Maintenance Precautions for R134A Refrigerator

The refrigerant HFC-134a, tetrachloroethane, has zero ozone depletion potential. At present, the main refrigerants used in household refrigerators are R12 (CFC-12), R134a (HFC-134a), R600a (HC-600a), and so on. The application technology of replacing R12 with HFC-134a refrigerant is becoming more and more mature. The box structure, refrigeration system, and electrical system of this type of refrigerator are basically the same, so there are many similarities between common faults and maintenance techniques. However, there are also some differences, mainly due to the different related materials and repair methods caused by the characteristics of the refrigerant. The following introduces some of the problems that should be paid attention to when repairing such faults.

1. HFC-134a compressor

Compared with the CFC-12 compressor, the HFC-134a compressor needs to increase the cylinder volume by 10~15% to ensure the same cooling capacity. The condensing pressure is higher and the pressure ratio is higher. In order to obtain the same cooling capacity, some changes have been made to the structure and material of the compressor. The motor with higher efficiency is used to adapt to the harsher system working environment. Other parts and components can be used in common with CFC-12, but there are strict restrictions on the reserves of moisture and impurities, and the cleanliness requirements are higher. In use, the HFC-134a compressor is slightly larger than the CFC-12 compressor.

2. Refrigerated oil

Since HFC-134a is insoluble in traditional mineral oil and alkylbenzene oil, new ester lubricating oil needs to be used, and the fat lubricating oil has extremely strong water absorption. Since HFC-134a compressors generally use lipids or polyglycol (PAG) oils with good compatibility with them, which are different from mineral oils used in CFC-12 compressors, they cannot be substituted for each other. Otherwise, not only will they fail to meet the lubrication requirements of the compressor mechanism, and they may solidify and block the refrigeration system, so do not mix them. When maintenance and evacuation, the vacuum pump must be replaced with a vacuum pump of lipid refrigerating oil. If an old vacuum pump or rebuilt evacuation equipment (refrigerant oil is mineral oil) is used to repair and remodel an old vacuum pump or a scrapped CFC-12 refrigerator compressor (refrigeration oil is mineral oil), it must be thoroughly cleaned with lipid oil. And replace the grease oil, and replace the connecting hoses, joints, and sealing rings. The HFC-134a refrigerant does not contain chlorine atoms, and an electronic leak detector should be used for leak detection. If you use soapy water to detect low pressure, it should be done after the shutdown pressure is balanced. When cleaning the pipes of the refrigeration system, they should be cleaned with a chlorine-free cleaning agent.

3. Dry filter

The HFC-134a refrigerator has high requirements for the moisture control of the refrigeration system. In addition to strict drying and dehydration with a special process during manufacture, a dryer and a filter should be installed in the refrigeration system, and molecular sieves are used to absorb the remaining residual moisture. Filter driers are generally installed in the liquid conduit between the condenser outlet and the capillary inlet. For CFC-12 system, choosing 4A molecular sieve, namely XH-5 type, can absorb water well. For HFC-134a system, XH-7 type (maximum diameter 3A) filter drier with strong water absorption, slightly larger volume, and molecular diameter between HFC-134a and water should be used. The two cannot be used in place of each other during maintenance.

4. Maintenance operation time

For HFC-134a refrigerators that require higher moisture content control in the refrigeration system, special attention should be paid to moisture control. During maintenance, the analysis methods of listening and touching can be used. Once it is determined that the drying filter is blocked or the compressor is faulty, after opening the refrigeration system, the disconnected nozzles should be sealed in time, so that they can be broken and welded quickly. It is required that the exposure time of all pipeline components should be as short as possible (within 10 minutes) during maintenance, and the drying filter and small pipe components should be assembled as soon as possible after unpacking. The evacuation time of the refrigeration system of the HFC-134a refrigerator is longer than that of the CFC-12, so as to ensure that the vacuum degree is lower than 60Pa. HFC-134a refrigerant and run the compressor for 20 minutes, and then evacuate the second time for 20~30 minutes. This can shorten the vacuuming time, and the effect is better. When brazing HFC-134a refrigerator refrigeration system, try to use dry flux.