Big_Spark said:
Very Good Phil, but what about Regulation 542-03-01...table 54A and more importantly...the old stallwart..table 54G
All earthing conductors should be selected by using 54G, the adiabatic equation is a red herring.
542-03-01 Just says to follow reg 543 and also gives csa for buried cable as I said above, so yes for buried cable you need to use 54A. I'll give you that one
Reg 543-01-04 basically says, if you can't or don't want to calculate csa using the adiabatic equation then you can use table 54G instead.
- Sorry for all the reg quoting. When I was a wee lad I used to play with toy soldiers and generally the winner of the games was the player who could take advantage of rules loopholes the best
Adam and other posts since,
Cheers for that, so if Zs was 1 Ohms then I would be 240A. I thought I must have something wrong.
So sticking this in the equation and also using a type S rcd that trips in 500ms would give S at least 1.2mmsq
The end result as far as I can see, is that for Zs at least 1 Ohm, with an RCD, protected from corrosion and mechanical damage 2.5mmsq is fine (as per securespark's OSG quote
), if no protection from mechanical damage 4mmsq needed and if buried see table 54A. If you don't want to or can't measure Zs then you have to use 54G
Thanks for all the input everyone, that's helped me immensely.