Finding a Neutral Earth fault

Thing is, John, if he was doing this for anyone else, he'd be in a bit of bother now - because, regardless of the cost to himself, he'd have to find the fault. Had he done the absolute minimum testing before a cu swap (i.e. Whole Board IR Test), he'd have known there was a fault 2 minutes after getting his screwdriver and tester out. Then he could have arranged to find the fault BEFORE fitting the new board.
No argument about any of that. However, my point there is that horse has already bolted, so nothing much is to be gained, at least in relation to this OP, by trying to close the gate - except in a headmasterly sense!

Kind Regards, John.

I don't think it is too late.

Maybe for this fault - but what other faults might he have missed that just 'switching on' the power hasn't shown up.

Maybe with the right criticism he'll have second thoughts and run the tests that he should have done in the first place.

Do you think, if he hasn't done a simple IR test, that he's done 'continuity of CPC'?
Or Zs?
Polarity??
RCBO times?

I have my doubts - he's probably just swapped the boards over and hoped for the best.
 
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I don't think it is too late. Maybe for this fault - but ....
That's the point. He's asked for advice in locating this fault. That was my one and only point.

.... what other faults might he have missed that just 'switching on' the power hasn't shown up.
As you imply, who knows - but, again, the OP hasn't asked about anything else.

Maybe with the right criticism he'll have second thoughts and run the tests that he should have done in the first place. Do you think, if he hasn't done a simple IR test, that he's done 'continuity of CPC'? Or Zs? Polarity?? RCBO times? I have my doubts - he's probably just swapped the boards over and hoped for the best.
I share your doubts, but one has to decide what the forum is about. A specific question has been asked. If BAS were awake, he'd produce a reading list, tell the OP he was not competent (or something ruder!) to be doing what he was doing (with a few mentions of the law, as well) and would not give an answer to the question. That's one approach. To not contribute to the thread at all is another approach. To attempt to answer the OP's question is another. I guess it is for each of us to decide what is right for ourselves!

Kind Regards, John.
 
I agree, to a point, John.

I did try to help with the question - without getting on my soapbox (as you know I sometimes do).

But it does get a bit annoying, and I can't blame some posters for criticising, when people come on here asking for help after they've done everything wrong......why don't they ask first....and do it right??

If he'd said..

I'm about to do a CU swap for my boss, but initial testing has shown low IR between Neutral and Earth......what's the best way to trace this fault?

Everyone would have been happy and he'd probably have got more replies.
 
On second thoughts, John, I have to disagree with these two posts:


Thing is, John, if he was doing this for anyone else, he'd be in a bit of bother now - because, regardless of the cost to himself, he'd have to find the fault. Had he done the absolute minimum testing before a cu swap (i.e. Whole Board IR Test), he'd have known there was a fault 2 minutes after getting his screwdriver and tester out. Then he could have arranged to find the fault BEFORE fitting the new board.
No argument about any of that. However, my point there is that horse has already bolted, so nothing much is to be gained, at least in relation to this OP, by trying to close the gate - except in a headmasterly sense!

Kind Regards, John.

I share your doubts, but one has to decide what the forum is about. A specific question has been asked. If BAS were awake, he'd produce a reading list, tell the OP he was not competent (or something ruder!) to be doing what he was doing (with a few mentions of the law, as well) and would not give an answer to the question. That's one approach. To not contribute to the thread at all is another approach. To attempt to answer the OP's question is another. I guess it is for each of us to decide what is right for ourselves!

Kind Regards, John.

The reason being - this isn't 'Private Messaging' - Ask Doctor Electric

This is a Forum - and lots of other people read the replies - so I think it's important to point out what someone has done wrong, as well as answering their question.

And John, I should warn you, if you find a way to disagree with this, then you really will argue about anything. :)
 
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I agree, to a point, John. I did try to help with the question - without getting on my soapbox (as you know I sometimes do).
Yes, I noticed, and was slightly surprised by the lack of any 'comment':)

I But it does get a bit annoying, and I can't blame some posters for criticising, when people come on here asking for help after they've done everything wrong......why don't they ask first....and do it right??
Yes, it is in a sense annoying, and maybe it would be appropriate for people to voice their annoyance - probably better than asking 'embarrassing questions'. The clock can't be turned back - so, in relation to this OP and this piece of work, the past cannot be changed.

If he'd said.. I'm about to do a CU swap for my boss, but initial testing has shown low IR between Neutral and Earth......what's the best way to trace this fault? Everyone would have been happy and he'd probably have got more replies.
Of course, but he (as so many other posters) didn't do/say that, so we have to decide how to deal with the situation we have in front of us.

