Advice about low voltage downlights

FunkyMunkey

I'm going to put four of these low voltage downlights into my Kitchen ceiling this week, and I need a little advice.

The lights are on a loop in-loop out circuit, and I understand that I have to replace the existing ceiling rose with a junction box like this:




I have a couple of questions:

1. The junction box should be 5 amp, right?
2. If I want to put 35W bulbs in the downlights, would a 50-300VA transformer such as this one be appropriate?
3. That transformer says that the output leads should be 2m max. Does this mean that the max distance between the transformer and the 4th downlight is 2m?
4. If I want each downlight to have a seperate transformer, how do I wire it? I assume I don't just put a transformer between each light.

I've already wired some mains voltage downlights into the bathroom without any problems, but this low voltage stuff has got me a bit foxed, so any help would be greatly appreciated!

Thanks

baldelectrician

One transformer for all lights in one area is not good. If 1 thing fails then no light
Should you be living in England or Wales then you need to follow the Part P rules. This (amongst other things) specifically applies to electrical work in a kitchen or bathroom.


I would suggest you use seperate tranformers.
The fact you have to ask these questions makes me think you should get qualified help in.

You should use a competent person for the work, links below
In Scotland:
Individuals registered;
http://www.sbsa.gov.uk/register/ListAC.asp
Companies
http://www.sbsa.gov.uk/register/SearchCo.asp?T=Construction&ID=2
In England and Wales:
http://www.competentperson.co.uk

27col

I have always preferred to use a larger JB say 15 or 20amp. This gives you more room in which to make connections. As baldelectrician says, using just one transformer is not a good idea.

totalsolutions

What's wrong with 230v lamps and you can dim them as well?

Fire_Fox

You might consider Philips Masterline ES or Osram Decostar IRC halogen lamps (20W = 35W) to reduce your running costs. If you don't mind spending a little more there are 7W and 9W CFL bulbs with MR16 pins available.

sunshine54

from you drawing, the cable (where it points to 12v) will be carrying nearly 9 amps and will get too hot if standard lighting cable is used

it is suppling 105 watts at 12v (105 divided by 12 = amps)

FunkyMunkey

totalsolutions wrote: »

What's wrong with 230v lamps and you can dim them as well?

Mainly because of the power consumption. And partly for a new challenge.

baldelectrician wrote: »

I would suggest you use seperate tranformers.
The fact you have to ask these questions makes me think you should get qualified help in.

Thanks, but I'd rather do the work myself and get my electrician to check it once I'm done. If we didn't ask questions, we'd never learn anything!

As I said, I put three mains voltage lights in the bathroom just fine, but they're not on seperate junction boxes and, as you said, with if one transformer goes, I lose all the light. So I'm just not sure how to connect the transformers. I was thinking it should look something like this, with each transformer and light coming off a separate junction box:



Is this right? Considering what 27col said, should these be 15/20 amp junction boxes?

Cheers!

totalsolutions

>Mainly because of the power consumption. And partly for a new challenge.

Don't get it or do you?

35 w bulb is 35w in 12v or 230v

35w @230v = 0.015A

35w @12v = 2.91A

Higher voltage means smaller cable, smaller junction box and no transformers to go wrong and all light stay on when one fails and you can dim them.

Just spotted this
>As I said, I put three mains voltage lights in the bathroom
Very naughty

FunkyMunkey

totalsolutions wrote: »

>Mainly because of the power consumption. And partly for a new challenge.

Don't get it or do you?

35 w bulb is 35w in 12v or 230v

But surely if understand correctly, a 35w low voltage downlight will give out more light than the equilavent mains voltage light. Basically, I need far more light in the kitchen than in my little bathroom.

totalsolutions wrote: »

Just spotted this
>As I said, I put three mains voltage lights in the bathroom
Very naughty

I thought that as long as they are IP44 rated, etc., it was OK. Let me know if I'm wrong, cos I'll defo get them changed.

sunshine54

no i reckon both will have the same light output.

Fire_Fox

FunkyMunkey wrote: »

But surely if understand correctly, a 35w low voltage downlight will give out more light than the equilavent mains voltage light. Basically, I need far more light in the kitchen than in my little bathroom.
.

If you want plenty of light why are you only putting in 35W lamps? Shouldn't you have 50W lamps or, even better, energy saving 50W equivalent bulbs?