Downlighting - construction and wiring of new ceiling

[Muzungo]

I'm planning a complete refit of my flat, and want to install a new ceiling in the living room to house various lighting circuits.
I haven't got much room to play with, so I can only afford 120mm space, but the spec I'm aiming for is:

1 (dining area): architectural cove lamps, s12d, 8 lamps, 400-800 W total
2 (dining area): general lighting: LV MR16 wide beam: 2 x 50 W
3 (dining area): spot lighting: LV MR16 narrow beam 3 x 20 W
4 (dining area): wall-washers: LV MR16 narrow beam 8 x 20 W

5 (living area): general lighting: LV MR16 wide beam 4 x 50 W
6 (living area): spot lighting: LV MR16 narrow beam 4 x 20 W
7 (living area): wall-washers: LV MR16 narrow beam 6 x 20 W

All circuits dimmed via RF in-line dimmers (Rako or similar)

Am I okay running that sort of load off an existing 5A ceiling rose ?

Another concern is heat. The total area of the ceiling is about 22 square metres, but given the low clearance (100mm, allowing for 20mm of plasterboard or similar), I'm worried I'll be chewing through trannies like there's no tomorrow.

Any tips ? Clearly I should be aiming to space the trannies and fittings as much as poss, but should I perhaps be thinking of introducing ventilation gaps ? (The dining area will have air circulation through the coving, but the living area will probably be flush)

Do more expensive trannies generate less heat ? I'd love to be able to afford Auroras, but I'm to keep withing budget, I'm probably going for these:
http://cgi.ebay.co.uk/25-LOW-VOLTAG...hZ020QQcategoryZ41499QQtcZphotoQQcmdZViewItem

The ceiling itself is concrete slab, so no fire regs worries (also, top floor).
Also, should I use plasterboard, or ply ?

I've seen people talk of downlighters which conduct the heat down into the room, rather than up - what should I be looking for ?

Many many thanks to anyone who can help out

 

[bernardgreen]

Add the wattage of all the lamps and divide by 230 and that will tell you how many amps these light will take.

If it is more than 5 amps you have the answer. And remember there will be other lights in the house on the same fuse so you may be well over the maximum permitted ( safe ) current for the existing wiring.

 

[Taylortwocities]

You should take some serious advice about this.

I do not fully understand the subject in depth but there are very specific recent regulations about ceilings in multiple occupancy buildings. As far as I understand it the fire break is the ceiling itself and the building regs make no reference to the fact that the construction above may be concrete or whatever.
The void will be filled with combustable materials and the ceiling will have been specifically designed to prevent fire spread between flats. You will wreck the fire resistance between dwellings if you make swiss cheese out of the ceiling.

You should make yourself fully aware of the requirements of The Building Regs - Approved Document B - Fire Safety
and in particular
section B3 compartmentation - 8.2 then Appendix A - table A1, item 3 Floors (a) -domestic floors 30min fire rating.

Further, do I gather that a plywood ceiling is in your thoughts? Did you know that wood is a combustible material? check out your downlight spec and I think you'll find you cannot run many 50W downlights on a flammable surface -you'd have to reduce lamp to 35W.

You may need to think again about fire-rated fittings......

 

[Dippy]

I'm in the process of planning new lighting for my own house so I might be able to provide some useful comment.

My first reaction is that 1120W (or more) is one hell of a lot of power for a 22m2 room! That's about the same size as my lounge, into which I am intending to install only about 250W of lighting (I will use a combination of halogen and CFL downlighting). I haven't designed my kitchen lighting yet, but I doubt I'll fit more than 400W and that's a 28m2 room.

I know that you are planning to have dimmers, but you still need to consider the full load and to me your seems very high.

Yes you can buy halogen lamps which reflect heat into the room. However my guess is that they will still cause your ceiling void to turn into an oven.

The better solution will be to use Philips Masterline ES or Osram IRC lamps which are more efficient (but more expensive) than standard lamps. The manufacturers suggest that a 35W lamp is as bright as a 50W standard lamp.

 

[jimsky007]

I calculated your total load to be approx 1.5kw divide this by 230 and you have a current of 6.5amps approx so no you cannot run it from the 5 amp supply you will have to put in a new 6amp supply to this section and remember they will have to be RCD protected if you cannot get the cable 50mm below wall surfaces
I would suggest you use gyproc for your ceiling as it is much cheaper and a lot easier to handle and allows you to fit your the lights stated
I would also recommend you use proper heatproof cable from the lights to the junction box

 

[ban-all-sheds]

Jim - it's been 2 years since the OP asked his question - I expect he's done the job by now.

 

[Chri5]

I'm not sure if T2C read the comment about you being on the top floor !


Most spot fitting have a footprint of over 100mm height, that will be a problem when you have only 100mm to work with

 

[ban-all-sheds]

Chri5 - it's been 2 years since the OP asked his question - I expect he's done the job by now.