HOLT Electricians Practice Exam

The branch circuit conductors of a 5 horsepower 230-volt motor with a nameplate rating of 25 amperes shall have an ampacity of not less than what value?

1. 20 amperes

2. 21 amperes

3. 22 amperes

4. 25 amperes

The correct answer is: 21 amperes

To determine the minimum required ampacity for the branch circuit conductors of a 5 horsepower 230-volt motor with a nameplate current rating of 25 amperes, it is essential to consider the guidelines set forth in the National Electrical Code (NEC). For motors, the NEC provides specific requirements for conductor sizing based on the motor's continuous load rating, which can often be different from the nameplate rating depending on factors like ambient temperature and the number of conductors bundled together. However, since the nameplate rating indicates that the motor draws 25 amperes, the conductors must safely handle this current to prevent overheating and ensure reliable operation. Typically, it is recommended to apply an additional safety factor when sizing conductors for motors. This is often achieved by increasing the ampacity by a certain percentage based on the continuous operation of the motor. For a motor rated for continuous duty like this one, the minimum conductor ampacity should generally be 125% of the motor's full-load current rating. Calculating 125% of 25 amperes gives us: 25 A x 1.25 = 31.25 A. The conductors must be sized accordingly to prevent overheating. In this specific scenario, while none of the options