When operating household appliances, users often encounter phenomena that seem paradoxical at first glance, for example, when the side walls of the unit become hot, but the inside remains icy cold. A logical question arises: why does heater in the refrigerator exist at all if the main task of the device is cooling? This is not a design error or a manufacturing defect, but an important part of the temperature and humidity control system.
In modern models, especially those equipped with the system No Frost, heating elements play a critical role in preventing the formation of ice jams and ensuring air circulation. If you feel warmth on the outer surface of the case, this may indicate either normal operation of the equipment or incipient problems. Let's figure out who warms whom in this system and why the temperature balance is so important for the longevity of the equipment.
Physics of the process: why heat to freeze?
The main function of the refrigeration circuit is to select heat from the internal chamber and dissipate it into the external environment. However, in the process of cooling the air, an inevitable phenomenon occurs - moisture condensation. If this process is not controlled, moisture will turn into frost on the evaporator, blocking air flow. This is where the heating elementwork comes into play, which periodically turns on to melt the formed ice.
From the point of view of physics, heat transfer occurs not only through the evaporator, but also through the walls of the housing where the condenser tubes pass. In older models or in certain operating modes, the tubes can become very hot, transferring heat to the side panels. The temperature of the side walls in operating mode can reach 50-60 degrees Celsiuswhich is an absolutely normal indicator for intensive heat dissipation.
There is a common misconception that heating the case is loss of energy. In fact, efficient heat dissipation through the walls allows the compressor to operate at its optimum. If heat were not dissipated through a large surface area, the system would overheat, and the pressure in the circuit would rise to critical values.
⚠️ Attention: If the body of the refrigerator becomes so hot that it cannot be touched, or the heating is localized to one point (for example, only in a corner), this may indicate a blockage in the system or a faulty fan.
Thus, the heating and cooling processes in the refrigerator are inextricably linked. Without proper management of heat flows, it is impossible to maintain a stable temperature in the main chamber. Understanding this principle helps owners not to panic when they detect hot surfaces, but to correctly assess the condition of the equipment.
Defrost heating element: the heart of the No Frost system
In refrigerators with the system No Frost the main "heater" is the evaporator defrosting heating element. It is located directly on the evaporator fins, hidden behind the back wall of the freezer. Its job is to briefly heat the evaporator during the defrost cycle to melt the frost that has frozen on it. The water flows into a special pan, from where it evaporates naturally.
The operation of the heating element is strictly regulated by an electronic control module or a mechanical timer. Defrost cycles typically run every 8 to 16 hours of compressor operation. The heating duration is from 15 to 25 minutes, after which there must be a pause so that the water has time to drain before the compressor starts again and begins to freeze the remaining moisture.
- 🔥 The defrosting heating element turns on only when the compressor is turned off, so as not to waste energy.
- 💧 Power The heating element usually varies from 150 to 300 W depending on the volume of the chamber.
- ❄️ Without a working heating element, the evaporator becomes overgrown with a “fur coat” and the refrigerator stops freezing.
If the heating element fails, the user notices that the freezer becomes warmer, and an ice build-up appears on the back wall. In some cases, ice can block the cold air damper in the refrigerator compartment, causing food in the main compartment to begin to spoil even if it is still cold in the freezer.
⚠️ Warning: Do not try to clear ice from the evaporator with a knife or other sharp objects. You can damage the aluminum tubes or the heating element itself, which will lead to expensive repairs.
Heating of the walls: capacitor or problem?
Many users confuse the operation of the defrosting heating element with heating the walls of the housing. It is important to understand: in cooling mode, it is not the heating element that heats the walls, but the condenser. A condenser is a coil in which the refrigerant gives off heat. In modern models, to save space and improve aesthetics (no black grille at the back), the condenser tubes are mounted directly into the side walls of the refrigerator.
The intensity of heating of the walls depends on several factors. The first is the load on the compressor: if you've just loaded a lot of warm food or open the door frequently, the system will work to the limit and the walls will be hotter than usual. Secondly, the temperature in the room matters: in summer, heat transfer is difficult, so heating can be more noticeable.
However, there are signs indicating a malfunction. If only the top of the refrigerator is hot and the bottom is cold, or if heating is accompanied by humming and vibration, this may be a sign of a clogged capillary tube or a lack of freon. In such cases, heat does not circulate throughout the entire circuit, but accumulates at the beginning of the system.
It is also worth mentioning the so-called “anti-condensation” heaters. They are located around the perimeter of the doorway and prevent dew from falling on the ends of the body. Their operation is less noticeable, but they also consume energy and contribute to the overall heat balance of the unit.
Diagnostics of malfunctions of heating elements
How to understand that something is wrong with the heating system? Primary diagnosis can be carried out independently, paying attention to indirect signs. The main symptom of a malfunctioning defrost heating element is the presence of ice on the back wall of the freezer when the compressor is running. Ice can completely block the air ducts.
For a more accurate check, you will need a multimeter. To get to the heating element, it is often necessary to partially defrost the refrigerator and remove the back panel in the freezer. Before carrying out any work be sure to disconnect the device from the power supply. The test is carried out in resistance measurement mode (Ohm).
