What happens to the system pressure after achieving the required recovery vacuum if refrigerant is trapped?

When the required recovery vacuum is achieved in a refrigerant recovery process, the system pressure can rise if refrigerant is trapped. This scenario occurs because, in a closed system, the vacuum can only draw out the refrigerant until an equilibrium is established. If there is trapped refrigerant in the system, particularly in places that are not effectively evacuated, it will create a pressure that is higher than the vacuum level being generated.

In practical terms, achieving a vacuum means that the pressure has been significantly reduced, but the presence of trapped refrigerant can lead to the formation of vapor or, depending on the temperature, liquid that contributes to an increase in the pressure reading. This rise is not due to an influx of refrigerant but rather the inability of the system to maintain a consistent low pressure owing to the physical limitations of refrigerant flow and evacuation.

Understanding this concept is vital for technicians because it emphasizes the importance of ensuring complete recovery of refrigerant to avoid inefficiencies and potential environmental hazards associated with refrigerant leaks. Additionally, recognizing that trapped refrigerant can affect pressure readings helps ensure that technicians take adequate measures to achieve a thorough recovery during service operations.