DIYbanter - View Single Post - Joining CPC's in Ring Main & Other Wiring

In article ,
(Mike Hall) writes:
"Andy Wade" wrote in message ...

Yes, provided that the circuits in question originate from the same consumer
unit or dis-board, and that the CPC for the ring remains in the form of a
ring.

Andy, but therin lies the crux of my question! - If I've joined all 3
cpc's, (2 halves of the ring and the lighting circuit) then the cpc
for the ring is now not a simple ring in itself.

I think that's fine. I can't quite remember exactly what the regs say,
but there are cases of ring circuits where the CPC clearly isn't a
ring, such as when it's provided by conduit or the outer of mineral
insulated cable. I think the important point is the CPC impedance at
any point must be no worse than if it was a ring, or you are going to
have to do calculations to ensure you are still withing allowable
earth fault loop impedance for whatever your protective devices are.
No amount of extra connections between CPC's can make it worse, actually
quite the opposite.

--
Andrew Gabriel