Earthing Armoured Cable

[David Simpson]

SWA(Steel Wire Armoured) cable must always be Terminated with the correct size of Brass Bush Glands, then covered with a black tapered PVC "Boot". The outer compression ring clamps the cut-back steel armouring. In the gland kit there should be an odd sized "figure of eight" earthing ring for connection to non-metal enclosures. In turn, that ring should be connected to the internal conductor used for earth & to the earth conductor of FT & earth cable (6242Y ?). Earth continuity between your consumer unit's earth bar & the appliance/metal bench/metal junction box/ machinery/etc. must be maintained throughout. Particularly for PME supplies. If in doubt, ignore quick lash-up advice, and get an NICEIC or ECA Qualified Electrician to do the work.
Two or three vigorous Forum threads on earthing have appeared in the last 18 months. See "Search". Well worth a study. Particularly now that the latest (18th Edition) IET Regulations are just out.
Safety - - If in doubt - don't fanny about!

Regards, David

[G6Tanuki]

Also note that there are two kinds of SWA gland: one rated for indoor use and one for outdoor. The outdoor version attempts to provide a degree of waterproofing of the armour-to-gland interface; this is not present on the indoor model.

Even when using the outdoor version I always overwind with self-amalgamating tape before sliding the boot over, "just to be sure".

[robin0577]

If you go for Wiska weatherproof junction boxes, they do a handy little brass bar for then for the specific purpose of maintaining armour continuity. https://www.tlc-direct.co.uk/Products/WKEC308.html

... and yes the armour must be earthed, especially if the cable is buried. 522.8.10 "...a cable buried in the ground shall incorporate an earthed armour or metal sheath or both..."

[David Simpson]

G6Tanuki's advice on self-bonding tape is spot-on - - take it. We in Scottish Hydro-Electric always had loads of it. Plus dollops of that dark pink plasticine putty. These days there is a wealth of "tube-gun" 21st century sealing compounds which I've seen sparkies & plumbers & CH guys use. Moisture ingress into SWA & Split-Concentric cabling must be prevented at all costs.

Regards, David

[broadgage]

Agree WRT to extra waterproofing via self amalgamating tape or other means.
When I worked as a maintenance electrician, among the most common faults was water ingress to external SWA joints or terminations.

[Graham G3ZVT]

Originally Posted by eaglework

Not sure you really need to this but I cannot see it would cause a problem if you did.
The important point is that your 'functional' earth in the cores of the SWA is continuous and adequately terminated as is the armour of the SWA.
I suppose what you propose would give some additional protection if the SWA armour were to fail at one of your intermediate connections.

On a small point of order-
My understanding is the term "Functional earth" is reserved for an earth connection that is not there primarily for circuit protection purposes, eg a telecoms signalling earth.

[dglcomp]

This video from John Ward should show you how to terminate SWA.
https://www.youtube.com/watch?v=5XST0DkotYw

[YoungManGW]

Thank-you for the links to the information on cut-outs. Yes, will be using external glands, boots, etc. Excellent advice re. self-amalgamating tape, Wiska boxes, and their earth continuity blocks, all of which I'll take. I have this clear in my head now - very many thanks to all.

Regards,
Richard