Failures in the operation of industrial refrigeration equipment are often associated with loss of refrigerant, which leads to damage to expensive products and disruption of technological processes. Freon charging is not just adding gas to the system, but complex technical regulations that require accuracy and compliance with safety standards. Industrial installations, such as Polair, Ariad or Mariochilado, have a complex design that differs from household analogues in the presence of several evaporators, receivers and complex automation.
Incorrect refueling can lead to compressor water hammer or insufficient cooling. Unlike household models, the weight of the refrigerant is critical here, and not just the pressure on the pressure gauge. In this article we will analyze in detail the stages of restoring the unit's functionality, diagnostic tools and the nuances of working with different types of refrigerants.
It is worth understanding that working with freon requires specific equipment, in particular, a vacuum pump and high-precision scales. Ignoring the stage of evacuation of the system often causes repeated breakdowns due to moisture and air entering the circuit. Freon R404A, most often used in low-temperature chambers, is a mixture, which imposes additional requirements on the charging procedure.
Diagnostics of leaks and preparation of equipment
The first step is always to detect the location of the leak, since simple refueling without eliminating the cause does not make sense. Leaks in industrial refrigerators often occur at the soldering points of copper tubes, at valve seals or in evaporators due to vibration. To search, use an electronic leak detector or the nitrogen pressure test method, which is considered the most reliable for industrial systems.
If a leak is found and repaired, it is necessary to prepare the workplace. You will need a pressure gauge station (preferably with electronic scales), a vacuum pump with a capacity of at least 2-4 cubic meters per hour and a refrigerant cylinder. Before connecting, check the integrity of the hoses and the absence of moisture in them.
⚠️ Attention: The use of an open flame to search for leaks in the system where refrigerant could remain is strictly prohibited due to the risk of the formation of toxic compounds (phosgene) upon contact with the flame.
The pressure gauge station is connected through the service ports located on the suction and compressor discharge lines. It is important to ensure that the valves in the station are closed before starting work to avoid the immediate release of residual gas. Correct diagnostics saves time and prevents environmental pollution.
Refrigeration circuit vacuum technology
Evacuation is the most critical stage on which the service life of the compressor and the efficiency of heat transfer depend. There should be no air, moisture or non-condensable impurities left in the system. The process is carried out using a vacuum pump connected to the low-frequency port (blue hose) or directly to the service valve.
The duration of the process depends on the volume of the system and the power of the pump. For industrial chambers, vacuuming time can range from 30 minutes to several hours. Monitoring is carried out using a vacuum gauge: the residual pressure should reach a value below 500 microns (or the corresponding reading on the vacuum gauge scale).
- 🔹 Connect the vacuum pump to the system through a pressure gauge station.
- 🔹 Open the valve at the station and start the pump.
- 🔹 Monitor pressure drop, making sure that it does not stop at intermediate values.
- 🔹 After reaching a vacuum, close the valve and turn off the pump to check the tightness (pressure rise test).
If the pressure gauge needle begins to creep up after turning off the pump, this indicates the presence of a hidden leak or evaporation of moisture inside the system. In this case, the procedure must be repeated, possibly using nitrogen purge. High-quality vacuuming ensures that there are no ice plugs in the expansion valve (thermostatic expansion valve).
Calculation of the amount of refrigerant and selection of the type of freon
The amount of freon in the system is determined strictly by the weight indicated on the nameplate of the compressor-condensing unit or in the technical documentation of the manufacturer. Dosage “by eye” or by pressure in industrial systems is unacceptable, as it can lead to failure of expensive equipment. The type of refrigerant is also important: most often used R404A, R134a or R507.
For an accurate calculation, it is necessary to take into account the length of the route, the number of evaporators and the volume of the receiver. If the route between the condenser unit and the chamber is long, the volume of refrigerant is calculated individually, adding grams for each linear meter of the line. An error in the calculations leads to an increase in condensation pressure or insufficient boiling.
| Refrigerant type | Temperature conditions | Filling features | Cylinder color |
|---|---|---|---|
| R404A | Low temperature | Filling only in the liquid phase | Orange |
| R134a | Medium temperature | Can be charged in the vapor phase | Light blue |
| R507 | Low temperature | Azeotropic mixture, liquid filling | Grey |
| R407C | Medium temperature | Only liquid phase (otherwise the composition will be disrupted) | Brown |
The use of weights when filling is a prerequisite for maintaining the proportions of the mixture.
