How to Add Refrigerant?

The refrigeration system uses refrigerant as the working fluid, and the refrigerant to be filled generally has two forms: liquid and gas. Today we will talk about the relevant knowledge about liquid refrigerants.

Is adding refrigerant liquid or gas?

Refrigerants can be divided into 3 categories: simple refrigerants, non-azeotropic mixture refrigerants, and azeotropic mixture refrigerants.

Whether the elemental refrigerant is in a gaseous or liquid state, the composition in it will not change, so the gaseous state can be charged when charging the refrigerant.

Although the composition of the azeotropic refrigerant is different because the boiling point is the same, the composition of the gas and liquid is also the same, and the gas can be charged.

Due to the different boiling points of non-azeotropic refrigerants, liquid refrigerants and gaseous refrigerants are actually different in composition. At this time, if a gaseous refrigerant is added, it will inevitably lead to different components of the refrigerant added. For example, only a certain gaseous refrigerant is added, so only a liquid state can be added.

That is to say, non-azeotropic refrigerants must be added with liquid. Non-azeotropic refrigerants all start with R4, which needs to be added. Common non-azeotropic refrigerants are: R401A, R403B, R404A, R406A, R407A, R407B, R407C, R408A, R409A, R410A, R41A. As for other common refrigerants, such as R134a, R22, R23, R290, R32, R500, and R600a, the composition of the refrigerant will not be affected by adding air or liquid.

In addition, it should be noted and emphasized that the non-azeotropic refrigerant must be added in a liquid state. For example, R410A refrigerant, its composition is as follows: R32 (difluoromethane): 50%; R125 (pentafluoroethane): 50%. Because the boiling points of R32 and R125 are different, when the R410A refrigerant cylinder is left standing, the boiling points of R32 and R125 are different, which will inevitably lead to the vaporized gaseous refrigerant in the upper part of the refrigerant cylinder. The composition is not 50% R32+50 %R125. Due to the low boiling point of R32, it is very likely that the upper part of the refrigerant is composed of R32. Therefore, if a gaseous refrigerant is added, it is very likely that the refrigerant added is not R410A, but R32.

Pay attention to common refrigerant injection methods and methods, such as:

1. Bubble filling method in sight glass;
2. Measuring high and low-pressure filling methods;
3. Measure the compressor’s current filling method;
4. Weighing injection method.

In fact, the most accurate method of charging is by weighing, which actually weighs the refrigerant added to the system. This method can only be used when the required charging volume of the system is known and the system requires full charging, which is usually the case for monolithic equipment.

In most cases, in refrigeration system maintenance, charging of gaseous or liquid refrigerant from the low-pressure side can be used. When the refrigerant charge is large, it can also be used to charge the refrigerant from the high-pressure side using the liquid charging method. requires attention! If the liquid refrigerant is charged from the low-pressure side, it must be added slowly to avoid liquid hammer! If you are afraid of liquid shock, it can also be filled 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, and then connect the fluorine tube of the fluorine bottle to the low-pressure three-way stop valve. on the bypass wire seat. Then, open the bottle valve of the refrigerant bottle, and slightly loosen the joint of the bypass wire seat of the three-way stop valve. Use refrigerant gas to drive out the air in the fluoride pipe. Tighten it as soon as you hear the sound of airflow at the joint, 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 work is over.