Determine the minimum standard size wireway required for a job. A section of wireway will contain thirty-two 3 AWG, forty-eight 2 AWG, and eighteen 3/0 THHN/THWN conductors.

Determine the minimum standard size wireway required for a job. A section of wireway will contain thirty-two 3 AWG, forty-eight 2 AWG, and eighteen 3/0 THHN/THWN conductors.

• A. 6 in by 6 in
• B. 12 in by 12 in
• C. 4 in by 4 in
• D. 10 in by 10 in

Answer: (D)

Wireway sizing is determined by conductor fill. You convert each conductor to its cross‑sectional area, sum them up, and then apply the permitted fill percentage for a wireway so the total area of conductors doesn’t exceed the interior area times that fill limit. After you know the required interior cross‑sectional area, you pick the smallest standard wireway size whose interior area meets or exceeds that value. For these conductors, the combined cross‑sectional area, using THHN/THWN values for 3 AWG, 2 AWG, and 3/0, yields a total that translates to an interior requirement of about 95 square inches. Among the standard sizes listed, a 10 in by 10 in wireway provides 100 square inches of interior area, which just meets the need, while the smaller options are insufficient and a larger option would be more than is necessary. So the minimum standard size that satisfies the fill is 10 in by 10 in.

Wireway sizing is determined by conductor fill. You convert each conductor to its cross‑sectional area, sum them up, and then apply the permitted fill percentage for a wireway so the total area of conductors doesn’t exceed the interior area times that fill limit. After you know the required interior cross‑sectional area, you pick the smallest standard wireway size whose interior area meets or exceeds that value.

For these conductors, the combined cross‑sectional area, using THHN/THWN values for 3 AWG, 2 AWG, and 3/0, yields a total that translates to an interior requirement of about 95 square inches. Among the standard sizes listed, a 10 in by 10 in wireway provides 100 square inches of interior area, which just meets the need, while the smaller options are insufficient and a larger option would be more than is necessary. So the minimum standard size that satisfies the fill is 10 in by 10 in.