What is installed between the manifold gauge assembly center port and the recovery machine?

The in-line filter drier is crucial in a system that involves refrigerant recovery. Its primary function is to remove moisture and contaminants from the refrigerant before it enters the recovery machine. This helps protect the recovery unit from potential damage caused by acid formation or clogging that can occur from moisture or debris within the refrigerant.

In HVAC/R systems, the presence of moisture can lead to significant problems, including corrosion and freezing, which can disrupt the efficiency of the system and create additional maintenance issues. By placing the in-line filter drier in this position, it ensures that the refrigerant being recovered is clean and dry, thereby enhancing the longevity and performance of the recovery equipment.

This makes the in-line filter drier the correct answer, as it directly contributes to the operational reliability of the recovery process. The other options, while relevant to various aspects of HVAC/R systems, do not specifically serve the same protective and filtering function in the context of the refrigerant flow between the manifold gauge assembly and the recovery machine.