What temperature does the thermostatic expansion valve bulb operate under?

The thermostatic expansion valve (TXV) bulb operates under the suction line temperature. The purpose of the TXV is to regulate the flow of refrigerant into the evaporator coil based on the cooling needs of the system. The bulb is filled with a refrigerant or fluid that responds to temperature changes by expanding or contracting. When the temperature of the suction line increases, which indicates a rise in evaporator temperature as the refrigerant absorbs heat, the pressure within the bulb increases as well.

This increase in pressure causes the valve to open further, allowing more refrigerant to flow into the evaporator. Conversely, if the suction line temperature decreases, the bulb pressure falls, leading to the valve closing to reduce the flow of refrigerant. This dynamic regulation helps maintain the proper balance within the refrigeration cycle, ensuring efficient operation and preventing issues such as flooding or starved evaporator conditions.

Operating on the suction line temperature enables the TXV to adapt to varying cooling loads effectively, providing optimal performance of the refrigeration system.