Hello guys
I have been asked to install a sub main supply cable 25mm SWA 4 core cable from a 63A isolator to supply a distribution board. I am however a little confused as 25mm is huge in my opinion and after checking the regs BS7671 a 16mm cable can handle 77A. Also 25mm will not fit into the terminals of the isolator, I can only assume that the person is talking about the total diameter of the cable. Any ideas are welcome as I have not installed a 3 phase system in a while of this size and it's not making sense to me.
Many thanks