Welcome aboard..:thumbup: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.
Wire in cable tray is in open air, but in pipe the wires will get hotter because they are close together and not on open air.