Swa armour earthing

[keniff]

Can anyone point me in the right direction as to find the size of conductor to earth the armour of swa? It's not being used as the cpc on the circuit it's 25mm 3core. I'm always trying to find this when I'm terminating armoured cable!! Thanks

 

[Inteificio]

look at the stickies

 

[Moses]

Can anyone point me in the right direction as to find the size of conductor to earth the armour of swa? It's not being used as the cpc on the circuit it's 25mm 3core. I'm always trying to find this when I'm terminating armoured cable!! Thanks

10mm for 25mm Neutral, if not used as an earth.

 

[rich.250]

http://www.electriciansforums.net/e...ulations/23288-can-we-use-armour-swa-cpc.html

 

[Moses]

http://www.electriciansforums.net/e...ulations/23288-can-we-use-armour-swa-cpc.html

Yes, but you need to make sure that the equivalent of the armour CSA, in copper CSA is what you need it to be.

 

[rich.250]

Is that not in the table?? or am i having a blonde moment here... lol

 

[keniff]

Thanks for the links, I don't want to use the armour as the earth I mean the size of the flyleads to earth the different sizes of cable.....

 

[Moses]

Is that not in the table?? or am i having a blonde moment here... lol

I think you are having a blond moment.

its not in the table.

You need the manufacturers tables.

 

[rich.250]

Im blaming the beer....
I'm sure it says steel c/a and equiv. in copper...
if not my bad

 

[i=p/u]

your right as for fly leads id say same csa as line conductor

 

[Engineer54]

Yes, but you need to make sure that the equivalent of the armour CSA, in copper CSA is what you need it to be.

Why would you need to know that ??? I can understand if you were using the armour as a combined CPC/Bonding conductor, but not purely for use as a CPC....

 

[Engineer54]

Thanks for the links, I don't want to use the armour as the earth I mean the size of the flyleads to earth the different sizes of cable.....

So what is this armour and fly lead doing then, ...If not that circuits CPC??? Have you by any chance run in a separate single CPC conductor along side the SWA cable??

Just to let you know, a 25mm 3 core SWA cables armour, is more than capable of acting as that cables CPC!! lol!!!

 

[telectrix]

from what i can gather from the OP, he's asking what size conductor should be used to earth the armour when the armour is NOT being used as cpc. i always try and use the same size as the cpc.up to 10mm. i.e. if it's a 6mm 3 core cable. i would use a 6mm fly lead to earth the armour of the SWA. ( assuming it's glanded into an insulated enclosure)

 

[Engineer54]

from what i can gather from the OP, he's asking what size conductor should be used to earth the armour when the armour is NOT being used as cpc. i always try and use the same size as the cpc.up to 10mm. i.e. if it's a 6mm 3 core cable. i would use a 6mm fly lead to earth the armour of the SWA. ( assuming it's glanded into an insulated enclosure)

Exactly, and effectively causing the armour to become a CPC if both ends are connected to say the MET at origin and EMT or other earthing terminal at the load end... Whether he has run a separate earthing conductor (CPC) or not!!

 

[telectrix]

agreed, the armour will become cpc ( or part thereof ) if connected at the downstream end, but not if it is only earthed at the source end to comply with being an earthed metallic sheath.

 

[Engineer54]

agreed, the armour will become cpc ( or part thereof ) if connected at the downstream end, but not if it is only earthed at the source end to comply with being an earthed metallic sheath.

To be totally honest Tel, i think this is another case where the OP has been wrongly taught, not to use the SWA as your CPC. lol!!!

 

[telectrix]

personally, i would connect both ends anyway. 2 cpc's for the price of a banjo. a while ago, virtually every spark i spoke to was saying you could no longer use the armour as cpc. i think this incorrect belief was started by sparks who could not work out if the armour was sufficient or not.

 

[Engineer54]

Agree with you there lol!! The only situation i can think of where i wouldn't connect both ends of a SWA, is where the earthing system changes from a TN system to a TT for arguments sake!! Even then, i'd need a good reason leave a TN system behind, rather than combining them.. lol!!

 

[telectrix]

agree 100%. even your TT rods can't compete with a decent TN system . LOL.

 

[telectrix]

in fact, i think mit was the same sparks who swore blind you could not export PME and anything metal in a property had to be bonded, even the cast iron cistern in the outside karzi.

 

[keniff]

Thanks for the response guys, I have been taught that the armour is ok to use as the cpc relevant to size, I just have a 3core cable in the ground so using the 3rd core for my earth. In my situation I have stripped the three cores so they gland off and pass through an adaptable box to the consumer unit.

 

[Engineer54]

Thanks for the response guys, I have been taught that the armour is ok to use as the cpc relevant to size, I just have a 3core cable in the ground so using the 3rd core for my earth. In my situation I have stripped the three cores so they gland off and pass through an adaptable box to the consumer unit.

There you have it then, nothing stopping you connecting both ends of your SWA cable to the relevant earthing points at both ends!! Double bubble if you like, SWA and your third core!!! LOL!!

If you like, it'll be like calling your third core your main earthing conductor and the SWA as your CPC!! lol!!

 

[telectrix]

so you need to earth the gland with a banjo and fly lead. use same size as the cpc conductor. (assuming it's a non-metallic ad. box)

 

[keniff]

I shall earth both ends, I have those piraña nuts (poor fish) the cable is fed by a metal switch fuse so I'll use the nut but use a flylead aswell to make sure a good connection