What could cause a recycling or recovery machine with a hermetic compressor to overheat while drawing deep vacuums?

A recycling or recovery machine equipped with a hermetic compressor relies on the refrigerant flow for cooling. In such systems, the compressor is designed to circulate refrigerant, which acts as both a working fluid and a coolant. When deep vacuums are drawn, the refrigerant flow may be significantly reduced or even halted, leading to inadequate cooling of the compressor's motor.

Since the refrigerant absorbs heat from the compressor during normal operation, a condition where there is insufficient refrigerant flow—such as during a deep vacuum—results in the compressor becoming unable to dissipate heat effectively. This can lead to overheating of the compressor motor, compromising the unit's performance and potentially causing damage.

The other options relate to different mechanical issues that could affect the overall operation of the compressor but do not directly connect to the refrigeration cycle's dependence on refrigerant flow for cooling. Blocked refrigerant flow could lead to overheating, but it wouldn’t specifically cause issues with a hermetic compressor operating under deep vacuum conditions in the same context as relying on refrigerant flow for cooling. Excessive oil in the compressor generally affects performance differently, and the need for external cooling doesn't apply to hermetic designs typically sealed and designed to self-cool through the refrigerant.