Odd Zs s

[baggy61]

Evening gents, I'm sure I'll get shot down for being stupid or missing the obvious , but here goes anyway.
TT supply to wooden building, Ze 88 ohms. (bonding disconnected). only service is water coming in in a poly pipe.
Zs on
one RCD between 0.5 and 1.5. on the other rcd between2 and 3. Got the same results with bonding to little bit of copper pipe on or off. R1 R2 all as expected.
Can,t figure out why Zs different on each rcd by the same amounts and why Zs so much better than Ze.
Hope I've explained it ok. Any answers appreciated.Any abuse will make me sad.
Regards,
Martin.

 

[ChrisElectrical88]

It's finding its way to earth somewhere much better on the Zs with all earth paths available I guess

 

[Deleted member 9648]

Have you IR tested?....could be a N-E fault on one of the circuits,which dont always trip RCD's on TT systems and will bring down your Zs readings as effectively the N and earth are joined.

 

[ChrisElectrical88]

It's Ra not Ze as well.

 

[baggy61]

Have you IR tested?....could be a N-E fault on one of the circuits,which dont always trip RCD's on TT systems and will bring down your Zs readings as effectively the N and earth are joined.

Bang on that man. Re did IRs, builder found some more nails and got cable twice on skirtings.
Suppose 'there's a lesson there.
Owe you a pint.
Martin.