I'm currently installing a separate ring for my kitchen but I've run out of ways in the consumer unit. Currently, the immersion heater is fed from its own 15A MCB in the consumer unit. If I re-wire the water heater as a fused spur off the upstairs ring this will free up the MCB that I need (re-rated to 30A). My question is - is it acceptable to wire the spur directly at the consumer unit