Likely cause of Consumer unit tripping?
Discussion
Our CU keeps tripping. The left hand side of the board has fuses/trip switches for kitchen, ground floor sockets, door bell, first floor lighting and then a larger one which is RCD Controlled Circuits.
It’s the larger one that trips and it’s an 80a Hager.
It went off early this afternoon when we had a few TVs going, washing machine was on and the Xmas tree lights but not much else. Then it went again this evening when the oven was on and pretty much immediately after I turned it back on.
The yellow “earth fault indicator” was highlighted and goes off when I flip the switch up.
It’s tripping now every 45/60mins or so now, with nothing but the living room tv on. I’ve now turned all the downstairs sockets off including switched fused spurs (yea, including the fridge!) to hear if it trips again.
I replaced a socket with a double about a fortnight ago but it’s been working fine since (it’s on a spur which was switched off for the past few times it’s tripped) but can’t think of anything that will have changed any time recently.
I guess at this time of year you’d expect it to be crazy Christmas lights but we have 2 small sets on the tree and the rest are battery operated fairy lights so I don’t think it’s that!
Any idea of likely causes before I call an electrician to find what may be something stupidly simple?
It’s the larger one that trips and it’s an 80a Hager.
It went off early this afternoon when we had a few TVs going, washing machine was on and the Xmas tree lights but not much else. Then it went again this evening when the oven was on and pretty much immediately after I turned it back on.
The yellow “earth fault indicator” was highlighted and goes off when I flip the switch up.
It’s tripping now every 45/60mins or so now, with nothing but the living room tv on. I’ve now turned all the downstairs sockets off including switched fused spurs (yea, including the fridge!) to hear if it trips again.
I replaced a socket with a double about a fortnight ago but it’s been working fine since (it’s on a spur which was switched off for the past few times it’s tripped) but can’t think of anything that will have changed any time recently.
I guess at this time of year you’d expect it to be crazy Christmas lights but we have 2 small sets on the tree and the rest are battery operated fairy lights so I don’t think it’s that!
Any idea of likely causes before I call an electrician to find what may be something stupidly simple?
earth leaks are one of the hardest things to find out. There is more than just the circuit MCB to be considered. Put it this way, you may have an MCB off when you are trying to find the fault and it trips you think it cant be that circuit because its off... Well no not strictly true.
What you can have is the current flow back down the neutral of the isolated MCB circuit to an intermittent fault and this can cause the main RCD to trip. It takes a lot of digging to find a fault like this, been looking for faults like this and finding it taking days to locate.
You will need to isolate each circuit and trace the neutral to the neutral bar for that circuit as well. if the neutrals are not identified to the respective circuit then you have to identify what neutral is associated with what circuit. so that you can delve in to it and try to locate where your issue is. Ive had split boards with everything off and the rcd tripping before. That was fun.
If you want any further information or explanations let us know....
What you can have is the current flow back down the neutral of the isolated MCB circuit to an intermittent fault and this can cause the main RCD to trip. It takes a lot of digging to find a fault like this, been looking for faults like this and finding it taking days to locate.
You will need to isolate each circuit and trace the neutral to the neutral bar for that circuit as well. if the neutrals are not identified to the respective circuit then you have to identify what neutral is associated with what circuit. so that you can delve in to it and try to locate where your issue is. Ive had split boards with everything off and the rcd tripping before. That was fun.
If you want any further information or explanations let us know....
I’ve just watched a YouTube video from a very articulate guy on how the circuit breakers only break the live and still allow flow through the neutral (makes me glad I always turn the full board off when I do anything!)
I’ll have another look at the new socket (it was a single to double replacement, not a new socket as such) but I’d be embarrassed if that’s the fault!
We’ve had a such a mix of appliances on whennit trips that I’d be surprised if it’s an overload issue (but then I’m not an electrician!) but it’s gonna be a royal pain if it’s a random leak somewhere!
I presume when you turn a switched fused spur off you’re still only turning the live off and as such the earth/neutral could still be a problem? If so, I hope it’s the new sockets that’s the problem!
