Why the compressor tube freezes: reasons and solution

The sudden appearance of frost or “coat” on the back wall of the refrigerator or, more alarmingly, directly on the metal tube coming out of the motor, often takes equipment owners by surprise. Many people mistakenly believe that the colder the unit is, the better it works, but the temperature balance in the refrigeration circuit is important, and not extreme cooling of external elements. If you notice that the refrigerator compressor tube is covered with ice, this is a signal of a violation of the thermodynamic cycle, which requires immediate attention.

The refrigeration unit is designed so that the refrigerant circulates in a closed circuit, changing its state of aggregation. Normally, the low temperature zone (evaporator) is located inside the chamber, and the high temperature zone (condenser and compressor discharge tube) is outside. When ice begins to build up in areas that should be warm or at ambient temperature, it is an indication that freon boiling happening is not where the design intended. Ignoring this symptom can lead to failure of an expensive motor.

In this article we will analyze in detail the physical causes of the phenomenon, consider typical malfunctions and determine in which cases you can handle it yourself, and when you need to call a specialist. Understanding the processes occurring inside your Bosch refrigerator or Indesitwill help you avoid panic and unnecessary spending. Let's figure out what exactly happens in the system when the metal is covered with frost.

Physics of the process: how the refrigeration circuit works

To understand the nature of freezing, you need to briefly refresh your memory on the principle of operation of the refrigeration machine. The compressor compresses the gas, increasing its pressure and temperature. In this state, the gas enters a condenser (usually a grate at the back or side walls), where it cools and turns into a liquid. Further, passing through the capillary tube and filter drier, freon expands sharply in the evaporator, where active heat absorption from the chambers occurs. refrigerant, increasing its pressure and temperature. In this state, the gas enters a condenser (usually a grate at the back or side walls), where it cools and turns into a liquid. Further, passing through the capillary tube and filter-drier, freon expands sharply in the evaporator, where heat is actively absorbed from the chambers.

In a working system, the suction tube through which the gas returns to the compressor may be slightly cool, but it should never become overgrown with a thick layer frost. If ice appears on the discharge tube (which should be hot) or in the area immediately after leaving the motor housing, it means that it does not have time to completely evaporate in the evaporator and ends up back into the compressor or boils in the wrong place in the circuit. This phenomenon is called “evaporator overflow” or “hydraulic hammer” in its worst manifestation. liquid freon does not have time to completely evaporate in the evaporator and ends up back into the compressor or boils in the wrong place in the circuit. This phenomenon is called "evaporator overfill" or "water hammer" at its worst.

The temperature regime is strictly regulated by the technical characteristics of the gas used. For modern environmentally friendly refrigerants, such as R600a or R134a, even a small deviation in the amount of substance or pressure in the system leads to a shift in the boiling point. Instead of boiling inside the freezer at minus 24 degrees, freon can begin to boil earlier, cooling the tubes outside the thermally insulated volume.

The main reason: refrigerant leak and leakage

The most common reason why a compressor tube freezes is trivial freon leakage. It would seem like a paradox: there is less gas, but more ice. However, the physics of the process explains this simply: as the amount of refrigerant in the system decreases, the pressure drops. According to the laws of thermodynamics, a decrease in pressure leads to a decrease in the boiling point of a substance. As a result, freon begins to boil not at the end of the evaporator, but at the beginning of the circuit or even in the suction line itself, causing it to freeze.

Leaks most often occur in places where copper tubes are soldered, in foamed parts of the housing (where the metal is in contact with an aggressive environment) or through microcracks in the evaporator that have arisen due to careless defrosting with a knife. Models with aluminum evaporators are especially susceptible to corrosion, for example, some series Atlant or Stinol. Over time, the microscopic hole expands and the tightness of the circuit is broken.

⚠️ Attention: If you find oil under the refrigerator or feel a specific chemical smell, this is a sure sign of depressurization. You cannot operate equipment with a leak - the compressor may burn out due to the lack of cooling of the motor with circulating gas.

Diagnostics of a leak at home is only partially possible. You can listen to the operation of the unit: the motor can work almost non-stop, trying to reach the set temperature, which it cannot achieve. In this case, characteristic uneven frost is visible on the tubes, which can be located in spots or only at the beginning of the area.

To eliminate this malfunction, you need to find the leakage point using a leak detector or soap solution (if access is open), solder the damage, replace filter drier and refill the system with freon. This is a job for a specialist with a vacuum pump and a pressure gauge station.

