What is the middle pipe called on the side of a reversing valve that has three pipes?

The middle pipe on the side of a reversing valve with three pipes is known as the permanent suction line. In a heat pump system, the reversing valve directs the flow of refrigerant, enabling the system to either heat or cool, depending on the needs of the space.

The middle pipe functions as a constant point for refrigerant to be drawn in, ensuring that the system has a consistent source of refrigerant for both heating and cooling modes. This is crucial because it maintains the stability of the system's operation. Understanding the role of the permanent suction line helps HVAC technicians properly diagnose and service heat pump systems, ensuring that they function effectively in various temperature conditions.

In contrast, other components such as discharge lines or hot gas lines are designed to carry refrigerant out to different parts of the system under pressure, while a bypass line may not be relevant in this context.