What issue may arise if a heat pump capacitor start-capacitor run compressor hums momentarily and then shuts down?

When a heat pump capacitor start-capacitor run compressor hums momentarily and then shuts down, the most likely issue is related to the pressure conditions within the system. When the compressor fails to start properly, it may be due to too great a pressure difference across its suction and discharge sides. This can occur if the refrigerant is not circulating correctly, potentially due to a blockage or if there is a significant difference in the pressure that the compressor is encountering.

As the compressor tries to start, it encounters a load that is too heavy, leading to the humming sound as it struggles to overcome the pressures. If the pressure difference is excessive, the compressor may shut down as a protective measure to avoid damage. This highlights the importance of monitoring pressure levels within the HVAC system to ensure proper operation.

In contrast, while options like electrical overload, inadequate start capacitor, and faulty compressor windings can cause operational issues, they do not directly relate to the situation of the compressor humming and immediately shutting down due to pressure imbalances. Therefore, addressing pressure differences within the system is critical to resolving this issue more effectively.