How to use armoured cable

Not terminating it properly into a suitable box will scream bodge-job ...

In one sense, you can use an armoured cable much as you would any other

- so long as you don't need to take advantage of any of the extra features you normally get from it being an armoured cable.

So for example, using it in place of T&E, ignoring the armour, not terminating it "correctly" you will in effect get T&E that is a bugger work with. However it will work electrically, and be no less safe.

The reason that armoured cable exists however is that it is suited to jobs that other cables are not. It can be buried directly in a trench with no other protection. It can be used outside and exposed to the elements. It is physically robust and resistant to damage.

However to be able to be used in those applications, you need the armour to be properly earthed and the cable properly terminated[1], since this is one of the things that makes it safe to use for some of these applications. So for example, in a trench, it will be far better at resisting your attempts to stick a spade through it in the first place, but if you do manage it, its design will ensure that in order to penetrate a live conductor, you will have to do so passing through an earthed shield. That will ensure the circuit protective device will operate as well.

Likewise with an external lighting install, one of the advantages of SWA is its resistance to the elements. Part of this comes from the waterproof glands that you use to make off connections to the lamps. So not only is it a physically very strong termination and strain relief, also a water proof one.

I see Andy has already posted the link on how to terminate it:

I disagree. It's a bigger danger if you use it like that as if the armouring becomes live then no MCB or RCBO will trip and you may have live SWA armouring.

The armouring must be earthed - even if at only one end.

By pond cable I assume you mean some sort of black flex.

ie a black flex with 3 cores.

If you did use that it needs to be at least a minimum of 1.0mm CSA

It is a good point, and in cases where one would normally use SWA I fully agree. In a very limited case where there is little risk of mechanical damage - and suitably labelled up - I would argue it is

Having said that, if T&E is what you need, buy some and save the "free" SWA until you need it for a job it was intended to do.

I would have said that the safest way,as mine was, was to make the metal armoured sheath, earthed, then if some idiot does damage it, hopefully the breakers will go. I mean, it seems common sense to me, even if it does not look pretty, as long as its firm and cannot break off or short anywhere, to me its good. Brian

Thanks very much all for your advice. By pond cable I mean something like this...

Thinking about it further, trying to bend the armoured cable would be v tricky so maybe best is to buy some new stuff? What's best / cost effective to use?

thanks

Lee.

Not sure I can visualise what you mean by "channelled into a rendered wall" here - or what the implications of terminating cables at this box would be?

You can swap cable types in different areas if required. Starting inside with 3&E, and transitioning to something else as you venture outside.

You can also use 3&E outside if suitably protected in conduit / trunking etc.

That does need further explanation. And will be obvious when Lee explains it.

Indeed. Something I do a lot. T&E on the inside and SWA on the outside etc

Agreed, but just to add to that it could not be used in buried conduit due to condensation collecting at the lowest point.

The cable Lee linked to was the old HiTuf TM cable. That is an excellent outdoor cable for this type of job if you do not want the bother of terminating SWA and is fitted within the regs.

Thanks John. To clarify what I meant above....

The current light switch and lights go to a junction box mounted on a rendered wall. This is where I need to run the new 3&E from to the new inside light switch. On it's route it goes through the following zones

1. I need to cut a grove out of the rendered wall, run the cable in it and render over it
2. Through a hole in the rendered wall
3. Through the flower bed about 100mm below the surface for around 200mm
4. Up into the stud wall
5. Through the brick built cupboard
6. Through the house wall and to the switch.

Hope that helps?

Which of these could I use standard 3&E in and for those which needs conduit?

Thanks again all

Lee.

ok it sounds like (working backwards), normal 3&E from the switch, through the brick cupboard, into the stud wall, as far as the exit point. Terminate in a surface mounting junction box there.

You could the use the NYY-J / HiTuff cable from there, or SWA. If you use NYY-J, then the section through the flower bed should be protected in a length of conduit. If using SWA then it can be buried direct in the bed.

The final bit is the connection to the outside junction box. If it has a visible flat side where you can mount a gland[1], and you don't mind that last bit of cable being visible then you can do that. If you want that bit of connection to be hidden, then you would need chase up to the junction box and behind it a bit, to bring the cable (or more likely just the inner bedding of the cable) in through a grommet protected knockout in the back of the box. (I would use adhesive lined heat-shrink to protect the end of the outer sheath (+armour if SWA), to the bedding).

So, if using HiTuff/NVV-J you would need 4 core to give you 2 way switching and earth. If using SWA, and terminating both ends with proper glands, then you can use 3 core, and the armour as the earth. If isolating the armour at the outside JB (i.e. only connecting it at the stud wall end), then you would also need 4 core.

Like:

Perfect thanks John :)