hello all, long time lurker, first time post.
So in prep for my hot date with the PSI examiner , I decided to give the old NEC a good page by page read through.
When I get to chapter 3 of the saga, I come across something that has always stumped me.
Can someone please explain the difference between 310.15(B)(2) (a) & (b) in layman's terms. All I'm getting is that "a" is for cable tray and "b" is in raceway or cable, but there seems to be more to it than that.