Possible Lighting Problem
 

Hi,

In my kitchen I have just in the process of installing four recessed
eye ball down lights. These are the mains GU10 type. They are laid out
in a square box shape with each fixture on a corner if you see what I
mean.

Anyway, after looking at the instructions for the fittings it states
the minimum distance for any object *in front* of the light before I
presume the heat could cause a fire. This is fine as they are mounted
in the ceiling.

However, one hole is reasonable close, I would say 10 to 15 cm to a
copper pipe and some mains cable that runs through the ceiling void.
So I put that fixture in and ran it for around 5 minutes, I then
removed it, shut off the power and had a feel around in the hole to
see if anything was heating up and it wasnt. I then repeated the
process up to 30 minutes running time and the cables and pipe didnt
feel warm at all.

So is the opinion on this that the fixture will be safe or am I
running the risk of setting my ceiling void on fire and burning down
my house. I guess the question is can dangerous levels of hear occur
behind the fixture and is there a safe distance or a minimum amount of
void that these things should be mounted in.

Thanks for the on going help.

CM.

Possible Lighting Problem
 

In message ,
(Charles Middleton) wrote:

Hi,

In my kitchen I have just in the process of installing four recessed
eye ball down lights. These are the mains GU10 type.

[...]

Anyway, after looking at the instructions for the fittings it states
the minimum distance for any object *in front* of the light before I
presume the heat could cause a fire. This is fine as they are mounted
in the ceiling.

However, one hole is reasonable close, I would say 10 to 15 cm to a
copper pipe and some mains cable that runs through the ceiling void.

[...]

I guess the question is can dangerous levels of hear occur
behind the fixture and is there a safe distance or a minimum amount of
void that these things should be mounted in.


I just bought a few GU/GZ10 fittings (simple recessed types, not
eyeball) and although I haven't fitted the things yet, I'm sure the
instructions contain details about clearance around the recessed part.
From memory, they are not to be covered with insulation, and at least
50mm (i.e. 5 cm) from any potentially flammable surface so I would have
thought that 100mm or 150mm would be fine, but check the instructions
in case the advice is different for yours. In any case I would expect
the copper pipe to be ok - even were it carrying gas, there's no air in
the pipe to let it burn, and copper is such a good conductor of heat
that the point temperature is likely to be lower than you expect. PVC
insulation on cabling doesn't like heat at all (normal PVC is only rated
up to 70C, though it won't actually "melt" at that temperature) so keep
the cable as far away as possible.

It is important however to realise the difference between GU10 and GZ10
laps which otherwise look similar and will fit the same connector bases.
One (GU10?) is dichroic and the other is a simple reflector. A simple
reflector reflects almost everything, including the heat, forwards. A
dichroic reflector allows much of the heat (infra red) radiation
*through* the reflector so that the area in front of the lamp is
comparatively cooler than an ordinary reflector. Of course, this means
that the area behind a dichroic lamp can get warmer than that behind a
simple reflector, though if the lamp is mounted vertically pointing
downwards you are unlikely to notice much difference after it has been on a
while.

FWIW, had I not been replacing the ceilings anyway, I would have cleared
the 70 years of dust and detritus away from the recessed parts of my
fittings, probably using a vaccuum cleaner, before turning them on.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Be *excellent* to each other

Possible Lighting Problem
 

In article ,
Martin Angove writes:

It is important however to realise the difference between GU10 and GZ10
laps which otherwise look similar and will fit the same connector bases.

They don't have same bases -- full reflector base has a bevel round the
bottom which stops dichroic lamps being fitted. Substituting the other
way round is OK. This is specifically to stop a dichroic lamp being
used in a fitting not designed to take the heat it dumps backwards.

--
Andrew Gabriel

Possible Lighting Problem
 

In message ,
(Andrew Gabriel) wrote:

In article ,
Martin Angove writes:

It is important however to realise the difference between GU10 and GZ10
laps which otherwise look similar and will fit the same connector bases.

