Discuss Insulation resistance problem in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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Hi all,

I have done an insulation resistance test on a ring final circuit today and when I do L - N I'm getting 0.01Mohm. Checked all sockets for loose connections but found nothing. I plan on splitting the ring tomorrow and testing each individual length from socket to socket. It's gonna be a long day but just wonder if any of you more knowledgeable people's might have any suggestions. If I am remembering correctly when I did N - E it was about 0.26Mohm which again is mighty low an I think L - E was 0.01Mohm again. This makes me think there is a problem with the line conductor somewhere. Lots of investigating ahead. Any advise is most appreciated.

Cheers

Mark

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First thing to check is that there are no appliances still connected to the ring. It's also possible that there could be a hidden switched fuse spur feeding some external lights or similar.

Why did you look for loose connections if the IR is low? I don't follow that logic at all?

It shouldn't be a long day to find it, and there's no need to test each length of cable individually, just follow basic fault finding procedures and you will have the fault located pretty quickly.

Separate all conductors at the CU, then estimate where the middle point of the ring is likely to be and separate the conductors there, then test each half of the ring to find which one has the fault on it.
You can then make the good half of the ring safe to energise and then identify which sockets are live and which are dead, stick a bit of tape on the dead ones so that you know where they are.
Then split the faulty half in half again at the rough middle point, make the good half of that safe to energise and then find which sockets have come back on, removing the bits of tape as you go.
In the end you will be left with one or two sockets with bits of tape on, the fault is there or between those sockets.

The chances are you will find an appliance still connected or something like that.


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Thanks for the advice. I am fairly new to this. My logic on checking all sockets was thinking if maybe a loose conductor was close to another but not touching as I am aware this would either cause RCD to trip with cpc fault or MCB to trip with short circuit. I will do what you suggested and see what comes up.
Thanks

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Thanks for the advice. I am fairly new to this. My logic on checking all sockets was thinking if maybe a loose conductor was close to another but not touching as I am aware this would either cause RCD to trip with cpc fault or MCB to trip with short circuit. I will do what you suggested and see what comes up.
Thanks

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Are you a trainee? If you are then you should be doing this under supervision of an electrician.

If not then you seriously need to consider whether you are competent to be doing testing, that answer clearly shows you haven't got a clue what you are talking about and are probably wasting someone's money who is paying you to take random guesses rather than taking a professional approach.
 
No not a trainee but just qualified and I expect you probably have low opinions of middle aged blokes doing fast track courses to try and change their life to be able to provide for their family but I personally don't worry about what people think of me. I paid good money to be taught something that I hope to get much better at. It's also my house that I'm testing so not wasting any ones time or Money. I may make some wrong decisions but isn't that why this forum is here? To help people like myself understand where we go wrong so we don't do it again. I totally understand if none of you want to help but just trying to learn more.
Thanks anyway

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Also are you saying that if CPC touched either neutral or line conductor it wouldn't create an imbalance between L and N therefore tripping the RCD. Also if L touched N that wouldn't cause a dead short therefore tripping the protective device. If I am wrong about these then clearly I don't have a clue. Just because I am uncertain of why I am getting low readings from an IR test you say I am incompetent.

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No I don't think I am competent to the extent of an experienced electrician but I am only just qualified so wanting to become as competent as possible. This clearly was the wrong place to come for advice.

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No I don't think I am competent to the extent of an experienced electrician but I am only just qualified so wanting to become as competent as possible. This clearly was the wrong place to come for advice.

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No its not mate, stick around,you get the odd silly comment but there is loads of knowledge on here :smiley2:
 
I think you need to understand the limitations of the course you went on, and how little you actually know. And it's not even competence "to the extent of an experienced electrician" because you're probably less competent than a first year apprentice.

You will learn a lot on here and get plenty of advice unless you keep getting shirty.
 
Nope none of those either. There is four sockets in one of the bedrooms that are on a spur with a SFCU and I was thinking maybe whoever put that there might have spurred off the downstairs ring. Will have to check that out for sure.

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As ever with fault finding approach it logically. If you don't you will find you end up chasing your tail...Davesparks has given you some good advice. Let us know what you find :)
 
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I think you need to understand the limitations of the course you went on, and how little you actually know. And it's not even competence "to the extent of an experienced electrician" because you're probably less competent than a first year apprentice.

You will learn a lot on here and get plenty of advice unless you keep getting shirty.
The whole reason I joined this forum was because I read a lot of posts and everyone seemed to be really helpful apart from a couple. So though I would join in. I've even joined in a couple of discussions here and there but the moment I ask a question I'm being called incompetent. All I want is advice not abuse and I've not once been shirty.

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