sunken ceiling lights and fibreglass problem/question

happyhero

Hi, I am a retired building services man, which means I am a qualified electrician, and no I don't have part P because I am retired. Despite being a qualified electrician I have never done a job like this at work as the work was more industrial than this sort of domestic type here, hence the question.

I am fitting some recessed mains voltage fire rated fittings in my extension. The void in the ceiling is approximately 6" to 8" deep with a plasterboarded ceiling and fibreglass wool insulation of about 4" thick. The hole I am cutting for the fittings is 62mm, ie not big enough to get my hand in.

I don't know what to do about the fibreglass, the whole is very small to successfully cut a hole in the fibreglass to allow the lamp to slot into or even have a gap round it and I am not sure if it is ok to just push the lamp in and allow the wool to rest on top of the fitting. These fitting are fire rated and so don't need a hood and I know that mains halogen get very hot but not sure how hot this will make the back of the fitting and if it will be ok touching. They are about 5" deep, so my guess is they wont be very hot at the back, and I don't think the wool would easily catch fire but I don't want to test the theory.

Can anyone advise me, as to what is supposed to be done in this situation and what would an electrician actually do, ie sometimes there is a method you should use and sometimes electricians do it a different way because it makes more sense. I am not after bodging it but I don't want to go to any unnecessary work.

Any advice appreciated.

roger56

Recently fitted 12 such things in a new build.
The instructions provided with the 90 minute fire rated downlight
(240V 50W max) stated:

- 100mm void depth (note this is dependant on the actual unit used)
- Where possible ensure there is adequate free air ventilation.
- the "luminaire" may be directly covered with continuous mineral insulation.

It also recommended using aluminium reflector replacement lamps to reflect heat forward.

I checked the ones I had after 30mins and they were warm to the hand.

Mine were similar to these:
http://www.tlc-direct.co.uk/Main_Index/Lighting_Menu_Index/Lighting_Downlights_Index/Downlights_Mains_Voltage_Halogen/index.html

Hope that helps.
Added:

I'd also note these had nice big sturdy connector blocks that made fitting and testing easy. They easily accepted two 1.5mm T+E cables.

happyhero

Hi roger56, thanks for your reply, yes they are the ones and from TLC too and they come with the aluminium lamps, but I connected one up on a test lead and I was shocked how hot they got , so I have gone for removing as much fibreglass as possible around the lamp which is what an electrician advised me to do. I left the light on for a couple of hours hanging from a ladder, and I could not touch it. Makes me wonder what they would be like if I hadn't used the aluminium type lamps.

I know the fibreglass is probably nonflammable but touching against it every day and cooking it every day is a bit too much like testing it out which scares me.

You are right though it does say in the instructions with the lamp that it may be directly covered with mineral insulation, which I am a bit surprised at now that I have tested one and seen how hot it gets.

roger56

happyhero wrote:

....
You are right though it does say in the instructions with the lamp that it may be directly covered with mineral insulation, which I am a bit surprised at now that I have tested one and seen how hot it gets.

I wasn't happy with that either - I assumed at worst case someone may buy cheap none aluminium bulbs which would get hot. So in spite of the instructions I do remove the insulation away to allow air circulation.
Also fit at least a couple of inches from joists (can be challenging to get spacings right!!).

roadster1

Why not use these and save on the lecky bill as well as running cooler I understand

happyhero

roadster1 wrote:

Why not use these and save on the lecky bill as well as running cooler I understand

Cheers roadster1 for your input, yes I have seen them (expensive though) and they are of interest to me for the future as the fittings I bought came with lamps, but have you used them?

The reason I ask is that they are energy saving lamps and most of the energy saving lamps I have seen don't give off such a nice light even compared to a ordinary GLS bulb, also some take a while to get to full brightness which I am not keen on. What are these like, do they give off a light anything close to a Halogen's lovely light? Also can they be dimmed?

roadster1

No, I haven't used them.....yet. I intend to decorate the kitchen in the near future and will replace the existing fittings.

My observations for what they are worth,

Replacing just the GU10 bulbs for energy saving equivalent wasn't an option as they protrude further than a standard bulb and don't look right.

Yes, they will take a few moments to "warm up"

Yes the quality of light will be different but I'm gradually replacing all the bulbs in the house with energy saving equivalents and you do get used to it.

These are the only fittings I found that tilt.

"The Megaman recessed downlight with 11w GU10 is product code 771530 (white). The fittings tilt to a maximum of 30 degrees. The cut out size is 70mm, with the size of the fitting being 80mm width by a depth of 86mm"

Hope this helps.

roger56

The GU10 flourescent lights are a good energy saving idea, but like most of the LED ones the light colour is very white and not so "comfortable".

You really need "warm white" LED versions. I know that such LEDs in component form are available from Luxeon, and have just found this
article on such LEDs (not yet packaged in GU10 format!!!!):
http://www.buildingtalk.com/news/lum/lum102.html

So far the other LED types I've tried are too white or too dim (LEDs tend to be more directional).


Hmmm, think there may be one available here but at £22.99 it's expensive:
http://www.yourwelcome.co.uk/acatalog/LED.html

This also looks promising at £17.99, it's 120deg coverage also:
http://www.initiallights.co.uk/product_info.php?cPath=21&products_id=93

ozskin

the megaman spots are very poor spots, for decreased heat and a much better light than gu10 use 12v low voltage also lamp life should be much better and solves the prob of using the right type of lamp

roadster1

ozskin wrote:

the megaman spots are very poor spots,

Thats very interesting, in what way? I haven't seen any of these used anywhere yet. What is the problem with them?

roger56

For info, I measured the following temperatures (after 5mins) on a
JC94002 (JCC lighting) 90 minute fire rated GU10 downlink using
a Sylvania GU10 50W lamp:

Side of metal case next to point where mounting clip attached: 49C
At air vent exit on top of metal case 73C

Instructions state Fire rated and suitable for all timber joist ceiling variants up to 90minutes.

The very last comment for these in instructions reads:
Do not install this product on new plaster and Artex ceilings.
(I've just lost the plot... )