KITCHEN SOCKETS tripping RCD

[dpm_dpmartin]

The Electrician visited today... no success so far and he's going to start tomorrow by removing all sockets and doing testing that sounded like what you guys have described.

Just to answer a couple of things...

I turned on the outside lights and they work fine - so are on the OUTSIDE LIGHTS MCB.

I have already found and isolated the integrated fridge freezer - as mentioned by someone else - and am currently running that from a socket in the living room via an extension.

I am frustrated by the situation that each time the RCD trips it takes out the boiler... it obviously restarts, but I am always nervous about boilers, so I did ask him if it was possible to put the boiler onto its own RCBO - he implied it was indeed possible. If it is possible, I'd like to do that.

What he did that was different to me, was test the RCD itself, by turning off all MCBs, then pressing the yellow button and turning on all circuits one by one, until it tripped again on KITCHEN SOCKETS... he's satisfied there's nothing wrong there, but mentioned that test was telling him something about "earth leakage". Oh, and he also checked behind the kitchen wall to ensure the room behind had no nails or screws in it - it hadn't, although we noticed a screw up by the coving in the living room (not within a "safe space" area) and I said to him that I thought a lot of wires do go places via the ceiling space rather than the floor - something to think about.

Beyond that he said the things I'd done so far, with guidance from here, were exactly what he would have done at the start... he reckons that it's something more fundamental. More to come, it seems.

 

[dpm_dpmartin]

The OP still hasn't confirmed whether the outdoor lights are still working, or not?

In the OP's situation, with his claimed lack of knowledge, I would at least try releasing the faceplate screws on the failed sockets, to see if the RCD would then successfully reset - that would at least move his issue a stage forward, towards diagnosis.

It's kinda out of my hands now. I do care about learning approaches, but I care more about the final solution now that I've decided to pay-up.

That an Electrician visited and didn't fix it within five minutes is kinda gratifying (in a perverse kind of way). I now realise I likely did all I could.

 

[terryplumb]

So the RCD trips as soon as the MCB for kitchen socket circuit is switched to on ,but does the MCB also trip ?

 

[dpm_dpmartin]

The first is definitely true.

The second I believe so.

It's been a few days since I can claim seeing KITCHEN SOCKETS on at all, I can't be 100%. I think he turned all MCBs on and left the RCD down at one point (we were talking things through while he was testing, sorry). I'll pay more attention upon his return.

 

[Harry Bloomfield]

What he did that was different to me, was test the RCD itself, by turning off all MCBs, then pressing the yellow button and turning on all circuits one by one, until it tripped again on KITCHEN SOCKETS... he's satisfied there's nothing wrong there, but mentioned that test was telling him something about "earth leakage". Oh, and he also checked behind the kitchen wall to ensure the room behind had no nails or screws in it - it hadn't, although we noticed a screw up by the coving in the living room (not within a "safe space" area) and I said to him that I thought a lot of wires do go places via the ceiling space rather than the floor - something to think about.

That just confirms the RCD will operate, it doesn't confirm it operates within spec..

If the sockets are fed down from the ceiling, then there is the extra possibility, that a floorboard nail, or screw, has works its way into one of the cables.

 

[ericmark]

As an electrician, two things I want to know, one is the RCD OK, and two is the fault solely due to the kitchen ring final, so cover off the consumer unit, and test the RCD here showing at what mA it trips at, also test it does not trip at 15 mA and does trip at 30 mA and at 150 mA within 40 mS etc, but the test shown is the main one with this fault, how many mA will make it trip, assuming OK then also test the insulation resistance using this tester so know if faulty or not, one may also test what the circuits which do not trip the RCD are leaking but at this stage not so important, so should now know how many MΩ both line to earth and neutral to earth.

Once one is sure there is a fault, next is to find it. Methods vary, we at first look for the easy, which seems unlikely in your case to find anything and the next is step by step hunt, the latter depends on the reading the insulation tester found, a 2 KΩ fault would need one to use the insulation tester while splitting the circuit into smaller and smaller sections, but with say a 2Ω fault the can likely use the multi-meter on buzzer, leaving it buzz, while disconnecting things, far faster if one can hear when the fault has been cleared. And using a 1.5/3/or 9 volt battery one can remove screws while under test, but using 500 volts, one does not want to be touching items while under test.

 

[ebee]

That just confirms the RCD will operate, it doesn't confirm it operates within spec..

Correct.
However , in my humble experience, an RCD that operates usually operates correctly and an RCD that does not operate does not operate at all.
(Others may have different experiences ).
That is why we test an RCD on its own with nothing else influencing it.
Then we test circuit by circuit (with the proper test gear) and find which circuit(s) are suspect in any way.
Once we find faulty circuit(s) then we investigate it further and find the location of the fault(s) and correct it (them) .

If the installtion is one "Front End" RCD then that is the most difficult .
Dual RCDs still difficult but a little easier.
If we have a split board with One RCD for some circuits and not for the other circuits them those non RCD circuits might or might not have an RCD for each circuit (RCBO).
Finally, an RCBO for each individual circuit is the easiest option and is the least inconvenient option in the case of a trip.
When RCDs started to become popular they were relatively expensive and they were mostly optional and as years went on they became cheaper and often mandatory for most circuits.
Some of us are old enough to remember the norm being rewireable fuses and extremely rare we might consider an ELCB (Earth Leakage Circuit Breaker) and have the choice of current operated or voltage operated models - the current operated ELCB became known as an RCD.

Divide and conquer

-

 

[dpm_dpmartin]

The Electrician is back and I've shown him some pictures from the 2017 renovation which clearly show the wiring is all in the ceiling space, but he said he would have found that out when he took the first faceplate off anyway. I also have measured, by eye, where that suspicious screw in the wall is and we've concluded it's not near any wiring. So, that's something. I've left him to get on with things... rather than hover over him.

I will speak to him about getting the boiler on an RCBO, though. An improvement coming out of a fault-fixing exercise is always nice to have.

 

[EFLImpudence]

So the RCD trips as soon as the MCB for kitchen socket circuit is switched to on ,but does the MCB also trip ?

The first is definitely true.

The second I believe so.

Can you please state whether the MCB does trip or not.

This is fundamental to finding the fault.

 

[dpm_dpmartin]

I visited again and it seems like he's got a handle on things... the kitchen has pretty much been taken apart, the washing machine is out, but he's told me that the wires leading to the isolation switch for the washing machine socket have historic evidence of mammalian rodent damage - historic because there are no droppings observed - and the same wires were tightly pressed against the rear wall and vibration from the machine, and the state of the wire, caused the issue to arise out of nowhere.

This is all very credible as the washing machine has been there since it was originally installed, before my purchase, back in 2010 / 2011 and if there was ever an issue with rodents (the evidence is taping around the wires) it was before my time.

He's already reached the point where some above-counter sockets will now work. He's gone to have lunch and get some specific junction boxes he wants for the cut / new wiring behind the washing machine.

He confirmed the issue is not related to anything the Tenants did and the consumer board has been working exactly as it's supposed to. He's agreed to talk to me about putting the boiler and Nest thermostat on its own RCBO later.

 

[dpm_dpmartin]

What is pleasing to learn, like I said before, is that this was always going to be beyond my capabilities... I thank everyone here for their input.