In modern household appliances, each element performs a strictly defined function, ensuring stable and safe operation of the entire unit. One of the key components, without which it is impossible to cool products, is refrigerator capillary tube. Many owners of equipment do not even suspect its existence until the moment of breakdown, but it is this unit that is responsible for creating the necessary pressure drop in the system.
The principle of operation of a seemingly simple copper element is based on the laws of thermodynamics and the physics of liquids. Understanding why is a capillary tube needed?will help you quickly diagnose the problem and avoid costly repairs at a service center. In this article we will analyze in detail the design of the throttle, its role in the refrigerant cycle and methods for restoring functionality.
Impaired circulation of freon is always a signal of a problem in the circuit, and most often the culprit is the throttle assembly. Capillary tube is susceptible to blockages, mechanical damage and kinks, which requires the intervention of a specialist or competent home repairs. Let's look at exactly how this element works and why it is called the heart of the cooling system.
Basic operating principle and purpose of the throttle
The main task of this unit is to create hydraulic resistance to the movement of the refrigerant. The compressor pumps freon under high pressure, turning it into a hot liquid, which then flows into the condenser. It is capillary tube that divides the system into two zones: high and low pressure, providing the necessary difference for evaporation.
Passing through a narrow channel with a diameter of less than a millimeter, the liquid refrigerant expands sharply. At this moment, a sharp drop in temperature and pressure occurs, which turns the liquid into vapor. This process is called throttling, and without it, effective cold release in the chamber is impossible.
The dimensions of the element directly affect the performance of the refrigerator. A tube that is too long or narrow will create excess resistance, overloading the compressor, and a short tube will not provide the required drop. Engineers calculate the parameters capillary tube individually for each model, taking into account the volume of the chambers and the type of refrigerant used.
Design and technical characteristics
Structurally, the element is a long copper tube of small diameter. The standard length varies from 1.5 to 4.5 meters, and the internal diameter ranges from 0.6 to 1.5 millimeters. This geometry allows you to create the necessary resistance to the flow of freon without the use of moving mechanical parts.
The material is exclusively copper due to its high thermal conductivity and ductility. However, copper is soft, therefore capillary tube often requires protection from external influences. In modern models, it can be placed in an insulating sleeve or integrated into the evaporator.
An important parameter is manufacturing accuracy. Even a microscopic change in diameter within a channel can upset the balance of the system. Below is a table with typical characteristics for different types of household appliances:
| Refrigerator type | Diameter (mm) | Length (m) | Pressure (bar) |
|---|---|---|---|
| Single-chamber | 0,66 - 0,70 | 2,5 - 3,0 | 8 - 10 |
| Double-chamber (No Frost) | 0,70 - 0,75 | 3,0 - 4,0 | 10 - 12 |
| Industrial | 0,80 - 1,20 | 4,0 - 6,0 | 14 - 16 |
| Automotive | 0,50 - 0,60 | 1,5 - 2,0 | 6 - 8 |
It is worth noting that refrigerator capillary tube often passes through the heat exchanger where it contacts with suction tube. This allows you to cool the freon before entering the evaporator and heat the vapors before the compressor, increasing the overall efficiency of the system.
Symptoms of blockage and system malfunctions
Determine what capillary tube stopped working its function can be determined by a number of characteristic features. Most often, the problem lies in partial or complete blockage of the channel with oil breakdown products or moisture. Moisture is especially dangerous, since at low temperatures it turns into an ice plug.
The first sign is that the temperature regimes are not operating correctly. The refrigerator may work non-stop, trying to gain temperature, or, conversely, turn on rarely, but not cool the food. If you notice that capillary tube the area after the filter drier is covered with frost, and then it is dry, this is a sure sign (of blockage).
⚠️ Attention: An attempt to break through the blockage by increasing the pressure with a compressor can lead to rupture of the tubes or damage to the motor windings. Use only approved cleaning methods.
Among the main symptoms are also:
- 🔊 Loud humming or knocking when starting the compressor, indicating that it is working on a vacuum.
- ❄️ Lack of cold in one of the chambers with the motor running.
- 🔥 Strong heating of the capacitor array only in the initial part.
- 📉 The compressor current consumption drops below the nominal values.
Diagnostics should be carried out comprehensively. Simply replacing a part without eliminating the cause of the blockage (for example, moisture in the system) is pointless - the problem will return in a few weeks.
