Hi i was reading an OLD post about shower consumer units and adding a circuit to an old fuse box. I have bought a 63a rcd with 50 amp mcb protection. Now in the old post it says pull the main service fuse, but what if this is protected by electricity board seals you cant do this. Can i link a feed from the cu to the shower cu without interfering with this seal. I have a henley box and understand that i can add a circuit as well as supplying the main cu with power. But how do i isolate mains power??