Mind you, another consideration is that those who are familiar with this forum might be very hesitant to post a message saying "I'm about to do a CU change....". I've expressed before my fear that some people are intimidated by this forum to the extent that they are more inclined to go ahead and do things without advice. At least they know that if they come running back for help after they've done it, they won't be told 'not to do it'!

Kind Regards, John.
 
On second thoughts, John, I have to disagree with these two posts ..... The reason being - this isn't 'Private Messaging' - Ask Doctor Electric This is a Forum - and lots of other people read the replies - so I think it's important to point out what someone has done wrong, as well as answering their question. And John, I should warn you, if you find a way to disagree with this, then you really will argue about anything. :)
You'll be relieved to know that I don't disagree. However, there are 'ways and ways' of doing this, and I think there are 'diplomatic' ways, better than asking 'embarrassing', almost sacastic , questions ('digs'), and certainly better (and much more diplomatic!) than the ways some of our friends here do it!! ... perhaps something along the lines of "You really should/should not have done XYZ (with reasons, as appropriate) but, in answer to your question, ..... ".

Of course, there are times when situations are so potentially dangerous that it is inappropriate to give any advice other than to get an electrician - but there are diplomatic ways of doing even that!

Kind Regards, John.
 
Assuming there is only one fault its location can be narrowed down by passing a test constant current through it from the cable end at the CU and then measuring the voltage between earth and neutral using a milli-volt meter. Along the cable route from the source to the fault the voltages measured at each point will be different. They will reduce in voltage as you move away from the source until you go past the fault. Voltages on the far side of the fault all be the same.

The change in voltage along the cable is caused by the volt drops along the cable due to the test current flowing in the cable to and from the fault. On the other side of the fault there is no current flow so no voltage drop along the cable.
 
Of course, there are times when situations are so potentially dangerous that it is inappropriate to give any advice other than to get an electrician - but there are diplomatic ways of doing even that!
Kind Regards, John.
Yes John, but in trying to be diplomatic your answer is often misinterpreted as in (I'm sorry Ms Merkel didn't you realise I meant we are considering (not) holding a referendum)?
In this instance, my initial request for test data before and/or even after has met with a stoney silence - conclusion it wasn't done before and hasn't been done since.
What is confusing is your attitude to testing and your focus on solving this particular problem instead of looking at the wider consequences of the op's failure to follow fundamental testing principles.
You are totally wrong to suggest that this is what we have and lets solve this problem.
The correct solution should have been to stop what you are doing and conduct proper tests on ALL of the circuits - this particular fault may be symbolic of a dangerous installation just waiting for a fire to start.
Failure to test has resulted in a scatter gun approach in trying to solve this particular problem without any real understanding what the REAL problem is or might be.
The op is out of his/her depth and should call an electrician - is that diplomatic enough for you?
 
In this instance, my initial request for test data before and/or even after has met with a stoney silence - conclusion it wasn't done before and hasn't been done since.
Maybe I wasn't clear enough. It was implicit in what the OP told us that he had not tested (at least not IR, very probably not anything) prior to the CU change, yet you asked him about the 'before' (in bold) test results (as well as 'and/or even after' tests). I suppose I reacted as I did because it niggles/annoys me when I see this 'technique' being used, quite commonly in this forum. Had you simply told the OP that he should have tested prior to the CU change, I would have said nothing.

What is confusing is your attitude to testing and your focus on solving this particular problem instead of looking at the wider consequences of the op's failure to follow fundamental testing principles.
I'm not sure what you think my 'attitude to testing' is. I certainly am not suggesting that testing should not be done, and never would, and nor would I do any work myself without testing. However, in the case we are discussing (as quite commonly), it is an unchangeable fact that 'before' testing was not undertaken - which is why I don't like the technique of asking for the 'before' results, which one knows don't exist. It's like the police officer looking at your car's seriously underinflated tyres and asking what the pressures were when you checked them prior to your journey (rather than asking why you didn't check them).

You are totally wrong to suggest that this is what we have and lets solve this problem.
Well, there is a problem which needs to be solved and none of the standard tests on that circuit would aid that process. Whether or not the OP has the ability or knowledge to do this (or any of the work already done) is a different matter - and I'm surprised that this thread ran for a fair while before anyone raised that, other than by your (early) innuendo.

The correct solution should have been to stop what you are doing and conduct proper tests on ALL of the circuits - this particular fault may be symbolic of a dangerous installation just waiting for a fire to start.
Again, if people had that view they should perhaps have said so, explicitly.

