We've come across an installation where there are 6 x 10A MCB-protected circuits on a small distribution board. Each circuit is wired to a 20A switch on a gridswitch plate and then wired out to a single socket outlet for each.
The CPC has been wired as a single run from the DB to the first socket, and is then daisy-chained to subsequent sockets. the CPC is the same size as the line conductor. All circuits are wired in singles in containment.
Whilst this is clearly not the best way to do it, from my reading of the regs it is actually compliant. 543.1.2 refers to protective conductors common to two or more circuits, and requires that these are calculated or selected to the most onerous/largest of the circuits. 543.1.4 permits selection of the protective conductor size in accordance with table 54.7, which this appears to be compliant with.
So, whilst clearly a bit rough and not best practice, is it actually a non-compliance?
Jason.
