CU change found IR fault

[mushka]

Evening fellas,

I've just changed a CU (in my house for NICEIC major job)

and after 2 days of trying in vain to find some load I'd forgotten to remove from the upstairs ring, I came to the conclusion that my results for Insulation resistance for the circuit of L-N = 0.00M ohms and L-CPC = 0.32M ohms

were probably a fault :_|

Anyway long story short, Ive traced it to part of the ring and disconnected either end of the cable in question and replaced the 32A mcb with a 16A for the time being, retested and got >299M ohms.

Now, I realise I need to sort this asap and reinstate the ring minus faults

BUT.....

I've got LABC waiting for the certs, and I'm pretty anxious to get the ball rolling on the NICEIC front as they can take ages to come round and assess you.

Have I done all I need to for the time being? (ie changed CU and made the existing installation as safe as I could under the circumstances)

Or am I going to get hauled over the coals for not rectifying all faults before issuing certs?

I realise I haven't explained myself very well but if you can decypher the ramblings.....

any advice would be greatly appreciated,

many thanks

Ben

 

[batty]

If you have l-n at 0.00mohms you must have something plugged in or connected with a dead short on cabling it will blow a fuse.

 

[matt.leung]

NIC also like to see a new circuit and see how this is installed (methods used)

 

[mushka]

If you have l-n at 0.00mohms you must have something plugged in or connected with a dead short on cabling it will blow a fuse.

That's what I thought but having disconnected this one section it's all fine and dandy! (although no longer a ring!)

I actually measured the resistance at 450Ohms on continuity, so it's only allowing about .5A to flow.

Do you still think it could be something else on the circuit?

cheers

 

[batty]

That's what I thought but having disconnected this one section it's all fine and dandy! (although no longer a ring!)I actually measured the resistance at 450Ohms on continuity, so it's only allowing about .5A to flow.

Do you still think it could be something else on the circuit?

cheers

Very differcult to diagnose faults without being on site I have enough trouble finding my own. So when testing was circuit a ring?

 

[mushka]

I think someone might have put a screw through a cable as I've pulled up some carpet seen a bunch of boards just wapped down with 2inch screws.

 

[mushka]

Very differcult to diagnose faults without being on site I have enough trouble finding my own. So when testing was circuit a ring?

yeah ring tested fine, in fact I got really nice results, it was only when I got to IR testing did the poo hit the fan

 

[seajayess]

If you have removed the fault from the cicuit, you have now turned the ring into 2 radials, as long as the cables have been removed from the sockets so you havn't got a loose live cable, you have installed a 16 amp mcb this is ok CJS

 

[mushka]

I'm still confused by the apparent dead short and the fact that I'm getting 0.32Mohms between L-CPC and also between N-CPC

And that 0.32 is just that for both live conductors to earth!!

Maybe I'm just missing something?

 

[mushka]

If you have removed the fault from the cicuit, you have now turned the ring into 2 radials, as long as the cables have been removed from the sockets so you havn't got a loose live cable, you have installed a 16 amp mcb this is ok CJS

ok, that'll do for me for the time being untill I've got a day when the mrs + kids will be out and I can sort it.

cheers

 

[batty]

Last one I had circuit was open circuit on phase but ring on other conductors so took all sockets of thinking it was lose cable in socket. Turned out somebody had nailed cable in wall years before which had blown conductor apart so open circuit on live and low resistance on live to earth. I did manage to pull a new piece of cable in without to much hassle. Now if you have a ring on condutors its unlikely to be a nailed cable as said dead short will have blown fuse.

 

[mushka]

as long as the cables have been removed from the sockets so you havn't got a loose live cable, CJS

They're still there just in wagos.

Still acceptable?

or should I start hacking?

 

[sparkytim]

Had similar problems on C U changes, last one found open cct on all ring conductors with low insulation readings.

Discoverd socket box coverd over on landing with two bare ends nicely curled up inside, socket having never been fitted 37 years before!

"I always wanted a socket on the landing" and now she has one, along with a real Ring main.

Never can tell whats hidden away

Have you split the two legs onto two MCBs?

When you cant pin down the fault this can get you up and running and have found often surfices if the load is spread between the two reasonable

In fact you can now have 2x 20 Amp Radial circuits and have not had call backs due to overload tripping MCBs even with normal kitchen loads.

 

[netblindpaul]

DAMN, yooz lot have been busy!

I pop out to get some passport photos for my JIB card and there's a ton of replies when I get back! :|

Evening fellas,I've just changed a CU (in my house for NICEIC major job)

and after 2 days of trying in vain to find some load I'd forgotten to remove from the upstairs ring, I came to the conclusion that my results for Insulation resistance for the circuit of L-N = 0.00M ohms and L-CPC = 0.32M ohms

were probably a fault :_|

So, you have a length of T&E between 2 points in your ring that is now 2 ends of the "same" cable.

First ditch the IR tester.

NEXT!!!

SAFE WORKING, to steal another

 

[SPECIAL LOCATION]

DAMN, yooz lot have been busy!I pop out to get some passport photos for my JIB card and there's a ton of replies when I get back! :|

My RED above.

HTH!

:Blushing :coat

I like your red thinking netblind! :Applaud

 

[SPECIAL LOCATION]

Just to add to what the other esteemed forumbulites have said....

Could you have a Junction box somewhere with damp in it?

This sort of bad readings on a circuit problem can be numerous causes...

I once had a problem that turned out to be a Junction box full to the brim with Mr & Mrs insect and webs and fluff and stuff..

But Also it was under a very slight dripping heating pipe!

so damp was arcing the conductors!

 

[paul b b]

could be spur going to something, outside socket with damp? or mabe someone has put a outsidelight off the ring. never assume.

have you got 2 radials? if so you need 2 mcbs.

my question is why are LBC waiting for certs? you will notify when you have passed assesment

 

[ianmacd]

could be spur going to something, outside socket with damp? or mabe someone has put a outsidelight off the ring. never assume.have you got 2 radials? if so you need 2 mcbs.

my question is why are LBC waiting for certs? you will notify when you have passed assesment

Not how it works. You have to notify them before you start and pay them up front. Then send them the certs when you finish. They should not accept any other way although they are unlikely to come out to test it if its beign used for an assessment.

 

[paul b b]

the reson i did not notify befor is they wanted 375 quid up front, i thought this was exsessive, so i phone again ant another guy said just notify after i have passed