I have a light switch where the CPC has been used for a lighting circuit and sleeved. Previously I would give this a C3 (411.3.1.1) and leave a sticker on the Consumer Unit to advise no CPC at accessory, only use class II accessories. However, the CPC from another switch the other side of the wall has been used to earth the back box. Does this now negate the sticker, but still code as C3 ?
I recall Amd 2, now makes it unacceptable to use CPC in any circumstances, does anyone recall the regulation, and what code would you now give this?
I'm not sure much has changed in the situation you are looking at, assuming that it's a twin and earth install.
The bare cpc conductor in a twin and earth was never acceptable to use as a live core, because it isn't insulated along its length. sleeving at one end doesn't fix that.
If it were a flex cable, with an insulated g/y core, then that was commonly over sleeved in brown at the terminations, particularly by heating engineers or in boiler applications.
The regs only require a cpc to be provided at every accessory. Assuming the accessory is Class 2, then it being missing I'd only ever code as a C3. And I've used the same stickers. That was the guidance for a while when changing consumer units with old lighting cables without cpc.
There is also reg 543.6.1:
"Where overcurrent protective devices are used for fault protection, the protective conductor shall be incorporated in the same wiring system as the live conductors or in their immediate proximity."
But in your case, the cpc for an adjacent light switch would meet that. Is it on the same circuit? If so, then no code at all for earthing.
So the main issue then is how to code a cpc being used as live (presumably a 2 way lighting install?)
If it's twin and earth, I'd be veering towards C2, though if there was RCD protection throughout, a C3 might not be impossible. Obviously if anyone broke into that cable half way they would expect the bare cpc to be earthed, and all sorts of problems could follow....
If it was flex, so sheathed earth then sleeved at the end, I'd go C3.
Edit:
Found the reg re protective conductors:
514.4.2
Protective conductor
The bi-colour combination green-and-yellow shall be used exclusively for identification of a protective conductor and this combination shall not be used for any other purpose. In this combination one of the colours shall cover at least 30 % and at most 70 % of the surface being coloured, while the other colour shall cover the remainder of the surface.
Single-core cables identified by green-and-yellow throughout their length
shall only be used as a protective conductor and shall not be overmarked at their terminations, except as permitted by Regulation 514.4.3.
A bare conductor or busbar used as a protective conductor shall be identified, where necessary, by equal green-and-yellow stripes, each not less than 15 mm and not more than 100 mm wide, close together, either throughout the length of the conductor or in each compartment and unit and at each accessible position.
(514.4.3 is for PEN conductors, so not applicable within domestic installs)
