How to add refrigerant to the cold storage? How much refrigerant should be added?

When adding refrigerant to the Freon cold storage refrigeration system, it is necessary to ensure that the refrigerant is dry, otherwise the refrigeration system will definitely cause ice blockage in the refrigeration system due to the non-drying of the refrigerant, which will affect the normal operation of the refrigeration system. Let us explain in detail the method of evacuating the fluorine refrigeration system, the method of charging the refrigerant, and the judgment of the charging amount.

1. Vacuuming and filling of cold storage with refrigerant

The newly-built cold storage system must be evacuated before charging with refrigerant, as for those without vacuuming Harm, our Refrigeration Encyclopedia public account has said many times, here is no longer wordy. To vacuum, first connect the three-way meter to the suction and discharge angle valves of the compressor, open the angle valve, and open the vacuum pump to vacuum. Generally, it is necessary to stop vacuuming after pumping to -0.1MPa (760mmHg). The vacuuming time should be determined according to the size of the cold storage and the size of the vacuum pump, and should be based on the pressure value displayed on the pressure gauge.

Need attention! It is strictly forbidden to use the compressor to vacuum, because as the vacuum in the refrigeration compressor housing deepens, the insulating medium will be lost between the exposed terminals in the housing or between the windings with small damage to the insulating layer. Once energized, the motor may be instantaneous. The internal short circuit burned out. If the shell leaks, it may also cause electric shocks.

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

For example, the insufficient amount of refrigerant in the cold storage will reduce the suction pressure and discharge pressure efficiency, especially for the return air cooling compressor, which may cause the motor to overheat ; If the refrigerant charge is too much, it may cause serious frosting of the evaporator, high condensing pressure or liquid back in the evaporator and damage the compressor. Even the same refrigeration equipment will have different optimal filling quantities due to differences in internal cold storage volume, evaporating temperature, and condensing pressure.

In cold storage refrigeration system maintenance, in most cases, gas or liquid refrigerant can be charged from the low pressure side. When the refrigerant charge is large, it can also be used. Use the liquid charging method from the high-pressure side to charge the refrigerant. requires attention! If the liquid refrigerant is charged from the low pressure side, it must be added slowly to avoid liquid shock! If you are afraid of liquid shock, you can also charge in 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 Rotate the direction to the end point, and then connect the fluoride tube of the fluorine bottle to the bypass wire seat of the low-pressure three-way shut-off valve. Then, open the bottle valve of the R22 fluorine bottle, and slightly Loosen it, use R22 gas to drive out the air in the fluoride tube, and immediately lock it when you hear the sound of 'sizzling' airflow at the joint, and the refrigerant charge begins. When the injection volume reaches the specified quality, close the fluorine bottle shut-off valve, turn the low-pressure three-way shut-off valve counterclockwise to the end, close the bottle valve of the R22 fluorine bottle, remove the fluoride tube, and the fluorine addition work is complete.

Two. Judgment of the refrigerant charge in the cold storage

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

Of course, it can also be judged according to the operating conditions of the system. First, the adjustment lever of the expansion valve must be set in the middle position, which is Keep the factory state (expansion valve generally do not adjust). Then add liquid until the low-pressure pressure is similar to the corresponding pressure of the cold storage evaporation temperature (5-8 degrees lower than the storage temperature) at that time. Experienced technicians can also judge according to the outlet 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 frosting shall occur in any part of the system! Only when the storage temperature is below 0 degrees, the first frost is on the outlet pipe of the expansion valve, then gradually extends to the evaporator, and finally the return pipe, until the compressor's suction angle valve is frosted.

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