Low Voltage Recessed Lighting

Galway_guy_33

I'm about to install recessed lighting in my kitchen. I've checked with my electrician and he has told me the circuit breaker is suitable to take the new load so im ok on that front.

I'm looking for advise on the best way to wire the lights with as few junction boxes as possible. Please see the attached diagram. Heres what im thinking:

One junction box for each light, looping the 1.5 twin & earth ( dont need the earth so i'll connected them together in each box with sleving). Both cables from the transformer enter the same junction box.

So inside the junction box i'll have two separate strip connectors:

1 connecting the mains voltage wires and another connecting the 12V power. Is this ok?

I also need to keep the transformer away from the light fitting and ensure no insulation is near both the light fitting and transformer. In order to do this i was thinking about screwing in two pieces of timber bridging between the ceiling joists i.e. making a box 10 inches by 11 inches or so which contains no insulation.


Is this the best way to do this?

Reyman

Maybe you're clear on this already but why do you need a junction box at each light ?

Why not loop the low voltage cables in and out of the light connectors to the next light and so on?

Galway_guy_33

I cant loop the 12 volt wire as each light will have its own transformer instead i loop the mains voltage wire in each junction box connecting it to a seperate tranformer each time. Both wires from the transformer are fed into the same junction box... I guess this is the bit im kinda worried about.. having two seperate strip connectors in the same junction both one connecting 230 volts wires and the other connecting the 12volts wires.

Reyman

I see what you mean. I agree that's not a great idea, someone could come along later and not realise the junction boxes have 220V and 12V cabling in them. Not advisable I'd say

I have those lights and 4 or 5 lights are fed from the one transformer so there's no problem. Can you not use them?

FX Meister

Loop your 1.5 in the connection boxes, connect both loops of 1.5 in each connection box into one side of your connector and the mains cable from your transformer into the other side. It depends on the rating on the transformer as to how many lights can run from it. I would have one transformer for each light.

patrido

why can't you connect directly from the traffo to the light fitting?

FX Meister

Maybe he wasnts to keep the low voltage connection in the junction box for extra protection?

jonnner

There is no need to put the 12V connection which is going to the light in a junction box unless there is a risk of water getting near it. Just put insulating tape around it.

The idea behind keeping the insulation away from everything is for heat dissepation, so boxing it in is a bad idea. Usually Electricians just push the insulation to one side.

Galway_guy_33

The light fitting didnt come with any connectors just a cable with the bulb fitting on one end and two bare wires on the other end... looks like the one below:


http://www.batteryspace.com/ProductImages/led/wire-connector.jpg

The Transformer is a sealed unit which has a 220V mains supply and 12volt outlet cable.

So rather than having two seperate junction boxes at each light fitting i connect them in the same box on different connector strips.

I bought outside GU10 lights which came with an extra fitting which attached to the light fitting frame this had a connector strip inside a little cover. But the ones i got for inside just came with the wire and bulb connector as show above this is the reason i've ran them back into the junction box.

Maybe i need to buy something like this seperatly:

http://www.alertelectrical.com/product.asp?typeID=62&subID=79&prodID=2152

Reyman

Just to correct my earlier post:

"Why not loop the low voltage cables in and out of the light connectors to the next light and so on?"

This is incorrect because the low voltage bulbs (12V) are carrying quite a high current - 5 amps for 60 watts. If 4 lamps are cascaded in series then the 1.5 mm2 cable has to carry 4I = 4x5 or 20 amps - far too high.

Each lamp must be fed individually from the transformer to keep the current down and prevent overheating.

Apologies, Iwas thinking 220V!

patrido

Galway_guy_33 wrote:

The light fitting didnt come with any connectors just a cable with the bulb fitting on one end and two bare wires on the other end... looks like the one below:


http://www.batteryspace.com/ProductImages/led/wire-connector.jpg

The Transformer is a sealed unit which has a 220V mains supply and 12volt outlet cable.

So rather than having two seperate junction boxes at each light fitting i connect them in the same box on different connector strips.

I bought outside GU10 lights which came with an extra fitting which attached to the light fitting frame this had a connector strip inside a little cover. But the ones i got for inside just came with the wire and bulb connector as show above this is the reason i've ran them back into the junction box.

Maybe i need to buy something like this seperatly:

http://www.alertelectrical.com/product.asp?typeID=62&subID=79&prodID=2152

ah... ok. in that case you could use a chocbox. a bit smaller than an obo box and has the required flex grips
http://www.tlc-direct.co.uk/Products/CHOCBOX.html

did you buy them over the internet? if so, are you sure that the light fitting meets the standards required by the etci national wiring rules? lv lamps create an awful lot of heat, and need high quality fittings. if in doubt, etci have a code of practice for recessed lighting, or better still, consult a reci/ecssa electrician.

EDIT: actually that one doesn't have flex grips... i'm sure i've seen them with grips, but can't find them now.

micks

Reyman wrote:

Just to correct my earlier post:

"Why not loop the low voltage cables in and out of the light connectors to the next light and so on?"

This is incorrect because the low voltage bulbs (12V) are carrying quite a high current - 5 amps for 60 watts. If 4 lamps are cascaded in series then the 1.5 mm2 cable has to carry 4I = 4x5 or 20 amps - far too high.

Each lamp must be fed individually from the transformer to keep the current down and prevent overheating.

Apologies, Iwas thinking 220V!

That current is on the secondary side of the trafo not primary and so there is not 20A load on the 1.5mm
You can get larger rated transformers (100w,200w,300w etc ) that can have more lights off each trafo.
There are transformers that have 2 or 3 connections on the primary side and so there is no need for JB on the 220v(not sure of the make though)

Reyman

micks wrote:

That current is on the secondary side of the trafo not primary and so there is not 20A load on the 1.5mm
)

The OP is using 1.5mm2 cable on the secondary as far as I can understand. But your general point is right - he should use a higher rated transformer with several outputs.

This avoids a whole lot of JBs, which are potential points of failure and a complication if you have to revist the installation later.

FX Meister

Galway_guy_33 wrote:

So rather than having two seperate junction boxes at each light fitting i connect them in the same box on different connector strips.

Just put the bulb connector cables into a porcelain connector with the LV output from the transformer.