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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

I think the conversation has drifted a little from my OP. We are all in agreement that the steel wire should be earthed.

I don’t know why the installer chose to use SWA, but the SWA installation did not have any exposed conductive parts. The SWA was terminated at both ends using non-metallic boxes and glands, the steel was not brought into the box, the steel was not used as a cpc – a scenario not covered in Guidance Note 8. So if your reason for earthing the Steel is ECP, then that wouldn’t stand up in this situation.

The installation was neat and tidy, and on the whole, the electrician looked as if he knew what he was doing. Now, if that electrician was Ajjewsbury or Chris Pearson, and I told them they had not complied with BS7671 they would come straight back at me with – “prove it!”…. So how do I prove it? My ‘opinion’ is irrelevant; Guidance is helpful but not enough. I would need to offer up a Regulation to demonstrate non-compliance or produce a regulation that reverses the situation where the installer has to demonstrate compliance.

In my view, although technically compliant with BS7671 from a safety perspective, the installation method is not compliant with cable manufacturer instructions – Hence my choice of Regulation 134.1.1 – “…The installation of electrical equipment shall take account of manufacturers instructions. “. If I raise this as a non-conformity, it will put the onus of the installer to demonstrate how their installation is compliant.
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0 Former Community Member over 3 years ago

I think the conversation has drifted a little from my OP. We are all in agreement that the steel wire should be earthed.

I don’t know why the installer chose to use SWA, but the SWA installation did not have any exposed conductive parts. The SWA was terminated at both ends using non-metallic boxes and glands, the steel was not brought into the box, the steel was not used as a cpc – a scenario not covered in Guidance Note 8. So if your reason for earthing the Steel is ECP, then that wouldn’t stand up in this situation.

The installation was neat and tidy, and on the whole, the electrician looked as if he knew what he was doing. Now, if that electrician was Ajjewsbury or Chris Pearson, and I told them they had not complied with BS7671 they would come straight back at me with – “prove it!”…. So how do I prove it? My ‘opinion’ is irrelevant; Guidance is helpful but not enough. I would need to offer up a Regulation to demonstrate non-compliance or produce a regulation that reverses the situation where the installer has to demonstrate compliance.

In my view, although technically compliant with BS7671 from a safety perspective, the installation method is not compliant with cable manufacturer instructions – Hence my choice of Regulation 134.1.1 – “…The installation of electrical equipment shall take account of manufacturers instructions. “. If I raise this as a non-conformity, it will put the onus of the installer to demonstrate how their installation is compliant.
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surface-mounted SWA – earthing

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