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surface-mounted SWA – earthing

Former Community Member
Former Community Member
Just trying to find a regulation that states a reason why the armoured metal of surface-mounted SWA needs earthing. Obviously, when buried underground, it does - 522.8.10.  I have read previous posts on this, but the question seems to have remained unanswered.

It would be considered best practice to at least earth the supply end, but best practice is not regulation. And, considering the statement at the end of Chapter 12, could it not be argued that short runs of surface-mounted armoured without earthing are ‘safe’? Where is the risk?

The armour does not meet the definition of an exposed conductive part when neatly terminated so it can not be touched – under what fault conditions could it become live?

SWA conductors are not double insulated, but is the risk any less than conductors in a plastic conduit?

Manufacturer instructions… it could be that they stipulate that the armour needs to be earthed, but where these are not available for review, how can a non-conformity be raised?

I’d appreciate any replies that point to a specific regulation or group of regulations.

Thanks in advance.

  • 0
    Back to the OP ...


    If the armour is serving as the CPC, which is normal, it is self-evident that it must be continuous with the earthing arrangements at both ends.


    If the cable is surface mounted, AND a core is being used as the CPC, AND the cable is neatly terminated into enclosures with insulating glands, then I agree that there are no ECPs, so the armour does not have to be earthed.


    If the cable is terminated into normal SWA glands, then they are ECPs. End of story!
  • 0
    125 The regulation applies to any conductor (other than circuit conductors), including the conductive parts of equipment, such as outer metallic casings, which can be touched and, though not live, may become live under fault conditions.


    EAWR
  • 0
    I am not typing it all out. 

    b9893d8b7cc91d518de8106284b102a5-original-20210530_200900.jpg
  • 0
    stuff:
    Just trying to find a regulation that states a reason why the armoured metal of surface-mounted SWA needs earthing. Obviously, when buried underground, it does - 522.8.10.  I have read previous posts on this, but the question seems to have remained unanswered.

    It would be considered best practice to at least earth the supply end, but best practice is not regulation. And, considering the statement at the end of Chapter 12, could it not be argued that short runs of surface-mounted armoured without earthing are ‘safe’? Where is the risk?

    The armour does not meet the definition of an exposed conductive part when neatly terminated so it can not be touched – under what fault conditions could it become live?

    SWA conductors are not double insulated, but is the risk any less than conductors in a plastic conduit?

    Manufacturer instructions… it could be that they stipulate that the armour needs to be earthed, but where these are not available for review, how can a non-conformity be raised?

    I’d appreciate any replies that point to a specific regulation or group of regulations.

    Thanks in advance.

     


    It may also depend upon what Voltage is present within the S.W.A. cable.


    Z.


  • Former Community Member
    0 Former Community Member
    Hi, Thanks for the above replies. It really is appreciated.

    I think all of the above could be argued against – which is what I am trying to avoid. I need a clear-cut regulation which, when I raise a non-conformity against, will put the responsibility on the installer to prove compliance rather than the other way around. I think I found my answer –

    Regulation 134.1.1 – “…The installation of electrical equipment shall take account of manufacturers instructions. “

    I don’t think any SWA manufacturer would approve a termination method that would preclude the earthing of the steel.

  • 0
    If there are metal glands at the ends, and the singly insulated cores pass through them are not sleeved, then the glands must be earthed. It is quite hard to earth the glands and not the armour. Of course there do not have to be glands at all if the end is just splayed out into free cores.

    However if this is an inspection failure and you are looking for the right code, one has to ask why the armoured cable was used at all. There is then the question of if the cable still is suitable for its environment if the armour is not earthed.

    That previous thread.



    Mike.
  • 0
    Surely as a conductive part in very close proximity to live conductors  its better to earth it just in case  then even if its only capacitive coupled to the live core its totally safe. In my view unless the regs share I definatley SHOULDNT earth it then it will be earthed
  • 0
    stuff:


    The armour does not meet the definition of an exposed conductive part when neatly terminated so it can not be touched – under what fault conditions could it become live?



     




    Single fault, a failure of basic insulation.


  • 0
    Why install the cable without earthing the metal containment?
  • Former Community Member
    0 Former Community Member
    Ok, Thanks again. 

    The scenario is SWA clipped along a wall. No metallic parts.

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