I would really appreciate some advice please, so that I can order the necessary parts and instruct my Electrician accordingly. I am installing a Ground Source Heat Pump which requires a supply using a 100ma RCD and 40amp C rated MCB. The instructions say this is to avoid nuisance tripping and the 100ma RCD is to provide protection against fire (BS7671 17th Edition). This is part of a new build conversion, so the starting point is a new BG metal clad twin 30ma RCD unit, which also allows for unprotected outways or RCBOs. This is fitted and supplies the house circuits. There is not much room in the cupboard to split the incoming meter tails, and I wondered whether we could use a spare unprotected fuseway with the 40amp C rated MCB into a separate enclosure and through the 100ma RCD to the heat pump, or is there an easier way ? With many thanks.