RCD tripping - why?

[mike-evans]

Hi all. Over the weekend I've had a strange electrical fault bugging me..

The washing Machine is tripping out the RCD, no other breakers..also the oven does the same, trips RCD but no other breaker???

Me and my father in law (he's a qualified Elecy) done a little digging on it last night, disconnected the Heating element in the WM and run it, and it run fine (seems ok as it's not heating the element)...
Then I turned the oven on (with WM running with Element disconnected) and it tripped the RCD...

If I unplug the WM and turn on the oven, it will trip..
If I turn the WM on and let it run for a minute or so, it's fine until it starts to warm the Heating element..

I find it a massive coincidence that both appliances that have independant circuits both have faults?

I'm thinking the RCD is at fault, as it protecst both of the circuits?

Can anyone shed some light on this?

House electrics are just over 5 years old, with no issues at all until now..

 

[Rockingit]

If it were me, I'd think about:

1) RCD's deteriorate through activiation, ie the more they trip (or are tested to trip) then the more unreliable they become - so ever decreasing circles.

2) Personally, I would get the leakage clamp meter out and see how much current is leaking BEFORE the suspect appliances are turned on. It's perfectly normal for healthy appliances to leak a little bit and the cumulative affect can cause issues.

3) Identify another circuit not on that RCD (assume you have a split board) and plug the washing machine into that side (via an extension lead) and see if the other RCD trips. Not the most technical of diagnostics I admit, but still effective. If you were careful to do so, you could also run up the cooker element this way too.

4) Both of these appliances are in the kitchen, right? So there is another common factor - the room itself. Any DIY recently? Any floods or leaks? IR the circuits thoroughly - FIL should be able to do this.

5) Thus far, you've not spent a bean. But if this helped, you can make a Help for Heroes donation!!

 

[Rockingit]

WM Element turns faulty as it heats up and expands this causing the fault to develop By time its cooled down and contracted faults gone so when you put meter on it Hey presto No fault as for oven sounds like element on it YES it can happen 2 things going faulty around the same time

I liked the old wind-up 4kV meggers for this!!

 

[mike-evans]

One thing I can add is, I use the tumble Dryer on the same ring main as what the WM is using (same 2 gang switch), what is the norm for a Tumble Dryer, 3KW?

does this confirm RCD is ok, and confirm faulty Oven and WM?

 

[kung]

A ramp test would tell you as said how is the oven wired ? plug in socket ? own radial ? do you get on with a neighbour ? if so see if you can plug the WM etc into an extension lead and pop it in next doors nearest socket ! some ovens run off a plug top and the hob is the item on its own circuit. what sort of oven is it ? did your F.I.L. test that ? what did he say regarding the oven ?