Earthing to armour of SWA

[sjm]

Seen it quite often where the armour of SWA is not earthed, at all, just removed and cores used as live, neutral and earth.
IMHO this is completely wrong for the first installation (what were they thinking??) and should be rectified urgently if found on an EICR ie code C1/2.


What do you guys think? What code? I'm interested to find out.


Thanks in advance.
Steve.

 

[Knobhead]

The outer cores of concentric are copper, no where near at tough as steel. Added to which for a domestic installation split concentric would have to be used giving the possibility of the CPC being severed and showing no signs in the operation of the installation until a fault occurs. Unless well protected, no, concentric will not replace SWA.

 

[Engineer54]

Concentric minimizes the risk of completely cutting through the neutral and earth without first completely cutting through the live cores.

Are you actually being serious with the above statement??

 

[FatBob]

The outer cores of concentric are copper, no where near at tough as steel. Added to which for a domestic installation split concentric would have to be used giving the possibility of the CPC being severed and showing no signs in the operation of the installation until a fault occurs. Unless well protected, no, concentric will not replace SWA.

I was not suggesting the removal of the steel armour

 

[Knobhead]

I was not suggesting the removal of the steel armour

What are you suggesting then? A completely new breed of cable?

 

[Knobhead]

Hang on, it's been done before

View attachment 12598

 

[FatBob]

What are you suggesting then? A completely new breed of cable?

Not really, unless I am mistaken it was made by BICC many years ago.

BS7870 SCC is suitable for underground and general use without an armoured shell.

 

[Engineer54]

Not really, unless I am mistaken it was made by BICC many years ago.

BS7870 SCC is suitable for underground and general use without an armoured shell.

You are very much mistaken, it is ''NOT SUITABLE'' for direct burial, without additional mechanical protection. As for general use, it again depends how and where your installing such a cable, ...it will need to meet exactly the same criteria as say T&E!!

Have you worked with this cable at all, i would love to see a photo of a termination completed by yourself, if you have??

 

[brman]

funny seeing this thread, I've just returned from the 2nd house in 2 days where I have found with SWA all over the garden without any proper termination or earthing. They are going to be a right pain to sort, particularly the ones where the SWA has just been run into the end of a bit of conduit so there is no box to terminate to....:banghead:

Unless someone can point me at an adaptor that will allow me to terminate SWA to the end of a bit of 20mm conduit?​

 

[Knobhead]

Constant pressure spring?
What they done? Chopped the armours where they enter the conduit?

I can see you having to pull the SWA inner serving back to thread and fit a gland and make it off properly.

 

[johnboy6083]

funny seeing this thread, I've just returned from the 2nd house in 2 days where I have found with SWA all over the garden without any proper termination or earthing. They are going to be a right pain to sort, particularly the ones where the SWA has just been run into the end of a bit of conduit so there is no box to terminate to....:banghead:

Unless someone can point me at an adaptor that will allow me to terminate SWA to the end of a bit of 20mm conduit?​

remove the cojcuit, and gland tour cable into a through box. This can then be earthedvia the M4 thread in the back, which will also earth the SWA. If required, you can then add to this with more conduit ect, or if its only to be used as a JB, it can be filled with "Magic Gel", to keep it completely water tight. Ive heard that you can also buy cast box lids, that will keep tension upon a rubber gasket, so that it will be at least IP44 rated, not like the rubbish thin galv box lids that bend when you sneeze

 

[brman]

Constant pressure spring?
What they done? Chopped the armours where they enter the conduit?

