Correct setting of the temperature regime is the foundation for high-quality preservation of products at the point of sale. Errors in calibration can lead to damage to the product, the growth of bacteria, or, conversely, to the freezing of vegetables and fruits, which makes them unsuitable for sale. Unlike household models, commercial equipment requires a more careful attention to the operating parameters of the compressor and evaporator.
Before you start changing the settings, you need to clearly understand what type of control is used in your display case. There are several main types of regulation: mechanical thermostats, electronic controllers with a digital display and complex microprocessor systems. The algorithm of your actions and the available functionality depend on this. In this article we will analyze all the nuances so that you can optimize operation equipment.
It is important to note that there is no universal “set 4 degrees” button, since each manufacturer has its own operating logic. However, the general principles of thermodynamics and refrigeration cycle control remain unchanged. Below we will look in detail at the setup process for various types of equipment.
Determining the type of control system
The first step is always a visual inspection of the control panel. If you see a rotary knob with numbers from 1 to 7 or a scale from Min to Max, you have a classic mechanical thermostat. Such devices are often found in budget models or old-style display cases. There is no exact display of degrees, only conditional divisions of cooling power.
In more modern equipment, electronic controllersare installed, which can be built into the case or placed on a separate panel. They display the current temperature inside the chamber and allow you to set precise values in 0.1 degree increments. Popular brands of such systems are Dixell, Danfoss, Carel. It is with them that store staff most often have questions due to the presence of hidden menus.
The third option is display cases with central control system (for example, in supermarkets), where all parameters are set remotely by an engineer. In such cases, a local attempt to change settings may be blocked or reset by the central server. If the lock icon is on the display or the communication indicator is blinking, self-adjustment may not be possible.
- 🔍 Visually inspect the panel: is there a digital display or only a rotary knob.
- 🏷️ Find the label with the controller model (usually written in small font under the display glass).
- 🔌 Check whether the display case is connected to the store's central monitoring system.
⚠️ Attention: If the display case is under warranty service, breaking the seals on the controller or changing the factory parameters may result in refusal of free repairs. Make sure you have rights to change settings.
Setting a mechanical thermostat
Adjusting a mechanical thermostat is an empirical process, since the numbers on the scale do not correspond to degrees Celsius. Usually the range from 1 to 5 or from Min to Max indicates the degree of valve opening or the duration of operation of the compressor. To to lower the temperature in the chamber, the knob needs to be turned towards higher values.
The main difficulty here is the inertia of the system. After turning the knob, the compressor will not change operating mode instantly. It takes time for it to enter a new cycle, and for the air in the display case to mix and cool. Therefore, experts recommend making changes smoothly, turning the knob no more than one notch at a time.
The ideal tool for such adjustments would be remote thermometerplaced in the center of the working area of the display case (not at the back wall and not at the door). Record it and observe the readings for 4-6 hours. Only after the readings have stabilized can conclusions be drawn about the need for further adjustments.
It's worth remembering that mechanical thermostats wear out over time. The spring inside may weaken, and the contacts may oxidize, which will lead to a “floating” temperature. If you notice that the display case has stopped holding the mode even at the maximum position of the handle, you may need replacement of the sensor or the entire thermostat.
Working with electronic controllers (Dixell, Danfoss)
Electronics provides much more opportunities, but requires knowledge codes and sequence of actions. Most controllers have two main modes: displaying the current temperature and programming mode. Entering the settings menu usually requires pressing and holding the "Set" (or "Enter") button for 3-5 seconds.
Within the menu, you will find various options indicated by alphanumeric codes. For example, for controllers Dixell parameter rS is often responsible for setting the set point temperature (Set Point), and HY for hysteresis (the difference between the on and off temperatures). The Danfoss logic may differ, but the principle is the same: search for the parameter responsible for the setpoint.
It is important not to confuse the compressor start temperature and the defrosting temperature. Changing the parameters in the Defrost section without understanding the process can lead to the display case stopping defrosting and the evaporator becoming overgrown with a “fur coat”, after which it will stop cooling altogether.
☑️ Algorithm for setting up the electronic controller
When setting hysteresis be careful. A range that is too narrow (eg 0.5 degrees) will cause the compressor to cycle on and off too frequently, shortening its life. Too wide a range (5-6 degrees) will lead to fluctuations in the temperature of the product, which is dangerous for perishable goods.
Calibration of sensors and correction of readings
Often a situation arises when the display shows +5°C, and an independent thermometer shows +8°C. This does not always mean failure. Electronic controllers provide a function offset calibration (Offset). It allows you to correct the sensor readings without physically changing it.
