Modern users of household appliances often encounter mysterious terms in service manuals or when talking with repairmen. One of these words is "mid". If you are wondering what mid in the refrigerator is, then we hasten to reassure you: we are not talking about some exotic detail or newfangled function. In fact, this is a slang or abbreviated name for the key element of the cooling system - evaporator.
It is this unit that is responsible for generating cold, which is then distributed throughout the chambers of your unit. Understanding its design and operating principle will help you better understand the causes of breakdowns, such as ice on the back wall or insufficient cooling of food. In this article, we will analyze in detail the design of the evaporator, its role in the system No Frost and typical problems that the owner may encounter.
Knowing how it functions refrigeration circuitwill allow you to quickly diagnose a malfunction and avoid unnecessary expenses on repairs. Often, craftsmen use professional jargon, and understanding the basic terms puts the client and the specialist on the same wavelength.
The main purpose of the evaporator in the cooling system
The evaporator, or “mid”, is a heat exchanger in which a phase transition of the refrigerant occurs from a liquid state to gaseous. This process is accompanied by intense heat absorption from the internal volume of the refrigeration chamber. In simple words, this is where the cold is born. The refrigerant, passing through the thin tubes of the evaporator, boils at very low temperatures, taking energy from the walls of the heat exchanger.
Structurally evaporator can be made in the form of a coil sealed into the wall of the housing (in older models), or in the form of a radiator with aluminum plates and a fan (in systems No Frost). In the second case, the fan forces air through a cold radiator, distributing the cooled flows throughout the entire volume of the chamber. This ensures uniform temperature and the absence of condensation.
The efficiency of the entire refrigeration unit directly depends on the condition of the evaporator. If a too thick layer of ice forms on its surface, heat transfer is disrupted. The compressor is forced to work longer and harder, trying to achieve the set parameters, which leads to increased energy consumption and wear of the motor.
It is important to understand that the evaporator is the heart of the cooling system. Any mechanical damage, corrosion or blockages in this area require immediate intervention. In modern models, access to it can be difficult, since it is often hidden behind plastic panels.
Design features and types of evaporators
Depending on the type of refrigerator, the design of the “mid” can vary significantly. Budget and older models often use an open evaporator, which is a metal shelf or a panel sealed into the back wall. In such devices, cooling occurs due to natural air convection.
Systems No Frost (or Full No Frost) use a more complex module. Here the evaporator is hidden in a special compartment, usually in the freezer or at the top of the refrigerator. It consists of copper or aluminum tubes strung on corrugated plates to increase the heat transfer area. A fan and a heating element (heating element) are always located next to it.
- 🧊 Open type: located directly in the working chamber, requires manual defrosting.
- ❄️ Hidden type: located behind a partition, works in tandem with a defrost system.
- 💨 Fan: provides air circulation, preventing the formation of “warm zones.”
The materials used for the manufacture of evaporators must have high thermal conductivity. Aluminum and copper work best for this. However, aluminum is more susceptible to corrosion when in contact with acids, so in such models it is forbidden to defrost the chamber with sharp objects.
B Some industrial or specialized models may have evaporators with forced airflow, but without an automatic defrosting system, which is an intermediate option. Understanding the type of device you have will help you properly care for it.
Operating principle and defrost cycle
The key point in the operation of the evaporator is cycling. During the cooling process, moisture from the air inevitably settles on cold tubes, turning into frost. If this frost is not removed, it will turn into an ice coat that will block air access to the heat exchanger. This is precisely why modern refrigerators provide a defrost cycle.
In systems No Frost this process is automated. A timer or electronic control module periodically (usually every 8-12 hours of compressor operation) turns off the cooling and turns on the heating element. The heating element melts the ice on the evaporator, and the resulting water flows into a special pan, from where it evaporates into the environment.
⚠️ Attention: If the defrost cycle is broken (the heating element is burned out or the defrost sensor is faulty), the evaporator is completely covered with ice. The fan begins to hum, touching the ice crust, and the cold stops flowing into the chamber, although the compressor continues to work.
In drip systems (“crying wall”), the role of the evaporator is played by the rear wall of the refrigerator compartment. Periodically, the compressor turns off, the wall thaws, and the drops flow down the groove. There is no active heating here, the process occurs naturally during idle time.
Why can’t you speed up defrosting with a hair dryer?
Using a hair dryer to speed up the defrosting of the evaporator can lead to uneven heating of aluminum tubes and their deformation or cracking. In addition, hot air can damage the plastic casing and seals.
Typical evaporator malfunctions and their symptoms
Despite its reliability, the “mid” can fail or cause the refrigerator to operate incorrectly. The most common problem is a violation of heat exchange due to freezing. But there are also more serious mechanical damage.
One of the critical problems is refrigerant leakage. If the evaporator is made of aluminum (and in modern models this is 90% of cases), it is very sensitive to mechanical stress. An accidental puncture with a knife during inaccurate defrosting leads to an instant release of freon and the cessation of cooling.
