HOLT Electricians Practice Exam

Motors with a nameplate temperature rise rating not over 140 C shall have the overload protection device sized at what percentage of the motor nameplate rating?

1. 20 percent

2. 25 percent

3. 30 percent

4. 35 percent

The correct answer is: 25 percent

The correct choice indicates that the overload protection device for motors with a nameplate temperature rise rating not exceeding 140°C should be sized at 125 percent of the motor nameplate rating. This guideline is based on the National Electrical Code (NEC) requirements for ensuring that motors operate safely without overheating and sustaining damage under overload conditions. When sizing overload protection, this percentage is determined to allow the motor to handle temporary overloads that may occur during startup or other operations without tripping the circuit. This margin (125 percent of the nameplate rating) ensures that the motor can continue to operate effectively under these conditions, while also providing adequate protection against sustained overloads that could lead to increased temperatures and potential failure. The other choices represent incorrect sizing parameters, as they either provide insufficient protection or do not align with the NEC standard for motors with a temperature rise rating not over 140°C. The 125 percent sizing ensures a balance between protecting the motor and allowing it to function effectively.