I installed a new split load CU today. RCCB tripped and the fault was traced to the downstairs ring main. A test with a multimeter showed no continuity across the neutrals at the CU end, however the circuit worked when installed on the non RCCB side of the CU. I can only presume that the fault has existed for some time and has been brought to light by the new install. Does anyone have any suggestions as to how I can go about locating the fault. I've removed some of the socket fronts in the kitchen and checked the wiring there. If I remove all the others on the downstairs ring main and find no problem is my only course of action to start lifting the floor? Any assistance most gratefully appreciated.