What is the MINIMUM ampacity for the branch circuit conductors for a single-phase motor rated at 2hp, 230V?

To determine the minimum ampacity for the branch circuit conductors for a single-phase motor rated at 2 horsepower (hp) and 230 volts (V), it is essential to convert the horsepower to watts and then calculate the current.

One horsepower is equivalent to approximately 746 watts. Therefore, a 2 hp motor would have a power requirement of:

2 hp × 746 watts/hp = 1492 watts.

Using Ohm's Law, the current can be calculated using the formula:

Current (I) = Power (P) / Voltage (V).

Substituting in the values:

I = 1492 watts / 230 volts = approximately 6.5 amps.

However, when determining the ampacity of conductors, it's crucial to adhere to the National Electrical Code (NEC) guidelines, which typically require factoring in service demand and potential running load factors. According to NEC guidelines, the conductors should usually provide a safety margin, and it's common practice to size the conductors based on the starting current and not just running current.

For a single-phase motor, the common practice is to multiply the running ampacity by a safety factor, and many installations will require that conductors are sized to at least 125