In a branch circuit supplied from a 120/240-volt, 3Ø, 4-wire panelboard, what is the minimum size SO cord needed for a motor connection?

To determine the minimum size SO cord needed for a motor connection supplied from a 120/240-volt, 3-phase, 4-wire panelboard, several variables must be considered. The actual sizing is guided by the National Electrical Code (NEC) and factors such as the motor's full-load current and the length of the run must also be taken into consideration.

The selection of a 9 AWG size SO cord is appropriate for motor applications because it provides sufficient capacity to handle higher amperages typically associated with motor loads while also offering good flexibility and durability, which is essential in varying environments where motors might be installed.

According to NEC guidelines, when selecting conductors for motors, the full-load current rating and the ampacity of the cable are critical. The selected SO cord dimensions should ensure it can safely handle the motor's starting current, which is often substantially higher than its running current.

For reference, larger gauge wires like 8 AWG or smaller wires such as 10 or 12 AWG may have their places in different applications, but they would either provide too much capacity or insufficient support for the specific needs of motor operation from a 120/240-volt setup. A larger wire could lead to increased cost and unnecessary