What is the line that connects the evaporator to the compressor called?

The line that connects the evaporator to the compressor is referred to as the suction line. This is a critical component in an HVAC refrigeration system. The evaporator absorbs heat from the surrounding environment, causing the refrigerant inside it to evaporate and turn into a gas. This gas is then drawn into the compressor through the suction line.

As the gas travels through the suction line, it is low in pressure and temperature. The compressor's role is to increase the pressure of this gaseous refrigerant before it moves on to the condenser. Understanding the function of the suction line is essential because it carries the low-pressure refrigerant gas that has absorbed heat from the space being cooled.

The other lines mentioned serve different roles within the system. The discharge line carries refrigerant from the compressor to the condenser, the expansion line is involved in throttling the refrigerant before it enters the evaporator, and the return line typically refers to lines in a hydronic system, not directly related to the vapor path of a refrigeration cycle.