Assembling industrial refrigeration equipment is a complex technical process that requires deep knowledge in the field of thermodynamics, electrical engineering and operation with refrigerants. Unlike household analogues, industrial units are created to work in intensive mode 24/7, withstanding significant temperature changes and frequent door openings. Errors at the installation stage can lead not only to the breakdown of expensive equipment, but also to damage to large batches of products.
Before proceeding with the physical connection of components, it is necessary to carefully calculate the thermal load and select the appropriate power. Industrial refrigeration unit often assembled from separate units: compressor-condenser block, evaporator, control panel and line. It is important to understand that each element must be ideally selected for the specific tasks of a warehouse or sales area.
In this article we will analyze the key stages of creating a reliable refrigeration system, paying special attention to the safety and tightness of the circuit. You will learn about the nuances of evacuation, refilling with freon and setting up automation, which is critical for long-term operation.
Design and selection of system components
The beginning of any work on creating a refrigeration chamber or cabinet lies in the plane of accurate calculations. Heat inflows through enclosing structures should be minimized, so the choice thermal insulation panels (sandwich panels) is the first step. The thickness of the insulation directly depends on the target temperature inside the chamber: for medium-temperature conditions, 100 mm is usually sufficient, while for low-temperature freezing, 150 mm or more is required.
The central element of the system is the compressor, which is often called the “heart” of the refrigerator. For industrial scales, semi-hermetic piston or screw compressors are most often used, capable of operating with more powerful refrigerants. When choosing a model, it is necessary to take into account the refrigeration capacity at specific boiling and condensation temperatures, and not just the nameplate capacity.
The correct selection of condenser and evaporatoris equally important. Their heat exchange surfaces must be sufficient for effective heat removal to the environment and rapid cooling of the chamber volume, respectively. A mismatch in heat exchange areas can lead to overheating of the compressor or failure to reach the set temperature.
Assembling the frame and installing thermal insulation
The tightness of the circuit is the foundation for the efficient operation of the refrigerator. Assembly begins with the installation of corner profiles and starting panels on a prepared, flat floor. Sandwich panels they are connected to each other using a special locking connection, which ensures the absence of cold bridges. Each joint must be foamed with polyurethane foam with a low coefficient of expansion and low moisture absorption.
Particular attention should be paid to corner joints and places where communications pass. Any gap, even microscopic, in conditions of negative temperatures will become a source of condensation and subsequent freezing, which will lead to depressurization and increased energy consumption. Aluminum profiles are often used to strengthen the structure in the corners.
☑️ Checking the quality of the body assembly
⚠️ Attention: When installing panels, avoid damaging the internal protective layer. Damaged metal in conditions of high humidity will quickly corrode, which will reduce the service life of the entire structure.
Installation of a compressor-condensing unit
Installation of the power unit requires compliance with strict vibration isolation rules. During operation, the compressor creates significant vibrations that are transmitted to the housing and pipelines. Therefore, installation is carried out on special vibration supports or rubber shock absorbers. The distance to walls and other obstacles should ensure free circulation of air to cool the condenser.
Attachment of the unit itself to the base should be rigid, but through damping pads. It is important to ensure horizontal installation, since misalignment can disrupt the circulation of oil in the compressor crankcase, which will lead to jamming. For screw compressors, the requirements for the levelness of the base are even higher than for piston compressors.
The electrical connection is made through a separate circuit breaker with thermal protection corresponding to the full load current of the engine. The connection diagram must strictly comply with the electrical diagram provided by the equipment manufacturer, with mandatory grounding of all metal parts.
Why is the oil level in the compressor important?
Insufficient oil level leads to dry friction and rapid wear of friction pairs, and excess leads to oil carryover into the circuit, which reduces the efficiency of heat transfer and can cause water hammer.
Installation of pipelines and starting fittings
The connection of all components of the refrigeration circuit is carried out with copper pipes, which undergo careful preparation. Before soldering, the ends of the pipes must be cleaned, degreased and flared with a special tool. The use of hard solder containing silver provides the necessary strength and tightness of the seam that can withstand high pressure.
During the soldering process, it is critical to flush the pipes with nitrogen. This prevents the formation of an oxide film (scale) on the inner surface of the copper. If scale gets into the system, it can clog the capillary tubes of the expansion valve or damage the compressor valves. Nitrogen is supplied under slight pressure during the entire heating and cooling process.
The necessary shut-off and control valves must be installed on the lines: solenoid valves, filter driers, sight glasses and thermostatic expansion valves (TRV). The expansion valve is installed as close as possible to the evaporator, and its sensitive element fits tightly to the outlet pipe of the evaporator and is insulated.
| Component | Function | Installation location |
|---|---|---|
| Filter drier | Removal of moisture and acids | On the liquid line before the expansion valve |
| Sight glass | Freon condition monitoring | After filter-drier |
| Solenoid valve | Automatic flow shut-off | Before the expansion valve or at the inlet to the evaporator |
| Pressure regulator | Pressure maintenance condensation | At the outlet of the condenser |
⚠️ Attention: The soldering temperature must be strictly controlled. Overheating of copper makes it brittle, and underheating leads to a poor-quality connection that can burst under pressure.
Evacuation and charging with refrigerant
After assembling the circuit and testing it for strength with compressed nitrogen (pressure testing), the evacuation stage follows. This is one of the most important processes, as it removes air and, most importantly, moisture from the system. Moisture in the system freezes in the throttling devices, forming ice plugs, and reacts with the oil, forming aggressive acids.
For industrial systems, two-stage high-performance vacuum pumps are used. The vacuum process must continue until a deep vacuum is achieved (residual pressure less than 500 microns). After closing the vacuum gauge, you must wait a period of time (pressure drop test) to ensure that there are no hidden leaks or evaporation of moisture from the system materials.
Refrigerant is charged in the liquid phase through the liquid line while the system is under vacuum, or in the gas phase through the suction line after the compressor starts (for some types of freons). The amount of refrigerant must strictly correspond to the calculated amount, weighed on an electronic scale. A lack of freon leads to overheating, and an excess leads to liquid hydraulic shock.
Setting up automation and commissioning
The final stage is setting up controller and protective automation. Industrial refrigerators use sophisticated electronic control units that regulate the compressor, condenser and evaporator fans, and defrost cycles. It is necessary to set the temperature delta, defrost time and frequency, protection against high and low pressure.
The first start is carried out under constant monitoring of the electric motor currents, suction and discharge pressure, as well as the superheated steam temperature at the outlet of the evaporator. Overheating is key parameter for proper operation of the expansion valve; it must be within the limits recommended by the manufacturer (usually 5-8 degrees Celsius).
During operation, it is necessary to regularly check the condition of the oil, the cleanliness of the condenser and the tension of the belts (if they are in the fan drive). Timely maintenance extends the life of the equipment and maintains energy efficiency at a high level.
How often do you need to change the oil in an industrial compressor?
The first oil change is made after break-in (usually after 500 operating hours), subsequent ones - according to the manufacturer's regulations, but at least once a year or when the color and acidity of the oil changes.
What to do if the compressor hums, but does not start?
It is necessary to check the voltage in the network, the condition of the starting capacitors (for single-phase), operation of the pressure switch and the presence of mechanical jamming. Often the reason lies in the activation of thermal protection due to overheating.
Is it possible to use different types of oil in the system?
Absolutely not. Mixing oils of different chemical bases (mineral, polyester POE, polyalphaolefin PAO) can lead to sedimentation, blockage of the system and destruction of the insulation of the motor windings.