Which device maintains the level of the refrigerant in the evaporator?

• A. Low side float valve
• B. High side float valve
• C. Pressure regulator
• D. Solenoid valve

Answer: (A)

Maintaining the refrigerant level in the evaporator is done with a device on the low-pressure side that senses how much liquid is present and adjusts feed accordingly. The float valve sits in the evaporator circuit and uses a floats mechanism to regulate how much liquid refrigerant can enter the evaporator from the receiver.

As heat is absorbed in the evaporator, liquid refrigerant turns to vapor, so the liquid level tends to drop. The rising float opens the valve just enough to let more liquid in, restoring the level. When the level is back up, the float closes the valve to prevent overfilling. This automatic feedback keeps the evaporator filled to the proper level for efficient heat transfer and protects the system from issues caused by too little or too much liquid.

High-side float valves regulate flow on the high-pressure side and don’t control the evaporator level. A pressure regulator changes pressure, not the liquid level in the evaporator. A solenoid valve controls flow but doesn’t inherently maintain the specific liquid level in the evaporator without the sensing mechanism of a float.