The op is out of his/her depth and should call an electrician - is that diplomatic enough for you?
Yet again, if that's your view, you probably should express it. In some senses, you're obviously right, since the OP is having to ask for advice in relation to the identified fault, but I presume your comment is intended more generally in relation to the work that the OP has tackled (and how it's been tackled).

Kind Regards, John.
 
As with other replies, before any criticism I told the OP how to find the fault.

Rather than replying with an acknowledgment and, for example, 'thanks, I'll do that' he came back with "Other test results to this point are irrelevant" (strange way to spell non-existent).

This is not a DIYer trying to learn or save money by doing it himself.
I don't think I will be proved wrong by saying he is a plumber who, presumably, said to his boss that he could do this job. Now he is stuck.
He can change a consumer unit but does not know how to find a fault.


Furthermore, judging by the quote below he does not seem too sympathetic when the boot is on the other foot.

Another strong argument for 'Being Careful What You Wish For'.
ANY 'filtering' service like this (and there are many, all competing in similar 'marketplaces') can only do so much 'checking'. If you believe otherwise, you're delusional. They couldn't afford to do it and if they did, too many people would fail the checks and tests, and they'd never make any money at all! Their objective is to make money, usually from trades AND customers.

Quite apart from that, very few of them have any intention of delivering any 'quality' at all. Some are no better than a scam.

Be warned!
 
As with other replies, before any criticism I told the OP how to find the fault.
You did, indeed, as did others - and it surprised me a little to see those responses without any 'reservations' or criticisms about the work that had been done (and the implicit absence of pre-energisation testing, let alone notification). I personally resisted the temptation to respond to the OP's question, since I was in two minds about the pros and cons of advising someone in relation to work I did not feel they should be doing.

It's probably apparent that my mind is 'all over the place' with this one, since one can view it at various different levels. In some senses, the OP is the victim of his/her own honesty. Had we been given no background, and had the question just been "a lighting circuit has developed a N-E fault; what is the best way of locating the fault?", then most of the tangential discussion would probably never have arisen. However, given the background which was provided (and given 'research' on the OP) it is indeed probably true that (s)he should not have been changing a CU (which was very probably done without notification), and certainly should not have changed a CU without at least pre-energisation testing

Rather than replying with an acknowledgment and, for example, 'thanks, I'll do that' he came back with "Other test results to this point are irrelevant" (strange way to spell non-existent).
As I've said, I was moved to comment because I don't really like the 'language technique' which was used - which I suppose one could describe as condescending or patronising. As for the the OP's response, I would say that it was perfectly reasonable for someone who was focussed on the specific problem/question in hand. If a N-E fault had been detected, the results of any other 'standard tests', undertaken before or after the CU change, would not help in locating/elucidating the fault - so I would think that (in terms of person focussed on the specific fault about which questions had been asked) "irrelevant" is not an unreasonable way to spell "non-existant".

This is not a DIYer trying to learn or save money by doing it himself. I don't think I will be proved wrong by saying he is a plumber who, presumably, said to his boss that he could do this job. Now he is stuck. He can change a consumer unit but does not know how to find a fault.
Yes, I think that's all probably true - but I have to say that I don't research the background of posters before responding to them (not that I have responded to the OP in this thread) - I simply take their posts/questions at face value. However, it is undoubtedly true that, quite apart from laws, regulations, knowledge and competence (to do the actual CU change), no-one (not even a 'qualified electrician') should be changing a CU if they do not feel confident that they can deal with any problems that the work might uncover or cause - hence my failure (as explained above) to respond to the OP's question.

Has BAS not noticed this thread?:)

Kind Regards, John.
 
From the op's original post i thought 'the boss'='the missus', not their employer!
 
From the op's original post i thought 'the boss'='the missus', not their employer!
That was also my interpretation - it seemed to me that 'the missus' would be far more likely to want an induction hob than an employer! However, others appear to have taken 'boss' more literally! ... not that this makes much difference to the issues being discussed.

Kind Regards, John
 
Does the RCBO hold in with all the light switches turned off, and all the lamps removed from ALL lights wether they are connected to the suspect circuit or not?

Are there only standard lights connected to the faulty circuit? No extractor fan / TV booster / burglar alarm / outside lights etc..?
 
Note to self: OP has not responded throughout this thread.

JohnW are you a moderator or politician?

All others spot on 'arse & elbow' in a nut shell, we know the crack and thats why we have an opinion.

However lets turn a negative into a positive and one of the brotherhood well get a job out of this to put it right and thats what its all about.

If in doubt phone a freind, or a freinds freind and get a spark in!

The C&G 2391 pass rate is 49% I wonder why.
Remember education is key not humiliation. so keep this forum friendly and helpful and we all can benefit from it.
 

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