A modern household refrigerator is a complex a thermodynamic system in which each element plays a critical role in maintaining low temperatures. One of the key components, but often hidden from the user’s eyes, is capillary tube. It is this thin copper channel that is responsible for throttling the refrigerant, creating a pressure difference between the condenser and the evaporator. Understanding where the capillary tube of the refrigerator is located is necessary not so much for daily operation as for competent diagnostics of malfunctions or carrying out professional repairs.
The location of this element directly depends on the design of a particular model Indesit, LG or Atlant. In some cases it is laid along the perimeter of the housing, in others it is integrated into the evaporation unit. If you hear an uncharacteristic hum or notice that the unit has stopped freezing, knowledge of the architecture of the cooling system will help you quickly navigate the situation. However, it is worth remembering that independent intervention in a sealed circuit without special equipment often leads to the final failure of the equipment.
In this article we will analyze in detail the anatomy of the refrigeration circuit, indicate the exact locations of the tube in various types of structures and discuss typical problems associated with this unit. You will learn how to distinguish a capillary from other lines and why its length and diameter are strictly calculated by engineers. The standard internal diameter of the tube is only 0.6–0.9 mm, which makes it extremely sensitive to any contamination.
The principle of operation and the role of the capillary system
The capillary tube, often simply called a capillary, acts as a throttle in the refrigeration cycle. Its task is to create high resistance to the flow of freon, due to which high pressure is maintained on one side (from the condenser side), and low pressure on the other (from the evaporator side). Without this pressure difference, the refrigerant would not be able to effectively boil at low temperatures, removing heat from the chambers.
The process occurs as follows: liquid freon under high pressure flows from the condenser into a narrow channel. As the liquid passes through a long spiral or straight section, it experiences strong friction against the walls. This leads to a sharp drop in outlet pressure, and the refrigerant turns into a vapor-liquid mixture, which then enters the evaporator. Throttling —this is the name of this physical process—is the heart of the operation of any compression refrigerator.
It is important to note that the dimensions of the capillary not random. The length can vary from 2 to 4 meters, and the diameter is selected with an accuracy of tenths of a millimeter depending on the power compressor and the type of refrigerant used (R134a, R600a). Replacing this element “by eye” without calculating the hydraulic resistance will lead to incorrect operation of the entire system.
⚠️ Attention: An attempt to clean the capillary tube by blowing nitrogen at high pressure without preliminary diagnostics can lead to rupture of thin-walled evaporator elements inside the housing.
Typical location in various refrigerator models
The answer to the question of where the capillary tube is located depends on the year of manufacture and brand of your device. In classic Soviet-made two-chamber models and early imported versions (Biryusa, early Zanussi), the capillary was often wound directly onto the suction pipeline (return line) or attached with clamps to it. This was done to organize heat exchange: warm gas from the evaporator heated cold freon before entering the compressor, preventing liquid from entering the cylinder.
In modern units with a system No Frost the situation is different. Here, the capillary tube is most often mounted directly into the foamed evaporator or laid in a special groove along the inner wall of the freezer. It is almost impossible to visually detect it in such models without opening the thermal insulation. It may be hidden under a layer of aluminum foil or plastic protection.
- 🔍 Rear wall: In older models, the tube often snakes along the rear metal grille inside the cabinet.
- 🔍 Door perimeter: In some designs, part of the capillary or associated door perimeter heating tube runs inside seal.
- 🔍 Evaporator block: In full know frost systems, the capillary is integrated into the aluminum evaporator box, hidden behind a plastic panel.
If you are looking for a place to solder the capillary for diagnostics, you need to look into the engine compartment. It is there, next to compressor, that the copper tube of the capacitor is connected to the beginning of the capillary section. Often, a filter drier is installed in this place - a cylindrical copper element, which is an obligatory companion of the capillary.
Visual identification: how to distinguish a capillary from other tubes
For a master diagnostician, visually distinguishing lines is not difficult, but it is easy for a novice in the engine compartment get confused. There are usually three types of piping present: discharge line (hot), suction line (cold, thick) and capillary line (thin). The capillary always has a significantly smaller diameter compared to the tubes going to the compressor.
Pay attention to the filter drier. The capillary tube is almost always soldered into this filter on one side. The filter is a copper cylinder about 10-15 cm long. Once you find it, you will immediately determine where the element you are looking for begins. A tube from the condenser will enter on the other side of the filter, and a thin capillary will exit from the opposite side.
Why is the capillary often covered with varnish or paint?
In the factory, the junction of the capillary with the filter and the initial section itself are often coated with heat-resistant varnish or paint to seal and protect against corrosion. This also helps to visually highlight the high pressure area.
Another sign is temperature. In a working refrigerator, the condenser tube (before the filter) will be hot, and the tube after the evaporator (suction) will be cold or covered with frost. The capillary itself at the initial point may be warm, but as it moves away from the filter, its temperature will drop, as the process of expansion and cooling of the gas begins.
Symptoms of blockages and malfunctions of the capillary tract
The most common problem associated with this unit is clogging. Since the diameter of the channel is extremely small, even a microscopic particle of oxide, dust or a clot of oil can block the freon current. There is also a so-called “ice plug”, when moisture that has entered the system freezes in a narrow place in the capillary, blocking circulation.
