Declan52 Posted March 24 Share Posted March 24 Have been having an issue with my main breaker in the electrical cabinet randomly tripping out. It might have happened once a year or so this past 9 years so sort of put up with it but from the start of the new year it's happened maybe 4 times. Nothing on my fuse board trips only the main trip outside. As it's not happening frequently enough to unplug appliances and see if that helps I'm at a loss. Link to comment Share on other sites More sharing options...
Alan Ambrose Posted March 24 Share Posted March 24 Wow that shouldn’t happen unless there’s a serious short/overload. This is the main switch in the CU or do you have a breaker upstream of that? Link to comment Share on other sites More sharing options...
Declan52 Posted March 24 Author Share Posted March 24 Main trip outside in the electrical cabinet. Nothing ever trips in the CU. Link to comment Share on other sites More sharing options...
ProDave Posted March 24 Share Posted March 24 Post a photo of this "main trip" so we know what it is. Link to comment Share on other sites More sharing options...
Declan52 Posted March 24 Author Share Posted March 24 It's the breaker on the right. The left hand one is power to my shed. I have left it off to rule that out and it still trips with that off. Link to comment Share on other sites More sharing options...
ProDave Posted March 24 Share Posted March 24 That's an RCBO I bet it is earth leakage tripping it, damp somewhere. How does that connect to the house? what sort of cable and over what distance? Do you have any test equipment like an insulation tester? Link to comment Share on other sites More sharing options...
Declan52 Posted March 24 Author Share Posted March 24 I take it a cable comes from that rcbo and goes into the house, 2m approx, to my CU. Wouldn't have a clue what type of cable it is. Have a multi meter if that is any use. Link to comment Share on other sites More sharing options...
ProDave Posted March 24 Share Posted March 24 3 minutes ago, Declan52 said: I take it a cable comes from that rcbo and goes into the house, 2m approx, to my CU. Wouldn't have a clue what type of cable it is. Have a multi meter if that is any use. Get an electrician. It might not even need RCD protection on that cable depending on it's routing. Post a picture of the consumer unit in the house as well. Link to comment Share on other sites More sharing options...
Declan52 Posted March 24 Author Share Posted March 24 13 minutes ago, ProDave said: Get an electrician. It might not even need RCD protection on that cable depending on it's routing. Post a picture of the consumer unit in the house as well. Link to comment Share on other sites More sharing options...
ProDave Posted March 24 Share Posted March 24 So you already have RCD's in the CU. So I would be looking to verify the cable routing from the meter box to the CU to confirm it does not actually need RCD protection and swap that for a plain MCB in the meter box not an rcbo. 2 Link to comment Share on other sites More sharing options...
Mattg4321 Posted March 24 Share Posted March 24 Better still get it swapped for a switch fuse (you can’t achieve selectivity with MCB upstream of MCB and a fault could trip both). Obviously only if cable type and routing allows. As above you need an electrician. Good chance this is just build up of ‘earth leakage current’ if the RCD’s in consumer unit don’t trip though. Easily verified with insulation resistance testing and an earth leakage clamp meter. 1 Link to comment Share on other sites More sharing options...
Alan Ambrose Posted March 25 Share Posted March 25 Other ideas: something to do with your PV wrt RCD type being upset with residual DC? Your PV is also sitting on the left hand RCD? The RCDs are all type AC which are a bit iffy for PV (they may not trip properly). The PV should really have a type B. Or ... possible something has got at the cable between the outside breaker and the CU? I might be inclined to replace the outside RCD for the house with a switched fuse as others have said. It's worth eliminating the other possibilities though as just masking a fault isn't always the best idea. I can't see where the shed supply comes from or where the house RCD <-> CU cable is? The bit of T&E from the outside house RCD looks a bit manky. 1 Link to comment Share on other sites More sharing options...
Trojan Posted March 28 Share Posted March 28 That is a RCD not a RCBO - it has no overcurrent protection. The more concerning part is that looks like your consumer unit is being fed by what looks to be a 10mm twin and earth with no overcurrent protection (other than main fuse). How far is your CU from this breaker? 1 Link to comment Share on other sites More sharing options...
Mattg4321 Posted March 28 Share Posted March 28 The whole thing looks like a shambles to be fair. Need to get hold of a good electrician to come and give you some advice. Seems like the last few haven’t been very good, including the PV installers shoehorning a Crabtree MCB into an M2 board. OT slightly, but why are solar installers nearly always so bad? MCS scheme is a total mess imo. 1 Link to comment Share on other sites More sharing options...
Declan52 Posted March 28 Author Share Posted March 28 7 hours ago, Trojan said: That is a RCD not a RCBO - it has no overcurrent protection. The more concerning part is that looks like your consumer unit is being fed by what looks to be a 10mm twin and earth with no overcurrent protection (other than main fuse). How far is your CU from this breaker? Other side of that wall approx 2m away. Link to comment Share on other sites More sharing options...
cjsparkey Posted March 28 Share Posted March 28 It’s not fully clear from that first picture but it looks like a 30mA RCD, are you on a TT earth rod ? Normal practice would be for this to be a 100mA or even 300mA unit to provide some discrimination as it is primarily protecting the circuit as far as the internal DB. Link to comment Share on other sites More sharing options...
Declan52 Posted March 28 Author Share Posted March 28 1 hour ago, cjsparkey said: It’s not fully clear from that first picture but it looks like a 30mA RCD, are you on a TT earth rod ? Normal practice would be for this to be a 100mA or even 300mA unit to provide some discrimination as it is primarily protecting the circuit as far as the internal DB. Wouldn't have the first clue. Link to comment Share on other sites More sharing options...
ProDave Posted March 28 Share Posted March 28 4 hours ago, Declan52 said: Wouldn't have the first clue. Can you see where the green/yellow wire that exits the meter box bottom left goes to? Link to comment Share on other sites More sharing options...
Declan52 Posted March 28 Author Share Posted March 28 Down the cavity and I assume to an earthing rod. Link to comment Share on other sites More sharing options...
Alan Ambrose Posted March 28 Share Posted March 28 >>> Wouldn't have the first clue. I don't mean to be antagonistic, and I'm all for the owner / DIYer improving their understanding and learning enough not to be taken advantage of .... and I know that many on here, myself included, know that they'll do a better job of some tasks than a lot of 'professionals'. But ... there is a time when you know you need to get the advice of someone who really knows what they're doing. Now, I also know that it's often difficult to tell a good professional from a bad one and that's a skill in itself. So, this may be the time when you need to get one or more people in to quote and see whether what they've got to say chimes with some of the very good advice you have got here. 1 Link to comment Share on other sites More sharing options...
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