Wireway Conductor Fill Limitation

NEC requirement on the conductor fill allowed in a metal wireway.

March 17, 2014

The sum of the cross-sectional areas of all contained conductors at any cross-section of a metal wireway shall not exceed _____.

a) 50%
b) 20%
c) 25%
d) 75%

See answer and applicable Code reference

The correct answer is: b) 20%

Article 376 of the 2011 NEC presents the requirements for installation of metal wireways. As clearly noted in 376.22(A), "The sum of the cross-sectional areas of all contained conductors at any cross section of a wireway shall not exceed 20% of the interior cross-sectional area of the wireway."