Medium temperature refrigeration equipment is the basis of the commercial turnover of food products, ensuring the safety of goods in a range that prevents them freezing, but inhibits the development of bacteria. Understanding exactly what temperature should be maintained inside the chamber is critical for both store owners and food service technologists. Errors in setting thermostats can lead to damage to thousands of units of goods or, conversely, to their substandard appearance.
Unlike low-temperature chest freezers, where the temperature is below minus 18 degrees, medium temperature cabinets they operate in a gentle mode. It is this range that allows you to store dairy products, chilled meat, drinks and finished culinary products within the established shelf life. The air temperature in the working volume is not just a number on the display, but a complex parameter that depends on the load, compressor operation and room conditions.
In this article we will examine in detail the physical principles of operation of such equipment, standard values of temperature conditions and methods for their precise adjustment. You will learn why thermometer readings may differ in different areas of the chamber and how to avoid common mistakes when operating refrigerated display cases cabinets.
Standard temperature ranges and the physics of the process
The main operating range for medium-temperature equipment is considered to be the interval from minus 5 to plus 10 degrees Celsius. However, for most products, the optimal and safest value is a narrow corridor from +2 to +6 degrees. It is with these parameters that the biochemical processes in products are slowed down as efficiently as possible without compromising their structural integrity.
The physics of the cooling process is based on the circulation of the refrigerant, which takes heat from the internal volume of the chamber and releases it to the environment through the condenser. In medium-temperature systems, as a rule, freon R134a or more modern environmentally friendly analogues are used. A thermostatic valve or electronic controller monitors the temperature of the evaporator and controls the flow of refrigerant to avoid freezing of the heat exchanger.
⚠️ Attention: The temperature at the surface of the evaporator is always lower than the air temperature in the chamber. If frost appears on the products, it means that they are located too close to the source of cold or the temperature is below the permissible minimum for this type of product.It is important to take into account the inertia of the system. After loading a large batch of warm products, the compressor will work in increased mode until it equalizes the temperature throughout the entire volume. At this moment, the sensor can show one value, and in the depths of the chamber - another. Regime stabilization is a process that requires time and proper air exchange.
📊 What type of equipment do you use most often?Sliding wardrobeOpen display caseRefrigeration tablesPrefabricated chamberThe influence of temperature on various groups of products
Different categories of goods require an individual approach to storage. There is no universal temperature for all products, so stores often use zoning or separate refrigerators. For example, meat deli and prepared salads require stricter control than canned drinks in containers.
Dairy products are extremely sensitive to fluctuations. When the temperature rises above +6 degrees in fermented milk products, the proliferation of lactic acid bacteria sharply accelerates, which leads to souring and swelling of the packaging. Conversely, chilled semi-finished meat products at temperatures close to zero can retain their presentation longer, but run the risk of losing moisture if the air humidity is incorrect.
- 🥛 Dairy products: optimal range +2...+4°C, it is critical to avoid freezing.
- 🥩 Chilled meat and fish: range 0...+4°C, high humidity required.
- 🥤 Drinks and canned food: allow range +4...+8°C, less demanding on stability.
- 🍰 Confectionery: +2...+6°C, it is important that there are no drafts so that the glaze does not dry out.
Particular attention should be paid to packaging. Vacuum packaging better preserves the product during temperature fluctuations, while open trays of meat or salads in gastronomic containers require strict compliance temperature control. Violation of storage rules not only shortens the sales period, but also creates risks for the health of consumers.
Fine-tuning the thermostat and controller
Temperature adjustment in modern refrigeration equipment is carried out through electronic controllers, such as Carel, Dixell or Eliwell. The interface can be push-button or touch-sensitive, but their operating logic is similar. Accessing parameters often requires pressing a key combination or holding down a setup button for a few seconds.
The main parameter you need to change is Set Point (setpoint). This is the target temperature value that the system will strive for. However, simply setting the desired number is not enough. It is also necessary to adjust the differential (hysteresis), which determines how many degrees the temperature can deviate before turning on the compressor.
Example of setting up a Dixell controller:1. Press and hold Set (3 sec).
2. 'St' (Set Point) will appear on the screen.
3. Use the up/down buttons to change the value.
4. Press Set to confirm.A common mistake is setting the differential too low. If the difference between turning the compressor on and off is less than 1 degree, the equipment will operate in a constant start and stop mode. This leads to rapid wear of the starting equipment and temperature instability in the chamber.
☑️ Checking the controller settings
Completed: 0 / 1Factors influencing temperature stability
Even a perfectly tuned refrigerator may not work correctly if external factors are not taken into account. The first and main enemy of stability is the room temperature. If it is hot in the sales area (above +25°C), the condenser does not have time to release heat, and the operating efficiency of the refrigeration unit falls. The second critical factor is correct loading. Products should not block ventilation openings or gaps between shelves. Air should circulate freely throughout the entire volume of the chamber, washing each product. “Dead zones” where there is no air movement become breeding grounds for bacteria. refrigeration unit falls.
