A modern refrigerator is a complex unit, the operation of which is built on the constant cyclic movement of the refrigerant, ensuring the maintenance of a low temperature inside the chambers. The central element of this heat exchange system is evaporator, without which the cooling process itself would be physically impossible. It is in this unit that liquid freon boils at low pressure, turning into gas and actively absorbing heat from the internal space of the refrigerator and freezer chambers.
An understanding of what is a refrigerator evaporatoris necessary for every owner of household appliances, since most malfunctions, such as freezing ice, insufficient cooling or complete compressor failure are directly related to this component. Unlike visible shelves and drawers, a hidden heat exchanger requires special attention during diagnostics, since its damage often leads to expensive repairs or complete replacement of equipment.
In this article we will analyze in detail the design of evaporators in No Frost and drip-type systems, consider the typical reasons for their failure out of order and provide step-by-step instructions for replacing the part. You will learn why The boiling point of freon in the evaporator is usually about -30°Cand how this physical process affects the safety of your products. A deep dive into the technical details will help you avoid common mistakes during operation and maintenance.
The principle of operation and the role of the evaporator in the cooling system
The main task of the evaporator is to extract thermal energy from the air inside refrigeration chamber. The refrigerant entering it at low pressure in the form of a mixture of liquid and gas actively boils. This process requires a large amount of energy, which freon “takes” from the environment, that is, from the air blowing through the heat exchanger tubes. As a result, the air cools down, and the refrigerant itself completely transforms into a gaseous state.
It is important to understand the difference between evaporator and a condenser. If the condenser (often the black grille at the back) releases heat to the outside, the evaporator, on the contrary, absorbs it from the inside. The efficiency of the entire refrigerator depends on the surface area of this heat exchanger and the quality of thermal contact between the tubes and the cooled air. The disruption of air circulation around the evaporator immediately affects the temperature of the products.
The design of the evaporator can be made in the form of a coil made of copper or aluminum tubes, often equipped with fins to increase the heat transfer area. In modern models, it can be built directly into the wall of the housing (foamed) or located separately in the freezer. Aluminum evaporators more susceptible to corrosion and mechanical damage, but cheaper to produce, while copper ones have better thermal conductivity and durability.
Differences in evaporators in No Frost and drip-type refrigerators
The design of the evaporator is radically different depending on the type of defrosting of the refrigerator. In units with a manual or drip system ("weeping wall"), the evaporator is often a tube mounted into the back wall of the refrigerator, or an open coil in the freezer. Here, cooling occurs due to natural convection or direct contact of products with a cooled surface.
In systems No Frost (without frost) one common evaporator is used, located hidden, usually in the upper part of the freezer compartment or behind the rear panel. The air is forced by a fan through this heat exchanger and distributed to all chambers through special channels. This allows you to avoid the formation of an ice crust on the products, since the main ice freezes on the ribs of the evaporator itself, and not on the walls.
- ❄️ Drip system: The evaporator is hidden in the rear wall, moisture condenses and flows into the drain, defrosting occurs automatically when the compressor is turned off.
- 🌬️ No Frost: separate powerful evaporator with a fan, cyclic defrosting by heating elements, complete absence of ice in the chambers when working properly.
- 🧊 Combined: there is a drip system in the refrigeration chamber, and No Frost in the freezer, which requires two circuits or a complex system of dampers.
Feature No Frost evaporators are equipped with a defrost system, including TEN (tubular electric heater), a defrost sensor and a timer. If one of these elements fails, the evaporator becomes overgrown with a “fur coat” that blocks the air flow, and the refrigerator stops freezing, although the compressor can work continuously.
Why does ice freeze only inside in No Frost?
In No Frost systems, ice freezes on the fins of the evaporator, which is hidden behind a plastic panel. The heating element periodically turns on, melts this ice, and the water goes into the drainage. The user sees only a dry box.
Main causes of freezing and malfunction
The most common problem faced by refrigerator owners is excessive freezing of the evaporator. If the ice crust becomes too thick, it begins to act as a heat insulator, preventing the freon from cooling. As a result, the compressor works hard, trying to gain temperature, but cannot do so. This often leads to failure of the motor-compressor itself.
One of the main reasons for the formation of a “fur coat” is a loose fit of the sealing rubber on the door. Warm, moist air from the room constantly enters the chamber through the cracks. Moisture instantly condenses on the cold evaporator and freezes. A malfunction of the defrost sensor in No Frost systems can also cause problems: if it is “stuck,” the heating element will not turn on in time to melt the ice.
⚠️ Attention: If you notice that the back wall of the refrigerator compartment is covered with an uneven layer of ice or a snow coat, this is the first sign of a violation of the tightness of the circuit or a failure in the defrost system. Ignoring this symptom can lead to depressurization of the system.
Other common reasons include:
- 🚫 Clogged capillary tube: disturbs the circulation of freon, causing local hypothermia and freezing of the inlet section.
- 🔧 Thermostat malfunction: compressor does not receive a signal to stop and freezes constantly, freezing the evaporator.
- 💨 Fan failure: in No Frost, stopping the fan leads to rapid fouling of the evaporator with ice, since cold air does not circulate.
