Further investigation IR below 2 Megohms or 20 Megohms??

Ah thanks, perhaps I should update my notes... ;-)  Mind you I bet I can damage a cable in a way that still passes at 20Meg as well as at 2. If you can, nothing beats a visual check before boxing or plastering things in.

Mike.

mapj1 said:

Mind you I bet I can damage a cable in a way that still passes at 20Meg as well as at 2.

Definitely ... even perhaps using a techs screw to penetrate just the line conductor in a flat T&E cable, making the steel frame of a steel-framed plasterboard wall live in the process, which then doesn't come to light until someone kneels in a puddle of water that's seeped under the wall, killing a plumber who was fixing the leak.

A non compliance with 522.6.203 and 522.6.204 then.

Z.

Yes, but still happened in real life in the UK, possibly preceding current 'rules', and not identified by testing (apparently)

Sounds similar to the Emma Shaw case. (Tried to post this under GKs post 2 up but system not having it).

Relatively similar, but different cases. There have also been incidents of cables run underneath roofing supports, where roofing fixings (perhaps for metal roofing materials) have penetrated If I remember correctly, dry/stud wall and roofing incidents have led to H&S prosecutions ... if I get a moment I'll have a look as they ought to be searchable on public record on the web.

All perhaps providing evidence for the fact that the "concealed < 50 mm from surface" rules are necessary.

Mind you what happens if the chaps had used a 2.5 inch screw... everyone has then followed 'best practice'  Who gets prosecuted for what exactly?

It may be better to recommend that folk consider cables with foil or braid  in metal lined voids and partitions etc, where the use of SWA is unreasonable but something to operate ADS of some sort (be that RCD or a fuse) is desired. I think with T/ E an 'instruments only' 'test' can still miss  screw damage and that damage may of course occur sometime after testing anyway. I also cannot see a conventional cable finder working well to spot things within a metal partition.

In many ways surface wiring or other methods (trunk or whatever) where you can see it is safer if not very aesthetically satisfying.

M.

Mind you what happens if the chaps had used a 2.5 inch screw... everyone has then followed 'best practice'  Who gets prosecuted for what exactly?

It may be better to recommend that folk consider cables with foil or braid  in metal lined voids and partitions etc, where the use of SWA is unreasonable but something to operate ADS of some sort (be that RCD or a fuse) is desired. I think with T/ E an 'instruments only' 'test' can still miss  screw damage and that damage may of course occur sometime after testing anyway. I also cannot see a conventional cable finder working well to spot things within a metal partition.

In many ways surface wiring or other methods (trunk or whatever) where you can see it is safer if not very aesthetically satisfying.

M.