What is the designation of the smaller refrigerant line?

The designation of the smaller refrigerant line is known as the suction line, which carries refrigerant vapor from the evaporator back to the compressor. The suction line is typically larger than the discharge line in terms of diameter, with the smaller refrigerant line being the liquid line.

By transporting low-pressure vapor back to the compressor, the suction line plays a critical role in the refrigeration cycle. It ensures that only vapor enters the compressor, allowing for proper operation and efficiency of the system. The other lines in the system, such as the liquid line, are characterized by carrying high-pressure liquid refrigerant to the expansion device, while the discharge line transports high-pressure vapor from the compressor to the condenser. This differentiation is key in understanding the function and operation of HVAC systems.