Hi there, I've recently moved into a new build with a detached garage. The garage already has a supply in SWA which terminates inside the garage in a 13A FCU, from which a double socket and lighting are run. The feed to the garage runs from a dedicated 16A MCB in the house CU and is RCD protected there too. Since it runs from the 16A MCB, why is there a need for the 13A FCU at the garage end? Thanks.