Which regulations(s) require the steel wire armouring of a S.W.A. cable to be earthed if it is NOT used as a circuit protective conductor?
Case 1. Cable buried underground.
Case 2. Cable NOT buried underground.
Z.
mapj1:AJJewsbury:But personally I like a large plastic stuffing gland into a plastic box at the load end if creating a TT island, rather than trying to fit heatshink over cut back armour.
But you need an accessible connection to the end of the armour in order to test Zs or R2.
At least the brass gland into a plastic enclosure arrangement (with a boot or heatshrink over the gland outside of the enclosure) gives access with the enclosure lid removed.
- Andy.slightly at cross purpose with my explanation. Select a stuffing gland that goes over the whole lot, and push enough of the cable jacket and armour inside the plastic box so you have probe access to the armour end for your meter as required, just not exposed to touch when the box is shut. I have been known to then treat the cores and bedding like a rather wilful flex and route it as one into the next enclosure before breaking the cores out, but strictly as others have noted the bedding is not supposed to be adequate to count as insulation, so it should be in trunking, conduit or other protection. In reality it is at least as good an insulator as the outer sheath on the average lawnmower flex after a few seasons so though I do not do it now, I do not feel that bad about having done it.
M.
... and potentially put electricians at risk?
The approach I'm describing reduces the risk (esp. longer cable run, of the order 0.5 to 1 km, where the risk of differing potentials increases):
mapj1:AJJewsbury:But personally I like a large plastic stuffing gland into a plastic box at the load end if creating a TT island, rather than trying to fit heatshink over cut back armour.
But you need an accessible connection to the end of the armour in order to test Zs or R2.
At least the brass gland into a plastic enclosure arrangement (with a boot or heatshrink over the gland outside of the enclosure) gives access with the enclosure lid removed.
- Andy.slightly at cross purpose with my explanation. Select a stuffing gland that goes over the whole lot, and push enough of the cable jacket and armour inside the plastic box so you have probe access to the armour end for your meter as required, just not exposed to touch when the box is shut. I have been known to then treat the cores and bedding like a rather wilful flex and route it as one into the next enclosure before breaking the cores out, but strictly as others have noted the bedding is not supposed to be adequate to count as insulation, so it should be in trunking, conduit or other protection. In reality it is at least as good an insulator as the outer sheath on the average lawnmower flex after a few seasons so though I do not do it now, I do not feel that bad about having done it.
M.
... and potentially put electricians at risk?
The approach I'm describing reduces the risk (esp. longer cable run, of the order 0.5 to 1 km, where the risk of differing potentials increases):