Armour termination

[ebee]

Split concentric, where the neutral and earth conductors surround the live core. Whilst this complies with the supply regulations for use by DNO, BS7671 requires the armouring of a cable to be connected to earth. As such, "split concentric" does not comply for use as an armoured cable on the customer's side of the meter. In order to comply with BS7671, you would need to run SWA.

 

[holmslaw]

..

 

[ebee]

The words were not chosen by me.
I plagiarised them actually.

A N may not be used as earthed armouring by us. Suppliers rules are a bit different though. That`s why you get PME on the supply side.

In the UK that is.

In Vanuatu it might differ

 

[holmslaw]

..

 

[SUNRAY]

Oi SUNRAY, are you going educate us all by putting up some links to MI's saying SWA can be terminated in earth bars. I won't hold my breath.

He'll be even more pleased when he realises SUNRAY's low level of competence.

It seems I have been able to make searches and enquiries, which others are unable to do.

So who's incompetent?

Its all out there on the internet and in manufacturers documents

 

[JohnW2]

N may not be used as earthed armouring by us. Suppliers rules are a bit different though. That`s why you get PME on the supply side.

Indeed, and that's why 'we' (as opposed to DNOs) cannot use straight con. However, split con is a different matter, since N & E are separate (the clue is in the 'split'). However, although 'we' can presumably use it, the E conductors neither form a complete 'sheath' nor are they (usually, if ever) made out of the right materials to be acceptable as armour, so we cannot use it as 'armoured' cable. That's my understanding, anyway.

Kind Regards, John.

 

[holmslaw]

..

 

[holmslaw]

..

 

[JohnW2]

You're wrong.

Wrong about what aspect? I'd be grateful if you would educate me.

Kind Regards, John.

 

[holmslaw]

..

 

[JohnW2]

You're wrong.

Wrong about what aspect? I'd be grateful if you would educate me.

Now you've involved yourself in this thread there is no point in continuing.

Thanks for that helpful and polite response. I wonder if anyone else could perhaps add a slightly more detailed explanation as to what was 'wrong' with what I wrote?

Kind Regards, John.

 

[ban-all-sheds]

My guess is that where you were wrong was saying that straight concentric can't be used.

OTTOMH I don't see why it can't be used in applications where no cpc or mechanical protection is required.

 

[JohnW2]

My guess is that where you were wrong was saying that straight concentric can't be used.

That's possibly what he meant - he is so helpful that one can but guess.

OTTOMH I don't see why it can't be used in applications where no cpc or mechanical protection is required.

Yes, I suppose that is strictly true, but the number of situations in which that would be applicable are obviously very few - maybe meter tails or sub-mains which didn't requiremechanical protection and which were accompanied by a separate CPC.

Returning to the original issue, and reaching rapidly for my flak jacket, I'm wondering about the method of terminating SWA was being described. Very unconventional, yes ... anathema to all those electricians who have had to learn SWA-terminating skills, yes - and, like you, I'm at least 'surprised' at being told that some manufacturers of SWA may actually 'advocate' it. However, in engineering terms, what is actually wrong with it? If the cable is adequately mechanically supported and the connection of armour to earth is (I would suggest) at least as good/reliable as that achieved with a gland, then what's the problem? Indeed, what we're talking about would be essentially identical, termination-wise, to what one would do (and would have to do) with split con, isn't it?

Kind Regards, John.

 

[LUG]

Hi

I have come across this site a number of times while Googling and usually have a look around while here.
This thread has prompted me to join and stick in my h'pence.

As an apprentice one of the techniques we were taught when wiring into an insulated fitting was to sleeve the armour and treat as any other earth wire.
I dont know if the practice has been withdrawn, or of any manufacturers details to back this up except to say that I trained with a company that a few years previous had been owned by Enfield Cables before they were bought out by Delta.

The other point that I was taught was the gland was only for the electrical connection and not to provide mechanical strain relief.

Lug

 

[SimonH2]

I have to say that just sleeving the armour and terminating it into an earth terminal does seem a neat way of doing it. Though, I do find myself thinking that on most cables I've dealt with, it would be a fairly thick bit of wire by the time you got all the strands together !