When a thermostat expansion valve is operating properly, what state will the end of the coil contain?

When a thermostat expansion valve is functioning correctly, the end of the coil will contain superheated vapor. This is significant because the role of the expansion valve is to regulate the flow of refrigerant into the evaporator. As refrigerant passes through the valve, it expands and absorbs heat, which allows it to vaporize and cool the surrounding air.

The presence of superheated vapor at the end of the coil indicates that the refrigerant has absorbed sufficient heat from the evaporator and has transitioned from a liquid to vapor phase. This state is crucial for ensuring that the vaporized refrigerant returns to the compressor without carrying any liquid, which could cause damage to the compressor.

In contrast, if the end of the coil contained liquid refrigerant or wet vapor, it would suggest that the refrigerant has not fully vaporized and could lead to compressor damage or reduced system efficiency. Therefore, the ideal state of superheated vapor at the end of the coil reflects the successful operation of the expansion valve in managing the refrigerant cycle effectively.