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

The correct answer highlights a crucial operational aspect of a hermetic compressor in a recycling or recovery machine. Hermetic compressors depend on the refrigerant for both its refrigeration cycle and its cooling. When drawing a deep vacuum, the flow of refrigerant through the compressor decreases significantly. This reduction impairs the compressor's ability to dissipate heat generated during the compression process, as refrigerant typically serves as a coolant.

Therefore, insufficient refrigerant flow can lead to overheating because the compressor is designed to cool itself using the refrigerant. Without adequate circulating refrigerant, the compressor may be unable to maintain a safe operating temperature, potentially damaging the unit.

Other choices also present concerns, but they do not directly address the specific cooling dynamics related to hermetic compressors. For instance, while a small compressor may struggle under high load conditions, it does not inherently cause overheating in the context of a vacuum draw. Similarly, insufficient airflow around the unit can be a factor in excessive heat, but it is the unique relationship between refrigerant flow and compressor cooling that is pivotal in this scenario. Excessive refrigerant in the machine can lead to other issues, but it doesn't align with the cooling mechanism of the hermetic compressor in the context of deep vacuum operation.