Motor Protection for Valve Actuators

Valve actuator motors as a category have never really been defined by NEMA, NEC, or any other group. Moreover, NEC Section 430-33 states that intermittent-duty motors need not have motor protection. As a result, the decision to protect motors and the selection of protector type are both left to the specifying engineer or the manufacturer. A guideline is presented to help the engineer and the manufacturer make both decisions. Our recommendations are based on field experience confirmed by laboratory testing.