Hi all. Changing a CU in an ex-council flat, pme system, no RCD's, and initially tried to IR test whole board L/N joined to earth, got a reading of 0.28 Ohms.

Then did each circuit individually (2 X RFC, 2 X lights, 1 X cooker), L/N joined to the circuit's CPC, and got between 0.25 and 0.30 Ohms on each one.

Any ideas what could be causing the low readings?

Thanks.
 
always get that with PME. it's because the N bar is tied to earth at the service head with bonding to services contributing.
 
With the main switch OFF? When you tested the circuits individually, did you remove the N's from the bar? If not, each test was still a global test, and an N-E fault on one circuit will show up on all.
 
Then did each circuit individually (2 X RFC, 2 X lights, 1 X cooker), L/N joined to the circuit's CPC, and got between 0.25 and 0.30 Ohms on each one.
Assuming the individual N was out during each test that is odd. Having a N-E fault on every circuit is a bit more than coincidence and more like an installation with some serious flaws!
 
if the 0.3 ohms reading per circuit is correct a global 0.06 ohms would be a global reading drawing 3.833 KW .either measurement errors , SPDs or item still in circuit (possibly wired incorrectly ) is there an RCD present?
 
Sorry, my mistake - I meant MegaOhms, not Ohms.

No RCDs, no SPDs and an empty property so I couldn't even find anything plugged in. I did the individual tests removing L, N and CPC from the board, so that's why I can't understand why they all had pretty much the same low reading. Wiring is singles in conduit, but can't see how that can make a difference.

It seems there is a problem but I can't even think what that problem might be!
 
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Title
Insulation resistance whole board.
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