Also used as an expansion device for flooded systems, the high-pressure float valve is located on the high-pressure side of the system and is in open connection to the condenser. It controls the evaporator level indirectly by maintaining a constant level of refrigerant inside the float chamber. The evaporator level therefore depends on the total refrigerant charge of the system, and must be adjusted to the system. If the charge is too great, it will lead to excessive flooding of the evaporator, while if the charge is too small it will lead to starvation. The function of a high-pressure float valve is shown in Figure 4.18.
The mechanical high-pressure float valve is now often replaced with an electronic alternative where the float provides impulses to control a solenoid valve.