Brand refrigeration equipment DEXP has gained popularity due to its affordable price and wide model range, covering both compact single-chamber models and spacious two-chamber units. Understanding the operating principles of this device is necessary for every owner for proper operation, timely maintenance and minimizing the risk of premature breakdowns. Despite external differences, all DEXP refrigerators are based on the classic vapor-compression cooling scheme, however, they can differ significantly in the type of defrosting and the refrigerants used.
The operation is based on a continuous circulation cycle refrigerant (most often environmentally friendly R600a or R134a) along a closed loop. Electrical energy consumed from the network is converted by the compressor into mechanical energy, which causes the refrigerant to move, changing its state of aggregation and temperature. It is this physical process that allows heat to be removed from the internal chamber of the refrigerator and dissipated into the surrounding space through the rear grille of the condenser.
Modern DEXP models are often equipped with electronic control systems that optimize motor operation and prevent overloads. Knowing exactly how your DEXP generates cold will help you not only save energy, but also quickly respond to the slightest changes in the sound of a running unit or the quality of frozen food.
Basic diagram of a vapor compression cycle
The central element of any refrigeration unit is compressor, which is often called the “heart” of the system. DEXP refrigerators use primarily hermetically sealed piston compressors that pump refrigerant at high pressure. When the refrigerant leaves the compressor, it is in a gaseous state and has a high temperature, after which it is sent to the condenser.
In the condenser, which is a coil on the back wall or hidden in the side panels, heat is transferred. Passing through the tubes, the hot gas cools and turns into a liquid state. This stage is critically important: if (heat transfer) is impaired due to dust or poor ventilation, the efficiency of the entire system decreases and the load on the motor increases.
Next, the liquid refrigerant passes through capillary tube or the throttle, where its pressure drops sharply. This leads to instantaneous cooling of the substance. Entering the evaporator inside the freezer, the refrigerant boils at a very low temperature, actively absorbing heat from the food. After this, the cycle repeats again.
Features of defrosting systems: Static vs No Frost
The DEXP model range is divided into two main groups according to the type of defrosting: the classic drip system (or static) and technology No Frost. In models with a drip system (Drop System), the evaporator is located on the rear wall of the refrigerator compartment. Moisture from the air condenses on a cold surface, turns into frost, and when the compressor stops, it melts and flows into a special groove.
The system No Frost ("without frost") works on a different principle. Here the evaporator is hidden in a technical compartment, usually behind the back panel of the freezer. Cooled air is forced to circulate inside the chambers due to the operation fan. This ensures uniform temperature throughout the entire volume and the absence of ice on the food and walls.
⚠️ Attention: In DEXP refrigerators with the No Frost system, the ventilation holes on the back wall of the chambers must not be blocked with food. Impaired air circulation will lead to local overheating of the compressor and poor-quality cooling.
Periodically, based on a signal from a timer or thermostat, the No Frost system goes into defrost mode. At this moment, the Heating element (tubular electric heater) turns on, which melts the ice accumulated on the hidden evaporator. The resulting water flows into a pan located above the compressor, where it safely evaporates.
Why does food dry in No Frost?
Very dry cold air circulates in the No Frost system. If products are not packaged in containers or bags, the moisture from them quickly evaporates, which leads to weathering. In contrast to the drip system, where the humidity is naturally higher.
The role of thermoregulation and electronic modules
Temperature control in DEXP refrigerators can be carried out by a mechanical thermostat or an electronic control unit. A mechanical regulator is a device that is sensitive to changes in gas pressure in a bellows or expansion of a liquid. When the temperature in the chamber reaches the set value, the contacts open and the compressor turns off.
In more advanced models, electronic moduleis responsible for the process, receiving data from several temperature sensors (sensors). This allows you to maintain the temperature with an accuracy of one degree, which is especially important for long-term storage of fresh food. Electronics also controls fan operation and defrost cycles.
- 🌡️ Thermostat - a mechanical switch that breaks the compressor power circuit when the desired cold is reached.
- 📡 Temperature sensors - electronic sensors (thermistors) that transmit accurate data to the board controls.
