Which listed conductor has a greater ampacity in a dry location compared to a wet location?

Which listed conductor has a greater ampacity in a dry location compared to a wet location?

• A. THHN
• B. RHW
• C. THHW
• D. THWN

Answer: (C)

Ampacity depends on the insulation’s temperature rating and the environment. In dry locations, insulation can usually handle higher temperature rise, so the conductor can carry more current. THHW is designed so that it has a higher permissible current in dry conditions than in wet conditions, because moisture reduces its effective rating. That makes its dry ampacity greater than its wet ampacity, which is why it’s the best fit for a scenario asking for higher current capability in a dry location.

Ampacity depends on the insulation’s temperature rating and the environment. In dry locations, insulation can usually handle higher temperature rise, so the conductor can carry more current. THHW is designed so that it has a higher permissible current in dry conditions than in wet conditions, because moisture reduces its effective rating. That makes its dry ampacity greater than its wet ampacity, which is why it’s the best fit for a scenario asking for higher current capability in a dry location.