What adjustment should be made to a TXV to increase superheat in heat pump systems?

To increase superheat in heat pump systems, the adjustment to the TXV (Thermostatic Expansion Valve) should be made by turning the adjustment clockwise. The TXV regulates the flow of refrigerant into the evaporator based on the temperature and pressure of the refrigerant. By turning the adjustment clockwise, you are effectively increasing the resistance to the flow of refrigerant, which allows less refrigerant to enter the evaporator.

As a result, this leads to a higher temperature at the evaporator outlet before the refrigerant enters the compressor, thus increasing the superheat. Superheat is crucial in ensuring that the vapor reaching the compressor is in a fully gaseous state, which protects the compressor from damage due to liquid refrigerant.

In contrast, turning the adjustment counterclockwise would decrease superheat by allowing more refrigerant to flow into the evaporator, potentially flooding the compressor with liquid refrigerant. Replacing the TXV with a larger one does not directly control superheat and instead changes the capacity of the system, while adjusting the evaporator temperature indirectly influences superheat but is not a direct adjustment made through the TXV.