What potential issue could arise if a refrigeration system is not properly evacuated before charging?

When a refrigeration system is not properly evacuated before charging, the primary concern is system contamination. Proper evacuation is crucial because it removes any moisture, air, and contaminants that may have entered the system. Moisture can lead to the formation of acids and ice within the system, which can cause significant damage to components such as the compressor and evaporator. Additionally, if air is present in the system, it can create a mixture that reduces the efficiency of heat exchange and can lead to operational failures. Contaminants can also affect the chemical stability of the refrigerant, compromising the system's overall performance. Therefore, ensuring a complete and thorough evacuation before charging the system is essential to maintaining its integrity and efficiency.