Correctly setting the temperature in a refrigerated display case is not just a matter of comfort, but a critical condition for maintaining the quality of products and complying with sanitary standards. Errors in thermostat calibration can lead to damage to an expensive product, the growth of bacteria, or, conversely, to excessive energy consumption due to excessive cooling. The owner of commercial equipment must clearly understand the difference between the temperature of the evaporator and the temperature inside the chamber, since these indicators are often confused.
Modern display cases are equipped with electronic controllers that allow you to set precise parameters in steps of 0.1 degrees, but the principle of their operation remains the same for most models. Thermostat reads data from the sensor and compares them with with a given value, turns the compressor on or off.
In this article we will analyze the algorithm for setting up popular controllers, look at a table of optimal modes for different products and discuss the nuances that will help extend the life of the equipment. Correct operation starts with a competent initial setup, which is often ignored by store personnel. Let's take a closer look at how to ensure the ideal climate in your display case.
The principle of operation of the refrigeration system and sensors
To effectively control the temperature, you need to understand the basic logic of the refrigeration unit. The compressor operates cyclically: it turns on when the sensor detects an increase in temperature above the set threshold, and turns off when the lower limit is reached. This range is called differential or hysteresis. If the differential is too large, the products will be subject to temperature fluctuations, which will negatively affect their safety.
The temperature sensor is usually located in the return air zone or on the evaporator, depending on the design of the display case. In models with static cooling air circulates more slowly, so the temperature difference in different corners of the display case can be significant. A dynamic fan system provides a more even distribution of cold, but requires proper adjustment of the rotation speed and defrost cycles.
⚠️ Caution: Never place test thermometers directly at the cold air outlet. You will receive falsely low readings that do not reflect the real situation in the chamber.
The key parameter is the freezing point of the product. For most vegetables and fruits it is just below freezing, so setting the temperature below -1°C may damage the cellular structure of the product. Electronic control units, such as Carel or Dixell, allow you to flexibly configure these parameters, but require careful handling.
Instructions for setting up electronic controllers
The process of setting the temperature depends on the model of the installed controller, but the general logic of actions is similar for most devices. First you need to unlock the keyboard if it is locked from accidental pressing. This usually involves holding down a specific key combination for a few seconds. After unlocking, you get access to the options menu.
Let's look at the algorithm using common models as an example. You need to find the parameter responsible for the temperature setpoint (often indicated as Set Point or St). Press the up and down arrow buttons to change the value to the desired value. Do not forget to save the changes, otherwise after exiting the menu the settings will be reset to the previous values.
☑️ Controller setup algorithm
It is also important to check the differential parameter (differential or dif). It determines how many degrees the temperature must rise above the set point for the compressor to turn on again. The standard value is 2-4 degrees. A differential that is too small will cause the compressor to turn on too often, which will shorten its life, and too large will lead to temperature fluctuations.
⚠️ Attention: If the display case is used to store different groups of products, focus on the requirements of the most sensitive group (usually dairy products or fresh meat).
Optimal temperature conditions for different products
There is no universal temperature for all products. Dairy products, meat gastronomy, vegetables and confectionery products require completely different storage conditions. A violation of the temperature regime by even a few degrees can reduce the shelf life of a product by half or change its taste.
Below is a table of recommended temperature conditions for the main categories of products sold through refrigerated display cases. These data are based on sanitary standards and recommendations of equipment manufacturers.
| Product group | Recommended temperature (°C) | Critical minimum (°C) | Storage features |
|---|---|---|---|
| Dairy products | +2.. +4 | 0 | Afraid of freezing, require stability |
| Fresh meat and poultry | 0.. +2 | -1 | High risk of bacterial growth when heated |
| Vegetables and fruits | +4.. +8 | +2 | Require high humidity, fear cold |
| Confectionery | +2.. +6 | +1 | Appearance is important, condensation is possible |
| Frozen semi-finished products | -18.. -22 | -15 | Only for freezer display cases (bonnet) |
Please note that the temperature in the center of the piece meat and the air temperature in the display case are different quantities. The air must be cooler to cool the product. Therefore, if you need to provide +2°C inside the product, the air in the showcase should have a temperature of about 0°C or +1°C.
