SWA armouring as Earth

[Paul Hamill]

At what size of SWA cable are you required to run an external earth ? I'm inspecting a distribution system and its a complete mess. No main earths anywhere but they have utilized the armour and are using at is their earth. I can't find anything in the regs book, is there possibly something in the guidance notes I can refer to ?

 

[Wilko]

Hi Paul - if you've got GN8 its Appendix B. There's a few tables, this is just the first one. Hope that helps

 

[Pete999]

At what size of SWA cable are you required to run an external earth ? I'm inspecting a distribution system and its a complete mess. No main earths anywhere but they have utilized the armour and are using at is their earth. I can't find anything in the regs book, is there possibly something in the guidance notes I can refer to ?

SWA CPC.pdf

 

[Ian1981]

For swa cables operating at 70 degrees max

 

[Paul Hamill]

Hi Paul - if you've got GN8 its Appendix B. There's a few tables, this is just the first one. Hope that helps

View attachment 37498

I have the guidance notes on my laptop just found them, thanks.

 

[westward10]

Ian you post that page much more you may have a law suit on your hands

 

[westward10]

If you are doing inspections you should know this being an electrical supervisor and all that.

 

[Risteard]

Don't forget that adiabatic calculations may permit other sizes to those listed.

 

[Ian1981]

Ian you post that page much more you may have a law suit on your hands

I don't think anybody looks at it to be honest

 

[davesparks]

At what size of SWA cable are you required to run an external earth ? I'm inspecting a distribution system and its a complete mess. No main earths anywhere but they have utilized the armour and are using at is their earth. I can't find anything in the regs book, is there possibly something in the guidance notes I can refer to ?

There is no limit on size where a separate conductor is required, it depends on the individual conditions of the installation.
When assessing an existing installation the table 54.7 can be used as a first reference, but if this shows that the armour is inadequate you must then use the adiabatic equation as that may show that it is adequate.
Table 54.7 often gives a larger conductor size than is actually required.

You also need to consider whether the cpc also needs to perform the function of a bonding conductor, this usually changes things considerably.

 

[Paul Hamill]

If you are doing inspections you should know this being an electrical supervisor and all that.

There's always one smart arse.

 

[westward10]

Was a fair question but a nice response.