What should overload sizing for a horsepower-rated motor be based on when operating at a specified voltage?

When sizing overload protection for a horsepower-rated motor, it is essential to base it on the nameplate amps with consideration for the service factor. The service factor is a crucial aspect as it indicates the motor's capacity to handle additional loads or operational conditions beyond its rated horsepower without overheating or failing.

Using the nameplate amps allows for a precise understanding of the motor's designed capacity under normal operating conditions. Additionally, incorporating the service factor acknowledges that a motor can reliably sustain some level of overload—typically up to the percentage specified by the service factor—without incurring damage or performance issues.

This approach ensures that the overload protection is correctly set to avoid nuisance tripping during normal operation while also providing enough allowance for the demands the motor may encounter in real-world applications. By taking into account both the nameplate rating and the service factor, you can ensure appropriate protection and longevity for the motor.