Conductor adjustment factors shall not apply to conductors in raceways having a length not exceeding how many inches?

• A. 12
• B. 24
• C. 36
• D. 48

Answer: (B)

When several current-carrying conductors share a raceway, their ampacity is typically derated to account for extra heat. There’s an exception: if the raceway length is very short, the adjustment factors aren’t required. Specifically, conductor adjustment factors do not apply to conductors in raceways whose length does not exceed 24 inches.

This means you can use the standard ampacity for the conductors (based on their insulation rating and the ambient temperature) without applying derating, as long as the raceway run is 24 inches or shorter. If the run is longer than 24 inches, the derating factors must be applied according to the number of current-carrying conductors in the raceway. This 24-inch threshold is the practical limit that allows a simple, direct use of the conductor ampacity for very short runs.