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..

 

[malcolmsanford]

1 Faulty RCD, so if you FiL is a sparks get him to do a ramp test

2 Accumulation of protection conductor currents (FiL) will know this being a sparky so clamp test the circuits with a clamp meter that will give you this reading

3. Elements breaking down on both the W/M and oven get the FiL to carry out an Insulation Resistance test on both appliances

 

[Deleted member 9648]

Big sigh.........have you done any IR tests......if not you should be.

 

[mike-evans]

I'm not a sparkie, just got a slight understanding of electrics, so I'm not touching anything :shades_smile:

FIL just had a meter with him last night, checked the WM element and was ok, just 1 reading slightly lower than the others, but it's not screaming out faulty...??

 

[kung]

no offence but if your f.i.l is a spark it should be an easy fix and he will know when a washing machine heating eliment goes (usually a burnt out hole) the chassis could become live.

 

[kung]

Soz just read your last post element ok.

 

[mike-evans]

No obvious burn marks on the Heating Element..

FIL is saying replace the WM element and go from there, but I'm thinking this could start being expensive by doing it this way...

 

[kung]

As said get him to do (which he will know) ir & ramp/half current tests and go from there ! if the heating element tested ok why replace it ?

 

[mike-evans]

As said get him to do (which he will know) ir & ramp/half current tests and go from there ! if the heating element tested ok why replace it ?

Exactly...
I dont want to replace parts as a trial and error process, because that could cost loads, I just want to nail the fault..

I'm just asking for views on here, are 5 year old RCD's known to be faulty at this age? at any age?

 

[malcolmsanford]

Mike yes RCD like everything else break down ..............................get your FiL to ramp test the RCD, or if he can't do that then as a sparks he must have a known decent one he could fit to see if it is the RCD .

 

[mike-evans]

I'm finding it hard to beleive 2 appliances have established faults on the same day....

So, how does this sound to the experts?
Is it possible that anoth of my appliances etc...has a slight leakage and then by switching on the WM or Oven will take it up over the 20mA to trip the RCD?

I'm gonna unplug every appliance tonight and just plug in the WM and try it, then unplug the WM and try the oven...

 

[BlueToBits]

Elements leak more current to earth as they get hot. If you test when cold you may find it's OK, but leaking may occur when at running temp.
With the element removed, connect up the IR leads and set to constant test. heat the element by moving a blowlamp along the element until it glows dark red. When you hit the position of the fault the IR will drop like a stone. It is quite possible that both elements are faulty.

 

[mike-evans]

Ive unplugged everything and tried the oven, and it trips...
Everything unplugged tried WM and it trips...

Im just doing basic tests as havent got any testers etc...here.
So surely this says both appliances at fault or RCD....

 

[Knobhead]

Get rid of the father outlaw and get someone that knows what their doing.

Sorry if it seems harsh, but to start spending money on an unproved fault is shear folly!

 

[telectrix]

there's also the possibility of a N-E reversal on the circuit. if f-i-l knows what he's doing, ne should have solved it by now. if not, then it's time to get on the dog&bone.

 

[kung]

Heard any knawing ? is the oven on a plugtop ? is it a split load twin rcd ? if so try swopping the socket circuit or oven circuit with comp ie 32a mcb on the other rcd and see if that holds ! if not see if F.I.L can get another RCD !
Best of luck buddy !

 

[kung]

You could have as said an over sensitive RCD that is caused by a wack from a faulty WM or Cooker etc etc. Dont get me wrong when i say this but is your F.I.L a qualified spark ? or a D.I ? or calls himself a spark because theres no law against saying your a spark if your not (alot of people have been had by diyers) but if he is a spark i will give him credit for knowing(should) know what he's doing but just seems odd to change the WM elem just as a trial and error method when it is an easy item to confirm or eliminate really.

 

[tombennetts]

have you installed anything new recently?

 

[mike-evans]

Yes he is a qualified spark, has been for about 30 years since he done his apprenticeship, he does not work on house electrics, hes a electrical engineer in a heavy plant/factory, but it all uses the same principles...He only had a meter with him, so unable to PAT test etc...This is the issue i got, I want a definate answer before I wack loads of money by just fault finding..One thing that stood out, we disconnected the WM element and run it, it run fine-Element at fault? But with this running, I turned on oven and it tripped the RCD..
Nothing has been recently upgraded/changed, exactly the same as it was 5 years ago..
The board only has 1 RCD, so I dont know what this tell you?

The bit that confusses me is, ok if the WM Element is faulty, that would make the RCD tirp-ok! but, cant understand why/how it would affect the oven??
My trade is Mechanical, so i might be applying Mech principles/ways of thinking here which could be miles of topic, and just confuses everything thing, so just excuse this..

My local Electrical call out company want £50 to come an have a look. for this I can replace both oven and WM elements..but might not be the fault.

 

[mogga]

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