Can someone explain CCC derating with troughs/gutters?

[mikecentola]

Hey all! Sorry for the noob question but I'm having a hard time understanding a situation where you might have multiple panels or even a single panel with a large conduit to a trough and multiple smaller conduits coming out of it. I understand the reason for using it, being that it looks nice and easy to organize runs to areas of a building, but it would seem that wire would have to be heavily oversized to account for derating requirements of 80+%. Can someone ELI5 for me? Pic as example (not mine).

 

[infinity]

If you do not exceed 30 CCC'S at any cross section there is no derating required. Once you get to 31 CCC'S or more at a cross section derating will then apply.

 

[mikecentola]

If you do not exceed 30 CCC'S at any cross section there is no derating required. Once you get to 31 CCC'S or more at a cross section derating will then apply.

OK Thanks. I do remember reading something like that. There is a requirement for that as well right? Something like within 24" right?

EDIT - This is different than say parallel feeders?

 

[don_resqcapt19]

In many cases, even where you have over 30 conductors at a cross section, you can use the Exception to 310.14(A) [310.15(A)(2) in older codes] and not have to apply any ampacity adjustments.