Diagnostics: how to understand that the evaporator is faulty
Diagnostics of the condition of the evaporator often requires a visual inspection, which is only possible after partial disassembly of the refrigerator. However, there are a number of indirect signs that indicate problems with the heat exchanger. If the refrigerator hums, but does not cool, or freezes only in one corner, most likely the problem lies in the distribution of the refrigerant or freezing of the channels.
In No Frost systems, a sign of a malfunction is often the absence of the characteristic noise of a working fan or, conversely, the appearance of extraneous sounds (friction of the blades on the ice). It is also worth paying attention to the operation of the compressor: if it turns on for a short time and immediately turns off, or works without stopping without reaching the set temperature, this is an alarming signal.
For an accurate diagnosis, technicians use thermal imagers or simply feel the tubes. Normal operation of the evaporator implies uniform cooling of its entire surface. If you see that one part of the tube is covered with frost, and the other is dry and warm, this may indicate a freon leak or blockage. Copper tubes During normal operation, they should be evenly covered with a thin layer of frost or condensation.
Instructions for replacing the evaporator with your own hands
Replacing an evaporator is a complex technical process that requires special equipment: a vacuum pump, a pressure gauge station and skills in working with a soldering torch. In domestic conditions, it is almost impossible to perform this operation efficiently without loss of refrigerant and the risk of damaging other components. However, knowledge of the stages of the process is necessary to understand the scope of work.
The first step is always to defrost the refrigerator for at least 24 hours and dismantle the inner lining of the chambers. After gaining access to the evaporator, you must carefully unsolder the copper tubes, observing safety precautions. The old heat exchanger is removed and a new one, similar in size and thermal power, is installed in its place.
Next comes the most critical stage - vacuuming the system. It is necessary to remove all air and moisture from the circuit by creating a deep vacuum. Only after this is the refrigerator filled with freon strictly according to the weight indicated on the nameplate. Violation of proportions or the presence of moisture will lead to rapid breakdown of the compressor.
☑️ Stages of replacing the evaporator
⚠️ Attention: Independent soldering and refilling with freon without a license and equipment is prohibited in many regions and is hazardous to health. Freon can displace oxygen in a confined space, and when in contact with an open flame it forms toxic compounds.
Table: Comparison of characteristics of evaporators
To better understand the differences in design and maintenance, consider a comparative table of the main types of heat exchangers used in modern household appliances.
| Parameter | Open evaporator (No Frost) | Foam evaporator | Plate (old models) |
|---|---|---|---|
| Location | For rear panel of the freezer | Inside the case wall | On the back wall inside the chamber |
| Material | Aluminium, steel | Aluminium, steel | Steel, aluminum |
| Maintainability | High (easy to replace) | Low (requires circuit installation) | Medium |
| Propensity to corrosion | High (contact with air) | Low (protected by foam) | Average |
As can be seen from the table, foam evaporators, which are often found in the refrigerator compartment, are practically irreparable in the event of a breakdown. Moisture penetrating through microcracks in the housing causes corrosion of the metal from the inside. Such a circuit can only be restored by installing an external evaporator (“crying”), which changes the appearance of the chamber.
Open evaporators in No Frost freezers are more accessible for maintenance, but require regular cleaning of dust and checking the integrity of the drainage system. Any mechanical impact on thin aluminum tubes can lead to instant depressurization.
Prevention and operating rules
For To extend the service life of the evaporator and the entire refrigeration system, simple operating rules must be followed. First of all, monitor the temperature of the products you load into the chamber. Placing hot or warm dishes causes a sharp jump in humidity and temperature, which leads to increased formation of condensation and ice on the heat exchanger.
Regularly check the condition of the rubber seal on the door. Wipe it with a damp cloth and check the seal. If the door does not close tightly, moist air constantly enters the chamber, causing the evaporator to work in increased mode. It is also not recommended to cover the ventilation holes inside the chamber with food, as this interferes with air circulation.
Once a year, it is recommended to completely defrost the refrigerator (even the No Frost system) for prevention and hygiene. This will remove the smell and check the drain hole for blockages. A clean refrigerator works more efficiently and consumes less electricity.
Is it possible to repair a broken evaporator by soldering?
Theoretically, if the evaporator is copper and access to the damage site is open, soldering is possible. However, in the case of aluminum evaporators (especially those with a foam casing), soldering is extremely difficult and often does not give a durable result. Most often, a complete replacement of the unit or installation of an external heat exchanger is required.
Why does the refrigerator take a long time to gain temperature after replacing the evaporator?
This may be due to several factors: insufficient freon charging, the presence of air in the system (poor evacuation) or a mismatch in the power of the new evaporator. Also, the primary cooling time can take up to 24 hours.
How often do you need to change the evaporator?
With proper operation and no mechanical damage, the evaporator lasts as long as the refrigerator itself (10-15 years or more). Replacement is required only in case of corrosion breakdown or mechanical damage to the tubes.
Is it dangerous to breathe freon vapors during repairs?
Yes, at high temperatures (for example, when freon comes into contact with an open burner flame), it decomposes to form phosgene, a poisonous gas. Also, in high concentrations, freon displaces oxygen. Work must be carried out in a ventilated area.