If the service factor for a motor is not given on the nameplate, what should you assume the service factor to be?

When a motor's service factor is not specified on the nameplate, it is common practice to assume the service factor to be 1. This assumption is based on standard industry practices where a service factor of 1 indicates that the motor can continuously operate at its rated load without risk of overheating or being damaged.

A service factor of 1 means that the motor is designed for normal operating conditions, allowing it to handle its rated capacity under standard operating temperatures and conditions. If the service factor is higher than 1, it would signify that the motor is capable of handling overloads or harsher conditions; however, without a noted service factor, adhering to the standard of 1 ensures reliability and safety during operation.

Other values, such as 0.75, 1.5, and 2, represent different operational characteristics not typically assumed as defaults. A service factor less than 1 could imply that the motor is overloaded under normal use, while a service factor greater than 1 suggests that it could handle more demanding conditions, which is not a safe assumption to make without clear manufacturer specifications. Hence, the best assumption in the absence of explicit information is a service factor of 1.