csa of protective conductor for swa cable

[omega]

Hi Guys,
Just looking for some advice. I'm currently installing power to a workshop via a 16mm swa 3 core cable.
The question is, what size protective conductor should i use for the swa at the supply end. The length of
the run is approx 40 metres. Cheers,

 

[omega]

I just thought i'd add that i'm aware the regs state minimum of 2.5mm if protected against mechanical damage and corrosion
but wondered if it's best practice to use larger cable, thanks again.

 

[rattlehead85]

???? you said you are using 3x16mm so the 16mm earth has answered your own question. Or is it you are on a T.T in which case are you buried or above ground?

 

[telectrix]

omega, is this 3 phase, by any chance?

 

[Engineer54]

If your asking what size CPC to run with the SWA cable, the answer is you don't need one as the SWA is more than capable of providing your CPC needs. And that's whether it's a 2/ 3/ or 4 core cable.

If it's a PME supply single phase, you can use a 3 core, and use the 3rd core as your bonding conductor and the SWA as your CPC. However, if PME 3 phase you'll need to run that separate bonding conductor!! Keep the size the same as the core conductors, though you may probably get away with a 10mm conductor!!

 

[omega]

Hi, yes it's a single phase and the 3rd core will act as the earthing conductor for the workshop final circuits. I'm just looking at the swa
itself, obviously this will need earthing at the supply end as per regs, just a bit unsure as to what size cable to use for this. By the way, it's a TNS supply.

 

[timbobelfast]

Work it out with the Adiabatic Equation......

 

[Engineer54]

Hi, yes it's a single phase and the 3rd core will act as the earthing conductor for the workshop final circuits. I'm just looking at the swa
itself, obviously this will need earthing at the supply end as per regs, just a bit unsure as to what size cable to use for this. By the way, it's a TNS supply.

If TN-S then the SWA really needs fly leads at both ends not just at the supply end!! The 3rd core being connected directly/indirectly to the workshops EMT... 6 to 10mm fly-leads will suffice for a 16mm cable, or as suggested use the Adiabatic Equation... lol!!

 

[omega]

Thanks for that, i was intending to use the fly leads at both ends anyway but was going to use 16mm. I'll probably go with eng54's suggestion and use 10mm, thanks again for the advice, much appreciated.