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What is the required size of a THHN conductor for a 2 horsepower, 230-volt, single phase motor?

No. 12

No. 14

To determine the correct size of a THHN conductor for a 2 horsepower, 230-volt, single phase motor, it is essential to calculate the full-load current of the motor. A standard method for calculating this is by using the formula for single-phase motors:

Full-load current (Amps) = (Horsepower × 746) / (Voltage × Efficiency × Power Factor)

Assuming typical values for efficiency (90%) and power factor (0.8) for a motor, the calculation would yield approximately:

Full-load current = (2 × 746) / (230 × 0.9 × 0.8) = 9.82 Amps (rounded to 10 Amps).

According to the National Electrical Code (NEC), a conductor needs to be sized for a certain percentage above the full-load current to account for safe operation, typically using a 125% rule for motors. This results in:

10 Amps × 1.25 = 12.5 Amps.

Based on NEC's ampacity tables for conductors, a No. 12 THHN conductor is rated for 20 Amps, which is suitable for this application. Therefore, while options that might suggest smaller conductor sizes are

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