For a single-phase motor fed from an underground source, where should the motor overload unit be placed?

The motor overload unit can be effectively placed in either the phase or neutral conductor because it is designed to protect the motor by detecting overcurrent conditions that can occur in either line. When an overload occurs, it is crucial to interrupt the current flow to prevent damage to the motor.

The reason for allowing placement in the neutral is tied to how current flows in a single-phase system. In a balanced load condition, the current in the neutral should ideally be zero. However, in unbalanced conditions or during faults, the overload protection in the neutral can still trip if a dangerous situation arises.

Additionally, placing the overload in the phase conductor is also standard practice since this is where the primary current flows to the motor. The National Electrical Code (NEC) emphasizes the importance of properly protecting motors, and having options for placement provides flexibility while ensuring safety and compliance.

Other choices might limit the protection options or complicate compliance with electrical safety codes. Thus, having the flexibility to place the overload in either conductor enhances redundancy and safety in the electrical system.