Has anyone else had any problems with LV Halogen downlights (20 watt)
melting their way through UPVC ceiling cladding?
Fortunately I had only done a small area of the ceiling but after
leaving the lights switched on for a large part evening, I noticed the
problem.
I have some pieces of cementitious strip (similar to asbestos), which
I wondered whether I would be able to cut donuts out of to line the
holes either side of the UPVC. I'm not sure if I would be able to
keep them hidden beneath the fittings and still be effective.
Is there an easier solution anyone can recommend? The cladding is
effectively hollow so is there something I could inject into the
cladding which would increase its strength/heat resistance around the
areas I need to put the lights?
I have already bought all of the downlights and the cladding so going
for a different combination of materials would be my least desirable
option.

Kevin wrote:
Has anyone else had any problems with LV Halogen downlights (20 watt)
melting their way through UPVC ceiling cladding?

Why did you think that hot halogen downlighters and PVC would ever be a
sensible combination?

Can't think of any solution that wouldn't involve removing the PVC near
the fittings or changing the fittings to LED or CC.

Lee
--
Email address is valid, but is unlikely to be read.

Lee wrote in message ...
Kevin wrote:
Has anyone else had any problems with LV Halogen downlights (20 watt)
melting their way through UPVC ceiling cladding?

Why did you think that hot halogen downlighters and PVC would ever be a
sensible combination?

Well thats a constructive comment. I expected the bulbs to get hot
but not the housing ! The problem seems to be specifically related to
the steel spring-clips which keep the downlights in place, this is
where the melt occurs.

I have checked the instructions and there is no mention that they
should not be used with PVC. Besides I know of other people who
appear to have used this combination effectively and yes I will be
asking if they experienced similar problems.

Can't think of any solution that wouldn't involve removing the PVC near
the fittings or changing the fittings to LED or CC.

Having checked again last night I have made the holes slightly smaller
than recommended. The instructions say 48mmm while I only have 44mm or
50mm drills. It could be that 44mm allows too much PVC to be in
contact with the metal causing the melting. I tested again using a
50mm hole and did not get the problem, however the clips have to be
very acurately placed or else they do not close properly.

Another thought has occurred, could I use small scraps of lead wrapped
either side of the PVC at the point where the clips would normally
come into contact.

Is Lead a good or poor conductor of heat in comparison to the steel
clips ?

Thanks.

Kevin wrote:

Lee wrote in message ...

Kevin wrote:

Has anyone else had any problems with LV Halogen downlights (20 watt)
melting their way through UPVC ceiling cladding?

Why did you think that hot halogen downlighters and PVC would ever be a
sensible combination?


Well thats a constructive comment. I expected the bulbs to get hot
but not the housing ! The problem seems to be specifically related to
the steel spring-clips which keep the downlights in place, this is
where the melt occurs.

I have checked the instructions and there is no mention that they
should not be used with PVC. Besides I know of other people who
appear to have used this combination effectively and yes I will be
asking if they experienced similar problems.


Can't think of any solution that wouldn't involve removing the PVC near
the fittings or changing the fittings to LED or CC.


Having checked again last night I have made the holes slightly smaller
than recommended. The instructions say 48mmm while I only have 44mm or
50mm drills. It could be that 44mm allows too much PVC to be in
contact with the metal causing the melting. I tested again using a
50mm hole and did not get the problem, however the clips have to be
very acurately placed or else they do not close properly.

Another thought has occurred, could I use small scraps of lead wrapped
either side of the PVC at the point where the clips would normally
come into contact.

Is Lead a good or poor conductor of heat in comparison to the steel
clips ?



Similar. Better to use slivers of wood, if what I think you are saying
is what you are really saying, if you see what I mean...


Thanks.

On 30 Mar 2004 01:16:19 -0800, in uk.d-i-y (Kevin)
strung together this:

Has anyone else had any problems with LV Halogen downlights (20 watt)
melting their way through UPVC ceiling cladding?

Why did you think that hot halogen downlighters and PVC would ever be a
sensible combination?

