My dishwasher which is on a spur from the kitchen ring after some minutes will trip the main switch on the CU. However running the dishwasher on the ring from an extension plug works fine. The wiring in the sockets seems fine. How can I check the spur cable if that is where the problem lies as it seems it must

  • What is a "ring"? What is a "main switch on the CU"? Please don't use abbreviations. – isherwood Apr 4 '16 at 15:45
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    Stack exchange is a global site, he used appropriate terms for his country. CU=consumer unit (what we'd call a "service panel", "breaker panel", "distribution panel" (among other names) in the USA), "ring" is a ring circuit, which is not used in USA residential wiring as far as I know. – Johnny Apr 4 '16 at 15:58

Just guessing from the information you provided:

If there is a partial ground in your dishwasher wiring it can draw enough current to trip the breaker.

When you run it through the extension cord it adds enough resistance to limit the current so it doesn't trip the breaker.

I would suspect if it is an older machine the motor is leaking current through the insulation on the windings.

It may be time for a new one but double check the wiring just in case.

Good luck!

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    This... i'm thinking the extra resistance is in the ground wire, because the extension cord doesn't connect the ground wire very well. Which is just awesome because now instead of faulting to ground, it's putting 230v on the chassis of the machine. I would measure voltage between chassis and a known solid ground (while using the dodgy cord). You might also measure current between chassis and good ground, however that will probably trip your GFCI, er, I mean RCD. – Harper - Reinstate Monica Apr 4 '16 at 19:36

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