Hi all,

For context this is a TP, N & E socket circuit supplying a machine. The machine supplier has recommended that the circuit be supplied from a 125A MCB, however the machining cabling is not supplied from a cable rated to 125A.

I'm being told that a cable size doesn't need to be sufficiently sized for the upstream breaker, when there is an overload unit downstream and that the cabling would withstand a short circuit disconnecting quickly

Is this true? I can't find anything explicit in the regs confirming either way, aside from Ib<In<Iz