Well thats a constructive comment. I expected the bulbs to get hot
but not the housing !

I wholly agree with Lee here, not really a top combination, heat and
PVC

I have checked the instructions and there is no mention that they
should not be used with PVC. Besides I know of other people who
appear to have used this combination effectively and yes I will be
asking if they experienced similar problems.

But did they say 'do not install in\on combustible surfaces'?

Is Lead a good or poor conductor of heat in comparison to the steel
clips ?

I think you'll find something non-conductive better. You seem to be
struggling with this heat\melt\conduct equation. Wood or plasterboard
would be the better material to use.
--

SJW
A.C.S. Ltd.

Lurch wrote
Is Lead a good or poor conductor of heat in comparison to the steel
clips ?

I think you'll find something non-conductive better. You seem to be
struggling with this heat\melt\conduct equation. Wood or plasterboard
would be the better material to use.

Totally agree about non-conductive, but I'm not sure about wood. I would be
worrying about it burning. And plasterboard + PVC would be too thick wouldn't
it? As a suggestion, how about cutting doughnuts out of those fibreglass mats
used by plumbers for shielding a blowtorch?

Peter

On Tue, 30 Mar 2004 18:42:06 +0100, in uk.d-i-y "Peter Taylor"
strung together this:

Lurch wrote
Is Lead a good or poor conductor of heat in comparison to the steel
clips ?

I think you'll find something non-conductive better. You seem to be
struggling with this heat\melt\conduct equation. Wood or plasterboard
would be the better material to use.

Totally agree about non-conductive, but I'm not sure about wood. I would be
worrying about it burning.

I suppose you could look at it like that, it won't get *that* hot
though. Each to their own.

And plasterboard + PVC would be too thick wouldn't
it?

I wouldn't have thought so.

As a suggestion, how about cutting doughnuts out of those fibreglass mats
used by plumbers for shielding a blowtorch?

Could be a bit pricier than bits of old plasterboard though.
--

SJW
A.C.S. Ltd.

(Kevin) wrote in message . com...
Has anyone else had any problems with LV Halogen downlights (20 watt)
melting their way through UPVC ceiling cladding?
Fortunately I had only done a small area of the ceiling but after
leaving the lights switched on for a large part evening, I noticed the
problem.
I have some pieces of cementitious strip (similar to asbestos), which
I wondered whether I would be able to cut donuts out of to line the
holes either side of the UPVC. I'm not sure if I would be able to
keep them hidden beneath the fittings and still be effective.
Is there an easier solution anyone can recommend? The cladding is
effectively hollow so is there something I could inject into the
cladding which would increase its strength/heat resistance around the
areas I need to put the lights?
I have already bought all of the downlights and the cladding so going
for a different combination of materials would be my least desirable
option.

If the problems that bad you need a lot of extra margin, not just a
little. halogens are the hottest of all domestic light sources. I
would consider the option of fitting CFL downlighters, these produce a
fraction of the heat.

Actually I wouldnt fit downlighters at all, nor PVC, but I understand
theyre what you want.


Regards, NT

OK, ignoring the fact that I must be a complete idiot for not
realising I was likely to get problems with my chosen combination of
materials. I can see that I didn't describe the problem very well.

The downlights I am using are retained in place by two spring clips.
These clips push downwards on top of the PVC and at the same time
outwards, pushing against the sides of the hole that I have drilled.
The problem seems to be caused where the clips are pushing against the
side of the hole and since the PVC is largely hollow it is not able to
resist the pressure when the clip gets hot. It may have been
misleading for me to describe the PVC as melting, it is actually being
distorted by a combination of heat and the pressure of the spring.

I have tried drilling pieces of plywood to the same diameter as the
hole in the PVC and then clipping the lights through both materials.
This seems to have been effective short term but I was worried that
this may not work long term as the clips are still in direct contact
with the PVC where they push against the sides and over a longer
period they may even burn the wood. Also the increased thickness of
the two materials together made it difficult to properly close the
clips.

