The replacement refrigerants for R22 – R404a
1. The biggest problem of using refrigerant R404A to replace refrigerant R22 is the problem of lubricating oil.
PVE ester oil must be used to replace the mineral lubricating oil for R22. Ester lubricants have high affinity with water and poor dehydration. Therefore, 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 is about 1.5 times that of R22. The exhaust flow rate increases and the resistance increases. Generally speaking, the heat transfer capacity of condenser is increased by 20% to 30% than that of R22.
3. The saturation pressure of R404A and R22 are different at the same temperature,
so the operating mechanism of R404A 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. 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. Such as accumulators and gas-liquid separators. At the same time, the safety valves and fusible plugs installed on the system accessories should be changed accordingly. Since the gas density of R404A is about 50% higher than that of R22 under the same displacement, the pipe diameter selected when R404A is used for piping design is larger than that of R22.
5. For the same compressor, the current of R404A 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.
6. Since the saturation pressure of 404A is different from R22,
the air tightness test pressure is greater than R22. At the same time, the vacuum of the system is higher than R22, and the water content is lower than R22. The refrigerant should be charged in liquid form when charging, to prevent R404A configuration changes.
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 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.
8. Because R404A refrigerant and lubricating oil itself 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 It is a relatively important indicator, and the corresponding filtering device in the system needs to be changed.
The above is the difference between R22 and R404A refrigerant, is need to pay attention.
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