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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.

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    You are making an assumption Andy, and that is that the sheath is undamaged.

    Not quite. My assumptions are that the SWA sheath is not lesser than the sheath found on an insulated & sheathed (e.g. T&E) cable, and in this particular case, SWA has been employed in a situation where T&E would have been acceptable (which seems to be the case from the OP's description).


    Yes, a single event could damage both the sheath and basic insulation at the same time - but that's exactly the same issue with T&E (if anything the mechanical properties of the armour in the SWA cables make simultaneous damage to the basic insulation somewhat less likely). In situations where we're relying on the armour for protection (underground, concealed in walls outside of zones, or in harsh environments) then yes clearly we can't rely on the sheath remaining intact. In this case however the situation seems no worse at all than if T&E had been used - as if that was acceptable, how can this one not be?


      - Andy.
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  • 0
    You are making an assumption Andy, and that is that the sheath is undamaged.

    Not quite. My assumptions are that the SWA sheath is not lesser than the sheath found on an insulated & sheathed (e.g. T&E) cable, and in this particular case, SWA has been employed in a situation where T&E would have been acceptable (which seems to be the case from the OP's description).


    Yes, a single event could damage both the sheath and basic insulation at the same time - but that's exactly the same issue with T&E (if anything the mechanical properties of the armour in the SWA cables make simultaneous damage to the basic insulation somewhat less likely). In situations where we're relying on the armour for protection (underground, concealed in walls outside of zones, or in harsh environments) then yes clearly we can't rely on the sheath remaining intact. In this case however the situation seems no worse at all than if T&E had been used - as if that was acceptable, how can this one not be?


      - Andy.
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