When using a 277/480-volt, 3Ø, 4-wire panelboard, what is the minimum size SO cord for connecting the motor?

The minimum size SO cord for connecting a motor to a 277/480-volt, 3-phase, 4-wire panelboard is determined by several factors, including the ampacity requirements, the length of the cord, and the type of insulation. For this specific voltage and phase configuration, the National Electrical Code (NEC) provides guidelines for wire sizing based on current-carrying capacity.

Choosing a 14-gauge SO cord aligns with the NEC’s guidelines for motors operating at higher voltages such as 480 volts. This size is typically suitable for smaller motors with lower current demands. The ampacity of 14-gauge wire generally supports around 15 amps, which is appropriate for smaller motors connected to a 480-volt system.

Using wire that is too small can lead to overheating due to excessive current, while using wire that is too large may introduce unnecessary costs and difficulty in handling. Thus, for many applications in this voltage range, a 14-gauge cord strikes a balance between safe operation and cost-effectiveness for smaller motors.