The maximum allowable ampacity of a 750 kcmil XHHW aluminum conductor is ___ amps when there are six current carrying conductors in the raceway, the raceway is installed in a wet location, and the ambient temperature surrounding the raceway is 22°C.

• A. 365.40
• B. 361.92
• C. 348.00
• D. 323.40

Answer: (D)

Ampacity depends on the insulation rating, location, number of current-carrying conductors, and ambient temperature. For XHHW in a wet location, you use the 75°C ampacity. Look up the base ampacity for 750 kcmil aluminum at 75°C, which is about 405 A. With six current-carrying conductors in the raceway, apply the derating factor of 0.80 (for 4–6 conductors): 405 A × 0.80 ≈ 324 A. The ambient temperature is 22°C, which does not require a temperature correction above 30°C. Therefore the maximum allowable ampacity is about 323.4 A, matching the given option.