High zs

[jimsparks]

Evening all,
Got a strange one that I could
Do with a little advice.

I have extended a radial circuit for an extra socket. R1r2 0.41 IR 84.5mohm and rcd trips in time.
When doing zs I got a reading of 6.83 when I was expecting about 0.63 ish when ze was 0.21 on tns supply .
Started to investigate disconnected that circuit from board and found that on the disconnected CPc I was getting continuity if I tested between that and earth bar. Took all the earths out of the Earth bar but the continuity disappeared except for testing between incoming Earth and the original one that was disconnected from the first circuit. I then tested zs on cooker circuit to see if that gave a proper reading but got 6.91 and then after testing the other circuits got similar readings ! A new split load board was fitted a yr ago and got the certs and obviously no issue.
If anyone has got any suggestions I would be very grateful.

 

[Murdoch]

What is the Ze?
What is the earthing arrangement?

 

[Fleeting]

What is the Ze?
What is the earthing arrangement?

TN-S.

 

[Fleeting]

Did you recheck your Ze I have has TN-S lose it's external impedance half way through testing.

 

[jimsparks]

yes, kept rechecking it. Since I posted I have started to break the circuits down I found broken earth on one of the ring circuits but not in socket or jb but the cable itself which I will replace. Another strange thing which I found just before I stopped for the day, set my tester to continuity and put one lead on neutral load side of rcd2 and then the other lead on neutral bar for rcd1 and I was getting continuity reading.

 

[Murdoch]

Are you using a plug in adaptor

How close is the cu to the service head?