# Trough Vs j boxes



## walkerj (May 13, 2007)

Any reason why they won't allow it?


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## Magnettica (Jan 23, 2007)

You'll want to look at article 376 for your trough information and article 312 for pull boxes/ junction boxes.


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## manchestersparky (Mar 25, 2007)

keepdry said:


> Looking for a little code info on trough vs large j boxes.
> Concerning use above or below panels. I know it has to do with the number of wires in a cross sectional area. Looking for the code redrence and year.
> *I know some inspector will no longer allow trough.*
> Thanks


Sounds like urban legend, like the code for grounds up


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## Techy (Mar 4, 2011)

Inspectors here make you derate in you have 30 current carrying conductors in the trough period, not just any cross section, the wording changed in-between the 1999 and 2002 cycles, to be less specific as o if the 30 ccc's is in a single cross section or total in the wireway


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## keepdry (Jul 24, 2012)

manchestersparky said:


> Sounds like urban legend, like the code for grounds up


Sorry, not urban legend. Last job I ran I was informed on a walk through by the inspector that trough would not be allowed under the panels. 
The scenario on that job was 24 branch circuit slab pipes feeding 3 panels. We intended to install trough under all three panels and 2" conduit nipples between the trough and the panels. He cited the code. I was like whatever. Anyway we had to have custom made boxes installed between the slab and the panels. 
I think the code section is 376.22 number of conductors in a metal wireway. The custom made boxes were 12" wide 6" deep and ran the length of the panels including wrapping around a corner. 

376.22 
"The sum of the cross-sectional area of all contained conductors at any cross section of a wireway shall not exceed 20% if the interior cross-sectional area of the wireway."
If we didn't install the custom trough we were going to have to derate the conductors per 310.15B2A.


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## htneighbors (Jan 23, 2009)

I think what is being discussed would fall under the definition of Auxiliary Gutters, Article 366 instead of Metal Wireways, Article 376. However, both prohibit more than 20% cross-section fill and have adjustment factors when more than 30 CCC are installed - 310.15(B)(3)(a). Dimensions of the gutter installed is not the determining factor of whether or not to derate - the number of CCC is. Custom fabricating a gutter should have had no bearing. 

Aux Gutters supplement enclosure wiring spaces. A wireway is a raceway. NEC requirements differentiate between the two at times. Aux gutters are not subject to NEC requirements only pertinent to raceways. 

Regardless, any inspector with a blanket rule to "no longer" allow a gutter under a panel is an idiot. As long as the NEC requirements are followed, WTH is wrong with him? That's what a gutter is for! 

Pull Boxes fall under Article 314 and could also be used for the purpose you describe. As long as the box-fill is not exceeded, there is no derating adjustment for pull boxes!  Put it in, call it a pull-box and you're good!


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## chicken steve (Mar 22, 2011)

Interesting to look this up , what is the consensus of this 10% rule, or this .'14 change of cross section. ....?




> *366.22 Number of Conductors. *
> (A) Sheet Metallic Auxiliary Gutters. The sum of the
> cross-sectional areas of all contained conductors at any
> cross section of a sheet metallic auxiliary gutter shall not
> ...





> *376.22 (B) Adjustment Factors. * The adjustment factors in
> 31 O.1S(B )(3)( a) shall be applied only where the number of
> current-carrying conductors, including neutral conductors
> classified as current-carrying under the provisions of
> ...





> *310.15Ampacitics for Conductors Rated 0-2000 Volts. (2) Selection of Ampacity.* Where more than one ampacity
> applies for a given circuit length, the lowest value shall be
> used.
> 
> ...


~CS~


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## backstay (Feb 3, 2011)

30 at any cross section is not the same as 30 in the trough.


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