RCD Keeps Tripping After Powercut

[Mattywing90]

Hi all. Please be patient as I don't know much about electrics!

We had a powercut in the area Tuesday 9th November afternoon - blown fuses in the sub opposite the property caused a 70 property outage. That was resolved Tuesday evening.
The main switch on the RCD flipped once that evening, I flipped it back up and it was all OK.

Wednesday 10th I started work (from home) at 7am. I'd been working fine until 9.30am when the RCD flipped again. This happened several times that morning, but there was no pattern - anywhere from 20 seconds to 90 minutes between me flicking the switch up and it flicking down.

It got to a stage where I couldn't work so I turned everything off and unplugged everything (literally everything even the boiler, fridge, freezer, went in the attic and turned off my aerial), and with nothing plugged in at all the RCD main switch was still flipping, again with no sort of pattern and it didn't happen straight away every time - sometimes id wait minutes or an hour and it would go.

Energy supplier said not their issue. Called an electrician out, he said something (please bear with me as I'm not too clued up), there were spikes or something of 20 ohms, and that it was an energy supplier issue.

I called the energy supplier again, they sent someone out. They checked whatever they checked outside and at the RCD and said no fault found. Sods law it didn't actually flip while they were here.

I phoned the electrician who came out to me earlier that day (private electrician) and they conversed and said something about being on a TT and needing to change to PME to fix the problem, but I'd have to pay quite alot of money for this change?

It was fine since Wednesday evening. All day yesterday was fine. I woke up this morning to no power again.

It doesn't make sense to me that everything has been fine until the area power cut, and the RCD is still tripping with literally nothing connected to the circuit at all, and there's no pattern to it - there's nothing I can do to replicate it, it just happens.

Just to mention, none of the other switches on the RCD flip either, just the main one.

Should I get another electrician for a second opinion? Or can anyone please help shed some light on this?

Thank you for your time.

Matthew

 

[timhoward]

Hi. In short - get another electrician.
If an RCD is tripping either the unit itself is faulty (which can be tested) or there is earth leakage downstream of it (this can be tested).
Having TT earthing is nothing to do with it at all.
You need a decent sparks who can methodically fault find.
Unplugging everything was a sensible step to try and pin down the problem, but the fault could be on other circuits e.g. lighting, immersion heater, cooker

If you post roughly where you are then a forum member may offer their services out of intrigue, some of us like detective work!
Hope you get it sorted soon.

 

[Mattywing90]

Hi. In short - get another electrician.
If an RCD is tripping either the unit itself is faulty (which can be tested) or there is earth leakage downstream of it (this can be tested).
Having TT earthing is nothing to do with it at all.
You need a decent sparks who can methodically fault find.
Unplugging everything was a sensible step to try and pin down the problem, but the fault could be on other circuits e.g. lighting, immersion heater, cooker

If you post roughly where you are then a forum member may offer their services out of intrigue, some of us like detective work!
Hope you get it sorted soon.

Brill, thanks.

I'm in South Wales just outside of Llanelli.

The sparky that was here originally said RCD problem, but then he changed to saying an outside problem when he saw some spikes of something.

I'll have a look about and see if I can find another.

Thanks.

 

[pc1966]

It is suspicious this started after a nearby fault, but it could be many different things.

Do you have a single RCD or several? If TT earth it is/was not uncommon to have a 100mA delay RCD as the incoming disconnection means (as your typical TT earth rod will not cause enough current to flow to disconnect most over-current devices like MCB or larger fuses), and then one or two 30mA "Instant" RCDs for socket outlets, etc, that need shock protection. Knowing which is tripping might help.

But as already said above, solving problems like this is a systematic process. Typically you test the RCD(s) without any load, you remove appliances, etc, and insulation test the cables (both L and N) and that ought to determine if you have a "fixed wiring" problem (i.e part of the property). If that finds nothing, then you try putting appliances back on and checking if they trigger any fault, though it can be a sod to deal with if it is an intermittent one (e.g. fridge de-ice element that only comes on once a week or so). Some electricians might have a "PAT tester" which is used typically in commercial/inductrial/rented properties to test appliances for leakage and poor earth bonding and that can help identify any that are faulty.

However, if your whole house is on a single 30mA RCD it might be it was freed up by the fault and it is now reporting too much leakage if you have a lot of electronics, etc. Again, a competant electrician would use a sensitive clamp ammeter to measure the leackage current ofindividual circuits and/or the whole house. If it is above around 10mA then realistically you need to look at a new CU (consumer unit = fuse box) that has, ideally, RCBO where each circuit has its own RCD and MCB comined. That way no one circuit should have accumulated too much leakage, and in the event of a fault (or spurious trip on a switching surge) the inconvenience is far less as you lose power on only one out of 5-10 circuits, and not the lot!

 

[Deleted account]

@pc1966 yep that would be my guess.

@Mattywing90 do you test your RCD button every quarter or 6 months.

RCDs if they are not tested can sneeze up. I’d say 95% of RCD’s are not tested ever. So if you don’t your not alone.

so if it’s seezed up after years of non testing and your installation has gradually declined the RCD will not function as it should.

then bang! Surge, the RCD is tripped. unseezing the rcd and gettin* it working correctly again.
the RCD is now doing it’s job. It is reading an imbalance and tripping.

this is a guess, but I think it’s probable.

 

[James]

I think @SparkyChick is somewhere near you if I remember right.

apologies if I am wrong!

 

[Calebp43]

However, if your whole house is on a single 30mA RCD it might be it was freed up by the fault and it is now reporting too much leakage if you have a lot of electronics, etc. Again, a competant electrician would use a sensitive clamp ammeter to measure the leackage current ofindividual circuits and/or the whole house. If it is above around 10mA then realistically you need to look at a new CU (consumer unit = fuse box) that has, ideally, RCBO where each circuit has its own RCD and MCB comined. That way no one circuit should have accumulated too much leakage, and in the event of a fault (or spurious trip on a switching surge) the inconvenience is far less as you lose power on only one out of 5-10 circuits, and not the lot!

If their house was on a single RCD then instead of changing the whole fuseboard, couldn't they just find the circuit that's causing a lot of earth leakage (if there was one that had something around the 10ma mark like you said) and change that to an RCBO? I suppose the issue then is that the upstairs light and upstairs sockets should be on seperate curcuits so a dual RCD board would be better... But if there was enough ways in the board and enough length oon the cable then someone could just install another RCD into the board and supply the circuits accordingly.

 

[Norah Nabino]

Hi. In short - get another electrician.
If an RCD is tripping either the unit itself is faulty (which can be tested) or there is earth leakage downstream of it (this can be tested).
Having TT earthing is nothing to do with it at all.
You need a decent sparks who can methodically fault find.
Unplugging everything was a sensible step to try and pin down the problem, but the fault could be on other circuits e.g. lighting, immersion heater, cooker

If you post roughly where you are then a forum member may offer their services out of intrigue, some of us like detective work!
Hope you get it sorted soon.

Spot on, suspected earth leakage on one of the circuits and a faulty RCD most probable.