☑️ Diagnostics of the heating element
If the multimeter shows one (infinite resistance), then the spiral of the heating element has burned out and requires replacement. If the resistance is close to zero, a short circuit has occurred. The normal resistance of a working heating element with a power of 200 W is approximately 200-250 Ohms.
In addition to the heating element itself, defrost sensors (defrost thermostats) often fail. They may "stick" in the "on" or "off" position. If the sensor does not give a signal to turn on the heating element, the ice will accumulate. If it does not give a signal to turn off, the heating element can heat up constantly, which is dangerous due to the melting of plastic parts.
How to check the defrost sensor?
The defrost sensor (defrost thermostat) is a bimetallic plate in a sealed housing. At room temperature it should “ring” (show a resistance close to 0 ohms), since the contacts are closed. To check the opening, you need to cool it (for example, put it in the freezer for 15-20 minutes), after which the resistance should become infinite. If it continues to ring during cooling, the sensor is faulty.
Table: Comparison of types of heating in the refrigerator
To systematize knowledge about thermal processes, consider the main heat sources and their characteristics in a summary table. This will help you quickly identify the heating source in your particular case.
| Heat source | Location | When it heats | Normal temperature |
|---|---|---|---|
| Condenser (in the walls) | Side panels, rear part | During compressor operation | 40-60 °C |
| Defrost heating element | Behind the rear wall of the freezer | During the defrosting cycle (compressor off) | Up to 100 °C (locally) |
| Anti-condensation heating element | Along the perimeter of the doorway | Continuously or humidity sensor | 30-40 °C (barely perceptible) |
| Compressor | Lower rear part | During operation | Up to 90 °C (body) |
The table shows that heat sources operate in different modes. If you observe heating while the compressor is silent, and this is not a defrost cycle (which does not last long), it is worth considering checking the thermostat or relay.
It is also important to consider that the design may vary in different models of refrigerators (for example, Indesit, LG, Samsung). In some budget models, the condenser is still placed outside in the form of a black grille, and then the side walls should not heat up at all.
The influence of the operating mode on the thermal balance
Do not forget that the user himself influences the operation of the heating elements. Frequently opening the door, adding hot food, or placing the refrigerator near the radiator causes the system to work in extreme mode. Under such conditions, the defrosting heating element may turn on more often, and the walls will heat up more.
If the room is too cold (below +10 °C), the refrigerator may not turn off at all, trying to gain temperature, or, conversely, not turn on if the thermostat is in a warm zone. This disrupts the cyclical operation and can lead to malfunctions in the defrosting algorithm.
To maintain optimal mode, it is recommended:
- 🌡️ Install the refrigerator away from heat sources (stoves, radiators, direct sunlight).
- 🚪 Minimize the time you open the door, especially in hot weather weather.
- 🧹 Regularly check the door seals: if they do not fit tightly, warm, humid air constantly enters the chamber, increasing the load on the defrosting heating element.
Following simple operating rules allows you to avoid situations when the “heater” (in the form of an overloaded system) begins to work against the owner, consuming excess electricity and wearing out the components.
Replacing the heating element: is it worth doing it yourself?
If diagnostics showed that the defrost heating element was burnt out and needed to be replaced. This is a consumable item and cannot be restored. The replacement process requires disassembling the freezer, which can be difficult on modern models. It is necessary to remove many plastic fasteners, which become brittle at low temperatures.
The main difficulty is not in replacing the spiral itself, but in correct connection and sealing. If you leave any gaps during reassembly, moisture will begin to seep into the evaporator again and the freezing problem will return within a couple of weeks. In addition, it is important to install the sensors correctly so that they read the temperature of the evaporator, and not the air in the chamber.
⚠️ Attention: When replacing the heating element, be sure to check the condition of the wire insulation. In conditions of low temperature and constant vibration, the insulation may crack, which will lead to a short circuit to the metal body of the evaporator.
If you are not confident in your abilities, it is better to contact a service center. Craftsmen have the necessary tools for accurate disassembly and know the nuances of fastening panels in specific models, such as Bosch or Electrolux. Self-repair without experience can lead to damage to the plastic elements, which you will then have to glue or look for new ones.
Why is the refrigerator hot on the side after defrosting?
After complete defrosting and turning on, the refrigerator begins to work in enhanced mode to cool the empty volume to the set temperature. During this period, the compressor works non-stop, and the condenser (built into the walls) actively releases heat. This is fine. After a few hours, when the temperature stabilizes, the heating should decrease and the operating cycles become intermittent.
Is it possible to turn off the defrost heating element permanently?
Theoretically, it is possible, but this will lead to rapid fouling of the evaporator with ice. The refrigerator will stop freezing after 1-2 weeks. Some “craftsmen” install a button for manual defrosting, but this requires discipline: if you forget to press the button, the ice will block the system. Factory automation is more reliable.
Does the heating element hum during operation?
The heating element itself (a spiral in a quartz tube or an open one) operates silently. However, as the evaporator's plastic housing and metal elements heat up and cool down, they may make cracking or clicking noises due to thermal expansion. If you hear a hum, most likely the compressor or fan is working, and not the heater.
How long does a defrost heating element last?
The average service life of a heating element is 5-10 years, but it greatly depends on the quality of the water (air humidity) and the frequency of defrost cycles. In conditions of high humidity and frequent door openings, the resource may be reduced to 3 years.