Corrosion is also common. In places where the paint layer is damaged or there are microcracks, aluminum oxidizes. Over time, this leads to the formation of “fistulas” - through holes through which the refrigerant evaporates. Restoring such an evaporator is often not economically feasible.
| Symptom | Possible cause | Necessary actions |
|---|---|---|
| Humming and crackling in the chamber | Ice on the blades fan | Checking the defrost system |
| The refrigerator does not freeze | Freon leak from the evaporator | Call a technician, look for a leak |
| Water on the floor or in chamber | Drainage clogged or defrost failure | Cleaning the drainage, checking the heating element |
| Severe freezing of products | Temperature sensor malfunction | Diagnostics electronics |
Another common (malfunction) is failure of the evaporator temperature sensor. This small element tells the control unit when to turn on the defrost heat. If it is “lying,” the refrigerator may either not turn on the defrost (leading to ice blockage), or heat the evaporator too often, which increases the temperature in the chamber.
How to independently check the status of the system
Diagnostics of the evaporator at home is limited, since it is hidden in systems. No Frost he is hidden. However, there are indirect signs that allow you to understand that something is wrong with the mid. First of all, listen to the operation of the unit.
If you hear the fan humming, crackling, or periodically stopping, this is a sure sign that the space around the evaporator is filled with ice. The fan blades simply touch the ice crust. In this case, it is necessary to completely defrost the refrigerator (for at least 24 hours) to check.
- 👂 Audience: listen to the sounds of operation - extraneous noise often indicates a problem.
- 🌡️ Temperature: check whether the refrigerator maintains the set mode.
- ❄️ Visual inspection: the presence of frost on food or walls is an alarming signal.
To check in models with access (usually these are freezers of older models or some budget options), you can carefully remove the back panel. But this should only be done with the power off and tools available. An internal inspection will allow you to see the degree of icing and the integrity of the tubes.
☑️ Primary diagnostics
Prevention and proper care of the evaporator
In order for the “mid” to serve for a long time and not cause problems, you must follow simple operating rules. The main recommendation is to avoid mechanical damage. Never use a knife, fork or other sharp objects to chip ice.
Regular defrosting (even for systems No Frostat least once a year for prevention) helps clean hard-to-reach places from dust and check the operation of the drainage system. Dust deposited on the evaporator plates acts as a heat insulator, reducing cooling efficiency.
⚠️ Attention: When washing the inside of the refrigerator, avoid getting large amounts of water on the back wall (in the evaporator area). Moisture may flow into the thermal insulation layer or damage the electrical contacts of the sensors.
It is also important to monitor the quality of the products that you place in the chamber. Do not place hot food - this causes a sudden increase in humidity and condensation, which increases the load on the defrost system. Cover liquid products with lids.
Repair or replacement: which is more profitable?
In the event of a serious breakdown, such as a leak freon from a sealed evaporator, the question of maintainability arises. In old refrigerators it was possible to install an external (“hinged”) evaporator, but in modern models with the system No Frost this is impossible or extremely ineffective.
Replacing the evaporator is a labor-intensive process. It requires:
- 🛠️ Dismantling: disassembling the case and removing the old assembly.
- 🔥 Soldering: connecting copper and aluminum tubes (special solder is required).
- 💨 Evacuation: removing moisture and air from the system.
- ⛽ Refilling: adding the exact amount of refrigerant.
Often the cost of such repairs is 50-70% of the price of a new refrigerator. If the unit is old, it is cheaper and more reliable to buy new equipment. However, if the problem is only in the defrost heating element or sensor, repairs are quite feasible and inexpensive.
The decision to repair should be made by a qualified technician after diagnosis. An independent attempt to replace the evaporator without special equipment (vacuum pump, pressure gauge station, scales) is doomed to failure.
Is it possible to operate a refrigerator if the evaporator is covered with ice?
Short-term operation is possible, but undesirable. Long-term operation with a frozen evaporator will lead to overheating of the compressor, increased energy consumption and, ultimately, to motor failure. In addition, food may begin to deteriorate due to lack of cold.
Why does the refrigerator not turn on for a long time after defrosting?
This is normal behavior for some models. The control unit waits until the sensors show a certain temperature before starting the compressor. There may also be a process of equalizing pressure in the system. If the refrigerator does not turn on for more than 2-3 hours after defrosting, you should contact a specialist.
Is it dangerous to breathe freon vapors when repairing the evaporator?
Modern refrigerants (R600a, R134a) in small quantities contained in a household refrigerator are not toxic to humans for short periods inhalation. However, R600a (isobutane) is explosive. Therefore, work on soldering and replacing the evaporator should be carried out in a ventilated area and only by professionals.
How often do you need to defrost a refrigerator with No Frost?
Technically, the No Frost system does not require manual defrosting. However, manufacturers recommend carrying out preventive defrosting and washing 1-2 times a year. This is necessary for hygiene, cleaning the drainage channels and removing dust from the heat exchanger, which inevitably accumulates over time.