Rcbo with higher than permitted zs

[pc1966]

Yes, not very good design but equally not dangerous.

The Zs is higher than UK regs on OCPD alone but given your 32A C-curve trip range for 230V covers Zs = 1.1*230/(5*32) = 1.58 ohms best-case down to 0.8 * 0.95 * 230 / (10 * 32) = 0.54 ohms worst-case, your measured 0.83 is going to be met for over half the tolerance range, and the RCD side always met.

 

[cliffed]

Agree, with the Rcd in circuit, R1+R2 tests, its compliant not ideal but ok.
The worry I have these days is that the lesser experience electricians, we’ve a high Zs reading put a Rcd on it.
Without the relevant tests it’s a major concern, days gone by you would certainly fix the problem

 

[pc1966]

Agree, with the Rcd in circuit, R1+R2 tests, its compliant not ideal but ok.
The worry I have these days is that the lesser experience electricians, we’ve a high Zs reading put a Rcd on it.
Without the relevant tests it’s a major concern, days gone by you would certainly fix the problem

Exactly, if it is just a rather long cable then it is not so serious, even though it is probably not meeting the VD spec either. But it could be something more serious that ought to be fixed (bad joint, etc) and not simply side-stepped with the RCD aspect.

 

[Highspark24/7]

Thank you all so much for the replies
And sorry for late response I'm working away at the moment and haven't had much time or that good internet connection I had noted on cert that it was a poor design and there is a few other issues I am due to go back and rectify once I am working back local thanks again the collective hive mind