They don't have same bases -- full reflector base has a bevel round the
bottom which stops dichroic lamps being fitted. Substituting the other
way round is OK. This is specifically to stop a dichroic lamp being
used in a fitting not designed to take the heat it dumps backwards.


Ok, I stand corrected. The point was valid though as many fittings are
designed for use with either, and the user may not be aware of the extra
problems with rearward heat build-up when installed in a confined space.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Some Do, Some Don't, Some Will and Some Won't.

Possible Lighting Problem
 

From memory, they are not to be covered with insulation, and at least
50mm (i.e. 5 cm) from any potentially flammable surface so I would have
thought that 100mm or 150mm would be fine, but check the instructions
in case the advice is different for yours.

Had another look at the instructions and nothing mentioned about the heat
from the top of the units. Ive done some more tests today and they seem to
be fine and there is no excess heat build up in the ceiling.

It is important however to realise the difference between GU10 and GZ10
laps which otherwise look similar and will fit the same connector bases.
One (GU10?) is dichroic and the other is a simple reflector. A simple

snip

Thanks for the info on that - I wasn't aware of that.

CM.

Possible Lighting Problem
 

In message ,
"Charles Middleton" wrote:

From memory, they are not to be covered with insulation, and at least
50mm (i.e. 5 cm) from any potentially flammable surface so I would have
thought that 100mm or 150mm would be fine, but check the instructions
in case the advice is different for yours.

Had another look at the instructions and nothing mentioned about the heat
from the top of the units. Ive done some more tests today and they seem to
be fine and there is no excess heat build up in the ceiling.


I've just found the instruction leaflet for mine - Aurora downlighters
from Screwfix (p163, 19324). The dimensions given are 135mm height -
i.e. in total from ceiling to nearest obstacle above, and 75mm *from
spring mount* to nearest vertical obstacle. The diagram shows a lamp
almost completely enclosed in a box of these dimensions though :-)

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... If I want your opinion I'll beat it from you

Possible Lighting Problem
 

"Martin Angove" wrote in message
...

I've just found the instruction leaflet for mine - Aurora downlighters
from Screwfix (p163, 19324). The dimensions given are 135mm height -
i.e. in total from ceiling to nearest obstacle above, and 75mm *from
spring mount* to nearest vertical obstacle. The diagram shows a lamp
almost completely enclosed in a box of these dimensions though :-)

Thinking about it what I didn't (foolishly) consider was the distance from
the fixture to the joist - its quite close. What's the heat tolerance of a
ceiling joist and how hot can these fixtures get? Has anyone known of these
units setting fire to things before - I imagine its a distinct possibility!

I'm starting to get a little concerned about the set up now - I would want
to have an fire in the void between my ground and 1st floor!

CM.

Possible Lighting Problem
 

In article , Charles Middleton
writes

"Martin Angove" wrote in message
...

I've just found the instruction leaflet for mine - Aurora downlighters
from Screwfix (p163, 19324). The dimensions given are 135mm height -
i.e. in total from ceiling to nearest obstacle above, and 75mm *from
spring mount* to nearest vertical obstacle. The diagram shows a lamp
almost completely enclosed in a box of these dimensions though :-)

Thinking about it what I didn't (foolishly) consider was the distance from
the fixture to the joist - its quite close. What's the heat tolerance of a
ceiling joist and how hot can these fixtures get? Has anyone known of these
units setting fire to things before - I imagine its a distinct possibility!

I'm starting to get a little concerned about the set up now - I would want
to have an fire in the void between my ground and 1st floor!


I think you are worrying unnecessarily. You would have to try quite hard
to start a fire with a LV downlighter. You certainly would not be able
to set light to a ceiling joist with one even if it was touching.

A lot of the clearance measurements are to give cooling to keep the lamp
life reasonable.

--
Tim Mitchell