I can see you having to pull the SWA inner serving back to thread and fit a gland and make it off properly.

yes, armour goes a few inches into the conduit (plastic btw) and is chopped off, cores carry on from there to the nearest junction box or accessory.
Excuse my ignorance, what is a constant pressure spring in this context?

remove the cojcuit, and gland tour cable into a through box. This can then be earthedvia the M4 thread in the back, which will also earth the SWA. If required, you can then add to this with more conduit ect, or if its only to be used as a JB, it can be filled with "Magic Gel", to keep it completely water tight. Ive heard that you can also buy cast box lids, that will keep tension upon a rubber gasket, so that it will be at least IP44 rated, not like the rubbish thin galv box lids that bend when you sneeze

I didn't mention in my post that it is plastic conduit which doesn't help with earthing. I suspect I end up using adaptable boxes to terminate the SWA where ever the armour ends and extend from there to wherever the next junction is in the conduit system.
It is just a pain as all I was asked to do was tidy up one of the cable routes, I wasn't expecting the whole lot to be such a mess. Still, I am still at the stage where the quote can be adjusted accordingly and the weather is nice for working out of doors at the moment

 

[Knobhead]

yes, armour goes a few inches into the conduit (plastic btw) and is chopped off, cores carry on from there to the nearest junction box or accessory.
Excuse my ignorance, what is a constant pressure spring in this context?

Forget the spring.

All you can do is pull it back and fit a box. But leave the inner serving in place and run a CPC to the gland.

 

[FatBob]

You are very much mistaken, it is ''NOT SUITABLE'' for direct burial, without additional mechanical protection. As for general use, it again depends how and where your installing such a cable, ...it will need to meet exactly the same criteria as say T&E!!

I did not know that Engineer54.

522.8.10 a cable buried in the ground shall incorporate an earthed armour OR metal sheath or both, suitable for use as a protective conductor.

Can you expand please?

Just looking in JW P203
Three types of cable may be installed underground
1 armoured or metal sheathed or both
2 PVC insulated concentric type
3 Any suitable cable enclosed in conduit or duct which gives at least the same degree of mechanical protection as an armoured cable.

 

[Engineer54]

I did not know that Engineer54.

522.8.10 a cable buried in the ground shall incorporate an earthed armour OR metal sheath or both, suitable for use as a protective conductor.
A split concentric cable has neither of these elements, thus does not conform to the requirements, of this regulation...

Can you expand please?

Concentric cables, split or otherwise are the same as any normal cable. With the split concentric cable it is basically the same as a T&E with bare earth conductors, except that all the conductors are laid out concentrically around a central conductor core.

Therefore you can't direct bury in the ground, this type of cable needs to go into a mechanically protective duct. Likewise using this cable in the fabric of a building, it needs to conform to all the requirements that say a standard T&E cable would. ..eg buried less than 50mm in walls etc will require additional RCD protection unless other mechanical protection is afforded...

Just looking in JW P203
Three types of cable may be installed underground

1 armoured or metal sheathed or both Fine

2 PVC insulated concentric type. .....Not unless is has an armouring, or an overall metal sheath incorporated, which to my knowledge they don't!!

3 Any suitable cable enclosed in conduit or duct which gives at least the same degree of mechanical protection as an armoured cable. Fine

However, the DNO use this type of cable to supply there service cut-outs, on TNC-S (concentric) TN-S (split concentric) systems, with or without ducting!! But then they work to a completely different set of rules/regulations, than you and BS7671... lol!!

 

[FatBob]

However, the DNO use this type of cable to supply there service cut-outs, on TNC-S (concentric) TN-S (split concentric) systems, with or without ducting!! But then they work to a completely different set of rules/regulations, than you and BS7671... lol!!

Thanks. I assume the acceptability lies in the interpretation of metal sheath suitable for use as a protective conductor.

Interstingly, the NICEIC G&G 17th guide lists insulated concentric cable as suitable
.....The cable must incorporate earthed armour or metal sheath, or both, suitable for use as a protective conductor, or be of insulated concentric construction.

BUT Neither party indicate where or why they have chosen to list concentric cable separately as it does not appear as such in BGB or BRB.

522.8.10 a cable buried in the ground shall incorporate an earthed armour or metal sheath or both, suitable for use as a protective conductor.

I have sent an email to John Whitfield, I will post the reply and thanks again for your explanation