The smallest conductors permitted to be run, paralleled in two separate conduits, between a 3Ø, 250 kVA generator and a 480-volt distribution panelboard are which size?

• A. 2/0
• B. 250
• C. 4/0
• D. 3/0

Answer: (A)

When conductors are run in parallel, the total load is split between the two paths, so each conductor must be able to carry about half the total current. The 250 kVA, 480 V three-phase setup draws roughly I = S / (√3 × V) ≈ 250,000 / (1.732 × 480) ≈ 300 A. Therefore each parallel path must handle about 150 A.

NEC rules allow paralleling conductors only if they are 1/0 AWG or larger for copper (and with the same material, insulation, and termination). Among the given options, the smallest size that can be paralleled and meet the ~150 A per-conductor requirement is 2/0 AWG copper. The larger sizes would also work, but the question asks for the smallest permissible size.

So, the smallest conductors permitted to be paralleled in two conduits for this setup are 2/0 AWG copper.