HOLT Electricians Practice Exam

For a 1 horsepower, 120-volt motor with a nameplate current rating of 14 amperes, can No. 14 THHN conductors be used?

1. True

2. False

3. Only if rated for 75 C

4. Only in specific conditions

The correct answer is: False

To determine whether No. 14 THHN conductors can be used for a 1 horsepower, 120-volt motor with a nameplate current rating of 14 amperes, it is essential to consider the current-carrying capacity of the conductors. According to the National Electrical Code (NEC), No. 14 copper conductors typically have an ampacity of 15 amperes at 60°C and 20 amperes at higher temperatures, depending on the insulation type and conditions. In this specific case, the motor draws 14 amperes, which is very close to the maximum ampacity limit for No. 14 conductors at 60°C. The key point here is that for continuous loads, conductors are generally required to be sized for 125% of the load current. In this scenario, 125% of 14 amperes is 17.5 amperes, indicating that No. 14 conductors would not be adequate for this load due to potential overheating and safety concerns. Thus, the characterization of the answer as false is correct because the use of No. 14 THHN would not comply with the necessary safety standards and regulations for this application, emphasizing the need to select conductors that