When adding refrigerant to the refrigeration system of the cold storage, it is necessary to ensure that the refrigerant is dry, otherwise, the refrigeration system will be blocked due to the lack of drying of the refrigerant, which will affect the normal operation of the refrigeration system. How to add refrigerant to cold storage.

　　1. Vacuuming and filling of refrigerant in cold storage

　　The newly built cold storage system needs to be evacuated before charging the refrigerant. As for the harm of not vacuuming, we have said many times on the public account of Refrigeration Encyclopedia, so I will not repeat it here. For vacuuming, first, connect the three-way meter to the suction and exhaust angle valves of the compressor, open the angle valve, and turn on the vacuum pump to vacuum. Generally, the vacuuming should be stopped after pumping too -0.1MPa (760mmHg). The vacuuming time should be determined according to the size of the refrigerator and the size of the vacuum pump and should be based on the pressure value displayed by the pressure gauge.

　　Need to pay attention! It is strictly forbidden to use the compressor to vacuum because, with the deepening of the vacuum in the refrigeration compressor shell, the insulating medium is lost between the exposed terminals in the shell or between the windings with slightly damaged insulation. It may be short-circuited and burned in an instant. If the casing leaks, it may also cause an electric shock to personnel.

　　After the vacuum is completed, prepare to add refrigerant. We need to understand that the correct amount of refrigerant in the cold storage is a key factor in determining the performance of the refrigeration system!

　　For example, insufficient refrigerant charge in the cold storage will reduce the efficiency of suction pressure and discharge pressure, especially in the return air cooling compressor, which may also cause motor overheating; if the refrigerant charge is excessive, it may cause the evaporator to Severe frost formation, high condensing pressure or liquid return to the evaporator damage the compressor. Even the same refrigeration equipment will have different filling amounts due to differences in the internal cold storage volume, evaporating temperature, and condensing pressure.

　　In the maintenance of the refrigeration system of the cold storage, in most cases, the gaseous or liquid refrigerant can be charged from the low-pressure side. When the refrigerant charge is large, the liquid charging method can also be used to charge the refrigerant from the high-pressure side. Need to pay attention! If you charge liquid refrigerant from the low-pressure side, you must add it slowly to avoid liquid shock! If you are afraid of liquid shock, you can also charge it in a gaseous state.

　　The method of adding refrigerant from the low-pressure side:

　　When charging gaseous refrigerant from the low-pressure side, first turn the low-pressure three-way stop valve counterclockwise to the endpoint, then connect the fluorine tube of the fluorine bottle to the bypass wire seat of the low-pressure three-way stop valve, and then open the For the bottle valve of the R22 fluorine bottle, loosen the joint of the bypass wire seat of the three-way stop valve slightly, and use R22 gas to drive out the air in the fluorine pipe. Lock it immediately and refrigerant charging begins. When the injection volume reaches the specified quality, close the stop valve of the fluorine bottle, turn the low-pressure three-way stop valve counterclockwise to the endpoint, close the bottle valve of the R22 fluorine bottle, remove the fluorine pipe, and the fluoride addition is over.

　　2. Judgment of refrigerant charge in cold storage

　　One of the common methods for determining the refrigerant charge in cold storage is to observe the flow of refrigerant in the sight glass in the liquid supply pipe. When the liquid flow is visible, it can be considered that the refrigerant has been charged correctly. If bubbles appear, it usually means that the refrigerant is insufficient, but it may also be a zoomed part of the liquid pipe of the sight glass or a rapid change in the condensation pressure, which makes the refrigerant Pressure drop. Therefore, the sight glass can be used as an effective method to determine the amount of refrigerant to be charged, not the basis.

　　Of course, it can also be judged according to the operating conditions of the system. First, the adjustment rod of the expansion valve must be set in the middle position, that is, to maintain the factory state (the expansion valve should not be adjusted in general). Then add liquid until the low-pressure pressure is similar to the corresponding pressure of the evaporation temperature of the cold storage (5~8 degrees lower than the storage temperature) at that time. Experienced technicians can also judge according to the outlet air temperature of the air-cooled condenser, the condensation or frosting of the return air of the compressor, the current, and the frosting of the expansion valve.

　　The principle of refrigerant charging operation in cold storage: when the storage temperature is above 0 degrees, no frost should appear in any part of the system! Only when the storage temperature is below 0 degrees, the outlet pipe of the expansion valve starts to frost, and then Gradually extend to the evaporator, and then the return pipe, until the suction angle valve of the compressor is frosted.