Refrigerated display cases are an integral part of retail equipment, ensuring the safety of perishable products under strictly specified parameters. Correct temperature adjustment is critical not only for compliance with sanitary standards, but also for extending the life of the compressor. Many store owners are faced with the need to switch equipment to deep cooling mode or, conversely, adjust indicators when changing assortment.
The adjustment process may seem complicated due to the variety of controllers used, such as Carel, Evco or Dixell. However, understanding the basic principles of operation of the refrigeration circuit and control algorithms allows you to quickly master this procedure. In this article, we will analyze specific steps for setting negative temperatures, consider common mistakes and answer frequently asked questions.
Before you start changing the settings, you need to make sure that your showcase model is technically capable of supporting the mode freezing. Not all low temperature cabinets can go below -5°C as this depends on the compressor power and the type of refrigerant. Ignoring this fact may lead to equipment breakdown.
⚠️ Attention: Before starting any work with the electrical part or controller parameters, make sure that the display case is connected to a grounded network. Voltage surges during setup can throw off the factory calibrations of the electronics.
Preparing equipment for setting modes
The first step should always be a thorough check of the current state of the unit. If the display case has just been defrosted or transported, it needs time to stabilize before making changes to the software. Typically this period is from 2 to 4 hours of normal operation.
Make sure that the doors are tightly closed and the seals are not damaged. The presence of cracks will make it impossible to achieve low temperatures, since the compressor will work for wear, unable to compensate for the influx of warm air. Also check the cleanliness of the condenser: dust on the radiator grille significantly reduces the efficiency of heat transfer.
It is important to understand the difference between static cooling and the system No Frost. In static display cases, cold air falls down naturally, so the sensor settings must take into account the temperature gradient. In systems with forced circulation, the air is mixed by fans, which allows you to achieve more accurate readings throughout the entire volume of the chamber.
Main types of controllers and their features
Modern display cases are equipped with electronic thermostats that control the cycles of turning the compressor on and off. The most common brands are Dixell, Carel and Evco. Each of them has its own interface, but their operating logic is similar: there is a user level of settings and a service level.
The user level allows you to change only the temperature setpoint, that is, the target value to which the air should be cooled. The service level, access to which is often protected by a password or a combination of buttons, allows you to configure hysteresis, start delays, sensor types and defrost modes. To set the minus mode, we first need the first level.
Below is a table showing popular controller models and their standard operating temperature ranges:
| Controller model | Control type | Setting range (°C) | Features |
|---|---|---|---|
| Dixell XR20C | Static/Ventilated | -50...+10 | Popular in medium-temperature display cases |
| Carel IR33 | Ventilated | -40...+10 | High precision, complex menu |
| Evco EVK412 | Universal | -55...+10 | Support for multiple sensors |
| Thermal control TD-15 | Simple | -40...+10 | Russian production, simplicity |
Please note that some models have marked "C" or "V" in the name, which indicates the type of refrigerated space. For the freezing mode, it is critical that the controller supports operation with low temperatures and has an appropriate defrost algorithm.
Step-by-step instructions: setting sub-zero temperature
The setup process may vary slightly depending on the model, but the general algorithm of actions remains the same for most devices. First you need to unlock the keyboard if it is locked from accidental keystrokes. Usually, to do this, you need to hold down the button with the key image or a combination of arrows for 5-7 seconds.
After unlocking, the value of the current setting will begin to flash on the display. Use the Up and Down arrow buttons to change the value. If you need to set the temperature to -18°C, reduce the value gradually. Some controllers require confirmation of the action: after selecting a number, you need to press the "Set" or "Enter" button.
Here is the sequence of actions for a typical display case with a controller Dixell:
- 🔑 Press and hold the "Set" button for 3 seconds until the setting indicator lights up.
- ❄️ The display will show flashing value of the current temperature.
- 🔽 Use the arrows to reduce the value to the required minus (for example, -18).
- ✅ Press "Set" again to save, or wait 10 seconds for automatic exit.
After changing the setpoint, the compressor will not turn on immediately. There is a start delay parameter that protects the engine from frequent restarts. This time can range from 3 to 10 minutes. During this period, the standby indicator may light on the display.
⚠️ Attention: Do not try to force cooling by setting the temperature to -30°C if the display case is designed for medium temperatures. This will lead to freezing of the evaporator and failure of the compressor due to liquid refrigerant.
