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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


    Btw – domestic – through cavity wall to outside.

     


    Just out of interest, please give more details. Length of run. Height above ground. Is the cable liable to receive knocks or thumps by anything? What does it run to? Why was S.W.A. chosen in the first place for this run? Have you any pictures of the run.


    Thanks,


    Z.


  • 0
    I will carry on earthing it, I’m not being convinced that earthing is not required.


    In reality earthing it is not much extra work, you have to trim the cable and armour utter regardless. The only extra work fitting a SWA gland instead of a stuffing gland is wiggling the conductors about to bell out the armour to take the cone of the gland and fitting an earth fly lead in the enclosure, which is hardly an excessive amount of work, it also ensures compliance with 526.1


    Andy B
  • 0
    The law in England is permissive, that is to say that you can do whatever you will unless it is forbidden.


    If you can demonstrate that not earthing the armour of SWA as we have discussed is forbidden, so be it. Otherwise, leave well alone.
  • 0
    It’s easy to find guidance telling electricians to earth the armour of SWA cables, such as this:

     

    Providing automatic disconnection of supply (ADS)



    Regardless of whether the armouring of the cable serves as a protective conductor, or not, it should always be effectively earthed to ensure the requirements of ADS are met. Should the armouring not be effectively earthed and a fault develops due, for example, to mechanical damage of a line conductor incorporated in the cable, the condition may leave the armouring attaining line voltage and pose a danger to persons in the vicinity of the installation or using the installation.

    https://www.voltimum.co.uk/articles/guide-installing-steel-wired-armoured


    Can anyone post a link to what seems to be an authoritative article saying that it’s not required? There’s plenty of “how to do it” videos on Youtube in which electricians say it’s not required, but I don’t count consider those authoritative. 


     


  • Former Community Member
    0 Former Community Member
    Chris Pearson:

    I think that the presumption here must be that if the installer has certified the work as being compliant, it complies.




    If only that were true ?


  • 0
    when SWA cable install on the surface in-wall or tray it may be safe  and can be visibly anybody but unsafety area as factory /or Roadway area can be damage rather  by knocking  vehicle or machinery by accidently  at the time live cable and armor guard can be connected together, cause of that can shock to people or damage  to equipment if armor guard earthed at the  sort circuit happening time power  can be automatically cut off  so that purpose always armor guard should have earthed

    Therefore I proposed armored guard must earth separately without connecting cable by metal gland and only use PVC gland to connect a cable to panel board for only neatness purpose
  • 0
    I think that the presumption here must be that if the installer has certified the work as being compliant, it complies.


    I would only accept the second electrician's opinion (it is no more than that) if he can demonstrate exactly how the work does not comply.


    Time to move on!
  • Former Community Member
    0 Former Community Member
    Replying to previous posts - This is the point of my OP.

    I’ve googled SWA data sheets but not found anything to say the steel ‘must be earthed’, but equally, I’ve not found any literature – anywhere -  supporting no earth…

    Where SWA is a requirement, you would expect the steel to be earthed, but in this scenario, the steel is surplus to requirements hence the installer's method of termination. Would a manufacturer support this method? I doubt it.

    To be honest, I don’t have an issue with it, but I have been tasked with approving the installation after another electrician has already condemned the lack of earth – so the issue needs to be resolved.  I feel, on this occasion, that it would not be unreasonable for me to ask the installer to prove compliance rather than me disprove.

    I’ll probably word the nc something along the lines of “ It is unlikely that the SWA cable manufacturer would support an installation where the steel armour is not earthed…”

    Btw – domestic – through cavity wall to outside.

  • 0
    Prove it is right! Apart from the buried scenario, the argument hinges on whether it is an ECP. I was asked to comment on an EVSE installation last week. Very neat job with 3no 7Kw 3-phase twin outlet units supplied from a new TPN board. The wire armour of the SWAs was not earthed either end. All in 100mmx100mm plastic trunking apart from a short length underground in 110mm Wavin. Wire armour cut back and insulated in the EVSE pillars and in the trunking all with what looked like heat shrink insulation and tape. 

    At least there is no chance of exporting the PME!
  • Former Community Member
    0 Former Community Member
    stuff:


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

     


    Hi stuff, what kind of wall is it? Domestic, commercial or industrial?


    And what is your involvement? Are you doing an EICR? Is the work in question certificated?


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