Problems to be Considered When Replacing R22 Refrigerant with R404a Refrigerant

In our daily life, no matter what product is used to replace another product, there are many problems with it, and refrigerants are no exception. Today, I will introduce the issues that need to be considered when replacing R22 refrigerant with R404a refrigerant.

1. The big problem of using R404a refrigerant to replace R22 is the lubricating oil problem. It is necessary to use PVE ester oil instead of mineral lubricating oil for R22. Ester lubricating oil has a high affinity with water and poor dehydration, so try to avoid contact with outside air during use. After the container is opened, it should be used as soon as possible, and it must be sealed and stored after use. Keep away from oxidants, strong alkalis, and strong acids, and store in a well-ventilated place. Avoid contact with skin and eyes during use, and avoid inhalation of its vapors and sprays.

2. The exhaust pressure of R404a refrigerant is about 1.2 times that of R22, and the mass flow is about 1.5 times that of R22. The exhaust flow rate increases and the resistance becomes larger. Generally speaking, the heat exchange capacity of the condenser is 20% to 30% larger than that of R22.

3. At the same temperature, the saturation pressure of R404a refrigerant and R22 is different, so the action mechanism of R404a refrigerant thermal expansion valve is different from that of R22. At the same time, due to the different compatibility of R404a refrigerant and lubricating oil to the sealing material, the sealing material of the expansion valve should also be changed accordingly. Therefore, R404A special expansion valve should be selected in the selection of the thermal expansion valve.

4. For the same compressor, the current of R404a refrigerant is larger than that of R22, so the diameter of the AC contactor, thermal relay, and cable of the compressor should be adjusted. In terms of system protection, the setting value of the high-pressure switch is adjusted from the original 2.45MPa to 2.7MPa.

5. Since the saturation pressure of R404a refrigerant is different from that of R22, the air tightness test pressure is higher than that of R22. At the same time, the vacuum degree of the system should be higher than R22, and the water content should be lower than R22. When charging the refrigerant, it should be charged in liquid form to prevent the configuration of R404A from changing.

6. R404a is a non-azeotropic mixed refrigerant. The composition concentration of the non-azeotropic mixture varies with temperature and pressure, which brings certain difficulties to the production, debugging, and maintenance of the refrigeration system, and also has a certain impact on the thermal conductivity of the system. Especially when the refrigerant leaks, the system refrigerant needs to be completely emptied and replaced, so as to ensure the proportion of each mixed component and achieve the designed cooling effect, otherwise it will get worse.

Since the R404A refrigerant and lubricating oil have good compatibility with water, the system’s requirements for moisture, residues, and cleanliness are higher than those of the R22 refrigerant. The moisture control and impurity control of the R404A system are relatively important indicators, and the corresponding filter devices in the system should be changed.