1. The big problem of using R404a refrigerant to replac […]
1. The big problem of using R404a refrigerant to replace R22 is the problem of lubricating oil. It is necessary to use PVE ester oil to replace the mineral lubricating oil for R22. Ester lubricating oil has high affinity with water and poor dehydration, so you should avoid contact with outside air as much as possible during use. After opening the container, use it as soon as possible. After use, it must be sealed and stored; stay away from oxidants, strong alkalis, and strong acids. Store in a well-ventilated place; avoid contact with skin and eyes, and avoid inhalation of vapor and spray.
2. The exhaust pressure of R404a refrigerant is about 1.2 times that of R22, and the mass flow rate is about 1.5 times that of R22. As the exhaust flow rate increases, the resistance becomes larger. Generally speaking, the heat exchange capacity of the condenser is 20% to 30% larger than R22.
3. At the same temperature, the saturation pressures of R404a refrigerant and R22 are different, so the operating mechanism of the 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 expansion valve sealing material should be changed accordingly. Therefore, the R404A special expansion valve should be used in the selection of the thermal expansion valve.
4. For the same compressor, the current using R404a refrigerant is greater than 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 pressure switch is adjusted from the original 2.45MPa to 2.7MPa.
5. Since the saturation pressure of R404a refrigerant is different from R22, the airtightness test pressure should be greater than 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 the refrigerant is charged, it should be charged in a liquid form to prevent the configuration of R404A from changing.
6. R404a refrigerant is a non-azeotropic mixture. The component concentration of the non-azeotropic mixture changes with temperature and pressure. This brings certain difficulties to the production, debugging and maintenance of the refrigeration system, and also affects the heat transfer performance of the system. It will have a certain impact, 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 refrigeration effect, otherwise it will get worse.
Because R404A refrigerant and lubricating oil have good compatibility with water, the requirements of the system for moisture, residues, and cleanliness are improved compared with R22 refrigerant. R404A system moisture control and impurity control are the same. For more important indicators, the corresponding filtering devices in the system need to be changed.
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