ICC Residential Electrical Inspectors Practice Exam

What is the permissible disconnecting means for stationary motors rated at 2 HP or less and 300 volts or less?

1. A general use switch having an ampere rating not less than twice the full load current rating of the motor

2. An emergency stop button

3. A circuit breaker rated at the maximum motor load

4. A fuse rated at the motor's full load current

The correct answer is: A general use switch having an ampere rating not less than twice the full load current rating of the motor

The permissible disconnecting means for stationary motors rated at 2 HP or less and 300 volts or less is a general use switch having an ampere rating not less than twice the full load current rating of the motor. This requirement is in place to ensure that the disconnect switch can safely handle the electrical load of the motor while providing an adequate margin of safety. Using a switch rated for at least twice the full load current ensures that it can withstand any inrush currents or additional electrical demands that may occur when the motor starts or operates under load. This is particularly important in preventing potential damage to the switch or the motor itself, as well as ensuring the safety of individuals working on or near the equipment. While other options like an emergency stop button, a circuit breaker rated at the maximum motor load, and a fuse rated at the motor's full load current could have their place in electrical installations, they do not specifically meet the requirement for a dedicated disconnecting means for stationary motors in this category. An emergency stop button is intended for quick shutdown in an emergency but may not provide reliable disconnection under normal operational conditions. A circuit breaker rated at the maximum load or a fuse rated at full load current may not provide the necessary safety margin required for disconnection