What does NEC 430.103 require a disconnecting means for a motor to do?

NEC 430.103 addresses the requirements for disconnecting means for motors, emphasizing safety and protection during maintenance or emergencies. The correct answer indicates that the disconnecting means must be capable of opening all ungrounded conductors. This is crucial because it ensures that the entire supply to the motor can be completely interrupted, preventing potential electrical shock hazards or accidental start-ups while maintenance is being performed.

Opening all ungrounded conductors allows the safe isolation of the motor from its power source, providing a safe working environment for any electrical repairs or inspections. If only some conductors were opened (for example, a single conductor or only opening the grounded ones), it could result in dangerous conditions where the motor may still be live or energized in some way, creating a safety risk.

The focus on ungrounded conductors aligns with NEC guidelines that prioritize safety practices by ensuring thorough disconnection from electrical power to protect individuals working on or near the motor equipment.