Swa armouring let it be Earth

[cliffed]

How come some qualified electricians will argue & argue about earthing the armouring of the cable.
Seen many jobs where they use plastic junction boxes & no earth continuity on the armouring.
Regardless of how many cores are used it still needs earthing.
Their biggest argument is it’s only for mechanical protection are they actually taught this @ College

 

[MJPD29]

It's a no brainer, it has to be earthed. There's no 2 ways about it. If it's only for mechanical protection it still has to be earthed to prevent the scenario where the armour becomes live due to damage to the cable.

 

[littlespark]

Much of the time the armour is being used as the cpc anyway so it should be habit to earth it.

 

[cliffed]

It's a no brainer, it has to be earthed. There's no 2 ways about it. If it's only for mechanical protection it still has to be earthed to prevent the scenario where the armour becomes live due to damage to the cable.

Exactly my external lights had Swa cabling to them I used 4c ….2Years later fault on the lights… 1core down to earth tripping Rcd….manage to reconfigure connections.
The guys had put hardcore then used a Wacker…most probably a stone had pierced the sheath & armouring then the cable.
Embarrassing I must say…sparky fault on his lights.
Had a go @ builder …he said you must of put a faulty cable in…

 

[littlespark]

No sand around the cable, cliffed?
Sounds like the builder used the wrong backfill materials.

 

[IAmSparkytus!]

Much of the time the armour is being used as the cpc anyway so it should be habit to earth it.

Tbh I've only just recently started using the armouring as the CPC. Used to always get 3core or 5core rather than 2core or 4core.

Company I worked for as an apprentice always did it that way so it was habit for me to do the same when I started to get the materials myself.

 

[buzzlightyear]

The outer earth or the inner earth to the core I say.

 

[Darkwood]

Firstly we assume we are discussing low voltage here and not extra low, if that is the case then the armouring must be earthed with no exceptions however depending on there been a separate earth core then that would denote if you only earth one end or both, if separate earth core then one earthed end is fine on armouring and good practice is at the supply end not the load to reduce fault current times and the vulnerability of load ends been more subject to wear and tear and alteration, although no regulation specifies this as inspections should routinely check all this.

 

[davesparks]

however depending on there been a separate earth core then that would denote if you only earth one end or both, if separate earth core then one earthed end is fine on armouring

If there isn't a seperate earth core then you can't earth both ends.

 

[timhoward]

There are also permutations of sizes and cores where the copper equivalent size of the steel isn’t up to scratch to use the armour as a cpc.
I think going back to first principles of ADS and fault protection for the distribution circuit and anything downstream is wise before assuming it’s ok to do this.

 

[Darkwood]

If there isn't a seperate earth core then you can't earth both ends.

Playing on words there, no earth core then your armouring is the earth and both ends need to be completed to provide an earth unless the load is double insulated where it negates the need to carry it to an earth terminal.... you knew what I meant

 

[DefyG]

unless the load is double insulated where it negates the need to carry it to an earth terminal.

Or the load end is converted to TT earthing system.

 

[pc1966]

Firstly we assume we are discussing low voltage here and not extra low, if that is the case then the armouring must be earthed with no exceptions

Absolutely!

however depending on there been a separate earth core then that would denote if you only earth one end or both, if separate earth core then one earthed end is fine on armouring and good practice is at the supply end not the load to reduce fault current times and the vulnerability of load ends been more subject to wear and tear and alteration, although no regulation specifies this as inspections should routinely check all this.

There are possible corner cases when the armour is not a low enough R2 on its own to meet disconnection times and/or fails adiabatic, then having a good copper CPC linking both ends will make sure that a cable L-armour fault is safely disconnected. In that case you could find regulations that demand it!

 

[Darkwood]

I'm fully aware of that but usually that is out of the scope of general chat on here and only needs mentioning if relevent, no one mentioned sizing and cores in the 120mm etc, with all respect if they are fitting them at that size then you expect some level of knowledge of said regulations.

 

[Darkwood]

Or the load end is converted to TT earthing system.

Absolutely!

There are possible corner cases when the armour is not a low enough R2 on its own to meet disconnection times and/or fails adiabatic, then having a good copper CPC linking both ends will make sure that a cable L-armour fault is safely disconnected. In that case you could find regulations that demand it!

 

[Darkwood]

Or the load end is converted to TT earthing system.

That is inclusive of my comment but yes I didn't specify it directly, the comment was circumstantial to not needing an earth at the load end which is inclusive of your relevent addition.