Derating NM cable

[LarryFine]

I also found this,.. thought I would share it .

So, they're basically saying that the 18"-minimum nipple functions as a large-scale cable clamp, but more for effectively closing off the enclosure opening than for clamping the cables, which is the purpose of the within-12" securing requirement.

 

[LarryFine]

There is so much load diversity in most applications where multiple NM's would be run thru as hole that I am willing to bet there is NO appreciable heat buildup.

I wouldn't make a blanket statement about that in either direction.

There's a big difference between, say, five NM cables (one feed and four switch-legs) running into a 4-gang switch box, where the entire hole's current would never exceed one circuit's rating, and five NM cables leaving a panel, where each cable is carrying a full circuit's load.

 

[Supersparky98]

Realistically, could you put 40 circuits with romex in their own romex connector in the top of a panel? NO it wouldnt physically be possible in a home panel or load center, maybe in a panelboard in which you could drill your own holes but i have doubts on that also.