Electric sockets tripping - mystery! Need help finding solution

[Bear]

I have checked around 1/2 the sockets in the kitchen but will check the remaining ones this weekend. Yes it is the same side of the CU that trips every time - only the sockets and cooker hood appear to be protected by the RCB. As for substitution I'm not entirely certain what you mean.

The trip can be reset first time after a trip, but last night I switched off the MCBs and then the RCB and unplugged all appliances. Then I switched on the RCB and MCBs. No problem until I started to plug in devices. As more were plugged in the RCB tripped (I couldn't isolate it down to either a device or socket). Resetting the trip wasn't always possible first time - some times I had to wait 10 seconds or more before it would reset.

[Dave Plowman (News)]

Have you got an ordinary DVM? If so try measuring the resistance between earth pin and neutral, earth pin and line on all the suspect appliances. Obviously with them unplugged - but switched on if they have a switch on them. And report the results. Not as good as using an insulation tester - but can often show a fault.

[Bear]

=A0 London SW

Excellent idea. I do have a DVM - will try this upon returning home this evening.

[John Rumm]

If you feel comfortable working in the CU, then you can also test for E N shorts in the circuit that way as well. With everything disconnected (i.e. unplugged) from the circuit, disconnect all wires of both ends of the ring circuit, and measure resistance (with the meter on its highest range) between the various ends. You should be able to verify that there is no shorts between any conductor. You can also verify that you have ring continuity between both ends of each conductor while you are at it (low ohms range). If you can gustimate the circuit length you can compare the results with: