Any a sudden breakdown of household appliances leaves the owner with a choice: call a technician or try to figure it out on his own. Capillary tube in the refrigerator is one of the key elements of the cooling system, the failure of which often leads to a complete lack of cold. Understanding its structure and principle of operation will help you more accurately diagnose the problem and make an informed decision on repairs.
During the operation of the compressor-condensing system, it is this thin element that provides the necessary pressure drop for the circulation of the refrigerant. If you notice that your Indesit or Atlant has stopped freezing, while the compressor is running without stopping, the reason may lie precisely in a violation of the patency of the capillary. Next, we will analyze in detail the physics of the process and methods for restoring the functionality of the unit.
Diagnostics of the cooling system requires careful attention to detail and compliance with safety precautions. The operating pressure in the system can reach 20 atmospheres, so any intervention requires special tools and knowledge. Ignoring this fact can lead not only to the final breakdown of the equipment, but also to injuries.
Purpose and principle of operation of the capillary
The main function of the capillary tube is to create hydraulic resistance for the flow of refrigerant. It divides the refrigerator circuit into two zones: a high pressure zone (after the compressor) and a low pressure zone (before the compressor). Without this element, efficient freon circulation heat removal from the chambers is impossible.
The operating principle is based on the physical effect of throttling. When high-pressure liquid refrigerant enters a narrow channel, its speed increases sharply and the pressure drops. As a result, part of the liquid instantly boils, turning into steam, which causes a sharp cooling of the flow. This process occurs immediately before entering the evaporator.
The length and internal diameter of the tube are selected by the manufacturer with high accuracy for each refrigerator model. For example, in models Stinol or Beko parameters may differ significantly from similar units in technology Liebherr. Changing the geometry of the channel upsets the balance of the system, making cooling impossible.
Design features and placement
The capillary is a copper tube of small diameter, usually from 0.6 to 2 millimeters. The element length varies from 1.5 to 4.5 meters, depending on the compressor power and the type of refrigerant. Copper was not chosen by chance: it has excellent thermal conductivity and ductility, which allows the tube to be laid in complex configurations.
In most household refrigerators, the capillary tube is soldered to the return circuit tube (suction line). This design solution is called a heat exchanger. It is necessary so that the liquid freon passing through the capillary is additionally cooled, and the freon vapors going from the evaporator to the compressor have time to warm up. This prevents the liquid fraction from entering the compressor, which could cause water hammer.
The location of the element depends on the type of defrosting system. In refrigerators with a No Frost system, the capillary is often hidden inside the thermal insulation or behind the body panels, which makes visual inspection difficult. In simpler models with a weeping evaporator, it may be partially visible on the rear wall of the unit.
Why copper?
Copper is resistant to corrosion inside the system, is easily soldered and does not react with compressor oil and refrigerants such as R134a or R600a.
Symptoms of blockage and malfunctions
You can determine the problem with the patency of the capillary tube by a number of characteristic signs. Most often, users are faced with a situation where the motor-compressor hums, trying to start, but there is no cold. This indicates that the system is clogged and freon cannot circulate.
There are two main types of blockage: oil blockage and ice blockage. An oil plug is formed due to thickening of the compressor lubricant, especially if the refrigerator has been idle for a long time or the wrong oil was used during a previous repair. Ice blockage occurs due to moisture entering the system, which freezes in the narrowest place of the capillary.
- 🧊 The compressor works constantly, but the temperature in the chambers does not drop below room temperature.
- 🔇 The refrigerator starts, runs for several minutes, then a click is heard and it turns off (the thermal relay).
- 🌡️ The freezer is working normally, but the refrigerator compartment is warm, or vice versa.
It is also worth paying attention to the condenser (grid at the back). If the compressor remains cold or only partially warms up while the compressor is running, this is a sure sign of a lack of refrigerant circulation. In good condition, the entire grill should be uniformly warm.
Causes of blockages
The main enemy of the refrigeration system is moisture. Even a minimal amount of water entering the circuit due to poor-quality repairs or due to depressurization can lead to serious consequences. Interacting with refrigerant and oil, water forms acids that corrode the compressor windings and ice crystals that block the capillary.
The second common cause is compressor wear products. During long-term operation, metal shavings, carbon deposits from burnt oil and other solid particles can migrate through the system. Passing through the filter-drier, they are delayed, but when the sorbent overflows or is destroyed, they enter the capillary tubecapillary tube
⚠️ Attention: Using the wrong refrigerant or oil during repairs can cause a chemical reaction, leading to the formation of resinous deposits, which are almost impossible to remove without completely replacing the pipelines.
In addition, the cause may be a manufacturing defect, for example, the presence of copper oxides inside the tube or poor-quality soldering, in which the solder blocked the flow area. Such defects usually appear in the first year of operation of the equipment.
