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Kuba

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I’m doing some tests on my board at home in order to prepare it for an upgrade. It’s an old plastic GE board with no rcd protection. Doing continuity of ring final circuit on the main ring. When it comes to end to end tests at the consumer unit I’m getting no reading between neutrals. All good between L-L and E-E. Figure of eight and I’m testing L-N on sockets and all readings come good (0.45-0.50 ohms) in every room. What could be the cause of this? ? Neutrals terminated badly at a socket somewhere? Rodents? JB?

Would taking one leg of ring out and looking with a Martin dale be a quick solution to find it before I start looking by splitting the ring?

Insulation resistance was L-N >299Mohms, L-E >299Mohms but N-E only 8Mohms.
 
No point doing the cross-connections (figure of 8) if you don't have rn continuity. That needs sorted first. Probably loose connection on the neutral in a socket-outlet or screwed onto insulation. So it might be worth checking all connections including the phase and cpc.

I presume you've checked that the neutrals aren't mixed up in the DB?
 
most likely is that a N has come out of a socket terminal. any case that's the easiest check to do, just by inspecting each outlet. if not, then short 1 end L-N at CU, go round sockets mesuring L-N resistance. this will track the fault location. or you could do N-E.
 
No point doing the cross-connections (figure of 8) if you don't have rn continuity. That needs sorted first. Probably loose connection on the neutral in a socket-outlet or screwed onto insulation. So it might be worth checking all connections including the phase and cpc.

I presume you've checked that the neutrals aren't mixed up in the DB?

Yes I have tidied up and dressed all cables so I’ve got a pretty clear view of what’s what.

Someone told me that disconnecting one leg and checking each socket with a Martin dale socket tester is an easy and quick search. Should I give this a go? Otherwise I’ll follow what @telectrix suggested ?
 
You suggest disconnecting one end of the ring, leaving the other powered, and going round with a Martindale to find the which are live L-N and which are dead. Yes, that will work, however it is a live test and where possible, dead tests with a resistance meter are often safer and possibly easier. If you short N-E at one end in the board and go round testing for continuity, you can open any suspect points immediately to check, without having to isolate, inspect, close up, re-energise and start testing again. The break could be at the last socket with continuity, the first one without, or somewhere between, so it could be a nuisance having to re-energise each time to use the Martindale.
 
@kropaske suggestion seems the best quick test.

Or do you have a wander lead? A really simple option is to connect it to one of the N (with both isolated) and go round looking for which socket has N continuity or not, where it changes is (at least one) of the fault locations.
 
You suggest disconnecting one end of the ring, leaving the other powered, and going round with a Martindale to find the which are live L-N and which are dead. Yes, that will work, however it is a live test and where possible, dead tests with a resistance meter are often safer and possibly easier. If you short N-E at one end in the board and go round testing for continuity, you can open any suspect points immediately to check, without having to isolate, inspect, close up, re-energise and start testing again. The break could be at the last socket with continuity, the first one without, or somewhere between, so it could be a nuisance having to re-energise each time to use the Martindale.

Thank you @Lucien Nunes for the advice ? I found it quite fast too.

No reading N-N end to end on a ring main 350BBB62-D619-428B-9F7D-949399732121 - EletriciansForums.net
No reading N-N end to end on a ring main A56FF968-9B00-4D04-9D09-63F2255D8EF6 - EletriciansForums.net
 
Don't know why they had to uncover the Busbar , BUT should have powered off anyhow as good practice.
Always good to get into that routine of safety first
 
It’s hard for me to do any testing in my house recently as my wife is working from home and can’t disconnect the power for too long ?‍♂️

Couple of days ago I checked IR on each circuit and I had 30M ohms on each ring and light circuit separately, smokes were >299M ohms (I only have four circuits).

I did notice in the past that some cables been chewed by rodents so this could be the reason. Rewire is unfortunately not gonna happen as we just finish decorating the whole flat ?

I have no rcd protection on anything and I want to add an rcd or ideally change the whole board with rcbos. Do you think it’ll just trip out my board?
 
I have no rcd protection on anything and I want to add an rcd or ideally change the whole board with rcbos. Do you think it’ll just trip out my board?
A 500V test giving 30M won't trip anything out, that is perfectly reasonable.

Given how cheap RCBO boards are now you really ought to go for that, and SPD, and have pretty good protection of things. RCD also provide a bit more protection against future rodent-damage possibly starting a fire, etc, as an leaking current on T&E is likely to end up on the unsheathed E and so tripping the RCD side of things.
 
A 500V test giving 30M won't trip anything out, that is perfectly reasonable.

Given how cheap RCBO boards are now you really ought to go for that, and SPD, and have pretty good protection of things. RCD also provide a bit more protection against future rodent-damage possibly starting a fire, etc, as an leaking current on T&E is likely to end up on the unsheathed E and so tripping the RCD side of things.

I would have changed the board if I could but that would mean I’d have to interrupt my neighbours supply (cut out has two separate lines but both neutrals go into same enclosure) so pulling out both fuses at once to do it safely would have been the way? Not to keen on bothering them (they’re both teachers and school online so need power on)... and I could just add an rcd and put a lock on my main switch, quick and easy hopefully ?
 

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