odd fault...

Hi all, called out to a RCD that wouldn't reset and initially thought it would be a faulty appliance. Twin RCD CU, so turned off all the mob's on the faulty side but still wouldn't reset and oddly it would only reset when the main switch was turned off. Not seen that before...Suspected a N->fault, but where.....

The tenant had tried to unplug everything to find what it was including taking out all the lightbulbs! The only thing she couldn't unplug was an integral dishwasher but there was no isolation switch or access to socket. Above the worktop was a blanked off double socket which I suspected fed a socket beneath so disconnect the neutrals and hey presto RCD reset. So dragged out the dishwasher, thoughtfully fixed with security screws, unplugged it and reconnected the neutrals and RCD tripped again. So cables I suspected were feeding the socket were not...
Traced them to an adjacent garden room where they were fused down to feed a couple of metal wall lights. Disconnected the supply to these completely and all is well. Didn't get time to find the actual fault but all the wiring looked bodgy but at least everything else is working.

 

Hi JP, thought it was the DW but couldn't get to the socket...but above it was a blanked off double socket with a bug**s muddle of connector blocks and cables going in/out. I assumed [wrongly as it turned out] that some of the cables fed the socket to the dishwasher socket so disconnected the neutrals and the fault went away. But when I unplugged the DW the fault was still there...turned out to be lights next door fed from the ex. socket.