For the motor sizing example, the minimum conductor size is

For the motor sizing example, the minimum conductor size is

• A. 3 AWG
• B. 10 AWG
• C. 6 AWG
• D. 4 AWG

Answer: (B)

Sizing motor conductors centers on carrying the motor’s full-load current with a safety margin to cover startup surges and temperature effects. The NEC requires the branch-circuit conductors to have an ampacity not less than about 125% of the motor’s full-load current. After determining that required ampacity, you pick the smallest conductor size whose ampacity meets or exceeds it, using the appropriate temperature rating. In this example, calculating 125% of the motor’s full-load current yields a required ampacity around 30 A. The next smaller conductor size that can carry at least that much is 10 AWG, whose ampacity with common insulation ratings is about 30–35 A depending on the table and temperature rating. Therefore, 10 AWG is the minimum conductor size that satisfies the requirement. Smaller sizes (like 12 AWG) would not meet the load current, so they’re not sufficient.

Sizing motor conductors centers on carrying the motor’s full-load current with a safety margin to cover startup surges and temperature effects. The NEC requires the branch-circuit conductors to have an ampacity not less than about 125% of the motor’s full-load current. After determining that required ampacity, you pick the smallest conductor size whose ampacity meets or exceeds it, using the appropriate temperature rating.

In this example, calculating 125% of the motor’s full-load current yields a required ampacity around 30 A. The next smaller conductor size that can carry at least that much is 10 AWG, whose ampacity with common insulation ratings is about 30–35 A depending on the table and temperature rating. Therefore, 10 AWG is the minimum conductor size that satisfies the requirement. Smaller sizes (like 12 AWG) would not meet the load current, so they’re not sufficient.