Understanding wireway uses and selection

• For exposed work in dry locations. For outdoor or wet locations, use Type 3R wireway. 
• If installed in inaccessible spaces, the use of wireway is permitted only for use with audio signal conductors (per NEC®† 376.10). 
• In hazardous locations as permitted by NEC®† sections 501, 502 and 504. 
• For extensions through walls, if the length passing through the wall is unbroken and access to conductors can be maintained from both sides.

The use of wireways is not permitted where a risk of severe physical damage or corrosive vapor is present.

Refer to NFPA 70, National Electrical Code for more information.

Sample calculation

The wireway selection calculator helps determine wireway dimensions as noted below.

1.       List cables by size and types

2.       List cable cross sectional areas

3.       List the number of each size of cable

4.       Multiply cable cross sectional areas by number of each cable

5.       Sum the total cross sectional areas of each cable type to obtain the total cross sectional areas for the conductors

6.    The wireway must first meet the dimensional requirements for the largest conductor. In the example above, the largest conductor is 750 kcmil. The minimum wireway cross section based on the largest conductor size requirements is 8” x 8”. See the engineering section of the B-Line series enclosure catalog for additional details.

7.      The wireway dimensions must meet 20% fill requirements. Based on the sum of the total conductor cross sectional areas (3.19 sq. in.), the minimum wireway cross section, based on the 20% fill requirements is 4” x 4”.  See the engineering section of the B-Line series enclosure catalog for additional details. 

In this example, the wireway dimensions must be the larger of the two cross sections obtained in steps 6 and 7. In this case, 8” x 8” wireway is required.