Wiring and their colours

Have you considered replacing the switches with Quinetic ones? No concerns about wiring (and no redecoration required), but some expense involved.

Thanks. Yes, I had been pointed in that direction before. Apart from it's black magic and must be the devil's work, I think I want the option of using metal switches, so need to get an earth into the switch box.

No you can't use live coloured conductors for earth & vice versa. From a safety pov it's not hard to use 12v on the switches, just need a psu & relay. I forget what the regs say about that.

Even if you sheath it in yellow/green? I could strip the insulation from one of the reds so it would look like a bare CPC.

So use the existing wiring at 12V. Are there specific colours for that?

Are you sure that's the case? I know that overmarking green/yellow to any other colour isn't allowed, but as far as I'm aware the other direction is fine. It's commonly done with three-core SWA cable - you usually get brown, black, grey and want brown, blue, green/yellow, so re-mark the black and grey with tape. (Yes, I'm aware that single-phase coloured SWA exists - it's not as easy to find as the three-phase stuff).

Mike

No need for an earth to the back box with Quinetic switches because there is no mains at the switch. And, metal switches are available. IIRC compatible with the Varilight range.

I don't think OP wants the devil as project manager :-)

But okay to reconfigure neutral to live (using brown or previously red) where there are two switches for the same light? This seems an artificial distinction.

I don't think that is actually true when talking about wires contained in a cable like T&E.

It *is* true for singles in conduit where a wire identified with green/yellow sheath can't be over marked for another purpose. (since the risk of confusion with other wires of the same colours would be very high)

So you can over mark another colour wire as an earth, so long as you do it at both ends of the cable.

Thanks. That's what I was hoping. So I can take one of my red wires and over mark it green/yellow.

What're the panel's views on using stranded cables? There are a few strands in each wire, not like flex, maybe only 5 or so strands.

Some parts of my house had/have multi-strand (not fine stranded like flex) T&E, is yours T&E or individual singles? I think 3x0.029" strand is rough equiv of

Some T&E is stranded. These days it tends to only be the larger CSAs (6mm^2 and over), but historically even 2.5mm^2 was available in stranded.

(and imperial T&E was also often stranded, and 7/.029" looks pretty similar to 2.5mm^2)

I thought I'd just check that your cable is copper since all the lighting circuits here were wired in stranded aluminium cable at some time in the sixties:

Mine is individual singles, not T&E. I'll have to count the strands when I'm at the house again.

You can get some metal clad switched that are also double insulated. So those could be used on a circuit without earthing.

How does one tell if it's aluminium, CCA, or copper? Does CCA and copper look the same?

I'm pretty sure some of the cabling is/was aluminium as one of my neighbours said that their electrician told them this. No reason not to assume that my house isn't the same. Would there be specific circuits that were aluminium in the 60-70s? Lights, rings?

Thanks. So now I have options. a) Over-mark one of the wires as earth and then ANY metal clad switch will be OK. b) Forget the earth (but I do have three wires present) and use double-insulated metal clad.

But now (in another thread) I need to ensure they're copper.

Not after you scrape it with a stanley knife.

If you're re-wiring, then option b isn't compliant with the regs, as an earth must be provided even if it's not used. It will be perfectly safe, of course, with a plastic or double-insulated switch - the issue is if it gets replaced later.

Option a would I think not be considered best practice, but does comply with the letter of the regulations. Ideally you use a cable that's the right colour to begin with, but overmarking is permitted as long as it's not *from* green/yellow to another colour. You also should mark the other two reds with brown tape, as the old colours aren't allowed on new work.

The gold standard would be to either replace the cable with new T&E, or use a non-mains switch.

Mike