How can you tell that the problem is in the capillary tube? Symptoms may be the following:
- ❄️ Lack of cold: The compressor runs constantly, but the chambers are warm. The evaporator is cold only at the entrance or completely warm.
- 🔊 Sound change: The engine hums more strained, trying to push freon through an obstacle, or, conversely, works quieter than usual due to the lack of load.
- 💧 Condensation: On frost or drops of moisture may appear in the filter tube or at the entrance of the capillary, which indicates a sharp temperature change due to a stop in flow.
⚠️ Attention: If after a long stop the refrigerator turns on, but does not cool, and the capillary is pinched - this may be a sign of blockage with corrosion products formed during downtime.
Diagnosis of blockages is often carried out by exclusion. If the compressor is working properly, there are no freon leaks (gas in the system), and there is no cold, the throttle element is most likely to blame. For accurate confirmation, a pressure gauge station is required: when turned on, the discharge arrow quickly goes into the red zone, and at suction it shows a deep vacuum.
Do-it-yourself replacement and repair technology
Repair of a capillary system is a complex technical operation that requires special tools: rolling, pipe cutter, torch and vacuum pump. Simply replacing a tube of the “same length” often does not work, since the hydraulic resistance of the new tube may differ from the factory one. Therefore, professionals often change the capillary together with the filter-drier, carefully selecting the parameters.
The replacement process is as follows:
1. Pumping out residual refrigerant from the system.
2. Dismantling the old capillary (often it is not removed from the foamed area, but simply cut off and left inside, connecting a new one in parallel or to the free end, if the design allows).
3. Soldering a new filter-drier and a new piece of copper tube.
4. Evacuate the system for 30-60 minutes to remove moisture.
5. Refilling with an accurate dosage of freon according to the scale.
☑️ Checklist before replacing the capillary
It is important to maintain cleanliness when soldering. The ingress of tin into the channel or the formation of oxides during heating without purging with nitrogen is guaranteed to lead to a new blockage in the near future. Using nitrogen when soldering is a mandatory rule for high-quality repairs.
Table: Comparison of capillary characteristics for different refrigerants
The parameters of the tube directly depend on the type of gas. Using a tube designed for R134a in a system with R600a (isobutane) will result in incorrect operation or damage to the compressor. Below are average data to understand the differences.
| Refrigerant type | Typical internal diameter (mm) | Typical length (m) | Features |
|---|---|---|---|
| R134a | 0.66 - 0.70 | 2.5 - 3.5 | Requires synthetic oil, sensitive to moisture |
| R600a | 0.75 - 0.85 | 2.0 - 3.0 | Explosive, requires shorter length due to gas properties |
| R12 (old) | 0.60 - 0.65 | 3.0 - 4.5 | Outdated freon, tubes are often longer |
As can be seen from the table, the difference in diameters can be tenths millimeters, but this critically affects throughput. When doing your own repairs, it is extremely difficult to find an analogue without the manufacturer's specifications.
Prevention and recommendations for operation
Is it possible to prevent clogging of the capillary tube? Since the main cause of problems is moisture and oil breakdown products, the key factor is the health of the compressor and timely replacement of the filter. If your refrigerator Liebherr or Bosch has been in operation for more than 10 years, the oil in the system could lose its properties and begin to oxidize, forming slag.
Do not allow equipment to remain idle for long periods of time in unheated rooms. Condensation inside the tubes during defrosting and subsequent freezing is a common cause of ice jams. If you plan not to use the refrigerator for a long time, it is better to leave it turned on at a minimum or preserve it according to the rules, purged with nitrogen (which is impossible in everyday life).
Monitor the temperature in the room. Operating a refrigerator at temperatures below +10°C or above +35°C creates extreme loads on the system, which can accelerate oil degradation and clogging of narrow capillary channels.
Frequently asked questions (FAQ)
Is it possible to clean the capillary tube without disassembling the refrigerator?
There is a method of “pushing” with nitrogen or a special solvent, but it is effective only for fresh, soft blockages (oil plug). If copper dust or solid oxides have formed in the system, cleaning is impossible - a section or the entire capillary must be replaced. In addition, this procedure still requires technological equipment.
Why did the refrigerator begin to freeze worse after replacing the capillary?
Most likely, the length or diameter of the new tube was damaged. A capillary that is too long will create excess resistance and performance will drop. Too short will not provide the required throttling, and the freon will not have time to completely transform into gas, which can lead to water hammer in the compressor.
Where to buy a capillary tube of the required diameter?
Sold in spare parts stores for refrigeration equipment in coils (usually 500g or 1kg). It is important to purchase tubing with an accurate internal diameter (ID) because the outer diameter (OD) can vary depending on wall thickness. Standard sizes: 0.66, 0.70, 0.75, 0.80 mm.
The capillary tube freezes - what to do?
If you see frost at the capillary inlet to the evaporator (after the filter), this often indicates the presence of moisture in the system. Moisture freezes in a narrow place, blocking the passage. It can only be treated by completely evacuating the system for a long time (up to 2-3 hours) and replacing the filter-drier with a fresh one.