# 30+ CCC Derating For Gutters



## chicken steve (Mar 22, 2011)

The 30 benchmark can be found repeated 366.22&23, 378.22, 386.22,392.80 Buzz....

~CS~


----------



## chicken steve (Mar 22, 2011)

*a little more focus....*



> *366.23 Ampacity of Conductors.*
> (A) Sheet Metallic Auxiliary Gutters. Where the number
> of current-carrying conductors contained in the sheet metallic
> auxiliary gutter is 30 or less, the adjustment factors specified
> ...


One would think the 20% fill would constitute more a factor than the 30 conductors here , given the same install in breaker panels ......

~CS~


----------



## buzzlightbeer (Nov 18, 2014)

chicken steve said:


> One would think the 20% fill would constitute more a factor than the 30 conductors here , given the same install in breaker panels ......
> 
> ~CS~


We're working with an existing 8x8 gutter and it's mostly #10's. I know I'm nowhere near the 20% fill. My concern is there are many places with well over 30 conductors in a cross sectional area. If i have to derate them 45% they're no longer gonna cut it for the 20 amp breakers they're attached to. 

What i don't understand is if 30 is like a zero starting point for derating or do i treat them the same as i would 30 conductors in a pipe. It seems kinda silly that 29 conductors in a gutter cross section would have no derating requirements but as soon as it hits 31 they all get cut down by 45%.


----------



## don_resqcapt19 (Jul 18, 2010)

In many cases you can apply the exception to 310.15 (A)(2) and not have to derate the ampacity of the conductors in the wireway.


----------



## chicken steve (Mar 22, 2011)

That's postworthy, thx Don...

*(2) Selection of Ampacity. *Where more than one ampacity 
applies for a given circuit length, the lowest value shall be 
used. 
_Exception: Where two different ampacities apply to cuUa-
cent portions of a circuit, the higher ampacity shall be 
permitted to be used beyond the point of transition, a dis-
tallce equal to 3.0 m (10 ft) or 10 percent of the circuit 
length figured at the higher ampacity, whichever is less. _

~CS~


----------



## don_resqcapt19 (Jul 18, 2010)

chicken steve said:


> That's postworthy, thx Don...
> 
> *(2) Selection of Ampacity. *Where more than one ampacity
> applies for a given circuit length, the lowest value shall be
> ...


Steve,
I like to make people get out their own code book, so often I just post the citation and not the actual section


----------



## chicken steve (Mar 22, 2011)

*a true pro!*



don_resqcapt19 said:


> Steve,
> I like to make people get out their own code book, so often I just post the citation and not the actual section


Well....i guess it _worked_ Don.....
:whistling2:~CS~:laughing:


----------

