Which force opens the TEV valve?

Which force opens the TEV valve?

• A. Evaporator pressure
• B. Spring pressure
• C. Bulb pressure
• D. Both Evaporator and Bulb

Answer: (C)

The force that opens a thermostatic expansion valve is the pressure in the sensing bulb. The bulb sits on the evaporator and, as the evaporator temperature rises, the refrigerant in the bulb expands, increasing its pressure and transmitting that pressure to the valve diaphragm. This added pressure pushes the diaphragm and lifts the valve needle, overcoming the opposing force from the spring and the evaporator-side pressure. Evaporator pressure on the opposite side tends to resist opening, and the spring provides the baseline closing force, so they don’t actively open the valve. When bulb pressure rises enough, the valve opens to allow more refrigerant flow; when bulb pressure drops, the valve closes.

The force that opens a thermostatic expansion valve is the pressure in the sensing bulb. The bulb sits on the evaporator and, as the evaporator temperature rises, the refrigerant in the bulb expands, increasing its pressure and transmitting that pressure to the valve diaphragm. This added pressure pushes the diaphragm and lifts the valve needle, overcoming the opposing force from the spring and the evaporator-side pressure. Evaporator pressure on the opposite side tends to resist opening, and the spring provides the baseline closing force, so they don’t actively open the valve. When bulb pressure rises enough, the valve opens to allow more refrigerant flow; when bulb pressure drops, the valve closes.