Faults in the thermostat and defrost sensors

The second most important reason for abnormal freezing is the incorrect operation of the control electronics. Thermoregulator (or electronic temperature sensor) is responsible for turning the compressor on and off. If its contacts are “stuck” in the “on” position or the sensor transmits incorrect data about the high temperature in the chamber, the compressor will operate continuously.

Long-term operation without shutdown cycles leads to the fact that the entire volume of freon in the system is supercooled. Excess cold is transferred to sections of the suction line. In systems with drip defrosting or No Frost, this may also indicate a malfunction defrost sensor or defrost timer. If the system does not start the evaporator heating mode, the ice coat grows, blocks the airflow (in No Frost) and begins to “crawl” through the tubes outward.

A symptom of such a breakdown is often that there is food in the main chamber freeze, and a monolithic piece of ice forms in the freezer. The compressor may be hot, but the tube at the outlet (in some circuits) or at the inlet will be covered with frost due to the system being oversaturated with cold.

You can check a mechanical thermostat by temporarily removing it from the circuit (by closing the contacts), but this must be done carefully to prevent defrosting of the food. In electronic models LG or Samsung diagnosis is carried out through the test mode or reading error codes from the display.

The influence of the capillary tube and filter drier

The third important reason lies in the bottleneck of the system - capillary tube. This is the thinnest copper tube that creates the necessary resistance for the pressure difference between the high and low circuit. If an ice or debris plug forms inside it, or if the filter drier becomes clogged, the circulation of freon is disrupted.

Clogging often occurs due to moisture that entered the system during poor-quality previous repairs, or due to decomposition products of oil and solder. At the site of the blockage or immediately after it, local freezing may occur, since the pressure in front of the blockage increases and then falls, causing a sharp boiling of the refrigerant. Sometimes frost is visible only on the filter-drier, which should normally be warm.

The blockage can be determined by the nature of the motor: it can turn on, hum for several minutes, then click (the thermal relay is activated) and turn off, since it cannot push gas through the plug. In this case, the tubes may be cold, but without the temperature gradient characteristic of normal operation.

⚠️ Attention: Attempts to clean the capillary tube yourself using a compressor or nitrogen without the proper equipment often lead to rupture of thin-walled elements. Professional blowing and vacuuming are required.

What is a filter drier?

A filter drier is a small cylinder filled with zeolite (a special substance) that absorbs moisture from the refrigerant. Its replacement is required whenever the circuit is opened, since it is disposable. If you do not change it, moisture will freeze in the capillary pipe and cause an ice plug, which will lead to freezing of the pipes and breakdown of the compressor.

Diagnostics: table of symptoms and causes

For the convenience of primary diagnosis, we suggest that you familiarize yourself with the summary table. It will help match visual signs with the most likely technical problems. Remember that only a master can make an accurate diagnosis using measuring instruments.

When analyzing the behavior of equipment, pay attention to the details. For example, if frost appears only after the door has been open for a long time, it may be condensation from humid air, and not a malfunction. But if the ice crust remains permanently and grows, this is a technical problem.

It is also important to take into account the model of the refrigerator. In two-compressor systems (separate motor for the freezer and refrigerator), freezing of the tube of one of the compressors localizes the problem in this particular circuit. In single-compressor models with one solenoid valve the problem may be a stuck valve that does not switch freon flows correctly.

Instructions: what to do if frost is detected

If you find ice on tubes, do not rush to grab the tools. The first step should be complete defrosting. Unplug the refrigerator, remove all food and leave the doors open for at least 24 hours (preferably two days). This is necessary so that the ice melts not only in visible places, but also inside the foam layer, where an ice jam could form.

After defrosting, turn on the equipment and observe its operation for several hours. If the problem was caused by a temporary failure or excess moisture in the air (for example, you put hot pots on), the system may return to normal. If after a day the picture repeats itself - the tube becomes covered with frost again, and the temperature in the chambers does not hold, then repairs are required.

You can independently check the integrity of the door seals. A loose fit leads to a constant influx of warm, moist air, which causes increased ice formation in the evaporator and subsequent freezing of the tubes. The check can be carried out using a sheet of paper: hold it with the door and try to pull it out - it should be pulled out with force along the entire perimeter.

Prevention and proper care refrigerator

To avoid problems with pipes freezing in the future, it is important to follow the operating instructions. Do not load warm food into the chambers - this puts excess stress on the system and leads to condensation, which then freezes. Monitor the condition of the seal