Originally Posted by
Barry
Good advice - and supports my comments made on another BMU thread.
However the current rating of the RCB fitted to the output should not exceed that of the transformer itself, so unless the transformer has a rating of 14.5kVA, the 63A rated breaker you mention is quite inappropriate, as it will only provide protection against differential currents but not for non-differential currents that exceed the current rating of the transformer.
A 750VA transformer can only supply an in-phase current of 3A, so the double-pole RCB ought not have a current rating much greater than that.