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surface-mounted SWA – earthing

Former Community Member over 3 years ago

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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0 Former Community Member over 3 years ago

Thanks for the response, Much appreciated.

The case I have described, the steel wire does not meet the definition of an exposed conductive part – as described in Part 2 - No part of the steel can be touched.

The scenario you mention is extremely unlikely; who would take a hammer and nail to a surface-mounted cable? The armour is pretty robust and would take a healthy battering in most situations. This could apply to any surface-mounted cable – a nail penetrates a live conductor without coming in contact with the cpc, and the nail remains live without tripping.

I'm not advocating that the steel should not be earthed. I'm just after the regulation that says it must? Opinion is great for guidance (sometimes), but if I raise a non-conformity against somebody's work, I need to back it up with a regulation or standard.
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0 Former Community Member over 3 years ago

Thanks for the response, Much appreciated.

The case I have described, the steel wire does not meet the definition of an exposed conductive part – as described in Part 2 - No part of the steel can be touched.

The scenario you mention is extremely unlikely; who would take a hammer and nail to a surface-mounted cable? The armour is pretty robust and would take a healthy battering in most situations. This could apply to any surface-mounted cable – a nail penetrates a live conductor without coming in contact with the cpc, and the nail remains live without tripping.

I'm not advocating that the steel should not be earthed. I'm just after the regulation that says it must? Opinion is great for guidance (sometimes), but if I raise a non-conformity against somebody's work, I need to back it up with a regulation or standard.
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surface-mounted SWA – earthing

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