Strange fault we had yesterday

[littlespark]

You really put all lights on one RCD and power on the other?

i think he said it was a split board…. Sockets on rcd, lights on non-rcd side.

 

[oscar21]

You really put all lights on one RCD and power on the other?

Just one RCD for the sockets, back in the dark days lighting and cable didn't need RCD protection, I would imagine today's H&S rule makers would need a long sit down at even the suggestion of doing that today.

 

[oscar21]

Anyway the fault was a N-E short on the kitchen sockets which sat on the "faulty" RCD, it meggered clear at the time but the kitchen was being tiled so when whoever it was that tightened the sockets onto the new tiles it nicked the neutral wire. Because there wasn't anything plugged into the kitchen sockets it didn't trip and there wasn't enough current draw on the lights to make it trip either.

The only sockets that were being used were the living room ones on the left RCD, when anything was plugged into them there must have been enough current being diverted through the right hand RCD to trip it, obviously the living room RCD stayed on as there wasn't any fault on that side of the board so everyone was oblivious to it tripping anyway.

As for the test button not working I can only guess that because the neutral side of the RCD was effectively linked out, when the test fault current was introduced to the RCD some of it must have back fed back through the RCD on the neutral side to confuse it, probably right on the limit so it was hit and miss whether the button worked or not.

We repaired the kitchen fault and everything was fine and dandy again. It does make a good case for RCBO boards though.

 

[westward10]

Just one RCD for the sockets, back in the dark days lighting and cable didn't need RCD protection, I would imagine today's H&S rule makers would need a long sit down at even the suggestion of doing that today.

I misread it.