Failure of the refrigerant circulation system is one of the most difficult malfunctions that the owner of household appliances may encounter. When capillary tube clogs with oil breakdown products or ice plug, the refrigerator stops freezing, and the compressor works non-stop, trying to compensate for the lack of cold. This part is the heart of the system, regulating the supply of freon to the evaporator, and its replacement requires high precision and special skills.
Many craftsmen recommend changing the entire circuit, but experience shows that a competent one replacement of the capillary can bring the unit back to life for many years. It is important to understand that the process requires not only technical knowledge, but also the presence of specialized equipment, such as a vacuum pump and a pressure gauge station. Without these tools, it is almost impossible to carry out high-quality repairs that meet factory standards.
In this article we will analyze all stages of the work: from diagnosing the blockage to final charging with refrigerant. You will learn how to correctly calculate the length of a new tube, why you can’t just take a piece of copper by eye, and what mistakes most often lead to repeated breakdown of the compressor. Compliance with technology is the only guarantee that your refrigerator will again enjoy a stable temperature.
Diagnostics of blockages and equipment preparation
Before proceeding with dismantling, you need to make sure that the problem lies precisely in capillary expander. Often the symptoms of a clogged tube are confused with a freon leak or a thermostat malfunction. If, when the compressor is running, the condenser (grid at the back) only heats up half or remains cold, and gurgling is heard in the evaporator or, conversely, complete silence, this is a sure sign hydraulic blockage.
To carry out the work, you will need to assemble a full set of tools. You should not skimp on consumables, since the quality of copper directly affects the reliability of the connection. There should be no moisture remaining in the system, so the use of nitrogen during soldering and evacuation are mandatory steps, ignoring which will lead to the formation of acids inside the circuit.
⚠️ Attention: Before starting any work with the pipes, make sure that the refrigerant is completely vented in a well-ventilated area. Residual pressure in the system can lead to oil splashing or eye injury.
List of necessary equipment for replacement:
- 🔧 Pipe cutter and a set of flaring tubes (diameter 6 mm and 8 mm).
- 🔥 Burner (gas or oxygen-acetylene) with solder and flux.
- 📏 Manometer station and nitrogen cylinder for purging.
- ⚙️ Vacuum pump and scales for refrigerant charging.
After preparing the instruments, you should disconnect the refrigerator from the network and get access to the motor-compressor. Modern models often require removing the rear protective panel. If you are changing the capillary tube for the first time, be prepared for the fact that the process may take several hours, including time for the solder joints to cool down.
Removing the old capillary tube
The process of removing the faulty part begins with disconnecting the condenser and filter drier. The capillary tube is usually sealed into the filter on one side and into the evaporator or heat exchanger on the other. When desoldering, it is important not to overheat adjacent elements, especially if there is a suction line nearby suction line.
Often a situation arises when the tube sticks to the evaporator body or freezes into the polyurethane foam insulation. In such cases, mechanical pulling can damage the thin walls of the evaporator, leading to costly repairs or disposal of the equipment. Experienced craftsmen use the method of “burning out” or careful jointing to free the line.
If the tube is pulled through the channel in insulation and does not give in, sometimes it is easier to leave the old piece inside, cutting it off at the inlet and outlet, and lay a new line along the outside of the unit. This is less aesthetically pleasing, but maintains the integrity of the thermal insulation, which is critical for energy efficiency.
Key points when dismantling:
- ❄️ Gently heat the solder joints, avoiding oxidation of the copper.
- 🛑 Do not use excessive force when removing, so as not to deform the evaporator.
- 🧹 Immediately close the open ends of the tubes with plugs to prevent dust from entering.
After removing the old part, carefully inspect the filter drier. If it turns black or shows signs of corrosion, it must be replaced. The filter retains moisture and solid particles, and reusing the old element will negate all efforts to clean the system.
Selection and calculation of the length of a new capillary
The most critical stage of repair is determining the parameters of the new tube. The capillary acts as a choke, creating resistance to the refrigerant flow. If the resistance is too high, the performance of the refrigerator will drop, and if it is too small, liquid freon may enter the compressor, causing water hammer. The length and internal diameter of the tube are selected depending on the power of the compressor, the type of refrigerant (R134a, R600a, R12) and the design of the evaporator. Standard diameters range from 0.6 to 0.9 mm. Using a tube with the wrong diameter is a gross mistake leading to unstable operation. water hammer.
The length and internal diameter of the tube are selected depending on the power of the compressor, the type of refrigerant (R134a, R600a, R12) and the design of the evaporator. Standard diameters range from 0.6 to 0.9 mm. Using a tube with the wrong diameter is a serious mistake leading to unstable operation.
Table of approximate lengths for different refrigerants
For R134a, the length is usually 2.5-3.5 meters, for R600a - 4-6 meters, for the old R12 - 2-3 meters. The exact values depend on the internal diameter of the selected tube.