☑️ Check after setup
Setting defrost parameters for low temperatures
When operating in deep freezing mode, frost inevitably forms on the evaporator. If it is not removed, it will block the air flow and the display will stop cooling, although the compressor will run constantly. For this purpose, the controllers provide an automatic defrosting function.
There are two main types of defrosting: electric (heating elements) and hot gas. Electric is most often used in display cases. You need to check the intervals between defrosts. The standard value is every 6 or 8 hours. The duration of one defrost is usually 15-20 minutes.
If you set the display case to minus, but did not check the defrosting parameters, the following problems are possible:
- 🧊 Insufficient duration: The heating element does not have time to melt all the ice, and with each cycle there is more of it.
- 🔥 Excessive duration: The products in the display case begin to thaw, as the temperature in the chamber rises sharply during the defrost cycle.
- ⏰ Invalid interval: Defrosting occurs too often, which leads to excessive energy consumption and thermal shock to the products.
Accessing these parameters often requires entering the service menu. For example, in controllers Carel you need to hold down two buttons at the same time. Inside the menu, look for options labeled "Idt" (interval) and "dt" (duration). Be careful: changing these values without understanding the process can disrupt the temperature regime.
What is defrosting by temperature?
This is a smart mode in which defrosting does not end according to a timer, but when the sensor on the evaporator shows that the ice has completely melted (usually +10°C). This is the most energy-efficient method.
Diagnostics of problems after setup
After you have set the desired temperature, you need to monitor the behavior of the equipment during the first day. If the display case does not go into mode or freezes too much, this indicates a malfunction or error in the settings.
A frequent problem is an incorrect temperature sensor reading. If the sensor “lies” and shows that it is already -10°C in the chamber, although in reality it is +5°C, the compressor simply will not turn on. Check the location of the sensor: it should not touch the walls of the chamber or the products, but should be in the air flow.
Also pay attention to the operation of the evaporator fan. On some models, the fan should stop when the door is opened. If this does not happen, or if it hums and does not turn, the cooling efficiency decreases. A clogged drain can also cause ice slush to form at the bottom of the display case, blocking circulation.
Error codes on the display may indicate the direction to search:
- ❄️ E1: Temperature sensor error (open or short circuit).
- 💨 E2: Problem with the sensor defrost.
- 🔌 E3: Communication error or low voltage.
If you see flashing symbols, refer to the instructions for the specific model. Ignoring error codes can lead to damage to an expensive product.
Rules for operating a display case in freezing mode
Operating equipment at subzero temperatures requires discipline from store personnel. Frequent opening of the doors leads to a sharp jump in humidity inside the chamber, which causes intensive formation of frost on the evaporator. This, in turn, causes the defrost system to operate more frequently, increasing the load on the network.
Products should be placed so as not to block the ventilation openings. Air should circulate freely throughout the entire volume. If you load a display case with warm goods, wait for the temperature inside to rise and do not panic - the automation will cope with the task, but it will take time.
Regularly check the condition of the seals. In deep freezing mode, rubber can harden and crack faster. Loss of tightness in this mode is more critical than in a conventional refrigerator, since the temperature difference with the environment is much higher.
⚠️ Attention: Controller interfaces and the exact names of parameters may vary depending on the firmware version and equipment manufacturer. Always check the technical documentation (data sheet) of your specific showcase model before changing service parameters.
Is it possible to set a household showcase to -18°C?
Technically, you can change the setting on any controller, but household showcases (medium temperature) are not designed to operate in this mode. Their thermal insulation is thinner, the compressor is weaker, and the refrigerant is selected for different boiling points. Long-term operation at maximum capacity will lead to rapid wear.
Why does the display case hum after being set to minus?
Increased noise may be due to more intense operation of the compressor or fan when trying to achieve a low temperature. However, if the sound becomes metallic or whistling, there may be air in the system or there is a problem with the expansion valve.
How often do you need to defrost the display case manually?
If the automation is working properly, manual defrosting is rarely required, usually 1-2 times a year for preventive cleaning. If the display case becomes overgrown with ice faster, check the tightness of the door and the serviceability of the defrosting heating elements.
What to do if the temperature fluctuates?
Jumps can be caused by a malfunction of the sensor, incorrect placement of products (overlapping the sensor) or problems with the electrical network. Check the tightness of the door and the absence of drafts in the room.