For the example with four 500 kcmil conductors and one 1/0 ground on a wooden pole 20 feet tall, what is the minimum Schedule 80 PVC trade size?

For the example with four 500 kcmil conductors and one 1/0 ground on a wooden pole 20 feet tall, what is the minimum Schedule 80 PVC trade size?

• A. 2 in.
• B. 2-1/2 in.
• C. 3 in.
• D. 3-1/2 in.

Answer: (D)

The main idea is how many conductors you can fit in a raceway without exceeding NEC fill limits. For a PVC raceway, you count the conductors inside and apply the permitted percent fill (for more than two conductors, the typical allowance is 40%). Grounding conductors are counted as one conductor for the fill calculation, so four 500 kcmil conductors plus one 1/0 ground total five conductors to account for. Sum of conductor cross‑section areas: four × 500,000 circular mils plus one 1/0 ground (≈105,000 cmil) equals about 2,105,000 circular mils. With a 40% fill limit, the interior area must be at least 2,105,000 / 0.40 ≈ 5,262,500 circular mils, which is about 4.1 square inches of interior cross‑section. That interior size corresponds to roughly a 2.3 inch inside diameter. In practice, and given standard Schedule 80 PVC trade sizes and packing/pulling considerations on a pole, the next standard size that comfortably meets the fill and provides adequate pulling space is 3-1/2 inches. So the minimum Schedule 80 PVC trade size is 3-1/2 inches.

The main idea is how many conductors you can fit in a raceway without exceeding NEC fill limits. For a PVC raceway, you count the conductors inside and apply the permitted percent fill (for more than two conductors, the typical allowance is 40%). Grounding conductors are counted as one conductor for the fill calculation, so four 500 kcmil conductors plus one 1/0 ground total five conductors to account for.

Sum of conductor cross‑section areas: four × 500,000 circular mils plus one 1/0 ground (≈105,000 cmil) equals about 2,105,000 circular mils.

With a 40% fill limit, the interior area must be at least 2,105,000 / 0.40 ≈ 5,262,500 circular mils, which is about 4.1 square inches of interior cross‑section. That interior size corresponds to roughly a 2.3 inch inside diameter.

In practice, and given standard Schedule 80 PVC trade sizes and packing/pulling considerations on a pole, the next standard size that comfortably meets the fill and provides adequate pulling space is 3-1/2 inches. So the minimum Schedule 80 PVC trade size is 3-1/2 inches.