What is the minimum amp rating of the disconnecting means for motor circuits rated 1000 volts or less?

The minimum amp rating of the disconnecting means for motor circuits rated 1000 volts or less is determined by the requirement that it must be capable of interrupting the full load current of the motor safely. According to the National Electrical Code (NEC), the disconnecting means, which often takes the form of a switch or circuit breaker, must be rated at a minimum of 115% of the motor's full load current to ensure it can handle potential inrush currents that occur when the motor starts.

This requirement takes into account factors such as the overcurrent protection that may need to be employed and the potential for temporary overloads during the starting process of the motor. Setting the rating at 115% ensures that the disconnecting means will operate effectively without nuisance tripping while still providing adequate protection for the motor circuit.

The other options reflect amp ratings below and above this standard, which do not meet the requirements set forth in the NEC for safe operation and protection of motor circuits. Therefore, the choice of 115% is established to balance functionality and safety considerations in electrical installation and maintenance practices.