“Overloads” are currents that can damage a circuit if allowed to continue for a sufficient time, whereas “short circuits” and “ground faults” are high currents that can cause immediate damage. Motor circuits get around this problem by dividing the two separate functions of an overcurrent protection device. However, if the overcurrent device is sized to protect the wire against overloads, the device might trip, and the machine would not be able to start. The inrush current lasts typically only about 6 electrical cycles, or 1/10th of a second - less time than it would take to damage the wire or its insulation.
The high “inrush” current can exceed the rating of a breaker or fuse sized to protect the wire. When a motor first starts, it draws a much higher amount of current than it does after it is running. The rules for protection to motor circuits are different than for circuits with simple resistive loads. Here is a good explanation I picked up somewhere:Ī/C condensers contain a hermetically sealed compressor motor as well as a fan to circulate air across the coils. It is over fused if a breaker larger than the manufacturer’s label calls for is installed.