Wireways - No more than 30 current carring conductors Article 376.22(8).

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nano

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I work for a company that doesn't believe in multi-conductor circuit so we pull a neutral with each hot on 120v and 277v circuits. Many times because it seems to take a while to get the panels in we mount wireways above the panels and bring our pipes into the wireways. In the past this has not been a problem but as of late it has been due to the enforcement of art. NEC? 376.22(8) which states, Wireway exceeding (30) current carrying conductors shall be subject to adjustment factors as defined in NEC Article 376.22(8).
From the wireway to the panel we use a couple of 2" conduits less than 24" in length. Where the wires enter the 2" you will in fact have more than 30 current carrying conductors in a 42 circuit load panel because you must count the neutral. Yet the code allows you to pack the 2" if less than 24" and the panel gutter has no restrictions for more than 30 current carrying conductors. So I'm wondering why do wireway have it?

I was told by the inspector that it was due to heat but that doesn't really make sense to me because the leakest part of any circuit is where you have terminations. Also if I used a couple of 10x10x6" j Boxes I believe this would be allowed because there is no 30 current carrying conductors rule for boxes.
I really just looking for some solid reasoning behind art 376.22(8). Your input would be helpful Thanks
 
Heat is the issue. It is the same reason lighting and appliance panelboards used to be limited to 42 circuits in one cabinet. Probably archaic, but needs to proven so. I wonder if the exception to 310.15(A)(2) could be used in this case? It depends on the length of your branch circuits.
 
This is very interesting.

This is very interesting.

Consider the following:

366.22 Number of Conductors.
(A) Sheet Metal Auxiliary Gutters.
 The sum of the cross-sectional areas of all contained conductors at any cross section of a sheet metal auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the sheet metal auxiliary gutter.
The adjustment factors in 310.15(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 310.15(B)(5), exceeds 30.
Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.
(B) Nonmetallic Auxiliary Gutters.
The sum of cross-sectional areas of all contained conductors at any cross section of the nonmetallic auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the nonmetallic auxiliary gutter.

376.22 Number of Conductors and Ampacity.
The number of conductors and their ampacity shall comply with 376.22(A) and (B).
(A) Cross-Sectional Areas of Wireway.
The sum of the cross-sectional areas of all contained conductors at any cross section of a wireway shall not exceed 20 percent of the interior cross-sectional area of the wireway.
(B) Adjustment Factors.
The adjustment factors in 310.15(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 310.15(B)(5), exceeds 30.
Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.

378.22 Number of Conductors.
The sum of cross-sectional areas of all contained conductors at any cross section of the nonmetallic wireway shall not exceed 20 percent of the interior cross-sectional area of the nonmetallic wireway.
Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.
The adjustment factors specified in 310.15(B)(3)(a) shall be applicable to the current-carrying conductors up to and including the 20 percent fill specified above.


Now you've got


Sheet Metal Auxiliary Gutters -- 20% fill -- derate over 30CCC
Nonmetallic Auxiliary Gutters -- 20% fill -- NO derating rules
Metal Wireway -- 20% fill -- derate over 30CCC
Nonmetallic Wireway -- 20% fill --[all] CCC

That said, I always thought that the fill and count applied to a cross-section of the raceway. So that I would not derate as long as I limited the number of CCC to 30 or less in any cross-section of a metal raceway (as listed above).

I'm wondering if I am inventing the cross-section as applying to derating. No inspector ever called me on it but I'll be submitting the question to the next IAEI code panel I attend.

I wonder if the differences in the derating are intentional or just accidental. Something interesting for 2014 ROP (and the 2014 isn't even out yet)!
 
Last edited:
fmtjfw said:
Consider the following:

366.22 Number of Conductors.
(A) Sheet Metal Auxiliary Gutters.
 The sum of the cross-sectional areas of all contained conductors at any cross section of a sheet metal auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the sheet metal auxiliary gutter.
The adjustment factors in 310.15(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 310.15(B)(5), exceeds 30.
Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.
(B) Nonmetallic Auxiliary Gutters.
The sum of cross-sectional areas of all contained conductors at any cross section of the nonmetallic auxiliary gutter shall not exceed 20 percent of the interior cross-sectional area of the nonmetallic auxiliary gutter.

376.22 Number of Conductors and Ampacity.
The number of conductors and their ampacity shall comply with 376.22(A) and (B).
(A) Cross-Sectional Areas of Wireway.
The sum of the cross-sectional areas of all contained conductors at any cross section of a wireway shall not exceed 20 percent of the interior cross-sectional area of the wireway.
(B) Adjustment Factors.
The adjustment factors in 310.15(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 310.15(B)(5), exceeds 30.
Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.

378.22 Number of Conductors.
The sum of cross-sectional areas of all contained conductors at any cross section of the nonmetallic wireway shall not exceed 20 percent of the interior cross-sectional area of the nonmetallic wireway.
Conductors for signaling circuits or controller conductors between a motor and its starter and used only for starting duty shall not be considered as current-carrying conductors.
The adjustment factors specified in 310.15(B)(3)(a) shall be applicable to the current-carrying conductors up to and including the 20 percent fill specified above.


Now you've got


Sheet Metal Auxiliary Gutters -- 20% fill -- derate over 30CCC
Nonmetallic Auxiliary Gutters -- 20% fill -- NO derating rules
Metal Wireway -- 20% fill -- derate over 30CCC
Nonmetallic Wireway -- 20% fill --[all] CCC

That said, I always thought that the fill and count applied to a cross-section of the raceway. So that I would not derate as long as I limited the number of CCC to 30 or less in any cross-section of a metal raceway (as listed above).

I'm wondering if I am inventing the cross-section as applying to derating. No inspector ever called me on it but I'll be submitting the question to the next IAEI code panel I attend.

I wonder if the differences in the derating are intentional or just accidental. Something interesting for 2014 ROP (and the 2014 isn't even out yet)!
Click to expand...

I believe that the word where implies at a cross section.
 
fmtjfw said:
...

Now you've got


Sheet Metal Auxiliary Gutters -- 20% fill -- derate over 30CCC
Click to expand...

The rule that in 366 for metal auxiliary gutters modifies the derating rule in 310
Nonmetallic Auxiliary Gutters -- 20% fill -- NO derating rules...
Click to expand...
There is no modifying rule in 366 for non-metallic auxiliary gutters, so the standard derating rules in 310 apply.
 
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