Intermittent Tripping

[MarcMCFC1986]

It seems you have a supply to your garage but there does not appear to be an separate mcb supplying the garage. Is it possible it is fed from the kitchen socket circuit & if so is there a junction box on an outside wall anywhere between the kitchen & garage? Damp in a junction box is a much more likely cause of intermittent tripping of an rcd.

Sorry, I just put garage as it's easier than explaining what it actually is. It's just a little storage room on the side of the house, where the Combi-Boiler is, and my girlfriend's treadmill. Whoever did the kitchen extension to the rear side had this put at the front of the house for extra storage. The sockets in there aren't on the kitchen circuit though.

 

[terryplumb]

If the electrician that you called would only do what you have done ,and then call in an appliance engineer ,he is either clueless or he just doesn't want to be bothered.

 

[terryplumb]

Is your combi boiler on the same mcb as kitchen sockets ? Incidentally ,every time you ran a hot tap ,the boiler would be firing up and using electricity. Just saying , as when you think nothing else is using electricity ,the boiler may be.

 

[MarcMCFC1986]

Is your combi boiler on the same mcb as kitchen sockets ? Incidentally ,every time you ran a hot tap ,the boiler would be firing up and using electricity. Just saying , as when you think nothing else is using electricity ,the boiler may be.

I'll double check when I get home - but I expect the boiler is on the circuit labelled 'Water Heater'. TBH, that's the only MCB I didn't switch off when checking the circuits as that's something I just assumed was labelled correctly, and didn't want to mess about with it.

However, I definitely wasn't running water at any of the times it has tripped off so far - once I was out of the house at work, once I was sat on the sofa watching a film, and last night I was in bed.

 

[MarcMCFC1986]

or he just doesn't want to be bothered.

I did wonder about this, but as I say - he is very reputable in the area, and lives literally a 1 minute walk (and an even quicker drive) from my house so wouldn't have been a huge burden on him to come and have a look. He seemed quite genuine when I spoke to him, but he said he had an almost identical case at weekend which turned out to be the fridge.

 

[terryplumb]

A few weeks ago a customer of mine had exactly the same problem as you. RCD tripping ,kitchen mcb turned off ,RCD doesn't trip. Combi boiler in the kitchen ,wired on a fused spur off the kitchen sockets ring final. Combi was the cause ,very slight water leak internally getting onto the boilers elecs.

 

[MarcMCFC1986]

A few weeks ago a customer of mine had exactly the same problem as you. RCD tripping ,kitchen mcb turned off ,RCD doesn't trip. Combi boiler in the kitchen ,wired on a fused spur off the kitchen sockets ring final. Combi was the cause ,very slight water leak internally getting onto the boilers elecs.

Thanks - I'll have a look tonight and check if it's on the kitchen circuit.

I have just spoken to another electrician, who I have used before, and he's said the same thing - "Check if it definitely is the fridge, freezer, or any other appliance, by plugging in an extension lead from another socket in the house and seeing if it still trips it. If not, call me back in a week or so and I'll come and have a look!"

 

[bernardgreen]

Using an extension lead to a socket on a different circuit ( MCB ) is NOT conclusive proof that the appliance is or isn't at fault if that socket is protected by the same RCD that is tripping..

 

[MarcMCFC1986]

Using an extension lead to a socket on a different circuit ( MCB ) is NOT conclusive proof that the appliance is or isn't at fault if that socket is protected by the same RCD that is tripping..

What do I do then!?

 

[terryplumb]

What do I do then!?

Put your food etc in the spare fridge and freezer ,and unplug the others. Are the Spare ones currently plugged in and working / were they during the RCD trip ?

 

[bernardgreen]

What do I do then!?

When looking for the cause of random tripping of an RCD the electrician should first check all circuits in the house for Neutral to Earth faults

This involves measuring the insulation resistance on all cables leaving the CU with Live(s) Switched OFF at the MCB and the Neutral(s) disconnected from the Neutral Bus bar in the CU and then repairing any circuit that shows less than 2 MegOhms

The last one I was involved in was water in an outside socket that is never used and has it's MCB permanently switch off. The RCD trips when a load of more than approx 2 kW was being used. The amount of load required to trip the RCD varied depending how damp / wet the socket was as this affected how much of the load current could by pass the sensor in the RCD. The socket has been full isolated. Live and Neutral disconnected from the CU, Earth left connected. No trips have occur since this was done in May this year.

 

[MarcMCFC1986]

Put your food etc in the spare fridge and freezer ,and unplug the others. Are the Spare ones currently plugged in and working / were they during the RCD trip ?

Yes they definitely work, but weren't plugged in during the RCD Trip.

Should I use a basic extension lead, or one with a safety cut out? I have one of those long, red extension reels with the safety cut out.

 

[terryplumb]

You can use any extension , but if you are not using a short one its wise to unwind it ,all your socket circuits are protected by the same RCD.
Proper testing ,as Bernard outlined above ,is the real way forward.

 

[MarcMCFC1986]

You can use any extension , but if you are not using a short one its wise to unwind it ,all your socket circuits are protected by the same RCD.
Proper testing ,as Bernard outlined above ,is the real way forward.

I agree - but nobody sounds keen on coming! I even just spoke to a domestic appliance repair guy, just to find out what he’d be able to do if we did pay for him to come out - and he said to get an electrician first! So the electrician told me to test them myself using an extension lead, or get a domestic appliance repair guy - and the domestic appliance repair guy said to get an electrician!

 

[EFLImpudence]

Perhaps they have experience of people being unwilling to pay for extensive testing when no fault could be found.

Unless you can replicate the fault at any time, it will be very dificult to find.