insulation resistance problem

[essexboy]

hi

just done a insulation resistance test on upstairs ring and got the following results

P-N >299Mohms
P-E >299Mohms

N-E>0.26Mohms ??????

as you can see the N-E result is unacceptable can anybody shed a bit of light on what the problem could be or how to find out where the cause of the low resisatnce reading is...

thanks for your replys

 

[adamh]

is it pme or is that just a daft answer lol

 

[PAUL M]

did you test the ring at socket or at ccu? did you remove the neutral and earth from the board to do test?

 

[essexboy]

thanks for your responses

the earthing system is tn-s but the test was done at the ccu end on the upstairs ring circuit only not through the meter tails .2 fused spurs feeding shower pump and tail rail were isolated there is no other vulnerable equipment on the circuit so tested between L-N ,L-E ,N-E

???

 

[PAUL M]

but did you remove the cpc and neutral from the board to do test?

 

[essexboy]

yes paul both all conductors of both ends of the ring were removed from the board

 

[sparkyork]

not sure but could it be the fused spurs are only single pole and your getting a reading through neutral earth that way, or did you physically disconnect the pumps as well?
failed socket outlet somewhere?
something somewhere still plugged in, tv amps, etc etc

hope you get it sorted matey

 

[jimes]

go to what you think would be furthest away from board and split the ring will narrow it down, prev post about single pole could be it or maybe a trapped cable etc

 

[EasyFox]

go to what you think would be furthest away from board and split the ring will narrow it down, prev post about single pole could be it or maybe a trapped cable etc

Divide & conquer
My money is on a doubled up neutral in backbox thats been nicked by plate screw.

 

[Shakey]

but did you remove the cpc and neutral from the board to do test?

as a side issue you cant do that anymore

17th says insulation test between live conductors and the cpc connected to the means of earthing

cant think why, but hey, there it is its in the regs.

 

[wayne]

as a side issue you cant do that anymore

17th says insulation test between live conductors and the cpc connected to the means of earthing

cant think why, but hey, there it is its in the regs.

ok leave the cpc connected but take the neutral and phase out
go with easy fox ,divide up and find the trapped wire /nicked wire (known it to be caught in capping before now)

 

[tc3]

as a side issue you cant do that anymore

17th says insulation test between live conductors and the cpc connected to the means of earthing

cant think why, but hey, there it is its in the regs.

Hi Shakey

do you know the reg number on that one. is it just for rings or all circuits.

thanks in advance

couldn't find my regs book before. i was just reading christopher kitchers book. p57 he says disconnect neutral or cpc.
found my regs book 612.3.1 ,can't see why, whichever is easiest would seem logical.
thanks

 

[Grae79]

612.3.1

 

[tc3]

thanks grae

 

[mdshunk]

At what voltage do you guys do insulation resistance checks at? When I get a really low reading like posted when I do them, I can't help but to think that I might have just blown up someone's television or computer accidentally. I never have, but my mind races for a few minutes, thinking like that. We check domestic wiring at the US typically at 500 volts.