For the safe use of A2L refrigerants in the refrigeration system, considerations can be made in aspects such as safety signs and instructions, control of the charging amount, and safety of electrical components and structures. Generally, following the usage instructions ensures safety.
Read the safety signs and instructions and pay attention to the fire - prevention signs. Set permanent fire - prevention signs on the nameplate (near the refrigerant type and charging amount information), prominent positions of the equipment (indoor and outdoor units), maintenance and filling ports, and the product outer packaging (packaging of indoor and outdoor units in non - single - package appliances). For example, in accordance with the requirements of IEC60335 - 2 - 40 and GB/T 21363 - 2018, the height of the nameplate and maintenance port signs should be not less than 10mm, and the height of the equipment and outer - packaging signs should be not less than 30mm. And the signs need to pass the wiping test. They should not fall off or curl after being wiped with a water - soaked and gasoline - soaked cloth for 15s each to meet the durability requirements.
In addition, the instruction - type signs and documents provide installation, maintenance, and operation manuals, and the content covers the relevant information in Standard Appendix DD "Maintenance Operations". For equipment relying on the refrigerant monitoring system, the manual or sign states "This appliance is equipped with a refrigerant leak detector for safety purposes. To ensure its effectiveness, the appliance should be powered at all times after installation except during maintenance services."; for appliances relying on the ventilation function to dilute the leaked refrigerant, it states "This appliance is equipped with electric safety measures. It must be powered at all times after installation except during maintenance services to ensure its effectiveness."; for appliances that require on - site charging of flammable refrigerants, provide a label indicating the pre - charging amount, on - site charging amount, and total charging amount.
According to the requirements of IEC60335 - 2 - 40, for A2L refrigerants, m1 = 6 * LFL (LFL is the lowest flammable value). If the system charging amount mc is less than m1, it is generally considered that a leak will not affect safety, and there is no requirement for room area and ventilation; if mc is greater than m1, the minimum area Amin of the usable room should be indicated. For example, if the charging amount of the R454C system is greater than 1.716kg, the equipment needs to be equipped with a sign indicating attention and the minimum room area, and the sign should be placed outside the appliance to ensure it is visible to the user. At the same time, corresponding warning contents should be given, such as prohibiting accelerated defrosting, and the appliance should be stored in a room without a continuous ignition source.
Importantly, in terms of the safety of electrical components and structures, for electrical components such as relays and contactors that may become ignition sources, explosion - proof electrical components that meet national standards or IEC standards (such as IEC60079 - 15 "Electrical apparatus for explosive gas atmospheres") can be used; or they can be installed in the same enclosed electrical box and sealed with potting compound. And the potted electrical box needs to pass the simulated leak test (observing whether there are bubbles when immersed in water at a specific temperature).
Thermal surface temperature limit: For thermal surfaces that may be exposed to A2L refrigerant gas, limit their maximum surface temperature. Generally, it is determined by subtracting 100K from the refrigerant's auto - ignition temperature (for refrigerants not listed), usually not exceeding 700°C. Taking R454C as an example, its auto - ignition temperature is 444°C, and it is recommended that the thermal surface temperature of the system does not exceed 344°C. At the same time, attention should be paid to the possible over - temperature problem of the metal electric heating pipes for defrosting and crankcase heating when they are dry - burned.
Pipe design and connection:
Protection and material requirements: The pipes should be protected to prevent mechanical damage during handling and use, which could lead to leakage. Low - melting - point brazing alloys (such as lead or tin alloys) are prohibited at the joints and pressure - bearing parts to avoid unreliable solder joints at high temperatures.
Pressure - bearing requirements: Use pipes that meet the pressure - bearing requirements. Components exposed to the high - pressure side should withstand 3.5 times the saturated vapor pressure of the refrigerant at 70°C, and components on the low - pressure side should withstand 2.5 times the saturated vapor pressure at 20°C. All connections should meet the ISO 14903 air - tight control level A1.
Monitoring and ventilation
Refrigerant monitoring system: For appliances using A2L refrigerants and meeting relevant requirements through the refrigerant monitoring system, the sensors should be installed where refrigerants are likely to accumulate. For example, inside units connected to rooms through the air - duct system, and inside units with a release height not exceeding 1.5m as determined by the standard. There are specific installation location regulations for different structural forms, and the sensors need to pass the tests specified in Standard Appendix MM. It is required that in the simulated leak test, there is at least a 90% response rate within 10s, an accuracy of ±1% when the gas concentration is between 20% - 30%, and the refrigerant concentration measured at the sensor position exceeds the set value within 90s.
Ventilation measures: Ensure good ventilation to dilute the leaked refrigerant. For appliances whose safety depends on the ventilation function, ensure the normal operation of the ventilation device and keep it powered on continuously after installation.
System installation and maintenance
Installation requirements: Newly installed refrigeration systems need to go through processes such as pressure - bearing tests, leak detection, sewage removal, and vacuum pumping. Only after confirming no leakage can the refrigerant be charged. When charging, open the valves slowly to prevent brittle fracture of the container.
Maintenance inspection: Regularly inspect the refrigeration system, including pipes, electrical components, and sealing conditions. Operators should follow the "Four Requirements", "Five Diligences", and "Six Timely Actions", that is, ensure safe operation, ensure the use temperature, reduce the condensing pressure, and give full play to the refrigeration efficiency; be diligent in looking at the instruments, checking the machine operation status, listening for abnormal noises in the machine operation, adjusting the valves, and checking for leaks in the system; be timely in adding and draining oil, releasing air, cleaning or replacing the filter, eliminating potential faults, removing scale from the condenser, and troubleshooting computer problems.