The capillary tube of the refrigerator is a critical element in the cooling system, often becoming the focus of troubleshooting. It is this thin copper channel that is responsible for creating the necessary pressure drop, allowing the refrigerant to effectively evaporate and remove heat from the chambers. Without the correct operation of this unit, a household refrigerator turns into a useless metal box, unable to maintain a low temperature.
Understanding the principle of operation of this part is necessary for anyone who plans to repair household appliances on their own. Unlike complex electronic components, capillary tube represents a mechanical element, however, its condition directly affects the performance of the compressor and the overall energy efficiency of the device. Let us consider in detail how this system works and what to do if it fails.
During the operation of the refrigeration unit, various situations may arise that require the intervention of a specialist. Clogging, ice blockage or mechanical damage are just some of the problems that equipment owners face. It is important to note that any manipulation with the system requires compliance with safety precautions and an understanding of the physical processes occurring inside the circuit.
Principle of operation and role in the cooling system
The main function of the capillary tube is to throttle the flow of refrigerant. Liquid freon under high pressure flows from the condenser into this narrow channel, where a sharp drop in pressure occurs. As a result of this process, part of the liquid instantly evaporates, turning into steam, and the remaining part is cooled to the boiling point at a new, lower pressure. Capillary choke ensures a stable supply of refrigerant to the evaporator, which is the basis for effective heat exchange.
Length and internal The diameter of the tube is calculated by engineers with high accuracy for each specific refrigerator model. A passage that is too narrow or long will create excess resistance, causing the compressor to work under overload, which can lead to premature failure. Conversely, a channel that is too wide will not create the required pressure drop, and the evaporator will not be cold enough.
Modern systems are often used capillary-tube heat exchangers, where the capillary tube is soldered to the suction line. This allows liquid freon to be cooled before entering the capillary and at the same time to heat the vapor going into the compressor, preventing the liquid fraction from entering the piston cylinder. This approach significantly increases the reliability and durability of the unit.
Design features and materials
For the manufacture of capillary tubes, only high-purity copper is used. This material was not chosen by chance: it has excellent thermal conductivity, ductility and resistance to corrosion within the system. The standard internal diameter usually varies from 0.6 to 2.0 mm, and the length can reach several meters when coiled into a compact spiral.
It is important to understand that copper is sensitive to mechanical stress. If handled carelessly during installation or transportation of the refrigerator, the tube may become deformed or even burst. Copper capillary requires careful handling, especially in soldering areas, where the metal has been subjected to heat treatment and has become more brittle.
In some modern models of refrigerators, especially inverter type, An electronic expansion valve can be used instead of a classic capillary tube. However, most household units manufactured in recent decades still use the time-tested capillary system due to its reliability and cost-effectiveness.
Why copper?
Copper has bacteriostatic properties and does not react with most refrigerants and oils, which ensures a long service life of the system without the formation of sediment.
Typical malfunctions and their symptoms
The most common problem is a clogged internal channel. This can happen for two main reasons: moisture entering the system with the subsequent formation of an ice plug, or the accumulation of oil breakdown products and solid particles. Symptoms of a blockage appear in the form of insufficient cooling of the chambers or a complete lack of cold when the compressor is running.
If you notice that the refrigerator operates cyclically: it turns on, cools, and then stops freezing, after which the cycle repeats, this may indicate a “floating” blockage. The ice plug can periodically thaw when the compressor is resting, and freeze again when it starts. Hydraulic hammer in the system is another dangerous phenomenon that can occur if improper charging or severe blockage.
Mechanical damage should also not be discounted. Shock during transportation, corrosion or vibration may cause the tube to become depressurized. In this case, the refrigerant quickly evaporates and the system stops functioning. A leak can often be determined by a characteristic hissing sound or by using a soap solution applied to suspicious areas.
- 🧊 The compressor operates continuously, but the temperature in the chambers does not drop below room temperature.
- 🔇 The unit turns on for a short time and turns off via a thermal relay, without having time to start.
- 🌡️ There is uneven cooling of the evaporator: one part is cold, the other is warm.
- 💧 The appearance of condensation or oily spots in the lower part of the refrigerator at the back wall.
Methods for diagnosing and finding blockages
Diagnostics of the condition of the capillary system requires attentiveness and the availability of basic tools. The first step is always to visually inspect and listen to the operation of the unit. If the compressor is humming, but there is no refrigerant circulation, most likely the problem lies in the throttle device or filter drier.