To perform calibration, you need to find a parameter in the menu, often designated as oF, SC or Cal. The default value of this parameter is 0.0. If your display thermometer is off by 2 degrees, you should enter a value of -2.0. After this, the controller will consider the real temperature to be 2 degrees lower than what the sensor shows and will adjust the operation of the compressor.
However, if the temperature difference exceeds 3-4 degrees, software correction may not be sufficient. In this case, there is a high probability of malfunction of the thermistor (temperature sensor) itself. Over time, their resistance drifts, and they cease to give an accurate picture.
Lower limit of the Set Point setting
| Parameter | Designation (Dixell) | Designation (Danfoss) | Function |
|---|---|---|---|
| Set temperature | rS |
St |
Temperature to be maintained |
| Hysteresis | HY |
di |
Delta between incl. and off compressor |
| Sensor correction | oF |
o1 |
Reading offset (calibration) |
| Min. temperature | LS |
Ld |
Why can a sensor lie?
Temperature sensors (NTC thermistors) change their resistance depending on the heat. Over time, due to vibrations, condensation and voltage surges, their characteristic curve may shift. The installation location also affects the readings: if the sensor touches the metal of the back wall, it will show the temperature of the evaporator, and not the air in the display case.
Setting specifics for different products
There is no universal temperature for all products. The operating mode of the display case must strictly correspond to the type of product being loaded. Violation of the temperature regime is a direct threat to the safety of consumers and financial losses of the store.
For dairy products, meat and ready-made food, the range from +2°C to +6°C is critical. Under these conditions, the reproduction of pathogenic microflora slows down. Setting the temperature above +8°C for such groups of goods is strictly prohibited by sanitary standards.
Vegetables and fruits require higher humidity and temperature, usually from +8°C to +14°C. If you cool them too much, processes of destruction of the cellular structure will begin, and the product will lose its presentation and taste. On the contrary, freezing is unacceptable for them.
- 🥩 Meat and fish: 0...+4°C (the lowest temperature without freezing).
- 🥛 Dairy products: +2...+6°C.
- 🥦 Vegetables and herbs: +8...+12°C (depending on crops).
- 🍫 Confectionery: +10...+15°C (so as not to flow and harden).
⚠️ Attention: Loading warm products into the display case temporarily increases the average temperature. At this moment, you should not urgently lower the setpoint to the minimum - this can lead to freezing of the evaporator and breakdown of the compressor. It is better to load the goods pre-cooled.
Typical problems after setup and their solutions
After interfering with the equipment settings, unforeseen situations may arise. One of the most common is insufficient cooling at the correct temperature. This may indicate a lack of refrigerant, condenser contamination or a fan malfunction, and not an error in the settings.
Another problem is frequent switching on and off (clocking). This is often a consequence of too small a hysteresis value. If the compressor turns on every 2-3 minutes, urgently increase the on/off temperature difference, otherwise the relay or starting device will burn out very quickly.
Also, users often encounter a situation where the display case “does not see” the change. This happens if the settings were not saved. In most controllers, you need to press the “Set” button again after changing the number, or simply do not press anything for 10-15 seconds to automatically exit and save.
Don't forget about the seasonal factor. In the summer, when store temperatures are high, it may be necessary to adjust settings or clean the condenser more frequently to ensure the display can reach the desired temperature. In winter, on the contrary, the equipment may work more efficiently, and the settings may require revision.
Why does the display case not maintain the temperature even after adjustment?
If the settings are correct, but the temperature “floats”, check: the tightness of the door seals, the cleanliness of the condenser grille (at the back or bottom), the operation of the blowing fans and the amount of loaded goods (the display case should not be clogged “to capacity”, a circulation gap is needed).
Is it possible to use a household thermometer for calibration?
Yes, you can, but with an error. Household alcohol or electronic kitchen thermometers have an error of up to 1-2 degrees. For accurate calibration of commercial equipment, it is better to use a certified laboratory thermometer or compare the readings with a reference device.
What to do if the password on the controller is lost?
Many controllers (for example, Dixell) have a default master password or the ability to reset via a combination of buttons when turning on the power. However, if the password was changed by the previous owner and is unknown, you will need to call a specialist with a programmer or replace the controller.
How often should you check the temperature in the display case?
According to trade rules and sanitary standards, temperature control should be carried out at least twice a day and recorded in a log. During hot periods or when the store is fully loaded, checks should be carried out more often.