How topical.
I was in <somewhere> only today and the subject of earthing came up - there being a fairly substantial earth ring for the systems being tested, but a requirement for a separate earth for other facility equipment off a different supply. And as I looked down at a metalclad socket with SWA in and out, there was a flylead from one banjo to the other (outside of the box) that didn't go into the socket itself.
I commented on this, and was told that the nut inside is designed to scrape the paint off as you tighten it - so the socket is earthed via that. It wasn't the right moment to "discuss" things further, but I was thinking that if they work then no need for the flylead, and if there's a need for the flylead then not much confidence that they do work.
But, one of the people I was with commented on how on a different installation there was a distribution board with "many" cables in it - and the installers had put the nuts the wrong way round. Apparently they were "rather unhappy" at having to pull every circuit in order to turn the nuts over.
I was in <somewhere> only today and the subject of earthing came up - there being a fairly substantial earth ring for the systems being tested, but a requirement for a separate earth for other facility equipment off a different supply. And as I looked down at a metalclad socket with SWA in and out, there was a flylead from one banjo to the other (outside of the box) that didn't go into the socket itself.
I commented on this, and was told that the nut inside is designed to scrape the paint off as you tighten it - so the socket is earthed via that. It wasn't the right moment to "discuss" things further, but I was thinking that if they work then no need for the flylead, and if there's a need for the flylead then not much confidence that they do work.
But, one of the people I was with commented on how on a different installation there was a distribution board with "many" cables in it - and the installers had put the nuts the wrong way round. Apparently they were "rather unhappy" at having to pull every circuit in order to turn the nuts over.