In modern refrigerators operating using the No Frost system, the evaporator defrost process occurs automatically, without the need for manual defrosting by the user. The key element of this system is a tubular electric heater, which in technical documentation is often designated as Heating element. It is responsible for melting the ice that inevitably forms on the evaporator radiator during compressor operation.
If you notice that a thick crust of ice or “coat” has formed on the back wall of the freezer, and the unit itself has stopped freezing with the same intensity, there is a high probability that heating element out of order. Understanding the principle of its operation will allow you not only to diagnose a breakdown, but also to avoid costly mistakes when trying to repair it yourself.
In this article we will analyze in detail how the defrost system functions, what types of heaters exist and how to correctly diagnose with a multimeter. You will learn why it burns out nichrome spiral and how to extend the life of your refrigerator, be it Indesit, LG or Atlant.
The principle of operation of the No Frost defrost system
The main task of the heating element is to heating the evaporator to remove ice. Unlike drip systems, where water drains naturally, in No Frost systems ice accumulates on the radiator slats hidden behind the rear panel. The defrost cycle is usually started by a timer or sensor signals when the compressor is resting.
At this moment, voltage is applied to the heater, which begins to radiate heat. The temperature rises quickly enough to melt ice, but is controlled to prevent overheating. As soon as the ice melts and the temperature of the sensor reaches a certain value (usually +10...+14°C), the circuit breaks and heating stops. defrost thermostatto prevent overheating. As soon as the ice melts and the sensor temperature reaches a certain value (usually +10...+14°C), the circuit breaks and heating stops.
It is important to understand that the heating element is not the only participant in the process. It works in conjunction with a timer, thermal relay and temperature sensor. If at least one of these elements is incorrect, the system may not turn on or, conversely, heat for too long, which is dangerous for the plastic parts of the chamber.
⚠️ Attention: An attempt to turn on the heating element directly, bypassing the sensors, may lead to melting of the plastic evaporator box and failure of the entire cooling system.
Some models use two heater: one main one, located under the evaporator, and a second one, which heats the tray for discharging melt water. This prevents the drainage channel from freezing, which often happens when the temperature in the freezer is low.
Design and types of heating elements
Technically, the heating element is a metal tube, inside of which there is a high-density nichrome spiral. The space between the spiral and the walls of the tube is filled with a dielectric filler, most often magnesium oxide. This design ensures high efficiency and safety, since the body is grounded, and current flows only along the internal spiral.
Several main types of designs are used in refrigeration technology:
- 🔹 Open Heating elements —the spiral is visible, installed in the lower part of the evaporator, often in the form of a zigzag or arc.
- 🔹 Closed (aluminum) heating elements —are completely sealed in an aluminum profile, which protects them from moisture and mechanical damage.
- 🔹 Glass heaters —are used less frequently, are characterized by a high heating rate and resistance to corrosion.
The choice of heater type depends on the model of the refrigerator. For example, in technology Samsung compact tubular elements are often used, mounted directly into the drainage system. While in older models Beko or Stinol you can find open spiral structures that are more susceptible to oxidation.
The power of household heating elements usually varies from 150 to 400 Watts. This is enough to melt an ice layer several centimeters thick in 15-20 minutes. Excessive power would lead to excessive energy consumption and the risk of overheating, and less power would not have time to melt the ice in the allotted cycle.
Fault symptoms and diagnostics
It is possible to determine that the heating element is faulty by indirect signs that appear long before the complete failure of the equipment. The most obvious symptom is icing on the back wall of the freezer. If you see a layer of ice that prevents the drawers from closing or touches the food, the defrosting system is not working.
However, you should not immediately blame the heater. The problem may lie in the timer or sensor. Therefore, before purchasing spare parts, you need diagnosis with a multimeter. To do this, you will have to remove the back panel of the freezer and gain access to the evaporator.
The test process is as follows:
- De-energize the refrigerator by unplugging the plug from the socket.
- Get to the contacts of the heating element (usually they are located under layer of insulation or in a plastic casing).
- Switch the multimeter to resistance measurement mode (Ohm).
- Attach the probes to the heater contacts.
