Borrowing cpc from local socket for lighting joint box

Welsh_sparky_21 · May 30, 2022

Wonder what’s peoples thoughts on this, upstairs lighting has no cpc throughout, 2 bedrooms on ground floor on same circuit have cpcs. Cables are wired using joint box method, Found joint box for upstairs lights with cpcs cut away, reterminated this joint box but still not getting a cpc on the circuit. Must be another joint box somewhere but unable to find it as lofts been converted. Client doesn’t want the upheaval of rewiring, there’s a socket local to the joint box. Would taking a 4mm from that socket to the joint box be okay? From what I’ve read I don’t see there being an reg against it.

stevethesparks · May 30, 2022

Make a note of it on the socket circuit cpc within the consumers unit.

pc1966 · May 30, 2022

Having any CPC is better than none!

Yes, it should be noted and of course ideally on RCD protected circuits, but fixing it via another circuit seems the least-worst option here.

brianmoooore · May 30, 2022

It was quite a common thing to do back in the decade or so after cpcs were made compulsory.
It's not ideal, but I'd only code it C3.

Welsh_sparky_21 · May 30, 2022

pc1966 said:
Having any CPC is better than none!

Yes, it should be noted and of course ideally on RCD protected circuits, but fixing it via another circuit seems the least-worst option here.

The DB is going to be replaced in the next few weeks also, one a those ones were it felt wrong but I couldn’t see anything to suggest it was lol!

Risteard · May 31, 2022

brianmoooore said:
It was quite a common thing to do back in the decade or so after cpcs were made compulsory.
It's not ideal, but I'd only code it C3.

It's compliant if done correctly so can't be coded.

brianmoooore · May 31, 2022

If you need to do it, there must still be cables associated with the circuit that don't have continuity of the cpc, or actually have one. This is not compliant with the current regs, so C3.

7029 dave · May 31, 2022

I would agree the actual circuit has no earth provided/continuity therefore it is not compliant.
IMO if the cables have earth conductors within, then borrowing cpc from another circuit is not an option, no matter how much upheaval it takes to rectify or replace.