Preventing halogen lights overheating under Rockwool

[Lobster]

Having installed some LV halogen lights in the bathroom, I need to protect them against overheating or causing a fire by buring them under 250mm of Rockwool.

I know this has been covered before here, and solutions of large inverted plant pots (don't have any) or proprietary incandescent shields (expensive) have been suggested.

I think I've come up with an alternative solution; that is, to use offcuts of 4" soil pipe or ducting as 'chimneys' to surround the fitting neatly and duct the hot air upwards (would also illuminate the roof space quite nicely! Don't have any spare of either unfortunately so was going to order up some Screwfix ducting (ref 15872 - five 350mm lengths for 5.95GBP).

So - do we think this would be OK? Or might it melt if it was that close to the fitting (50W bulb)?

Thanks David

[G&M]

If your ceiling can take the weight, why not use the old style "clay" underground pipes. You can pick them up for next to nothing and they definitely won't burn.

[Robert]

In message , G&M writes

I used up-ended terracotta plant pots.

[[news]]

may be of use

[Lurch]

On 23 Jun 2004 12:02:06 -0700, [e-mail] (Lobster) strung together this:

That's exactly I have done in the past, a perfect solution.

[rrh]

Or you could cut lengths of 100mm diameter aluminium ducting hose.

[David]

I think what you have here pretty much covers the issue of isolating the lights fom the rockwool but ideally you also want to minimise any path for water vapour to enter the loft as well, especially as they are in the bathroom. The design of the light fittings and how well they are installed will play a part in this and obviously the current ventialation to the bathroom will affect things..

Potentially you would expect more water vapour to get through using an open pipe arrangement than using the old teracotta pot which can also be sealed to some extent.

cheers

David

[sPoNiX]

Use large metal tin cans with both ends removed.

I'm thinking catering sized tins or maybe old paint cans.

sPoNiX

[IMM]

use plantpots, as these are cheap and fireproof. Seal up the hole if there is one. Cut a notch in the rim for the cable and seal around the rim with silicon.

[usenet]

How does this help? The requirement is to stop the light getting too hot, if you completely enclose it in a flower put and even seal it up then it'll get even hotter won't it?

[David]

Is the requirement to stop them getting hot?? they are designed to go into enclosed spaces not just open lofts so I don't think heat build up around the lamps is a problem, the requirement is to keep materials away from the lamp so an upturned clay pot is a good solution, I did this to mine years ago without problem.

[usenet]

Well the original subject is "Preventing halogen lights overheating under Rockwool". The loft insulation is hardly going to suffer from the heat of the lamp so what good is the plant pot doing?

[David]

Its keeping the rockwool away from the lamp, when I said that the lamps go into enclosed spaces I didn't expect anybody to read that as its ok to pack them in rockwool, its possible that packing them tight with rockwool and then having that combination in close proximity to a joist, rafter, boarding or anything else combustible could have potential for trouble

[IMM]

It is keeping an air space around the lamp and the insulation away from the lamp too.

[usenet]

It may give you "warm feelings" (ha, ha!) but I fail to see what good it's done for anything.

The lamp will probably run hotter as it's in a very enclosed space with no ventilation.

The insulation won't care either way as it's decidedly not inflammable.

The one thing it *might* do is protect adjacent joists from the heat of the lamp but I'm not all that convinced that "no flowerpot" will make the joist any warmer than "flowerpot" will.

The idea of a 'chimney' of some sort (i.e. a largeish tin with both ends cut off) seema a much more sensible approach to me.

[David]

This is what I was trying to say in my first reply, does it matter if it runs hotter in an enclosed space? I don't think so

If you are into insulation and draught proofing though, you have created a hole in your ceiling unless you use the sealed lens type units, by putting a pot over and sealing around the edge you prevent this

[Will]

Light fittings are designed to give sufficient ventilation to allow the lamp to run at its optimum temperature.

By altering the potential airflow - and thus the cooling efficiency - of the fitting, you will cause the lamp to run in excess of its optimum temperature, which will lead to premature failure. Not to mention the premature failure of the fitting itself.

I can't say that I have noted the effect in low voltage lamps - they are largely disposed to early failure anyway - though gls and reflector lamps exhibit the same tendency...

[David]

In article , Will writes

I'm not sure if you are agreeing with me or not :-) I'm saying that these type of lamps are designed to run in confined place so get all the cooling they need without the addition of 'cooling chimneys,

I have mine enclosed in upturned pots and can't say that mine fail any earlier than anybody else's

[usenet]

But what's the point then?

You are probably also doing something awful to the fire proofing.

[David]

In article , [e-mail] writes

That the lamp is not the problem and doesn't need cooling as it's designed to run in a confined space BUT if its totally encapsulated in rockwool then this combination may get hot enough to cause a problem to nearby joists, boarding, whatever, so all the pot does is keep the insulation away from the lamp and as air circulation around the lamp is not a problem as its designed to go into a confined space you might as well seal up around the edge of the pot to stop draughts from the ceiling space into the room below and vise versa, whew