Diagnostics and methods for cleaning the system
For accurate diagnostics, technicians use a pressure gauge station. By connecting the device to the process pipe, you can see negative pressure (vacuum) when the compressor is operating, which confirms the presence of a plug. If the pressure is normal, but there is no cold, the problem may be a freon leak.
There are several methods for clearing the blockage. The simplest, but not always effective, is capillary massage. The tube is carefully squeezed with blunt-nosed pliers in different places, trying to loosen the plug. However, this method only helps with fresh oil blockages.
A more reliable method is nitrogen purging. To do this, the system is unsoldered, a cylinder with dry nitrogen is connected and pressure is applied to 15-20 atmospheres. The gas flow pushes out foreign bodies. If the plug is icy, you can try to warm the capillary with a hair dryer, but this must be done extremely carefully so as not to damage the insulation and soldering.
☑️ Diagnostic tools
Replacing the capillary tube: step-by-step instructions
If cleaning does not help, a complete replacement of the element is required. This process is labor-intensive and requires a supply of copper tube of the required diameter and length. It is important to choose an analogue that is as close as possible in parameters to the original, otherwise the refrigerator will not work correctly.
First you need to dismantle the old capillary. To do this, carefully solder its ends from the condenser and evaporator. Often the tube is glued to the evaporator body, so it must be carefully removed so as not to damage the aluminum channels. After dismantling, measure the length and diameter of the old tube.
A new capillary is soldered in place of the old one. Particular attention is paid to the quality of soldering: the seam should be smooth, without solder deposits inside the tube. After installing a new element, the filter-drier must be replaced, since the old one is already saturated with moisture and will not be able to work effectively.
| Parameter | Standard value | Tolerable deviation |
|---|---|---|
| Inner diameter | 0.66 - 0.80 mm | ± 0.02 mm |
| Tube length | 2.5 - 4.0 m | ± 5 cm |
| Crimping pressure | 15 atm | Not less than 10 min |
| Residual pressure | less than 50 microns | Before charging |
Refrigerant charging and evacuation
After replacing the capillary and filter-drier, the system must be sealed and checked for leaks. To do this, the circuit is filled with nitrogen under pressure and left for several hours. If the pressure gauge shows a drop in pressure, it means there is a fistula or poor-quality soldering somewhere.
The next critical stage is evacuation. Using a vacuum pump, all air and moisture vapor are removed from the system. The pumping time depends on the pump power and the volume of the system, but is usually at least 30 minutes. Poor evacuation is guaranteed to lead to the re-formation of an ice plug.
Only after creating a deep vacuum is the refrigerant charged. The amount of freon is strictly regulated by the manufacturer and is indicated on the refrigerator tag. Overdosing or underfilling will lead to improper operation and increased energy consumption.
Prevention and recommendations for operation
To extend the life of the capillary system, frequent defrosting of the refrigerator should be avoided using a knife or sharp objects. Mechanical damage to the evaporator leads to moisture and air getting inside the circuit, which is the main cause of future problems.
It is also not recommended to install the refrigerator close to the wall. Impaired air circulation around the condenser leads to overheating of the system, increased pressure and accelerated aging of the compressor oil, which increases the risk of oil plugs.
If you plan to transport the refrigerator, this should only be done in a vertical position. An inclination of more than 40 degrees can lead to oil flowing into the refrigerant circuit, which will cause water hammer on first start-up or blockage of the capillary.
⚠️ Attention: After transporting in a horizontal position, the refrigerator must stand in a vertical position for at least 4-6 hours before turning on, so that the oil flows back into the compressor crankcase.
Frequently asked questions (FAQ)
Is it possible to clean the capillary tube without opening the system?
Unfortunately, it is impossible to effectively clean the capillary without access to it. Traditional methods like “heating with a hairdryer” or “tapping” have a very low success rate and only help in rare cases of fresh oil plugs. In 90% of cases, a full repair is required with filter replacement and evacuation.
How much does it cost to replace a capillary tube during service?
The cost of work varies depending on the model of the refrigerator and the region. The price usually includes the cost of materials (copper, freon, filter drier) and the work of the craftsman. On average, repairs cost 30-50% of the cost of a new refrigerator, which makes it economically feasible.
Why does the refrigerator freeze worse after replacing the capillary?
This may be due to incorrectly selected parameters of the new tube (diameter or length), poor-quality evacuation (moisture remains) or incorrect dosage of refrigerant. It is also possible that the compressor has residual output and does not create the required pressure.
Is it possible to use a capillary from another refrigerator?
It can be used, but only if the parameters (inner diameter and length) match the original ones. Installing an unsuitable capillary will lead to an imbalance in the system: either the compressor will work with overload, or the cooling capacity will drop to zero.