The process of filling the system with refrigerant
Direct charging is carried out after successful evacuation and leak testing. The freon cylinder is installed on the scales, and the tare value is reset or fixed. For mixtures such as R404A, the cylinder must be turned upside down so that it is liquid freon and not vapor that enters the system.
When opening the valve at the pressure gauge station, monitor the readings of the scales. Refueling is done in portions: we started a little gas, let the system work, checked the currents and temperatures. A sudden injection of a large volume of liquid can cause water hammer in the compressor, which will lead to mechanical destruction of the valve group.
- 🔹 Turn over the freon cylinder (for mixtures) and open the valve.
- 🔹 Open the blue valve of the station, monitoring the weight on the electronic scales.
- 🔹 Inject the calculated amount of refrigerant into the switched off system (primary charging).
- 🔹 Start the compressor and continue charging under pressure and current control.
During operation, watch for freezing of the suction line. If the pipe freezes up to the compressor, this is a sign of overflow (excess freon). If the evaporator does not freeze completely or only at the entrance, there is not enough freon. Balancing The system takes time, do not rush to add gas right away.
☑️ Filling control
Pressure control and automatic settings
After refueling, you must make sure that all operating parameters correspond to the norm. The suction and discharge pressure depends on the ambient temperature and the temperature inside the chamber. For R404A at an evaporation temperature of -25°C, the suction pressure will be approximately 1.6-1.8 bar, but these values may vary.
Pay special attention to the compressor motor current. It must not exceed the nominal value indicated on the nameplate. Exceeding the current indicates an overload, which can be caused by excess freon or contamination of the capacitor. Lack of current indicates an underload of the system or problems with compression.
⚠️ Attention: System pressure is a secondary parameter. The main guideline when setting is the superheated temperature of the steam at the outlet of the evaporator and the temperature difference (delta T) at the inlet and outlet.
Adjust the pressure switches and thermostats according to the requirements of the technological process. If the system is equipped with a thermostatic expansion valve (TEV), the static superheat may need to be adjusted. This is done by rotating the adjusting screw on the body of the expansion valve, but only after the temperature conditions have stabilized.
What is steam superheat?
Steam superheat is the difference between the temperature of the refrigerant at the outlet of the evaporator and the boiling point at a given pressure. Normal overheating is 5-8 degrees Celsius. Too low a superheat threatens liquid getting into the compressor, too high - underutilization of the evaporator surface.
Typical mistakes and safety measures
One of the most common mistakes is filling “to pressure” without taking into account weight. The pressure in the system strongly depends on the ambient temperature, so relying only on the pressure gauge is a gross mistake. The need to replace the filter drier after opening the circuit is also often ignored, which leads to contamination of the system with moisture and acids.
Personnel safety comes first. Freons are heavier than air and displace oxygen, so in confined spaces (storage chambers) there may be a danger of suffocation. When working with large volumes of gas, it is necessary to ensure good ventilation of the room.
- 🔹 Do not use an open flame near a working refrigerator.
- 🔹 Protect your eyes and skin from contact with liquid freon (risk of frostbite).
- 🔹 Do not release freon into the atmosphere unless necessary (environmental aspect).
- 🔹 Check the tightness of the connections with a soap solution after refueling.
Remember that industrial cold does not tolerate negligence. Every detail, from the condition of the insulation to the cleanliness of the capacitor, affects the efficiency of operation. Regular maintenance extends the life of equipment and keeps products fresh.
Frequently asked questions (FAQ)
Is it possible to refill an industrial refrigerator with R404A if it used to have R22?
No, a direct replacement is not possible. R22 i R404A have different operating pressures and require different types of compressor oil (mineral versus synthetic). To switch to another type of freon, a complete rework of the system, replacement of the oil and, possibly, the compressor is necessary.
Why does the compressor get very hot after refueling?
This can be caused by several reasons: excess freon (liquid hydraulic shock), air getting into the system, a malfunction of the compressor itself, or problems with cooling the electric motor. It is necessary to check the currents and discharge pressure.
How often should the filter drier be changed?
The filter drier is changed every time the refrigeration circuit is opened, as well as when moisture is detected in the system or after combustion of the compressor windings. Scheduled replacement is recommended at every major maintenance.
Is it dangerous to inhale freon vapors?
Yes, inhaling freon vapors in high concentrations is dangerous to health, since the gas displaces oxygen and can cause suffocation, as well as have a toxic effect on the central nervous system and heart.