Thanks Malcolm but to ask a stupid question if these regs were taken literally would every conduit box not require earthing even say through boxes cables are just passing through as these also have a cpc connection ?
No mate 411.4.2 is concerned with an exposed conductive part having to be earthed, if your using a metal conduit and singles as in your case then yes you need to make sure the conduit is earthed. Normally that is via a bush/coupling arrangement
4220.127.116.11 I assumed your click accessory was a plastic class II type, but if it was metal then you refer back to 411.4.2.
418.104.22.168 tells us that you need to have a CPC at each point.
Every conduit box is earthed mate, via the conduit continuity I would hope, as if it's a metal BESA box it is an exposed conductive part. I think what your meaning is fly leads and they only have to be at the click termination as in reg 543.2.7 if your using the containment as a CPC
What Malcolm is saying, is that the conduit itself is already earthed (or dam well should be) and is classed as the circuits CPC. So you will need to extend that conduit CPC by means of a fly lead or the CPC of a multi core cable, to the metal box or BESA box at every point where you have an accessory, be it a lighting fitting, switch, fan, Socket outlet or whatever etc.
Your not earthing the conduit, your extending the earthing (CPC) provided by the conduit to whatever you are connecting to that circuit!!!
Ok back in the years of the 14th edition ie Electrically & Mechanically sound in other words if the conduit is continues and is terminated or bushed to a metal DB then it was good to go as the main cpc hence why the conduit box has a 4mm threaded hole that if you did it right you fitted a flying earth lead via a earth stud if not you used a m4 screw. So what changed all of this well the 15th when crazy for earth bonding and running separate earth cables plus we now use a lot of plastic equipment ie 95% of CUs in domestics are plastic.
I challenged one of the Schemies up here as there is a lot of villa houses and council houses that were fitted with conduit and rewired in the early 80s they did not have a separate earth and I said well it was installed to ?? edition and it is E&M sound so there is no reason why you cannot use the conduit as a cpc because the guy upstairs will not let you rip up his laminate floor to get to the joint or draw box and they agreed as long as you fit an earth stud on the conduit box this I did plus I tap out the old 2BA or 3/16 screws to 5mm job done.