The reason I mentioned using lead is because it is malleable and I can
shape it to wrap around the hole such that the clips don't need to be
in direct contact with the PVC at all. Also, even if the thermal
properties of the lead and the steel clips were identical, the heat is
now spread across a much larger area and therefore less likely to
cause distortion. I did in fact test this last night and after
several hours the temperature of the lead did not increase beyond the
point where I could comfortably keep my finger pressed on it. It is
effectively acting like a heat sink, so I think I may have found my
solution.

One final comment for anyone else who might want to use these types of
downlights (with or without PVC). I initially fitted five downlights,
only two of them caused visible distortion when fitted directly to the
PVC. On these two, the lugs on the downlights which keeps the spring
clips attached to the fitting were twisted. This caused the clips to
be closer to the bulb and in one case almost touching, than on the
other downlights. Twisting the lugs back slightly increases the gap
between the bulb and the clips and consequently the clips don't get
quite as hot.

The Natural Philosopher wrote in message ...
Kevin wrote:

Lee wrote in message ...

Kevin wrote:

Has anyone else had any problems with LV Halogen downlights (20 watt)
melting their way through UPVC ceiling cladding?

Why did you think that hot halogen downlighters and PVC would ever be a
sensible combination?


Well thats a constructive comment. I expected the bulbs to get hot
but not the housing ! The problem seems to be specifically related to
the steel spring-clips which keep the downlights in place, this is
where the melt occurs.

I have checked the instructions and there is no mention that they
should not be used with PVC. Besides I know of other people who
appear to have used this combination effectively and yes I will be
asking if they experienced similar problems.


Can't think of any solution that wouldn't involve removing the PVC near
the fittings or changing the fittings to LED or CC.


Having checked again last night I have made the holes slightly smaller
than recommended. The instructions say 48mmm while I only have 44mm or
50mm drills. It could be that 44mm allows too much PVC to be in
contact with the metal causing the melting. I tested again using a
50mm hole and did not get the problem, however the clips have to be
very acurately placed or else they do not close properly.

Another thought has occurred, could I use small scraps of lead wrapped
either side of the PVC at the point where the clips would normally
come into contact.

Is Lead a good or poor conductor of heat in comparison to the steel
clips ?



Similar. Better to use slivers of wood, if what I think you are saying
is what you are really saying, if you see what I mean...


Thanks.


Thermal conductivity in W per m per degree K

Mild steel 63
Stainless steel (18 cr/8 Ni) 150
Lead 35

Hence Stainless is 4 1/4 times more conductive than lead.

However

Wood (oak) 0.15
Cork 0.05
Nylon 0.25

However looking down my list of metallic solids Lead is the lowest
conductivity cheap and easy available one,Titanium sneaking in with
29, so perhaps it wasn't such a bad idea. I suspect there hasn't been
much of a market in titanium spring clips for fitting downlighters
into PVC though....


dear o dear what a nerdy post...

Eric

N. Thornton wrote:
(Kevin) wrote in message
. com...
Has anyone else had any problems with LV Halogen downlights (20 watt)
melting their way through UPVC ceiling cladding?
Fortunately I had only done a small area of the ceiling but after
leaving the lights switched on for a large part evening, I noticed
the
problem.
I have some pieces of cementitious strip (similar to asbestos), which
I wondered whether I would be able to cut donuts out of to line the
holes either side of the UPVC. I'm not sure if I would be able to
keep them hidden beneath the fittings and still be effective.
Is there an easier solution anyone can recommend? The cladding is
effectively hollow so is there something I could inject into the
cladding which would increase its strength/heat resistance around the
areas I need to put the lights?
I have already bought all of the downlights and the cladding so going
for a different combination of materials would be my least desirable
option.

If the problems that bad you need a lot of extra margin, not just a
little. halogens are the hottest of all domestic light sources. I
would consider the option of fitting CFL downlighters, these produce a
fraction of the heat.

Actually I wouldnt fit downlighters at all, nor PVC, but I understand
theyre what you want.

I assume that the PVC wouldn't drip onto people below in the event of a
fire....?