I’ll have another look at the new socket (it was a single to double replacement, not a new socket as such) but I’d be embarrassed if that’s the fault!
We’ve had a such a mix of appliances on whennit trips that I’d be surprised if it’s an overload issue (but then I’m not an electrician!) but it’s gonna be a royal pain if it’s a random leak somewhere!
I presume when you turn a switched fused spur off you’re still only turning the live off and as such the earth/neutral could still be a problem? If so, I hope it’s the new sockets that’s the problem!
AlmostUseful said:
Our CU keeps tripping. The left hand side of the board has fuses/trip switches for kitchen, ground floor sockets, door bell, first floor lighting and then a larger one which is RCD Controlled Circuits.
It’s the larger one that trips and it’s an 80a Hager.
Just a point, as the way you've written that is as if they're separate - the RCD is protecting the same circuits as the circuit breakers. The circuit breakers protect against over-current and the RCD for earth faults. It’s the larger one that trips and it’s an 80a Hager.
Sheepshanks said:
AlmostUseful said:
Our CU keeps tripping. The left hand side of the board has fuses/trip switches for kitchen, ground floor sockets, door bell, first floor lighting and then a larger one which is RCD Controlled Circuits.
It’s the larger one that trips and it’s an 80a Hager.
Just a point, as the way you've written that is as if they're separate - the RCD is protecting the same circuits as the circuit breakers. The circuit breakers protect against over-current and the RCD for earth faults. It’s the larger one that trips and it’s an 80a Hager.
Yeah, RCD feeds the MCBs.
RCD compares incoming and outgoing flow and trips if they don't match, typically because it's going to earth. It's also two pole, to cuts both live and neutral.
Modern boards have two RCDs, mid age is half RCD half not, older all off one (oldest has none) photo of CU may help.
.
MCB is just current overload, so typically much less likely to go, but you have to have one for each cable or else they would all have to be huge cables. Only switches lives as said.
Sockets often only switch live, as do appliances, so unplug to be sure as it could be either side failing to earth.
It will either be something new, or something like a power brick that's failed internally, or in this weather could be something that's got damp. Outside light, pir sensor? If it's the socket you swapped, which I doubt, it's likely a trapped wire, always push the socket back then do up the screws, don't wind it in on the screws.
An hour is a while to wait, but if nothing is coming up trumps, turning all the MCBs (bar say one light/skt circuit, then try with all bar another) off has a better the 50% chance and is an easy try.
If that still doesn't do it, your next step is to take the front of the CU and start pulling the neutrals out of the neutral bar till you find it that way. They should be numbered and match against the MCB.
Dad found it was a cheap eBay spec GU10 that had fallen apart and grounded to the fitting, when it happened to us it was the gas hobs ignition circuit.
Good luck!
Daniel
RCD compares incoming and outgoing flow and trips if they don't match, typically because it's going to earth. It's also two pole, to cuts both live and neutral.
Modern boards have two RCDs, mid age is half RCD half not, older all off one (oldest has none) photo of CU may help.
.
MCB is just current overload, so typically much less likely to go, but you have to have one for each cable or else they would all have to be huge cables. Only switches lives as said.
Sockets often only switch live, as do appliances, so unplug to be sure as it could be either side failing to earth.
It will either be something new, or something like a power brick that's failed internally, or in this weather could be something that's got damp. Outside light, pir sensor? If it's the socket you swapped, which I doubt, it's likely a trapped wire, always push the socket back then do up the screws, don't wind it in on the screws.
An hour is a while to wait, but if nothing is coming up trumps, turning all the MCBs (bar say one light/skt circuit, then try with all bar another) off has a better the 50% chance and is an easy try.
If that still doesn't do it, your next step is to take the front of the CU and start pulling the neutrals out of the neutral bar till you find it that way. They should be numbered and match against the MCB.
Dad found it was a cheap eBay spec GU10 that had fallen apart and grounded to the fitting, when it happened to us it was the gas hobs ignition circuit.