To accurately select the length, they often use the method of comparison with a factory sample or calculation using the tables of compressor manufacturers. If there is no original tube, the length is determined experimentally by measuring the suction pressure and current consumption when operating on a test bench.
| Refrigerant type | Inner diameter (mm) | Approximate length (m) | Features |
|---|---|---|---|
| R134a | 0.71 - 0.85 | 2.5 - 4.0 | High operating pressure |
| R600a | 0.60 - 0.75 | 4.0 - 6.5 | Explosive, low charge |
| R12 (old) | 0.66 - 0.80 | 2.0 - 3.5 | Compatible with mineral oil |
When purchasing material, pay attention to state of copper. The tube must be annealed (soft), clean inside and out. The use of hard, unannealed copper will lead to difficulties during rolling and possible cracking at bends.
Technology for installing and soldering connections
Installation of a new line requires cleanliness. The inner surface of the tubes must be free of oxides and chips. Before soldering, the ends of the tubes and fittings must be cleaned with fine sandpaper to a shine, ensuring ideal adhesion of the solder to the metal.
The soldering process is performed using flux (borax) and silver or copper-phosphorus solder. It is important to heat the connection evenly on all sides. If you use a torch with an open flame, make sure that the fire does not fall directly on the solder - the connection should melt, not the solder itself from the flame.
☑️ Soldering quality control
The capillary tube is often welded to the return line (suction) for heat exchange. This prevents the formation of condensation on the suction and increases the efficiency of the cycle. The length of the heat exchange section is usually 15-20 cm, and it must be tightly pressed or soldered along the entire length of the contact.
After soldering all connections, the system is assembled into a single circuit. At this stage, it is important to check the geometry of the pipe routing. They should not touch moving parts of the compressor or sharp edges of the housing, so that vibration does not lead to chafing and a new leak in a short time.
Nitrogen purging and evacuation of the system
One of the most important stages is cleaning the system from moisture and residual air. Moisture in the system is the main enemy, which at low temperatures turns into ice, clogging the capillary, and in combination with oil and freon forms aggressive acids that corrode the compressor windings.
The system is purged with dry nitrogen under a pressure of 10-15 atmospheres. Nitrogen pushes out excess moisture and checks the system for gross leaks. If the pressure remains stable for 10-15 minutes, you can proceed to vacuuming.
⚠️ Attention: Never use regular air from a compressor or, especially, oxygen for purging. Moisture and oil in compressed air are guaranteed to cause system failure within a few months.
Evacuation is carried out with a vacuum pump for 30-60 minutes. The residual pressure should be no more than 50-100 microns (or 0.1 atm if there is no micron pressure gauge). This allows you to remove water that boils and evaporates at low pressure even at room temperature.
Useful advice: If after evacuation the system does not hold a vacuum (the pressure gauge needle creeps up), it means that there is a microcrack in the soldering or a poor-quality seam. Repeated evacuation without eliminating the leak is pointless.
Filling with refrigerant and checking operation
The final stage is charging the system with refrigerant. The amount of freon is strictly regulated by the manufacturer and is indicated on the compressor nameplate or inside the refrigeration chamber. For accuracy, use electronic scales, since an error of 5-10 grams can significantly affect the operation of the unit.
It is better to refill in the liquid phase (by turning the container over) through a filter drier or a special valve, controlling the suction pressure. For different refrigerants, the suction pressure will be different: for R134a it is lower than for R12, and for R600a it is even lower.
After refueling, turn on the refrigerator and let it run for 15-20 minutes. Check the evaporator temperature (should be uniform), condenser temperature (heats up to 2/3 of the height) and compressor current consumption. The current should not exceed the rated current indicated on the engine tag.
If all parameters are normal, the solder joints on the suction line can be finally soldered (if fittings were used). Tightness is the key to durability. Do not forget to install a new filter drier before final sealing, if this has not been done previously.
Possible problems after replacement
Even if the technology is followed, nuances may arise. If the refrigerator freezes poorly, perhaps the length of the capillary is chosen incorrectly or there is air left in the system. If the compressor gets very hot and turns off by the thermal relay, there is likely an overflow of freon or a clogged filter.
Sometimes an “oil plug” occurs when oil accumulates in the evaporator and does not return to the compressor, creating a false feeling of blockage. In such cases, careful heating of the evaporator or a short-term increase in pressure to push the oil helps.
Monitor the temperature of the compressor housing. If it is hotter than normal (above 90-100°C), this may indicate "overheating" operation due to improper throttling. In the long term, this will lead to combustion of the windings.
Is it possible to replace the capillary without a vacuum pump?
Theoretically, some craftsmen use the method of “squeezing out” the air with the refrigerant itself, but this is extremely unreliable. Residual moisture will quickly damage the system. For high-quality repairs, a vacuum pump is required.
Which solder is best to use for soldering?
For copper connections in refrigeration technology, copper-phosphorus solder (BCuP), which does not require flux, or silver solder with a silver content of 5% or more is optimal for increased strength and elasticity seam.
Why does the compressor inlet freeze after replacing the capillary?
This is a sign that the capillary is too long or the diameter is too small, or there is an excess of freon in the system. The liquid refrigerant does not have time to evaporate and enters the compressor, which is dangerous for its mechanical part.
Is it necessary to flush the system with oil after the compressor burns out?
Yes, if the capillary is replaced after the engine has burned out, the system must be flushed with a special solvent or freon under pressure to remove combustion products and acid, otherwise the new compressor will burn out in a couple of months.