Domestic Lighting cable sizing

[Welly]

Our house was built 2003 and all the lighting wiring is 1.5mm T&E.

I fitted 12v transformers upstairs running downlights but have started to convert them all to mains power LED's.

I was terminating 6 x downlights last weekend and it was a pain getting two cable ends into the fittings' terminal blocks when wired in parallel.

Started thinking that 6 x 5 watt LED's only rates at 30 watts!

I've ordered some 1.0mm T&E for the next batch - 1.0mm is ok surely? there's no regulation against it?

[Bailes1992]

Your cable size is dictated by the size of your protective device. If you have a 6A MCB then I would suggest you'd be just fine with 1.0mm.

It wouldn't surprise me if in the near future we start using smaller sized circuits for lighting. With LED's they are often well oversized. Only issue is the mechanical strength of cable when pulling it in.

[Welly]

Yes the house is divided into 4 x 6 amp MCB's for Lighting.

I did consider the strength of the cable, I'm not 'pulling' though - one tip I picked up on YouTube was when using 1.0mm then bend the ends over double before inserting into the terminals as they can break when screwed down hard.

[Bailes1992]

If you're doing up terminations to the point where cables are breaking then you're doing them up too tight

[steve_earwig]

They do that here, a good fitting screwdriver and give it some. I'm always surprised they don't sheer the screws off.

A quick check of screwfix... 1.0mm twin 'n' earth is as low as it goes (at the moment). Lighting always used to be 1.0, I'm not sure where they get this 1.5 malarkey but it's all that's available here.

Can't you wire it up with speaker wire?

[PeterN]

Used to be 1/044 or 3/029 in my day - but that was a long time ago. With the advent of LED lights the power required is very much less now, but as Bailes says you need cable which will carry the max current of the circuit.

Peter

[steve_earwig]

It do make sense for the fuse to be the weakest link (ho ho), rather than the wire turning into a heating element.

[Welly]

Dubious calculation alert:

I have 4 x 6 amp MCB's for lighting only.

4 x 6 amp x 240v = 5760 watts max power.

5760 watts/5w LED lamp = I can have 1152 downlighters - I think that will be enough

Bailes - I saw one of those 'electricians day' vids where he was called to a new-build apartment in that London, he was moaning about how the sparkies had placed 1.0mm straight into the terminal and screwed it down, the 1.0mm is fairly weak and he sees a few break as soon as you move the fitting/switch so bending then end over double would help a lot I guess.

[steve_earwig]

I've remembered now, the sparkies here crimp ferrules on the wires, then crank 'em down. Yes, one more potential poor connection/fire risk...

[stevewalsh]

Regardless of the power draw for your LED lights, It needs to be done to the building regs, Someone in the future may fit other types of lighting.

[Bailes1992]

I've remembered now, the sparkies here crimp ferrules on the wires, then crank 'em down. Yes, one more potential poor connection/fire risk...

I suspect that's because they're using fine stranded cables. I actually quite like using 6181B style cables with ferrules on the ends, they're very robust and tough.

[steve_earwig]

I suspect that's because they're using fine stranded cables.

You'd think so but no.