Downlighters

[Norry]

Can someone tell me what are the relative advantages and disadvantages of Mains against LV downlighters and can either type be used in any situation? Also these lights must generate a lot of heat, are there any restrictions on the dimensions of the ceiling space (joist size). Would I need to get approval for putting 6 downlighters in my sitting room?

 

[AliasOmega]

In personal experience i would advise to use the 240v downlighters as its in the living room. I would use the low voltage downlighters in bathrooms etc...places where steam, water would collect on light fittings.

In the past we have not considered the heat affects of these lights, aslong as there was nothing covering them from the attic / floor side of things (ie loft insulation). If you were concerned, it takes 2-3 mins to check to see if the surrounding plaster board has been affected.. Not that chalk does like..

The advantage for the 240v again the low voltage is that these can be dimmed, where the lv versions would need to have dimmable transformers.


These lights are no different than a normal light, so therefore no permission is required for fitment.

If you were to modify the house, i would inform you landlord, the owner etc for permission, as with downlighters its not a simple case of a little filler and some paint.

I would advice using 5amp junction boxes on the connections, rather than the supplied plastic connector blocks as you are dealing with a 240v connection, not a 12v connection.

Have fun..

Alias

 

[Norry]

Thanks for the reply, very helpful, the reason that I raised the question of heat generation is because the lights I want to install would be in the ceiling of the sitting room, the downlighters would of course be in the void between the bedroom floor and the sitting room ceiling. Are there any precautions one needs to take in this situation?

 

[Norry]

The permission I was referring to, was from the council building regs department as I am not a suitably qualified person as defined by the new regulations as of 1st Jan 2005.

 

[Scoby_Beasley]

We have 5" void between ceiling and floor and had no problems in 2 yrs. You can get "heat shields" (beam me up Scotty ) which fit over the inner (void) workings, usually used when you go into the loft void with insulating material.

 

[Norry]

Thanks for that Scoby_Beasley

 

[delmel]

No comparison, in my opinion low voltage every time

lamp life - low voltage much better and cheaper always use branded products.

Light source - Low voltage much crisper whiter light

Lux levels at 2mts distance (ie around work top height
Low Voltage = 1050 lux
Mains GU10 = 285 Lux

If you like changing lamps and needing more fittings then gu10 all the way

 

[Norry]

Thanks Delmel, Low voltage does sound like it has many advantages, but it also sounds a lot more complicated. I have been doing some research and I am confused about the size of cable. For example I have accessed a site that computes the size of the cable between the Transformer and the LV light, the cable size it comes up with goes from .5 metre distance between Tx and Lv needing 4mm cable, up to 2 metres distance which needs 10mm. I appreciate the reason for this (low voltage needs high Amperage) However I want to install a group of 8 downlighters which will be disbursed over quite a large area (about 2 metres * 3 Metres. I assume that the group is wired in parallel but what size cable should one use between the light fittings any chance of you pointing me in the direction of a web site that could give me a circuit diagram with cable sizes and positioning of Transformer/s or Splitter/s

 

[ban-all-sheds]

The cable sizes you've calculated are needed because of voltage drop rather than high current.

For example, with 100W of lighting at 12V, 6mm² will go to 7.8m. At 230V it'll go almost 2.9km... As another comparison for the same current at 230V (i.e. 1.917kW), 6mm² will run to 151m.

But if you are using 1 transformer per light (the recommended approach), then you can put them close to the light, and keep the run of ELV cable short.

If not, then you should consider changing your plans so that you are.

If you're still determined to press ahead, wiring from a central point should make each ELV run about 2m, say 3m to avoid diagonals - ordinary 2.5mm² should be fine for each of those. TIP - make each cable the same length, even if they don't need to be to reach, or the lamps will be at different brightnesses....

 

[Norry]

Thanks for all your help guys, I now have a much clearer idea of where I am going with this project.

PS what have you got against sheds

 

[ban-all-sheds]

That's ban all sheds as in:

not

 

[Norry]

That's OK then because I have to say I am rather fond of my old shed.

 

[delmel]

If you are still looking IBL do a pre wired fitting complete with individual lamp and transformer, just wire the mains in and loop out and onto then onto the next. What is your location Senate Electrical stock these usually