Per Table 310.16, what is the allowable ampacity of a 6 AWG copper THWN conductor (75°C column), not more than three current-carrying conductors in a raceway?
Not quite. The answer is B: 65 A
6 AWG copper reads 55 A in the 60°C column, 65 A in the 75°C column, and 75 A in the 90°C column. THWN is a 75°C-rated insulation, so 65 A is the correct row/column intersection. Grabbing the 60°C or 90°C figure instead of matching the insulation's actual rating is the single most common lookup error on this table.
Reference: NEC 2023 Table 310.16 (Allowable Ampacity of Insulated Conductors)
Checked against multiple published sources
A Southwire spec sheet (ampacities stated as based on the 2023 NEC Table 310.16) and a Cerrowire ampacity chart agree on the 6 AWG copper values of 55/65/75 A. Neither is the code text.
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