Adjusting defrost cycles and their effect on temperature
During operation, frost inevitably builds up on the showcase evaporator, which interferes with heat transfer. To remove ice, the system automatically enters defrost mode, temporarily stopping cooling. Setting the defrost frequency and duration directly affects the average temperature in the chamber.
If defrost cycles are set too often or last too long, the temperature in the display case may rise above acceptable values, especially in the summer or when fully loaded with products. Defrost parameters are usually designated as dp (duration) and idf (interval). The standard interval is 6 hours, but in a hot room it can be reduced to 4 hours.
There are several types of defrosting: electric (heating elements), hot gas or natural. Electric defrost is most common in small display cases. It is important to make sure that after defrosting is completed, a pause is included before starting the compressor, so that drops of water do not fall on the food and freeze again.
Incorrect defrost setting is one of the most common causes of complaints about “floating” temperature conditions. If you notice that the temperature rises sharply at a certain time of the day, check the defrost timer settings in the controller menu.
Factors affecting temperature stability
Even an ideally configured display refrigerator may not maintain the temperature if external factors are not taken into account. The first and most important of them is the thermal curtain. In open display cases (slides), the main barrier between the cold air inside and the warm air outside is the air flow created by the fans. If this flow is disrupted, the cold “leaks” out.
The second factor is the loading of products. You cannot place goods above the maximum load line (usually marked with a red line or sticker). If products block the ducts, circulation is disrupted, causing some areas of the display to be warm and others to be excessively cold. Air ducts must remain free to operate effectively.
The third factor is ambient temperature. Most display cabinets are designed to operate indoors at air temperatures up to +25°C. If it is hotter in the sales area, for example +28°C or +30°C, the equipment will work overload and may not cope with cooling, regardless of the thermostat settings.
⚠️ Attention: Installing the display case in direct sunlight or near heating devices is strictly prohibited. This will lead to constant overheating and failure of the compressor.
Diagnostics of problems: when the settings do not help
There are situations when you set the temperature correctly, but the actual indicators do not correspond to the set ones. If the display case “does not freeze” or, on the contrary, “freezes” with the correct settings, the problem may lie not in the electronics, but in the technical condition of the unit. Let's look at the main symptoms and their causes.
If the compressor runs constantly, but the temperature does not drop, this may indicate a refrigerant leak, a malfunction of the evaporator fan, or contamination of the condenser (radiator). A dirty capacitor is the most common cause of poor performance, especially in the summer. It must be cleaned from dust and fluff regularly.
If the temperature fluctuates too much, check the tightness of the doors (if any) and the integrity of the seals. In open display cases, the cause may be a malfunction of the air curtain system. It is also worth checking the calibration of the temperature sensor itself - over time it may produce an error.
Independent refilling of freon or repair of the compressor without special equipment and skills is prohibited. However, basic diagnostics, such as checking fan rotation and cleaning heat exchangers, should be carried out regularly by store personnel.
Frequently asked questions (FAQ)
How often should you check the temperature in the display case?
According to sanitary standards, a temperature log should be kept at least twice a day (in the morning and in the evening). However, ideally, control should be automatic, using a monitoring system that sends notifications in case of deviations.
Is it possible to load warm products into the display case?
It is strictly not recommended. Loading warm products creates an extreme load on the compressor, leads to abundant condensation and a temporary increase in temperature in the entire chamber, which can spoil the goods already lying there.
What to do if condensation appears on the products?
Condensation indicates high humidity or a sharp temperature change. Check to see if food is blocking air flow. Also make sure that the room is not too humid and the display case is not in a draft from the air conditioner.
Why is the display case noisy during operation?
A slight hum of the compressor and the noise of the fans is the norm. If there is a whistling, knocking or vibration, check whether the display case is level (adjust the legs) and whether there are any foreign objects near the fan.