Reasons and Solutions for Frosting at the Compressor Return Port

Frosting at the compressor return port is a common problem, usually indicating that the compressor return temperature is too low. When the liquid refrigerant cannot absorb enough heat to reach the predetermined pressure and temperature, a situation where the return air temperature, pressure, and volume are all low will occur.

There are two main reasons for this problem:

1. The liquid refrigerant supplied by the throttle valve is normal, but the evaporator cannot absorb heat and expand normally.
2. The evaporator's heat absorption function is normal, but the amount of refrigerant supplied by the throttle valve is too large, that is, the refrigerant flow rate is too high.

In addition, a small amount of refrigerant may also cause frost formation in the return air of the compressor. When the refrigerant flow rate is too low, the local temperature of some areas of the evaporator drops sharply, forming local frost and gradually spreading to the entire evaporator and compressor return pipeline.

For these issues, we can adopt the following solutions:

• For situations where the throttle valve supply is normal but the evaporator cannot absorb heat and expand, the hot gas bypass valve can be adjusted. The specific method is to open the rear end cover of the hot gas bypass valve, use a hexagonal wrench to clockwise turn the adjusting nut inside, and slowly adjust until the frost phenomenon of the compressor disappears.
• For problems caused by a low amount of refrigerant, the starting pressure of the condensing fan pressure switch can be appropriately increased. The specific method is to turn the adjustment screw on the pressure switch, slowly adjust it, and observe the frost formation.

When dealing with frost phenomenon, it is necessary to pay attention to the adjustment process not to be too fast, and let the system run for a period of time before deciding whether to continue adjusting. When the operation is stable and the frost phenomenon of the compressor disappears, remember to tighten the end cover.