How to add refrigerant to a commercial refrigerator?

Refrigerant, known as the "blood" of the refrigeration system in commercial refrigerators, directly determines whether the equipment can maintain a stable low-temperature environment. In commercial scenarios such as supermarket cold chain cabinets and restaurant cold storage, refrigerant continuously transfers heat from inside the cabinet to the external environment through a cyclic process of compression, condensation, expansion, and evaporation, ensuring that food ingredients are stored within the optimal preservation range of 0-8°C. Once refrigerant leaks or its quantity is insufficient, it will cause the evaporation temperature to rise and the compressor load to increase sharply, not only resulting in a more than 30% increase in power consumption, but also potentially leading to food spoilage due to refrigeration failure, bringing merchants economic losses of thousands of yuan per day. Therefore, mastering scientific refrigerant charging methods is not only a core skill to ensure the efficient operation of equipment, but also a key link to reduce operating costs.

Preliminary Preparation and Leak Detection

The preparatory work before adding refrigerant directly affects the operation effect and system safety. First, it is necessary to confirm the refrigerant model of the target equipment. Common refrigerants for commercial refrigerators are R404A (for medium-temperature cold chains), R134a (for display cabinets), or R507 (for low-temperature cold storage). Mismatched models can cause compressor damage, and the model can be found through the equipment nameplate or instruction manual.

Required tools include: a double gauge valve with a pressure gauge, a suitable fluorine charging hose (with a pressure resistance value ≥3MPa), a vacuum pump (with a pumping speed ≥2L/s), a leak detector (electronic halogen leak detectors have better accuracy), and protective equipment (chemical-resistant gloves, goggles).

Leak detection is a crucial and indispensable step. Commercial refrigerators are prone to micro-leaks at evaporator interfaces and condenser welding points due to frequent door opening and closing, pipeline vibration, and other reasons.

After turning off the equipment power, first recover the residual refrigerant (slowly release it into a designated container through the pressure gauge), then charge 0.5MPa nitrogen into the system, and move the leak detector probe along the pipeline interfaces. If an alarm sounds, mark the leak point; if no instrument is available, apply soapy water, and the bubbling area is the leak point. Small leak points can be repaired by silver brazing, while severely damaged ones require pipe replacement. After repair, leak detection should be performed again to ensure tightness.

Vacuum Pumping and Refrigerant Charging Process

Vacuum pumping aims to remove air and moisture from the system. These impurities can cause an increase in condensation pressure, a decrease in refrigerating capacity, and even ice blockage. Connect the vacuum pump to the low-pressure interface (blue) of the double gauge valve, and connect the other end to the process port of the refrigerator compressor (usually a φ6mm copper pipe). Open the high and low-pressure valves of the double gauge valve, start the vacuum pump, and run it for at least 30 minutes (for large cold storage, it needs to be extended to 1-2 hours). Observe the pressure gauge; if the low-pressure gauge stabilizes at -0.1MPa (absolute pressure is close to 0), close the valves and stop the machine, then maintain the pressure for 30 minutes. If the pressure rise does not exceed 0.005MPa, it is qualified; otherwise, leak detection needs to be re-performed.

Refrigerant charging must strictly follow the principle of "first gaseous then liquid". Keep the refrigerant cylinder upright (for gaseous charging), connect it to the high-pressure interface (red) of the double gauge valve through the fluorine charging hose, slowly open the cylinder valve, and discharge the air in the hose (loosen the hose connector to release air for 3-5 seconds). Open the low-pressure valve of the double gauge valve, start the refrigerator compressor, and let the system suck in the refrigerant during operation. When the low-pressure gauge shows that the pressure reaches the evaporation pressure marked on the equipment (for example, R404A is about 0.38MPa at 0°C), close the cylinder valve and observe the operation for 30 minutes. If the cabinet temperature does not reach the set value (for example, the refrigerated cabinet does not drop below 5°C), a small amount of refrigerant can be added. After each addition, the machine must be stopped for 10 minutes before detection to avoid pressure fluctuations affecting the judgment.

For large commercial refrigerators (refrigerating capacity >10kW), it is recommended to use the weight method for charging: first weigh the empty cylinder, record the initial value, weigh it in real-time during the charging process, and stop immediately when the reduction amount is equal to the charging amount marked on the equipment nameplate. This method is more accurate than the pressure method, especially suitable for multi-component mixed refrigerants (such as R404A).

Operational Specifications and Safety Precautions

Safe operation is the core principle of refrigerant addition. All operations must be carried out in a well-ventilated environment to avoid oxygen deficiency caused by refrigerant leakage (halocarbons such as R404A will replace oxygen in the air); open flames are strictly prohibited in the operation area, as some refrigerants (such as R32) are flammable and may cause explosions when exposed to sparks. Operators must wear goggles and chemical-resistant gloves. If refrigerant comes into contact with the skin, it must be rinsed with clean water immediately for 15 minutes; if it gets into the eyes, medical treatment is required.

Equipment operation and maintenance are also crucial. After charging, the compressor current must be detected. If it exceeds 10% of the rated value, it may be due to overcharging, and part of the refrigerant needs to be released slowly; when the compressor is running, listen to it. If a "liquid hammer" sound (similar to the impact of flowing water) is heard, it indicates that liquid refrigerant has entered the compressor, and the machine should be stopped immediately for discharge. It is recommended to check the pressure gauge every quarter. If the pressure drops by more than 0.05MPa, leak detection and repair must be performed again to avoid resource waste caused by repeated charging.

The refrigerant management of commercial refrigerators is not only related to refrigeration efficiency, but also affects food safety and operating costs. Only by following scientific charging procedures, attaching importance to leak prevention, and standardizing the use of tools can the equipment always be in the best working condition. For merchants lacking professional experience, it is recommended to entrust technicians with refrigeration operation certificates to perform the operation. On the premise of ensuring safety, it can achieve the dual benefits of extending the equipment life by 2-3 years and reducing energy consumption by 15%-20%.