- ⏱️ Defrost timer - a device (mechanical or electronic) that sets intervals for turning on the defrost mode.
If the DEXP refrigerator stops turning off or, conversely, does not turn on, the problem often lies in the elements of the system thermoregulation. A faulty sensor can “lie” to the control module, reporting that the chamber is warm, although in fact it is already deep frozen, or vice versa.
The refrigerants used and their properties
Environmental friendliness and operating efficiency directly depend on the type used refrigerant. Modern DEXP refrigerators are most often filled with isobutane (R600a) or tetrafluoroethane (R134a). Isobutane is considered more modern and energy efficient, it does not destroy the ozone layer, but is a flammable gas.
Tetrafluoroethane (R134a) is also safe for ozone, but operates at slightly higher pressure. It is less energy efficient than R600a but has better lubricity for the compressor. You can determine the type of gas by the sticker on the compressor or the technical plate on the housing.
| Parameter | R600a (Isobutane) | R134a (Tetrafluoroethane) |
|---|---|---|
| Energy efficiency | High (class A+ and above) | Medium (class A) |
| Working pressure | Low | Average |
| Safety | Explosive if leaked | Does not burn, safe |
| Oil type | Mineral | Synthetic (POE) |
Diagnostics of typical faults
Understanding the device allows you to quickly identify the cause of the breakdown. If your DEXP refrigerator is humming but not cooling, the compressor may have failed or there is a freon leak. If the unit operates continuously, it is worth checking the tightness of the door and the condition of the seal, as well as the operation of the thermostat.
A frequent problem in No Frost models is clogging of the drainage channel for discharging melt water. Water begins to accumulate at the bottom of the refrigerator or freezer. The fan may also fail: in this case, the cold will stop flowing into the chambers, although the evaporator will freeze over with ice.
⚠️ Attention: Constant operation of the compressor without shutdowns may indicate not only a breakdown, but also an incorrect installation. If the refrigerator is too close to a wall or heaters, the system may not dissipate heat effectively.
A multimeter is often required to diagnose electronics. The contacts of the starting relay, the integrity of the compressor windings and the resistance of the defrost heating element are subject to check. In models with inverter compressors, diagnostics are more complicated and require special equipment to check the frequency converter.
☑️ Primary diagnostics of the refrigerator
Recommendations for extending service life
In order for the DEXP refrigerator to serve for many years, you must follow the operating rules. It is important to provide adequate ventilation to the rear of the case. The distance to the wall should be at least 5-7 cm. Regular cleaning of the condenser from dust (with a vacuum cleaner or a soft brush) significantly reduces the load on the motor.
Do not load hot products into the chambers. This not only disrupts the temperature regime, but also leads to increased formation of condensation and ice, which is especially critical for No Frost systems. It is also recommended not to fill the chamber with products more than 70% so that air can circulate freely.
Check the condition periodically door seal. If the rubber band is cracked or has lost its elasticity, warm, moist air will enter the chamber, causing the compressor to wear out. Wiping the seal with a soft cloth and checking its fit is a simple but effective preventive measure.
Why does the DEXP refrigerator make gurgling sounds?
Gurgling and liquid pouring is a normal sound of refrigerant circulating through the system pipes, especially immediately after turning the compressor on or off. If the sound is not accompanied by a lack of cold, there is nothing to worry about.
How often do you need to defrost a DEXP refrigerator with No Frost?
The No Frost system does not require manual defrosting to remove ice, as this happens automatically. However, once every 6-12 months it is recommended to completely defrost and wash the chambers to maintain hygiene standards and eliminate odors.
Is it possible to transport the DEXP refrigerator lying down?
It is extremely undesirable. When transported lying down, oil from the compressor may leak into the refrigerant circuit, resulting in water hammer upon first start-up. If transportation cannot be avoided, after installation the unit must stand upright for at least 4-6 hours.
What to do if it is too cold in the DEXP refrigerator compartment?
Check the thermostat settings. If the mechanical handle is at maximum, reduce the power. On electronic models, check if the settings are lost. If the problem persists, the compressor relay may be stuck or the temperature sensor is faulty.