RCD adaptor plug and CU RCD

L

live4weekends

Originally posted this on the Appliance forum, probably by mistake since its more relevant here I think

I have an intermittent tripping with the RCD in my Consumer Unit. I think, but can't prove, its the dishwasher which is now about 5 years old and we have hard water etc.. I had thought, mistakenly I now think, that I could prove it was the dishwasher by using a plug in RCD adaptor for the dishwasher. Trouble is, now if there is a trip they both (the RCD adaptor the dishwasher is plugged in to and the main RCD in the CU). My house also has a main RCD between the meter and the CU, this rarely trips at all.

I've had a quick look through the forums but I can't see an answer explaining how I can prove 100% its the dishwasher, or the washing machine. Obviously we could stop using it, but sometimes its several week between trips and I would want the wife to ruin her hands by getting the Fairy out :) I could also plug in the dishwasher to a circuit on the non-RCD side of the CU and see if the main RCD trips, but again I wouldn't want to do this for weeks at a time.

I'm guessing that even if I get a spark in with his test equipment it would only show positive if the dishwasher had a continual earth leak, as opposed to an intermittent one caused by water on the wash/dry cycle.

Any ideas?
 
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As you have found, 2 RCDs usually means they both trip (or sometimes only one, but it is not really predictable which one it is).
However the adaptor plug for the dishwasher will only trip if there is a fault on whatever is plugged into it. A fault elsewhere would not cause that one to trip, only the main one in the consumer unit.
This suggests it is the dishwasher causing the problem, unless the adaptor is the type where removing the power causes it to trip.

To be certain - plug the RCD adaptor into a socket, plug a small appliance into it (e.g. a table lamp). Switch on.
Now switch off at the socket only, then switch the socket on again. Does the lamp come on - or do you need to press the 'reset' button on the RCD again?
 
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Your best bet will be to find a socket that is not on the consumer unit's RCD. Dioes your cooker switch have a socket on it too?

Plug an extension lead into there with your RCD adaptor. Run the dishwasher. If the RCD trips its down to Comet for a new dishwasher.

OR (better). Find a sparky with an insulation tester or PAT tester and have him test the dishwasher.
 
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L

live4weekends

hmmm...just tested it. damn, the RCD needs resetting when the power is switched off so this isn't going to help me!

does anyone know of an RCD adaptor that doesn't require this?
 

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