Precautions for using R404A refrigerant instead of R22 refrigerant
R22 refrigerant still firmly occupies an important position of refrigerant consumption in the cold industry, but because R22 refrigerant has a certain destructive effect on the ozone layer, and has a high greenhouse effect. As an environmentally friendly refrigerant with similar refrigeration performance to R22, R404A has become the best choice to replace R22 refrigerant.
Although the refrigeration performance of R404A refrigerant and R22 refrigerant is relatively close, there are still some differences in actual use, which must be paid attention to. Next, we will list the specific issues that need to be considered when replacing R22 refrigerant with R404A refrigerant.
1. The big problem of using R404A instead of 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 a 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.
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. The exhaust flow rate increases.
Increase, the resistance increases. Generally speaking, the heat transfer capacity of the condenser is 20%~30% larger than that of R22.
3. The saturation pressure of R404A and R22 is different at the same temperature, so the action mechanism of the R404A thermostatic 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, R404A expansion valve should be used in the selection of the thermal expansion valve.
4. Since the saturation pressure of R404A is higher than that of R22, the design pressure of the pressure vessel in the system must be changed to ensure safety. At the same time, the safety valve and fusible plug set value installed on the system accessories such as the accumulator and the gas-liquid separator should also be changed accordingly. Since the gas density of R404A is about 50% greater than that of R22 under the same displacement, the pipe diameter should be larger than R22 when using R404A refrigerant for piping design.
5. For the same compressor, the current using R404A is greater than R22, so the diameter of the compressor's AC contactor, thermal relay, and cable 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.
6. Since the saturation pressure of R404A 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.
7.R404A is a non-azeotropic mixing working fluid. 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, as well as to the heat transfer performance of the system.
Especially when the refrigerant leaks, the system refrigerant is recommended to be completely emptied and replaced, so as to ensure the proportion of each mixed component and achieve the designed refrigeration effect.
8. The refrigerant R404A is a mixed refrigerant, which is composed of 44% R125, 4% R134A, and 52% R143A. Two refrigerants cannot be mixed. R22 is a primary refrigerant, and R404A is a mixed secondary refrigerant. The boiling point and pressure are different from azeotropic and non-azeotropic.
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.
As an expert in refrigerant research for many years, Fortech can share with you some professional suggestions. If you want to know more about the content after reading the above, you can get a comprehensive solution by contacting us.
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