For a more accurate diagnosis, technicians use the nitrogen purging method. Having disconnected the capillary tube from the condenser and evaporator, compressed air or nitrogen under pressure is supplied through it. If the flow is free, then there is no mechanical blockage, and the problem may be an ice plug or leak. If purging is impossible, it is required cleaning the capillary or its replacement.
Also an effective method is to observe the behavior of the tube during operation. In a working system, the section of the capillary after the condenser should be warm, and after leaving the evaporator it should be cold. A sharp change in temperature or its absence may indicate the location of the problem. Use a thermometer or just tactile sensations (with caution) to assess.
☑️ System diagnostics
Replacement and cleaning technology
The process of replacing a capillary tube is complex and requires specialized equipment, such as a burner, vacuum pump and pressure gauge station. First you need to carefully desolder the old tube without damaging the adjacent elements. Then a new element with similar characteristics is installed. Particular attention is paid to soldering connections to avoid oxidation of the copper inside.
If the decision is made to clean an existing tube, a hydraulic flushing or high-pressure purge method is used. Sometimes the method of “pushing” the blockage using compressed nitrogen is used, but this method is risky and can lead to rupture of the tube if the blockage is too dense. Replacing the filter drier is mandatory for any intervention in the system, since the old filter will no longer be able to effectively remove moisture.
After When installing a new element or cleaning, the system must be evacuated. This is a critical step to remove any remaining moisture and air. Vacuuming should last at least 30 minutes until a deep vacuum is achieved. Only after this is refrigerant charged in strict accordance with the weight indicated on the refrigerator nameplate.
| Type of malfunction | Symptom | Elimination method | Required tool |
|---|---|---|---|
| Ice plug | Cyclic operation, absence cold | Evacuation, filter replacement | Vacuum pump, burner |
| Mechanical blockage | Compressor does not start, hums | Purge nitrogen, tube replacement | Nitrogen cylinder, cutter |
| Leak in tube | Oil stains, hissing | Soldering or replacing section | Solder, flux, burner |
| Deformation | Reduced productivity | Replacement of the capillary line | Set of copper pipe products |
⚠️ Attention: Work with refrigerants and open flames require professional skills. Improper soldering can lead to the ignition of oil or an explosive mixture, and the entry of moisture into the system is guaranteed to damage the compressor within a short time.
Prevention and operating rules
To extend the life of the capillary system and the entire refrigerator, you must follow a number of simple rules. First of all, avoid opening doors frequently and do not leave them open for long periods of time. This minimizes the entry of moist air into the chambers, which then condenses and can reach the evaporator and capillary.
Regular defrosting (for refrigerators with manual defrosting) is also an important preventive measure. A thick layer of ice on the evaporator impairs heat transfer and creates additional stress on the system. In addition, try not to overload the refrigerator with food to ensure free air circulation.
Be careful when transporting the refrigerator. Do not drop the unit and do not allow impacts on the rear wall where the tubes and condenser are located. Transport bolts (if they are included in the compressor design) must be installed during transportation to prevent damage to the motor mount.
- 🧹 Clean the condenser (grid) regularly behind) from dust and animal hair to improve heat transfer.
- 🚪 Make sure the door seals are tightly sealed to prevent a constant flow of warm air.
- 🌡️ Do not install the refrigerator near heating appliances or in direct sunlight.
⚠️ Attention: Specifications and refrigerant requirements may vary depending on environmental standards and models. Always check the manufacturer's technical documentation before starting work.
Frequently asked questions (FAQ)
Is it possible to replace a copper capillary tube with an aluminum one?
It is strictly not recommended. Aluminum and copper have different coefficients of thermal expansion and electrochemical potentials. This will lead to rapid corrosion at the connection and possible leakage. Use only copper tubes with similar parameters.
Why does the refrigerator not freeze well after replacing the tube?
Most likely, the refrigerant dosage was violated or air/power remained in the system due to poor evacuation. It is also possible that the length or diameter of the new tube does not correspond to the original specifications, which upsets the pressure balance.
How to determine that it is the capillary that is clogged, and not the filter?
Often it is the filter-drier, which is located in front of the capillary, that becomes clogged. If, when the tube is disconnected from the filter, there is a strong pressure of gas, but air does not pass through the capillary itself, this is the problem. If the filter is clean, then the channel itself is clogged.
Is it necessary to change the compressor when replacing the capillary tube?
Not necessary if the compressor is working properly and has not been damaged by water hammer or overheating. However, if the system was open for a long time, moisture could get into the oil, which requires flushing the system or replacing the compressor oil.