Have used used an eye bolt for a short catenary to an alloy greenhouse which is tt,d.The cat by others uses the same eye bolt,but I have no access to other units.Both cables are swa,so wondered if better to insulate my catenary since an uncleared earth fault onto the other cat wire could make my greenhouse live without my rcd tripping,or vice versa.Thanks for any advice.hz
My understanding (which may be completely wrong) is that the "catenary" includes a load-bearing cable from which the current-bearing cable is suspended; in which case I cannot see how two circuits would bother each other any more than two which are installed in say, a steel shed.
my worry was,if a voltage appeared on the metalwork of another alloy greenhouse,due to an earth fault,via the joined catenaries,my greenhouse could be raised to the same voltage.Or maybe I,m being paranoid.
In effect the catenary wire is interconnecting two TT earthed green houses, to make one larger TT zone. This is only an issue if there is an RCD failure and then instead of one live greenhouse you have two. I suspect the risk is low, and acceptable - no worse than say a metal fence or similar beside the greenhouses.
You could over sleeve the catenary wire or the hook, or even use an egg insulator in the caternary wire, example
but I cannot see that the risk is high enough to warrant it.
I agree if the cables are properly installed the catenary wire shouldn't need to be treated as an exposed-conductive-part.
If however it (or they) interconnect two (or more) buildings (e.g. greenhouses) with metallic structures, they could act as extraneous-conductive-parts as far as each building is concerned (so technically might require main bonding). Either way it risks importing hazardous voltages from one building to another - and if one of the other buildings isn't TT'd might undermine the very reasons for TT'ing your building (greenhouse) in the first place - say risking shocks from a broken supply CNE.
