Insulation resistance....Head scratching moment

[danny124]

Hi guys got a right head scratching moment..... Wondered if anyone has come across this situation...

I did a rewire for a property (downstairs only), Started doing the testing, everything was good untill i got to the IR test. No SELV, no bulbs, nothing pluged in etc etc...

Example testing the lighting and getting IR readings of 750-ish, but really in i want >1000Mohms as its all new. other circuits like cooker im getting 820 Mohms.

I disconnected all the lighting and did an IR on every leg and then got a resistance on every one as >1000. reconnected and went back to the 750...

I then did an IR test on another job, and got >1000M ohms straight away.

Has anyone has this problem before, i got a right head scratching moment here....

 

[shaun c]

was there a RCD in the board turned on?

 

[robskiing]

You will very rarely get 1000 meg ohms depends if it is surface chopped in only needs to be a little pressure somewhere in a metal back box or a little tight where the plasterer has fitted his plaster board onto the walls im happy with 200 meg ohm and above i dont think you will get perfect readings not in the real world

 

[danny124]

thanks for your reply guys....

all circuits were tested induviduallay and as a whole, with and with out rcd....

so..Robskiing as if my readings are like that and written on cert it should be ok, no questions asked... I just never seen or had this before....

 

[odigi]

Danny, what were you testing between to get those results?

Scott

 

[robskiing]

Yes mate thats fine greater than 200 meg the onsite does state that anything about 2meg should require further investigation

 

[danny124]

Hi odigi, was testing the lighting (with no transformors connected at that point, no bulbs) and cooker and ring, cooker wasnt connected at that point, and nothing plugged in either.....

Cheers rob, just got my registration, and just being cautious. Maybe being too cautious...

 

[odigi]

oh, I meant between L-E etc - or did you get the same results for all of them

 

[robskiing]

Normally when im doing an install at the new board i strip and sleeve the new cables to where they are going and test each circuit individually usually r1 & r2 first then i do my insulation resistance before i connect them this saves a little time nothing is worse than connecting a board up then you have to take them out again to test but everyone has their own way of doing it you will in time find one way that suits you

 

[danny124]

haha, your not on your own, thats what i do... Thats how i came across my problem..

 

[Des 56]

haha, your not on your own, thats what i do... Thats how i came across my problem..

danny 124 You dont have a problem
Remember that the insulation resistance test is an"whole of installation test "
Individual readings do not give the correct installation reading

 

[Deleted member 9648]

750 Mohm!!!.......watcha worried about mate

 

[danny124]

cheers guys, i take it im worrying to much about this then....

 

[Sintra]

Don't worry megger test instuments only read up to 299 Mohms