New Build IR Testing RFC, can't find the issue

[JaegerZero1984]

I am currently testing a 2 bed flat, all other circuits read clear. Flat Ring not so much.

Using a Megger MFT1721

L - E Reading 300Mohms but slowly
L - N Reading 400 Mohms but slowly
N -E Reading 200Mohms but slowly

Have tried breaking the ring and narrowing down the problem but both sides come up with higher readings.

Have replaced half the ring and still no change.
Each leg reads +999
You pit a couple of sockets together it starts to drop. Tried replacing parts of ring with 2.5 to see if I can clear it but its not working.

Trying replacing a lag at a time tomorrow...

The plot is a new build so I would expect the readings to jump above 300 right away, so slow readings mean I'm having to investigate.

Does anyone here have any idea what could be causing these readings?

 

[willy fixit]

My meter only goes to 200MegOhms! Should I get a new one! And the house I tested last week had IRs of 170M maybe I should condemn the installation!

 

[westward10]

I use an analogue meter, as long as I don't see the needle with my right eye all is fine.

 

[ipf]

I use an analogue meter, as long as I don't see the needle with my right eye all is fine.

......Always thought you were a bit of a winker.

 

[123]

Anything above 2 meg ohms is acceptable .....

Not too sure I'd be happy with that on a rewire or new install, damp from plaster or not.

 

[Deleted member 26818]

Change MFT.
Get one that only goes up to 299 Mohm.

 

[Baker1988]

I really wouldn't worry about it all all reading are perfectly acceptable just record the results and move on to next job, or go for a pint.

 

[static zap]

Not too sure I'd be happy with that on a rewire or new install, damp from plaster or not.

Surely this comes from the experience of un-doing all the sockets , letting them breath , getting a much better reading .. logic .
( if worried about tracking damage - I can see AFDs turning up sooner)
Is this "Damp from New Build plaster" effect common only in hot weather ?

 

[telectrix]

if it's a new build, it won't only be the plaster drying. the roof will leak. the plumbing willl leak, the plasterboard will be mouldy.

 

[telectrix]

any rate, my megger BM80 goes up to 100Gig on the 500V range, so ner,ner. .