Analysis and Treatment of Frost on Thermal Expansion Valve in Refrigeration System Mar 13, 2021

I believe that many of my friends will encounter such a problem, the frost behind the expansion valve! So why is it frosting? How to solve this problem? With these questions we will look down.

Discussion and analysis:

1. Someone will first consider whether the expansion valve is blocked or the opening is too small.

2. Some people will consider whether it is caused by a fault in the fan.

3. Of course, some people will analyze it from the direction of frost.

Of course, this is only part of the reason that a small group of friends think of. To sum up, about the direction of frosting in the refrigeration system. Everyone knows that the frosting direction is divided into different directions, there are mainly the following two kinds:

1、Starting from the compressor's return port, frost will gradually form towards the evaporator.

2、Frost forms from the expansion valve to the evaporator.

Frost on Thermal Expansion Valve in Refrigeration System

1. Frost begins to form on the air return

Frost begins to form at the air return, which is mainly analyzed from the following two aspects:

1). Refrigerant

The reason is that too much refrigerant enters the evaporator, resulting in incomplete evaporation, so the return pipe is still evaporating, absorbing the heat of the suction pipe, so the return pipe is frosted first.

The reasons are:

a. Too much refrigerant;

b. The expansion valve opening is too large;

2). The evaporator

The evaporator cannot absorb heat normally, or the cold generated by the evaporator cannot be taken away, which will cause incomplete evaporation, and the refrigerant will continue to evaporate and absorb heat in the return air pipe, resulting in frosting of the return air pipe.

The appearance is that the return liquid temperature and pressure are normal or slightly lower, and the frosting starts from the compressor air return port to the evaporator. After a long period of time, it freezes from the compressor air return port to the evaporator and the throttle valve to the evaporator section. , And finally there is low pressure.

The reasons are:

a. Check if the air filter is clean;

b. Check whether the fan speed is normal;

c. Whether the evaporator is clean;

d. Whether the air supply system is blocked;

2. the expansion valve begins to frost

The frost behind the expansion valve is mainly analyzed from the following three points:

1). Less refrigerant (leakage)

The return liquid temperature of the condenser is high but the pressure is not high, and the frost starts to form gradually toward the evaporator from the throttle valve.

2). The opening of the expansion valve is too small

The return liquid temperature and pressure of the condenser are normal or slightly lower, and frost begins to form at the throttle valve gradually toward the evaporator.

3). Check the sight glass

Depending on the condition of the refrigerant, serious foaming may be caused by system leakage; the refrigerant in the sight glass does not bubbling or seldom bubbling, it may be that the expansion valve is opened too small or blocked. Generally, there will be a large temperature difference before and after the blockage.

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