The second critical factor is proper loading. Products should not block ventilation openings or gaps between shelves. Air should circulate freely throughout the entire volume of the chamber, washing each product. “Dead zones,” where there is no air movement, become breeding grounds for bacteria.
Influence factor Impact on temperature Recommended action Loading with warm goods Sharp temperature jump upwards Cool the goods before loading or reduce the set point temporarily Opening the doors Intake of warm moist air Minimize the opening time, check the seals Condenser contamination Reduced cooling capacity Regular cleaning of the heat exchanger from dust Fan malfunction Uneven cold distribution Replacing the fan or repairing the power circuit It is also worth mentioning the influence of direct sunlight. If the display or cabinet is exposed to the sun, the temperature sensor may read incorrectly, or one side of the chamber will become hot while the other is too cold. Installation of the equipment should be done away from heat sources and windows.
⚠️ Attention: If the refrigerator is installed in a niche or close to the wall, make sure that the gap for ventilation of the condenser is at least 10-15 cm. The lack of air flow to the rear wall is guaranteed to lead to overheating of the compressor.Diagnosis of problems: when the temperature does not hold
The situation when the actual temperature in the chamber differs significantly from the one set on the controller requires immediate diagnosis. The first step should always be to check that the temperature sensor itself is working properly. Often the sensor can “lie”, showing the norm, while the products are already beginning to deteriorate.
Among the common causes of instability is a refrigerant leak. In this case, the compressor works almost non-stop, but there is not enough cold. A characteristic sign is a warm condenser (heat exchanger on the rear wall) and the absence of the characteristic noise of freon murmuring in the system.
- ❄️ Evaporator freezing: heat removal is impaired, defrosting or checking the heating element is necessary.
- 🔌 Electrical problems: burning of relay contacts or malfunction starting capacitor.
- 🚪 Loose fit of doors: wear of magnetic seals (rubber bands).
- 💨 Fan malfunction: cold does not spread throughout the chamber, remaining at evaporator.
If you notice that the compressor turns on too often or, conversely, very rarely, but the temperature inside rises, this is a signal of a violation of heat exchange or loss of tightness of the circuit. In such cases, self-repair is only possible at the level of cleaning and replacing seals; complex work requires calling a specialist with a tool for working with freon.
Why does the relay click?
Clicks when starting the compressor are normal operation of the start relay. However, if the clicks are frequent, the compressor hums for a couple of seconds and turns off - this is a sign of a faulty starter or a jammed compressor. Relay replacement or motor diagnostics is required.
Prevention and care of refrigeration equipment
To maintain a stable temperature in a medium-temperature refrigerator, it is not enough to simply set the settings. Regular maintenance is the key to long equipment life. At least once a quarter, it is necessary to carry out complete defrosting (if the system is not NoFrost) and thoroughly washing the internal surfaces.
Particular attention should be paid to the drainage system. Water draining from the evaporator must flow freely into the evaporation tank. If the drainage hole is clogged with crumbs or ice, the water freezes, forming an ice plug that blocks the operation of the evaporator and disrupts the temperature regime. Cleaning the condenser is a mandatory procedure, especially in dusty rooms or stores with a large flow of people (shopping centers). Dust, mixing with fatty fumes (if cooking is nearby), forms a dense crust, which acts as a heat insulator, preventing the freon from cooling. temperature regime.
Cleaning the condenser is a mandatory procedure, especially in dusty rooms or stores with a large flow of people (shopping centers). Dust, mixing with fatty fumes (if there is cooking nearby), forms a dense crust that acts as a heat insulator, preventing the freon from cooling.
Do not forget to check the condition of the magnetic door seals. Over time, they lose elasticity, crack or become deformed. A simple test with a piece of paper (hold the sheet in a door and try to pull it out) will help determine whether the rubber band needs to be replaced. If the sheet is removed too easily, the cold goes away.
Is it possible to store food at a temperature of +8...+10 degrees?
Short-term storage is possible, but this is the upper limit for medium-temperature equipment. For most perishable products (meat, milk, fish), this temperature is already considered a dangerous zone where bacteria multiply at high speed. Long-term storage at +10°C is unacceptable.
Why are there different temperatures in different corners of the chamber?
This is a natural process associated with the physics of the movement of air masses. Cold air is heavier and sinks, and it is also more intense at the source of the cold (the evaporator). A difference of 2-3 degrees between the zone near the fan and the far lower corner is considered normal for static cooling.
How often should you defrost a medium-temperature refrigerator?
The frequency depends on the humidity in the room and the frequency of opening the doors. On average, complete defrosting is recommended every 3-6 months. If you notice a layer of ice on the evaporator thicker than 3-5 mm, defrosting must be done immediately, regardless of the schedule.