a smoke detector though.

I would have had a problem with them had they penetrated a fire resisting ceiling with bedrooms above though, unless they had hoods and as John says the correct bulbs.  
As it is,  it does give you another option when looking at progressive horizontal evacuation.

[Paul2886]

Thanks all. Always good to hear other opinions on these matters

[John Webb]

If you can arrange some ventilation into the roof at the low end and outlets on the sides near the highest point to ensure there is no heat buildup, you should be OK. But it would be worth checking the temperatures reached in the void particularly (a) when the lights are on (b) in Summer sunshine, just to check that the wiring is not operating at an excessive ambient temperature contrary to the requirements of the IEE Wiring Regs (BS7671).