Where must you connect a hose to recover liquid refrigerant?

Connecting a hose to recover liquid refrigerant should be done on the liquid line. The liquid line carries refrigerant in its liquid state from the receiver or condenser to the expansion device. When performing recovery, it's crucial to access this line because it allows for the efficient transfer of liquid refrigerant into the recovery machine without introducing issues that could arise from vapor.

In contrast, connecting to the vapor line would introduce refrigerant in a gaseous state, which is not ideal for recovery, as it would not effectively remove the liquid refrigerant from the system. The discharge line, which carries high-pressure gas from the compressor, also wouldn't be suitable for liquid recovery. Lastly, the suction line, which carries low-pressure vapor back to the compressor, similarly does not facilitate liquid recovery. Thus, connecting hoses to the liquid line is the best practice for effective and safe recovery of refrigerant.