The breaker is the part of the circuit for the other circuits you'd have something like gen -> circuit A -> main bus -> circuit b-> load

The breaker is the part of the circuit for the other circuits you'd have something like gen -> circuit A -> main bus -> circuit b-> load | main fuse/switch | outside So loads on circuit A would not be protected by any fuse but ones at circuit B would. Also circuit A would allow full generator amps to the devices there, no RCD protection either.