domestic PIR no end to end reading on Neutrals

freedomrun · Sep 22, 2011

Domestic PIR (TN-S, 60A MAIN, 16MM EARTH, MAIN BONDING 6MM). Neutrals on end to end test at a S/O give zero ohms, Live gives 0.30 ohms & cpc gives 2.7 ohms at same S/O. I'm thinking that if this is a ring then the Neutral is loose somewhere on this cct. Any advice please - i may be overlooking the obvious - (i have measured 230v at all S/O on the cct) - Thanks.

ezzzekiel · Sep 25, 2011

Reducing the mcb size would still leave a unterminated broken conductor lying around somewhere, the fault would need to be located and the damaged leg removed or repaired

dagrat · Sep 26, 2011

I agree with ezzekiel, finding the broken neutral is a priority if your leaving the cable in circuit.

SPARTYKUS · Sep 26, 2011

dagrat said:
I agree with ezzekiel, finding the broken neutral is a priority if your leaving the cable in circuit.

And I agree with Ezzzekiel too, the point I am making is that dependant on your remit, i.e. what you can and can't or have been paid / asked to do, that might not actually be possible in the real world, in which case a five minute job to make it safer is to downrate the MCB. Maybe then on the two weeks until the job is put right and the fault traced, there is no chance of the cable being overloaded.

It depends on the job. I have for example PIR'd a house and reinstated a few things, and found the lighting circuit on a 40A MCB (wired in 1.5 T+E). The job was NOT for me to go fixing everything and setting the world and his dog to look like a carbon copy of the regs, so I disconnected it, turned it off, took pictures and made damned sure the owner understood why.

That was all. It's all very well saying what must be done, but sometimes it might take 6 months for it to happen. My post was meant to offer a slightly more tactical approach. The strategic would be to clear the fault :carolers:

ezzzekiel · Sep 26, 2011

Better clarification now i see the point you are making

But your original reply would appear to the op as leaving on a smaller mcb would suffice

Personally i would choose this option as a temp overnight fix if it was too late in day to repair the break