I have a small outbuilding that has one socket in it, for a tumble dryer (no lighting) The cable supplying the socket is 2.5mm T+E run underground in a plastic duct, over a distance of approximately 15 feet. In the consumer unit the cable is connected to the RCD side of the split load consumer unit via a 16A MCB. Now for the problem, the RCD started tripping out and carried on tripping until the MCB for the outbuilding was switched off. This indicated a fault on the outbuilding circuit. So, I removed the socket to check for moisture ingress and found none. I then left the socket disconnected and tried to re-energise the circuit, but the RCD tripped again. To me, this indicates a cable fault. It will be very difficult to replace this cable and I would like to know if I can transfer the cable over to the non RCD protected side of the consumer unit, and then install an RCD protected socket in the outbuilding. I would also like to 'megger' the cable before transfering it in the consumer unit and would like to know what an acceptable insulation value would be. Please can you tell me if what I propose is ok?