HI All,
I have been asked by a designer on a job I'm working on in a factory to provide a temp supply for some machines, via a DB to be supplied with a 160mm 3ph & n, SWA. He has specified a separate 90mm "earth" to be installed but I am unsure why, as the armour will be used as the earthing conductor for the new DB, any advice?

I've never seen a 160mm2 SWA - I gues you mean 150mm2.

If it's XLPE it won't comply with Table 54.7 of BS 7671, and as such the designer has asked for a minimum of Line size/2 as a CPC - ie a minimum of 75mm2, the nearest being 95mm2.

In the absense of source impedance data and CPC type, he probably had little option.

Of course when calculated the armour may well 9will almost certainly0 comply - but i guess the calcs haven't yet been done.

failing that, he doesn't trust the installer to make the glands off properly

regards

OMS

-------------------------
Failure is always an option

Could it be because the armour will also be used as a bonding conductor?

Dave.

Thanks lads, I do not think there is need for it to be used as bonding as it will be in the same building, guess it is due to lack of calcs as oms says.

Cheers
lee