What is the larger diameter tube called during a heating cycle on a heat pump?

During a heating cycle on a heat pump, the larger diameter tube is referred to as the hot gas discharge line. This is because, in the heating mode, the refrigerant is compressed in the compressor, resulting in a high-pressure and high-temperature gas that is then discharged into this larger diameter line. The purpose of the hot gas discharge line is to transport this heated refrigerant to the outdoor coil, which acts as the evaporator in heating mode, allowing heat to be released into the space that needs to be warmed.

The design of the hot gas discharge line is critical because it needs to handle high-pressure refrigerant effectively and ensure efficient heat transfer. The larger diameter helps to minimize pressure drop as the refrigerant travels through the system, which helps maintain system efficiency. By contrast, the other lines in a heat pump system serve different functions; for instance, the liquid line transports refrigerant after it has condensed, and the suction line carries low-pressure vapor back to the compressor. Understanding the roles and characteristics of these lines helps HVAC technicians troubleshoot and maintain heat pump systems effectively.