If the device shows “infinity” (one in the extreme left position or OL on digital models), then the spiral is broken and The heating element burned out. If the resistance is from 200 to 500 Ohms (depending on the power), the element is working. It is also important to check the breakdown on the body: one probe to the contact, the other to the metal tube. There should be “infinite” resistance here.
Table of typical resistance values
For ease of diagnosis, we provide reference data. Please note that the actual resistance may vary slightly depending on the temperature of the metal and the error of the device.
| Heating element power (W) | Approximate resistance (Ohm) | Typical application | Probability breakdown |
|---|---|---|---|
| 150-200 | 300 - 400 | Drain trays, small evaporators | Medium |
| 250-300 | 180 - 250 | Standard household refrigerators | Low |
| 350-450 | 100 - 160 | Chest freezers, large cameras | High |
| 500+ | < 100 | Industrial equipment | High |
As can be seen from the table, the more powerful the heater, the lower its resistance. If you see a value close to zero, this indicates a short circuit inside the spiral, which is rare, but possible with severe mechanical damage.
⚠️ Attention: If, after replacing the heating element, the refrigerator stops defrosting again after 2-3 weeks, the problem is not in the heater, but in the defrost timer or thermostat, which does not give the command to turn on.
Step-by-step instructions for replacing the heating element
Replacing a heating element is a procedure of medium complexity that requires accuracy. The main rule: no rush. Plastic becomes brittle at low temperatures, and careless movement can lead to breakage of the fasteners.
First you need to completely defrost the refrigerator. Even if you change the heating element, the presence of ice will make access difficult and may damage the new element during installation. Leave doors open for at least 12 hours. Then remove the shelves, drawers and back plastic panel.
Next follow the algorithm:
- 🔸 Disconnect the wires from the old heating element, having previously photographed the connection diagram.
- 🔸 Carefully remove the heater from its seat. If it is stuck, do not use metal tools, it is better to soak it with warm water.
- 🔸 Install a new heating element, making sure that it fits tightly to the surface of the evaporator for better heat transfer.
- 🔸 Connect the wires, check the reliability of the contacts.
After assembly, start the refrigerator and monitor the first defrost cycle. Water should flow freely into the drainage hole without overflowing over the edge of the tray. If everything went well, the temperature in the chamber will stabilize within 4-6 hours.
Why the heating element burns out: the main reasons
The resource of a high-quality heating element is 7-10 years, but in reality they fail much earlier. The main enemy of the heater is corrosion. Moisture condensing on cold parts, in combination with atmospheric oxygen, gradually destroys the protective shell of the tube.
The second common reason is poor-quality assembly or manufacturing defects. Cheap Chinese analogues often have thin walls or irregularities in the density of the magnesium oxide packing. When heated, such elements are deformed, which leads to rupture of the spiral.
It is also worth mentioning power surges in the network. Although heating elements are quite stable, regular changes can shorten their service life. In rare cases, the cause is malfunction of the defrost temperature sensorwhich “keeps” the heating on for too long, causing thermal destruction of nichrome.
Do not forget about mechanical damage during cleaning. If you use a knife or scraper to remove ice, there is a high risk of damaging the heater tube without even noticing it right away. A microcrack will eventually become fatal.
Frequently asked questions and answers (FAQ)
Is it possible to operate a refrigerator if the heating element is burnt out?
Technically, the refrigerator will freeze, but its operating efficiency will drop sharply. The evaporator will become covered with ice, blocking the airflow. The compressor will work non-stop, trying to gain temperature, which will lead to overheating and failure in 1-2 months. Therefore, operation is only possible in emergency mode for a short time.
How to replace the original heating element if it is not on sale?
You can use a universal heating element, selecting it according to its geometric dimensions (length, diameter, shape) and power. Power deviation is allowed within ±10-15%. The main thing is that the new element fits into the standard mounts and does not touch the plastic walls.
Why does water pour onto the floor after replacing the heating element?
Most likely, the drainage hole is clogged. When replacing a heating element, ice chips or dirt often form and fall into the channel. It must be cleaned with a special flexible brush or soft wire, and then poured with warm water to check the drainage.
How often should the heating element be checked?
There is no need to specially check it. However, if you notice that the refrigerator has begun to freeze worse or frost has appeared on the walls, you should check it immediately. A preventive inspection every 3-4 years when cleaning the condenser will be useful for older models.