Good luck!
Daniel
Thanks! Very detailed response there. I’ll check the socket I do when it gets light. Have just come downstairs and it’s obviously tripped again, the saving grace is that downstairs lights is on the right hand circuit and not the left one that keeps tripping and all the upstairs stuff is also fine!
I put the rcd back on and it tripped within a minute just now. I’ll try again with the MCBs off and gradually turning them on. Then call and electrician, I’m not taking the front off the CU - this isn’t my ball game!
I put the rcd back on and it tripped within a minute just now. I’ll try again with the MCBs off and gradually turning them on. Then call and electrician, I’m not taking the front off the CU - this isn’t my ball game!
When I fitted some new socket I used a tester like below after fitting
https://www.amazon.co.uk/Tacklife-EST03-Advanced-2...
Might help locate your problem.
https://www.amazon.co.uk/Tacklife-EST03-Advanced-2...
Might help locate your problem.
That looks useful! I’ve decided so far (on little other than the GF sockets tripping quickly) that everything can be on except the GF sockets, that loop would also most likely be the oldest wiring in the worst condition - for a bit of history our house is 1930’s and used to have timber flooring but the grand piano went through the floor so they were replaced with concrete.
Lots of the wiring is surface mounted but some is underground - I could see that being a problem (albeit it’s been fine the past 20 odd years that it was done!) so Sod’s law it’ll be some underground stuff we cant get to that will be nackered!
Might get one of those testers to have a look, and also go around and look at any areas I can think of that might be dodgy before calling anybody out. I can run power downstairs with an extension lead to keep the fridge going in the event that it drops again, and if I can’t find anything glaring i’ll call a spark We’ve got about 3 who live within 200yds so are spoilt for choice!
Lots of the wiring is surface mounted but some is underground - I could see that being a problem (albeit it’s been fine the past 20 odd years that it was done!) so Sod’s law it’ll be some underground stuff we cant get to that will be nackered!
Might get one of those testers to have a look, and also go around and look at any areas I can think of that might be dodgy before calling anybody out. I can run power downstairs with an extension lead to keep the fridge going in the event that it drops again, and if I can’t find anything glaring i’ll call a spark We’ve got about 3 who live within 200yds so are spoilt for choice!
To help to narrow down the cause...
Unplug everything in your house - TV, kettle etc, then plug one item back in and use it to see if it trips, then the next item etc...
I did this when my RCD kept tripping, and discovered it was the kettle that was causing it to trip. Plugged in a different kettle and it was fine. The kettle must have been faulty, even though it still worked.
Or try flicking everything off at the RCD, then turn one of them back on, say the ground ring main, and see if it trips. If not, turn the next one on and do the same until it trips again.
Unplug everything in your house - TV, kettle etc, then plug one item back in and use it to see if it trips, then the next item etc...
I did this when my RCD kept tripping, and discovered it was the kettle that was causing it to trip. Plugged in a different kettle and it was fine. The kettle must have been faulty, even though it still worked.
Or try flicking everything off at the RCD, then turn one of them back on, say the ground ring main, and see if it trips. If not, turn the next one on and do the same until it trips again.
PRTVR said:
When I fitted some new socket I used a tester like below after fitting
https://www.amazon.co.uk/Tacklife-EST03-Advanced-2...
Might help locate your problem.
I use this but in this case it wont help the OP. The issue is with an earth leak and that requires to be located. Every item being supplied from the affected RCD needs to be disconnected. and nothing connected at all. Then see if the RCD stays on. every item includes all the items that are connected through switchfuse spurs. There needs to be nothing at all connected.https://www.amazon.co.uk/Tacklife-EST03-Advanced-2...
Might help locate your problem.
Now reconnect every item one at a time with a good time delay to see if the new item connected causes it to trip. Once you connect an item back in and it trips then disconnect that last item and give it a good check just to ensure that its not any of the previous items.
As said it can be a long drawn out affair.
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