Diagnostics: how to check the patency of the tube
Before starting any work, you need to make sure that the problem is in the throttle, and not in a freon leak or a compressor malfunction. To check, you will need a pressure gauge station and a source of compressed air or nitrogen. Capillary tube should provide resistance, but allow gas to pass through.
The testing process begins by disconnecting the refrigerator from the network and accessing the rear panel. The technician cuts off the tube at the inlet to the evaporator and connects a pressure gauge. When purging with nitrogen under a pressure of 10-15 atmospheres, the throughput of the channel can be assessed. If the pressure does not drop or drops too slowly, there is a blockage.
☑️ Diagnostics of the cooling system
Visual inspection of the entire length of the copper line is required. Often in places of bends, especially in No Frost freezers, the metal becomes thinner or flattened.
If purging shows a complete lack of gas passage, it is necessary to use special solvent liquids or the method of soaking in oil followed by purging. However, in 80% of cases, the element needs to be replaced with a new one.
Technology for replacing a capillary tube
Replacement capillary tube is a complex process that requires special tools: a rolling machine, a burner, a vacuum pump and scales for charging freon. Doing it yourself without experience often leads to damage to the compressor or re-clogging.
The first step is dismantling the old part. It is necessary to carefully remove the tube from the filter drier and evaporator, being careful not to damage adjacent elements. Then a new tube of similar length and diameter is selected. Using the tube “by eye” is unacceptable.
The installation process includes the following steps:
- 🔧 Soldering in a new filter-drier (mandatory replacement when opening the circuit).
- 🔥 Hermetically sealed tube connections with evaporator.
- 💨 Thorough evacuation of the system for 30-40 minutes to remove moisture.
- ⚖️ Refilling with a strictly calculated amount of refrigerant according to the scale.
⚠️ Attention: Residual moisture in the system after replacing the tube will freeze in the new capillary after a few hours of operation. Evacuation is a critically important step that cannot be ignored.
Is it possible to use a tube from another refrigerator?
Using a tube from another model is possible only as a last resort and subject to an exact match of the internal diameter and length. A difference in length of more than 10 cm or in diameter of 0.1 mm will change the pressure in the system, which will lead to improper operation of the thermostat or freezing of the evaporator. It is better to use original spare parts or universal kits with the possibility of cutting.
Adjustment and tuning after replacement
After installing a new part and filling with freon, the system requires adjustment. Capillary tube selected according to calculated data, but real conditions (room temperature, compressor wear) may make adjustments. The technician must check the temperature of the suction tube.
Normally, the tube at the outlet of the evaporator (in front of the compressor) should be slightly cool, but not covered with frost. If it becomes overgrown with a “fur coat,” it means that too much freon has been pumped into the system or the throughput of the tube is high. If the tube is warm, there is not enough freon or the tube is longer than needed.
The debugging process takes from 1 to 3 hours of continuous operation of the refrigerator. At this time, readings from current clamps and pressure gauges are taken. Only after making sure that the parameters are stable can you seal the process pipe.
Modern inverter systems are even more sensitive to the condition of the throttle assembly. In them the capillary tube (mark used here for a unique fact) is often replaced by an electronic expansion valve, but in classic models the copper capillary remains the standard of reliability, provided it is installed correctly.
Frequently asked questions (FAQ)
Is it possible to clean the capillary tube without replacing it?
In some cases, blowing nitrogen under high pressure in the opposite direction or using special solvents. However, if the blockage is caused by oxidation of copper or moisture entering with the formation of acid, cleaning will only give a temporary effect. It is safer to replace the unit.
What diameter of the capillary tube should you choose if there is no original?
You cannot take the tube “at random”. It is necessary to select the closest analogue in terms of internal diameter. Length adjustment is allowed: if the diameter is slightly larger, the tube is lengthened, if less, it is shortened. The calculation is carried out using special equivalence tables.
Why does the refrigerator freeze but does not turn off after replacing the tube?
This may indicate an incorrect length of the installed tube (too much resistance), a freon leak, or a malfunction of the thermostat. It is also possible that during evacuation, all moisture was not removed, and a micro-plug formed.
How much does it cost to replace a capillary tube in the service?
The price consists of the cost of materials (tube, filter, freon) and the complexity of the work (access to the evaporator baked in polyurethane foam). On average, repairs cost 30-50% of the cost of a new refrigerator, which often makes it economically feasible.
Is it possible to use an aluminum tube instead of a copper one?
Absolutely not. Aluminum has different thermal conductivity, ductility and chemical resistance. The capillary tube must be made of copper or special alloys compatible with oil and freon. Aluminum quickly corrodes and bursts when vibrated.