Increasing Zs readings on a ring as I progress through the house.

[buzzlightyear]

those max figures are coming down aren't they!)

you can sing to this when you get good results and not football ones .

 

[Liamsparks]

Thread conclusion!

The customer at last agreed to the fault finding on the high Zs results.

I returned today, the customer told me his son had opened up the conservatory sockets and may have fixed the problem!! I tested the Zs, it was now 12Ω rather than 4Ω

I opened the socket that I thought was were they had extended the ring and found 3 earths loosely connected together and one earth not connected at all. Connected it all up properly and the Zs is now 1.06Ω. (Still close to the 1.1Ω max Zs for a 32A Type B MCB, those max figures are coming down aren't they!)

A happy customer as he thought I was going to be there much longer, as did I!

Good work there HHD, but as stated above - as you've installed a 30mA RCD to every circuit as your additional protection you have in turn increased your max Zs reading to 1667ohms for every circuit.

 

[HappyHippyDad]

Good work there HHD, but as stated above - as you've installed a 30mA RCD to every circuit as your additional protection you have in turn increased your max Zs reading to 1667ohms for every circuit.

Surely that's not right Liam?
I fully understand the 1667 figure but the RCD is 'additional' protection and we should still focus on ADS and therefore meet the max Zs figures.
I can't see an inspector saying 12ohms is ok. Plus with a particularly high Zs on a tns or tncs it may well be a fault (as it was in this case) as with a Zs of 4ohms that would have to be a mighty long run.

 

[Liamsparks]

If you have the 30ma rcd it would be perfectly fine to put the 1667ohms in max zs option.

However that said, it's not to say with the knowledge you have as a sparks not to further investigate an abnormal reading. It's all in the regs book.

 

[Baddegg]

Technically fine yes but still poor design......