Minimum CPC wire for singles

[Alexander Lamaison]

I've heard it said (possibly on here) that when wiring singles the CPC conductor must have the same size as the line conductor, but I'm struggling to find evidence that backs this up. If 2.5mm T&E can have a

1.5mm CPC, why would the situation be different for singles?

The closest the regs come to agreeing is 543.1.4 and table 54.7, but surely I'm allowed to use the adiabatic equation (543.1.3) to arrive at a possible smaller CPC size, or not?

Alex

[Andy Wade]

It isn't. Using a same-size single CPC is common practice (at least for the smaller sizes) but isn't mandated. There is a minimum size of 1 mm^2 of course, except for the cores of multicore flexibles.

Yes you can. Same-size CPC avoids the need for any calculation: provided you meet the voltage drop requirements fault protection of the line and CPC is assured. Strictly speaking any use of a reduced CPC requires an adiabatic calculation but in most cases the outcome will be obvious - and in any case you can use the standard circuits in the OSG.