Borrowing a cpc from another cct for lighting cct coded C2 in PE magazine codebreakers.

hertzal123 said:

Thought this was allowed under 543.1.2  if the borrowed cpc was of adequate size?

But not permitted in general under Regulation 542.6.1 unless ADS is provided by RCD alone:

542.6.1 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.

So if you really do "pinch the cpc from another circuit", it does not comply in many TN systems.

Chris Pearson said:

If you have wired in singles in galvanised conduit, and used the conduit as cpc, it is shared by all the circuits.

And is the "same wiring system", so there is no problem ... no code required in that case ... but this doesn't apply to pinching the cpc from another circuit wired in T&E etc.

OlympusMons said:

Also you are allowed to share CPCs in 543.7.2.201(c) between two identical circuits having high protective conductor currents

But in that case, each circuit would have a cpc of its own (to comply with Regulation 542.6.1), along with a "reinforcing cpc" from another circuit to meet the additional requirements of Regulation Group 543.7 ?



At the end of the day, though, a cautionary note for those who think the guidance quoted in the OP is poor advice. What if someone doesn't realise the cpc is taken from another circuit. The circuit from which the cpc is taken is isolated for maintenance, leaving some of the installation intact, and a fault occurs, and someone disconnects the cpc to work on it ... I have only at this point to quote CDM Regulations and Designer's Duties to bring the whole discussion back on an even keel ... only "pinch a cpc" if it's well documented and signposted.

gkenyon said:

Chris Pearson said:

If you have wired in singles in galvanised conduit, and used the conduit as cpc, it is shared by all the circuits.

And is the "same wiring system", so there is no problem ... no code required in that case ... but this doesn't apply to pinching the cpc from another circuit wired in T&E etc.

That's why I chose galvanised conduit. I think that you might well want a separate cpc for each circuit in PVC conduit (or other containment), but you would have to be very careful to identify which is which at the DB.

gkenyon said:

Chris Pearson said:

If you have wired in singles in galvanised conduit, and used the conduit as cpc, it is shared by all the circuits.

And is the "same wiring system", so there is no problem ... no code required in that case ... but this doesn't apply to pinching the cpc from another circuit wired in T&E etc.

That's why I chose galvanised conduit. I think that you might well want a separate cpc for each circuit in PVC conduit (or other containment), but you would have to be very careful to identify which is which at the DB.