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What causes abnormal frosting of the expansion valve?

2022-12-05

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

2 Some people may also consider whether the fan is faulty.

3 Of course, some people will analyze it from the perspective of frosting.

Of course, this is only part of the reason that a small number of friends think of.

To summarize, regarding the direction of frost in the refrigeration system.

As we all know, the direction of frost formation is divided into different directions, and there are mainly two types: starting from the air return port of the compressor and gradually forming frost towards the evaporator.

Frost forms from the expansion valve toward the evaporator.

Analyzing the differences between these two types of frost, the causes are opposite. Therefore, when friends are troubleshooting the problem, "you can't just see the frost on the expansion valve, evaporator, and return pipe. You must also distinguish the frost." direction."

1. Frost begins to form on the air return port

Frost begins to form on the air return port, mainly from the following two aspects:

Refrigerants

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

The reasons are:

1. Too much refrigerant;

2. The expansion valve opening is too large;

Evaporator

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

The symptom is that the liquid return temperature and pressure are normal or slightly low, and frost begins to gradually form from the compressor return port to the evaporator. After a long time, the entire section from the compressor return port to the evaporator and the throttle valve to the evaporator freezes. , and finally low pressure appears.

The reasons are:

1. Check whether the air filter is clean;

2. Check whether the fan speed is normal;

3. Is the evaporator clean?

4. Is the air supply system blocked?

5. Whether the belt is too loose.

2. The expansion valve begins to frost

Frost formation behind the expansion valve is mainly analyzed from the following three points:

1. Less refrigerant (leakage)

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

2. Expansion valve opening is too small

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

3. Check the sight glass

Look at the condition of the refrigerant. If the foaming is serious, it may be a system leak. If the refrigerant in the sight glass does not bubble or rarely bubbles, it may be that the expansion valve is opened too small or is blocked. Generally, there will be a large temperature difference before and after the blockage. .

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