For Motor #1, the smallest circuit conductors between the wireway and the safety switch (75°C terminations) are which AWG?

• A. 8
• B. 10
• C. 6
• D. 12

Answer: (B)

When sizing conductors for a motor, you must use enough ampacity to carry the motor’s full-load current, and you can use the 75°C ampacity column if the termination devices are rated 75°C. So you look up the motor’s full-load current on its nameplate and then pick the smallest conductor size whose 75°C ampacity is at least that current.

For this motor, 12 AWG at 75°C is typically about 25 A, which isn’t enough if the motor’s full-load current is higher than 25 A. Moving up to 10 AWG provides about 30 A of ampacity in the 75°C column, which meets or exceeds the motor’s full-load current. Although 8 AWG would also satisfy the requirement, the goal is the smallest size that meets the rating, so 10 AWG is the correct choice.