Purpose of Gland - The Sequel

dunny · 15 Jun 2005

I was reading a recent post re the purpose of glands when connecting SWA to a CU.

This got me thinking. My brother has got a 2.5mm T&E spurring off the back of a socket into an external JB connected to armoured cable via a 30a chock block. All cables are connected like for like (L -L,N-N,E-E). The armour of the cable isnt earthed to anything and instead of the metal (copper) type of gland he has a plastic one (which the armour tightens into).

This sounds as if its not acceptable presumably because if the armour became live it has no path to earth (despite that fact that its buried in the earth). Am I right? Does he need to add a gland and earth it to the armour?

andy · 15 Jun 2005

dunny said:
I was reading a recent post re the purpose of glands when connecting SWA to a CU.

This got me thinking. My brother has got a 2.5mm T&E spurring off the back of a socket into an external JB connected to armoured cable via a 30a chock block. All cables are connected like for like (L -L,N-N,E-E). The armour of the cable isnt earthed to anything and instead of the metal (copper) type of gland he has a plastic one (which the armour tightens into).

This sounds as if its not acceptable presumably because if the armour became live it has no path to earth (despite that fact that its buried in the earth). Am I right? Does he need to add a gland and earth it to the armour?

the armour MUST be earth. a core can also double as an earth. if you dont eartht he armour and there is a fault, the armour can become live and since its not connected to earth, will not trip MCB/fuse and a shock could be received

ban-all-sheds · 15 Jun 2005

dunny said:
My brother has got a 2.5mm T&E spurring off the back of a socket into an external JB connected to armoured cable via a 30a chock block. All cables are connected like for like (L -L,N-N,E-E). The armour of the cable isnt earthed to anything and instead of the metal (copper) type of gland he has a plastic one (which the armour tightens into).

Who did that?

dunny · 15 Jun 2005

Well it wasnt me

I am not exactly sure, the main conservatory was done professionally. This has armoured cable running out of the main CU into the conservatory and powering the sockets, this is definitely earthed and has a gland on it. The lights are spurred off the sockets on a fused spur/switch.

The other bit was done later, I noticed as the point where the cable enters the conservatory (vi a JB) is close to the JB that provides some outside power.One has a tin warning plate on it the other hasnt.

mapj1 · 15 Jun 2005

If an internal core is used as the earth, a conductive gland is only needed at one end, usually the supply end. There is no harm in using two, and having a core and a braid in parallel
With a floating braid, much of the protection of armourclad is lost - the idea being the unlucky pick-axe or fencing spike is earthed by the armour before it reaches the live conductor, and the power goes off, but damage and shock risk is minimised. Otherwise it becomes no better than a strong but non-armoured cable.
Sometimes an isolating gland is used at the load end if independent earthing is required - a radio installation like a GSM base-station requiring a TT local supply, but from a PME riser for example. However, that is only done just before the RCD, the armour is still earthed at the feed end.
Similar things are done at caravan and boat shore power boxes, but not normally as you describe.

dunny · 16 Jun 2005

Cheers, I will earth it for him to be on the safe side.

ban-all-sheds · 16 Jun 2005

dunny · 17 Jun 2005

Using one of these:-

SWA Gland Packs ( CW )
3 Part External / Internal Glands for SWA Cable
Terminates and secures cable amouring.
Provides a seal on outer sheath of the cable IP66

From banjo on gland back to earth on radial socket circuit (back of the socket that feeds outside socket).

This what you would expect?

ban-all-sheds · 17 Jun 2005

Sounds good to me.

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Purpose of Gland - The Sequel

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