Am I correct in thinking that metal kopex is not suitable for use as a CPC, therefore can not be used to run cables outside the prescribed safe zones?
Metal kopex and safe zones.
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543.2.3 says flexible conduit cannot be used as protective conductor so I would say you are correct.
The reg does indeed say that ... but what if the cable within has an acceptable 'protective conductor' (CPC) and the flexible conduit is being used only as an outer earthed 'protective covering'?
Kind Regards, John
It won't be reliably earthed though, which is precisely why it can't be used as a cpc.
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Yes, but as I said, what if it's not being used as a CPC?
Even if it's only being used as an earthed protective covering (with a conductor within the cable being the CPC), there clearly is a need for it to be 'reliably earthed', so I would have thought that there would be some recognised way of achieving that?
Kind Regards, John
522.6.204(i) says only a metallic covering which does meet the requirements of a CPC of the circuit comply.
Thanks. I found the regs quoted above after I posted the question so we all agree 
Indeed. I suppose it does rather beg the question as to what that sort of flexible conduit is actually useful for - I suppose only if it is 'exposed' and being used to provide a bit of mechanical protection?Thanks. I found the regs quoted above after I posted the question so we all agree
Kind Regards, John
Used to get fitted to machinery supplies. Probably still does, just that it's a long time since I was in a factory.
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Yeah I remember using a bit of it back in the 80's to feed some 3ph motors.
Yes we use it a lot to supply motors, limit switches and anything like that which needs a bit of tolerance to movement.
It's not as tough as rigid steel, but it's fine in the right environments, and more resistant to impact, fauna etc than PVC.
It's not as tough as rigid steel, but it's fine in the right environments, and more resistant to impact, fauna etc than PVC.
Presumably you earth it? How easy is it to get a 'reliable' electrical connection to it, and how does one do that - does it perhaps come with some sort of 'glands'? (you can tell that I've never used the stuff!)
Kind Regards, John
You use a gland like this. The coarse thread screws inside the kopex, and the other side is a standard M20 thread.
It's never going to be a guaranteed connection and could be pulled apart without too much aggression, which is why the regs don't allow it to be used as a CPC.
Thanks. Not that much different from the plastic 'glands' I have used for flexible PVC conduit, which I've occasionally used just to reduce the risk of 'abrasion damage' in places like garages and cellars!
Kind Regards, John
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