a little more derating

[arnettda]

I have a conduit run that I am derating for. 13 pipes into a j box,out the back and through block wall into a gutter. Out bottom of gutter into top of panel. If nipple through wall and nipple into panel are both under 24" each.I do not have to derate. Would this being permissable? 2 3" pipes through block would be easier than 13 1.5" pipes. wall nipple is 12" and nipple into panel will be about 20".
Do I count each nipple seperate? And is this how the more experienced would do it?
Thanks Dave

 

[billsnuff]

Have you complied with 376.22(A)? If so you may be OK, but see what the others say.

 

[daleuger]

Less pipes but bigger pipes to make cooperate. You, my friend, have a catch 22.

 

[480sparky]

But more CCCs in a larger pipe simply causes more (percentage-wise) derating. If you put, say, 100 CCCs into 13 raceways, you have an average of 7-8 or so in each, and derating isn't that big of an issue since you only derate 70%. If you're installing 14, 12 or 10s, it's a non-issue.

But put those same 100 CCCs into 2 pipes, and you've got 50 per pipe..... Now you derate to 35%, and your cost of copper skyrockets.

 

[infinity]

24" or less nipples and no derating is required. The nipple can only be filled to 60%. That's about all the limitations you'll encounter with the installation that you've described.