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Conduit earthing

Former Community Member
Former Community Member
On an Test and Inspection is no earth wiring in a conduit system.

Do people code C2 or C3
  • 0

    sowie1959:

    On an Test and Inspection is no earth wiring in a conduit system.

    Do people code C2 or C3




    I took that as no earth and wiring is in a conduit system, I didn’t actually take it as the conduit provides a good earth, but there is not a CPC conductor run inside the conduit.


    So I retract what I said above, as I assumed the conduit was not providing an earth, and go from C2 to no code at all.


    That leaves you to figure out the appropriate recommended date for the next periodic inspection and test if you have concerns about the life expectancy of the conduit system.


    Andy Betteridge 

  • 0
    When I was contracting many of our jobs were new schools where SWA, trunking and steel conduit was the order of the day. Never did we use a separate cpc. It was never specified by the consultants and never considered necessary by the contractors. Things have changed to almost the opposite and if you are a younger man I can see why you might be uncomfortable with the absence of the cpc within the conduit. I, on the other hand, am from a different vintage and would have absolutely no difficulty with the situation. Nonetheless, I don’t think that you can throw a C2 at it just because it’s not standard practice nowadays and, in any event, using steel conduit as a cpc is perfectly ok as far as 7671 and it’s predecessors is concerned. I might suggest that a well-constructed steel conduit system is as good, if not better than a cable with an integral cpc.
  • Former Community Member
    0 Former Community Member
    I start in 1975 and have never done a job with steel conduit did not have a earth wire in the conduit.

    I know it was acceptable in those days.

    The conduits are connected to mem fused DB`s which have been used as a joint box to fit a hager 18way with rcbo`s

    These are poorly fitted with rust forming around the old mem board.

  • 0
    It goes without saying that the conduit must be earthed. If not, it's C2.


    If a separate CPC will fit, I'd prefer to install it because it abolishes the risk of the conduit joints becoming poorly conductive. If e.g. metal clad sockets have the proper connexion betwixt back box and plate; and if flexes to luminaires use the tapped hole in BESA boxes to connect the CPCs, we end up with loads of parallel paths. What's not to like?


    However, provided that the R2s are satisfactory there is no requirement for a separate CPC any more than there is with SWA. If any R2 is high it's a C2.


    So for me it's probably a C2 or nothing.
  • Former Community Member
    0 Former Community Member

    lyledunn:

     I might suggest that a well-constructed steel conduit system is as good, if not better than a cable with an integral cpc. 



    It will be better from a perspective of safety - for any given value of R1, the relative R2 will be very small and thus you would have a very low touch voltage by default


    Almost as good as wiring the installation in MICC


    Regards


    OMS
  • 0

    sowie1959:

    I start in 1975 and have never done a job with steel conduit did not have a earth wire in the conduit.

    I know it was acceptable in those days.


     




    I thought you must be young asking such a query. Of course it is OK. It isnt even a C3.

    I had a similar argument with my Manager a couple of years ago, he was in his early 30's, and was insistent that conduit wasnt suitable as the CPC. He never did show me which Regulation was being broken.

    In the engineering company I started at in 81, it was the norm to use the conduit as CPC. Everything was metal conduit,supplying large metal machines, firmly bolted to the floor, with metal roller conveyor system running all around the factory at floor level. They saved thousands in not putting in that extra cable which would provide no extra safety benefit.

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