came across this yesterday. called out to a park home to reported fault, RCD tripping with RFC fuse inserted. client was using socket outlet on cooker point to power fridge/freezer since night before. opened CU ( 6way wylex with 4 HRCs and 2 MCBs, 30mA standalone RCD front end). got out the trusty megger 400, IR readings on RFC of 0.1M, L-E, but, in addition, no continuity end/end on L and E. 4 years ago, he'd had an "electrician " install some extra sockets, 3 in total, spurred off RFC, every one had been fitted with no cpc sleeving, just bare cpc floating about behind sockets. first thought was possible S/C so sleeved and re-terminated all these, faults still there. now time to split RFC. guessed mid point and split. m1 leg IR >99M. other leg 0.1M. next S/O, same. next one , think i've found it. leg between 2 S/O's down. traced leg under home ( 2' cavity under, pulled it out suspecting rodent damage. IR tested loose cable-definitely low IR of 0.1M. closer inspection of cable revealed approx 6" from 1 end, L conductor broken and arcing damage burnt through cpc and char marks inside sheathing. 5m length of 2.5T/E installed, back to CU, >99M on RFC and E/E reinstated at 0.45 L, 0.46 N, 0.65 E.
just goes to show how easily you can go down a wrong path looking for the most obvious.
just goes to show how easily you can go down a wrong path looking for the most obvious.
