Discuss I.R test before cu changeI in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

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This is a very good topic, and many people have differing and interesting views, which we could all benefit or even learn something from, therefore, can we please stick to the OP's query.

The other thread has been pulled. End of.

KEEP IT CIVIL.

Thank you.




 
I agree Jason, there does seem to be some very differences of opinion, this has been a cracking debate, and yet we all seem to be going aaround in circles somewhat, know its been pulled other people cannot really see what the debate is all about, do you think you could very simply break it down and re-issue a laymans term possibly and other lads can see what it was about.
My own opinion is , although yes it remains the fact that you would have to un-plug and take lamps out, i would still do an I/R test, it sorts the lot out then, you can see straight away what problems there are, before you do a C/U change, and then you can verify with the customer the costings appropiately and everyones singing from the same hymn sheet.
 
My own opinion is , although yes it remains the fact that you would have to un-plug and take lamps out, i would still do an I/R test, it sorts the lot out then, you can see straight away what problems there are, before you do a C/U change, and then you can verify with the customer the costings appropiately and everyones singing from the same hymn sheet.

Thats all I was trying to say, I wasn't trying to force my opinion on anyone just giving my take on the OP, nothing more.
 
hi just wondering when carryin out an insullation resistence test with the old wiring colors black neutrel red line if the metre is set on mega ohms scale 500v dc and the scale goes to 2.95 would tht be a pass as its over the 1 meg ohm minimum cos i was thinkin the scale had to go all the way across? my tester is the 1502/2 megger multi fuction tester any help would be great
thanks
 
thts wot i thought i gotta go bk 2moz and find the fault, i did a board change supplyin ring circuit 3lights circuits everythin else i tested was ok went the full range on me tester, i got good reading for R1 + R2 im surprised nothin showed up on thm eather, appently the guy who lives at the house did the wiring himself got me round to fit the board theres no way im takin responsablity for is job so i issued him with a pir insted.
 
The previous thread has been edited and opened to view for reference only, as requested by a few members.

I will be keeping a close eye on this thread although i do welcome a good debate.



 
What attracted me to this thread in the first place was a bad experience last week and begs the question where do you stop with pre testing.

I changed a CU for a friend and it turned into a nightmare. The IR readings prior to the change were fine so ahead I went as I always have done. The problem came with the end to end L-L, N-N & cpc-cpc continuity tests on the ring. The L & N were fine but the cpc was open circuit. I figured just an earth fell out of a socket.

However every socket had an earth present shown by a tester. The fault took over half a day to find and rectify and was found by linking the 2 neutrals and one cpc together and then doing a N-CPC continuity test on every socket. I found 6 sockets without readings and the fault turned out to be in a JB under a carpet covered chipboard floor where a spur had been added and one cpc was just not connected. Oh, I forgot to mention it was just one ring throughout the house with the exception of the kitchen, about 30 sockets in total.

So although every outlet had a cpc the worrying thing is that the broken cpc ring means not enough current carrying capacity in event of a fault.

After a 9 hour job the upshot is that in future I would virtually do a complete test before a change never mind just IR.

Cheers, Ron
 
Hi Ron,

When testing the RFC R1+R2 cross connected at the CU, and then going round all the sockets, this should have highlighted the problem.

An IR test would not pick this up as there was a break in the circuit, which to be honest, probably made the readings quite good!
 
I think this is a good decision Jasonas most of the members do not seem to involve themselves in personal abuse. And alhough the guy had some good points I think it will vindicate Lenny as he was only trying to put his point across.
In my opinion the other guy took offense at Lenny's point of and things got out of hand

Most unfortunatre
 
Hi Ron,

When testing the RFC R1+R2 cross connected at the CU, and then going round all the sockets, this should have highlighted the problem.

An IR test would not pick this up as there was a break in the circuit, which to be honest, probably made the readings quite good!

It highlighted the problem but only in the same way as the end to end continuity test. It did not help find the break because RI+R2 cross connected at the meter with a break in R2 gives open circuit at every socket on the ring. Linking the 2 N's & 1 cpc (or 2 L's & 1 CPC) was the only way I could think to find the break.

You hit the nail on the head though regarding the IR test and on the basis it was good I went ahead but in future it will make me think.

Cheers, Ron
 
It highlighted the problem but only in the same way as the end to end continuity test. It did not help find the break because RI+R2 cross connected at the meter with a break in R2 gives open circuit at every socket on the ring. Linking the 2 N's & 1 cpc (or 2 L's & 1 CPC) was the only way I could think to find the break.

You hit the nail on the head though regarding the IR test and on the basis it was good I went ahead but in future it will make me think.

Cheers, Ron

Yes good point.

This does go to show however, that any testing is not always conclusive.

At least you found the fault.:)
 
IEE guidance note 3 section 2.7.4 The sequence of tests, sets out the corect order in which tests should be performed.

Regards

Quite correct and the first on the ring is the end to end continuity.

But also think carefully about the tests and not one of them would help pinpoint this fault, they would only show a fault i.e open circuit. You have to think about ways to locate it and they are not in the book.

Cheers, Ron
 

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