What is the minimum size (3 wire + ground) SO cord that could be used as a flexible connection for the motor supplied from a 120/240-volt, 3Ø, 4-wire panelboard?

What is the minimum size (3 wire + ground) SO cord that could be used as a flexible connection for the motor supplied from a 120/240-volt, 3Ø, 4-wire panelboard?

• A. 9
• B. 8
• C. 12
• D. 10

Answer: (A)

Sizing a flexible motor connection hinges on the motor’s full-load current and the NEC rule that the conductors must have ampacity at least 125% of that full-load current. For a motor fed from a 120/240 V three‑phase, four‑wire panel, the cord must carry three current‑carrying conductors plus a ground and be rated to meet that 125% requirement. In this scenario, 9 AWG SO cord is the smallest size that provides enough ampacity to satisfy the 125% rule, while smaller sizes would be undersized and larger ones would be unnecessary. Therefore, 9 AWG is the minimum size.

Sizing a flexible motor connection hinges on the motor’s full-load current and the NEC rule that the conductors must have ampacity at least 125% of that full-load current. For a motor fed from a 120/240 V three‑phase, four‑wire panel, the cord must carry three current‑carrying conductors plus a ground and be rated to meet that 125% requirement. In this scenario, 9 AWG SO cord is the smallest size that provides enough ampacity to satisfy the 125% rule, while smaller sizes would be undersized and larger ones would be unnecessary. Therefore, 9 AWG is the minimum size.