cable choice for new downlights

[sidb]

Hello,
I want to install a run of 6 mains (GU10) downlights into a previously unlit area. The downlight fitting instructions say that the lights are double insulated and must not be earthed. My question is what type of cable to use: the usual twin-core and earth (where the earth will not be used), or is just 2-core cable OK (if there is such a thing as 2-core cable, or is it always flex?). It is not likely that the lights would be changed to some other type, so is an earth wire necessary?

Thanks in advance for any advice.

 

[philrosenberg]

I have been told the best way is to run regular twin and earth to a junction box for each light then use heat resistant cable to go to the light fitting. You can use cable with earth but at the light sheath it then terminate in chock block. This way if the lights are ever replaced by something thaty does need earthing it is there and the cables do not need replacing

 

[jj4091]

Heat proof cable not required as fittings will have heat proof sleeve on the wires to the connector(usually).

 

[Steve]

Just get a load of 3 core 1mm² flex and loop it fitting to fitting (1.5mm² is a very tight fit / impossible in some fittings) Terminate the earth wires in a seperate terminal block, maintaining continuity to the last fitting.

 

[sidb]

Thanks for the suggestion, but I don't see how 3-core flex offers any advantage over twin-core+earth cable. Being the lazily person I am, I don't want to bother joining the earth wires together all the way along the light run.

Possible reasons that I can think of for needing an earth wire are:
a) regulatory
b) safety (in this case I am using double-insulated fittings)
c) future-proofing, for changing or adding light fittings later on.

And as far as I can tell, (c) is the only valid reason.

 

[Mighty Quinn]

Just get a load of 3 core 1mm² flex and loop it fitting to fitting (1.5mm² is a very tight fit / impossible in some fittings) Terminate the earth wires in a seperate terminal block, maintaining continuity to the last fitting.

That's what I use. ( Heat resistant ). It's much easier to connect up, apart from the obvious benefits. Anyone who has seen the effects of T & E overheating will understand why.

 

[bernardgreen]

I have been told the best way is to run regular twin and earth to a junction box for each light then use heat resistant cable to go to the light fitting.

Provided the JB is accessible ( through the hole when the light is removed ) this is the best way. Any heating problems are removed. The stiff PVC cable is clear of the lamp and a far more flexible cable to the lamp makes fitting it much easier.

 

[RF Lighting]

Anyone who has seen the effects of T & E overheating will understand why.

 

[Pensdown]

Your photo library never ceases to amaze me

 

[con1_uk]

How did that happen please?


Thanks.

 

[RF Lighting]

It was sat on the back of a GU10 downlighter.

It was not the only cable found in this state, in the same room.

The DLs were installed by "pros"

 

[sidb]

Can ANY cable withstand direct contact with the back of a GU10 bulb? I had a quick look for heat-resistant cable, plus a search for the surface temperature of halogen bulbs, and it looks like the answer is going to be no.

If I use flexible cable, there is no guarantee that the cable won't drape across the back of the bulb as the fitting is pushed up into the mounting hole. At least with T+E cable, the stiffness of the T+E cable should prevent this happening.

I have stopped wondering about whether I need an earth wire, now I'm worried that I'm going to start a fire.

 

[davy_owen_88]

Do you have access to the room above where you intend to fit the lights? You could just lift some floorboards to ensure the cables are where they should be...

 

[RF Lighting]

I use silicone insulated flex for rewiring theatrical lanterns, and this will withstand the heat of a 2000W lamp

At over £160 for a drum of H05SRF3G1.5 it is not justifiable for use on downlighters

 

[bernardgreen]

I use silicone insulated flex for rewiring theatrical lanterns, and this will withstand the heat of a 2000W lamp

At over £160 for a drum of H05SRF3G1.5 it is not justifiable for use on downlighters

From RS Components a reel of 25 metres 0.75m mains silicone insulated is £22 plus VAT