Turning Socket on Trips RCD Occasionally

[theindicator]

Hi, in our kitchen we have an integrated washing machine and dishwasher which are both plugged in to a double socket that sits inside the adjoining cupboard under the sink (but away from the pipes). We keep the devices switched off at the socket when not in use and occasionally when we go to switch the washing machine on at the switch the RCD in the CU trips, but then we could switch it off and on multiple times after and its fine. CU just has a single RCD for all circuits and a MCB. It's only the RCD that trips. Within the kitchen we have a circuit for the Cooker and a separate one for the sockets.

The heating element of the washer has been checked and is ok, all wiring internally and externally looks ok and I have used an insulation resistance tester on the plug and all appears ok so nothing jumping out with being an issue with the washing machine…or dishwasher either.

So I then checked the socket itself, all wiring is connected up to all terminals fine, everything inside the box is dry so no moisture either.

So not sure what else I can check? Is there a way to check the wiring that is powering the socket to see if that has a problem? Its all wired from behind the units so not sure where its being fed from but will be on the kitchen sockets circuit somewhere.

Thanks

 

[EFLImpudence]

To verify - it never trips when you turn on the dishwasher?

 

[theindicator]

To verify - it never trips when you turn on the dishwasher?

I don't believe so. I have only had it happen twice to me, one for sure was the washing machine (I was actually plugging the plug into the socket that was already switched on at the time), the other i'm unsure. But yesterday the wife switched the washing machine on and it tripped.

First thought was is it the socket or wiring that's the problem. Appreciate that may not seem teh cause if the dishwasher doesnt have the same effect though.

I also wondered if it was water related. The bathroom is above the kitchen and we had a small flood in there a couple of months back which resulted in a couple of small spots becoming visible on the ceiling but can't think where water may have got to electrically further down into the kitchen as there is nothing between the kitchen and bathroom floor as far as I know until you reach the sockets in the kitchen wall.

 

[conny]

Is the washing machine plug a moulded one that came with the machine or one that you can fit yourself?
There may be a 'whisker' off one of the leads in the plug causing it to track, but I would have thought the MCB would trip.

 

[theindicator]

Is the washing machine plug a moulded one that came with the machine or one that you can fit yourself?
There may be a 'whisker' off one of the leads in the plug causing it to track, but I would have thought the MCB would trip.

It's a moulded plug

 

[Harry Bloomfield]

The heating element of the washer has been checked and is ok, all wiring internally and externally looks ok and I have used an insulation resistance tester on the plug and all appears ok so nothing jumping out with being an issue with the washing machine…or dishwasher either.

Just to be clear - What sort of tester is that, which you used?

 

[theindicator]

Just to be clear - What sort of tester is that, which you used?

Not sure of the exact one, but after a quick google it looks a bit like this and ran it at 250v across the earth and neutral pins. Also used a multimeter on the heating element of the washer with the ohm setting

 

[EFLImpudence]

Sometimes - we don't really know why - RCDs trip when switches are operated.

You could just try a new socket to eliminate it.

 

[opps]

Have you tried running it off an extension lead (plugged in to another socket on the same ring)?

 

[theindicator]

Sometimes - we don't really know why - RCDs trip when switches are operated.

You could just try a new socket to eliminate it.

Yeah I guess that's my only option for now unless anyone has any other ideas to check. The plugs wont reach any other sockets due to their location so will have to be a messy extension lead into another socket for now I guess!

 

[theindicator]

Have you tried running it off an extension lead (plugged in to another socket on the same ring)?

Jinx!

 

[Harry Bloomfield]

Not sure of the exact one, but after a quick google it looks a bit like this and ran it at 250v across the earth and neutral pins. Also used a multimeter on the heating element of the washer with the ohm setting

That should do it, but really ought to be on the 500v setting, except you said across the E & N pins, pins of what, and what reading did you get?

A multimeter is not really of much use, for testing the insulation of anything. Use your insulation tester, between either the L to E, or N to E.

A possibility, is that the trip might be due to filters, on the input to your items. Filters, by design, have leakage. Add several of them on a single RCD circuit, and it might prove enough to cause a trip at switch on.

 

[EFLImpudence]

Ah, of course - what about just swapping the WM and DW plugs and see what happens.

 

[theindicator]

That should do it, but really ought to be on the 500v setting, except you said across the E & N pins, pins of what, and what reading did you get?

A multimeter is not really of much use, for testing the insulation of anything. Use your insulation tester, between either the L to E, or N to E.

A possibility, is that the trip might be due to filters, on the input to your items. Filters, by design, have leakage. Add several of them on a single RCD circuit, and it might prove enough to cause a trip at switch on.

It was on the pins of the plug itself as its a moulded plug. Reading was 1 M Ohm (mega ohm is it?)

Yeah that was also another thought about whether I just have too many things under one RCD now

 

[Harry Bloomfield]

It was on the pins of the plug itself as its a moulded plug. Reading was 1 M Ohm (mega ohm is it?)

Yep, Meg/Million.

Always test, all the possibilities - L to E, N to E, L to N.

Yeah that was also another thought about whether I just have too many things under one RCD now