What rating is permitted to be used when the branch-circuit protection required for motors does not correspond to standard ratings?

When the branch-circuit protection for motors does not align with standard ratings, it is permissible to use a higher rating. This allowance is grounded in the need to accommodate the specific characteristics of motor operation, particularly their starting currents, which can be significantly higher than their running currents.

Using a higher rating ensures that the protection device can handle these inrush currents without tripping unnecessarily. When a motor starts, it draws several times its full-load current for a brief period. A protective device rated too low might interrupt the circuit due to this temporary surge, which is undesirable in motor applications.

Additionally, applying a higher rating must still comply with the National Electrical Code (NEC) requirements, which provide guidelines for safe and effective motor protection. It ensures that the branch-circuit conductors and associated equipment are adequately protected from overloads while allowing the motor to operate correctly without hindrance from the protection device.

Thus, using a higher rating is not only permitted but often necessary for effective motor protection in situations where standard ratings do not apply.