[xani_]

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.