What is the opening pressure in a TXV?

The opening pressure in a thermal expansion valve (TXV) is determined by the bulb pressure. The bulb is typically located at the outlet of the evaporator, where it senses the temperature of the refrigerant. This temperature is then converted into a pressure that acts upon the diaphragm in the TXV, regulating the flow of refrigerant based on the evaporator's needs.

When the temperature in the evaporator rises, the bulb pressure increases, leading to the TXV opening further to allow more refrigerant to flow into the evaporator. Conversely, if the temperature drops, the pressure decreases, and the TXV restricts refrigerant flow. This self-regulating mechanism is crucial for maintaining efficiency and performance in heat pump systems.

In contrast, the evaporator pressure refers to the pressure of the refrigerant in the evaporator itself, which is not what directly influences the opening of the TXV. Condensing pressure pertains to the pressure at which the refrigerant is condensed in the outdoor unit and does not relate to the TXV's function. Liquid line pressure is the pressure of the refrigerant in the liquid line before it enters the evaporator, which also does not determine the TXV's opening pressure.