A breakdown of the heat removal system in the refrigerator often leaves the owner with a difficult choice: call a technician or try to fix the problem independently. Capillary tube is one of the key elements of the refrigeration circuit, ensuring throttling of the refrigerant and its transition from liquid to gaseous state. It is here that a sharp drop in pressure occurs, necessary for effective boiling of freon in the evaporator.
If you notice that the refrigerator has stopped freezing, and there is no characteristic heating on the back grill, or an obvious gas leak is detected, you may need to replace or solder this unit. Repairing a capillary tube - process technically complex, requiring not only theoretical knowledge, but also specific equipment. Without the tightness of the system, the refrigerator will not work, so the quality of the connection comes to the fore here.
Before taking active steps, you need to understand that the work is carried out with a closed circuit under pressure. Any mistake in soldering can lead to a repeat leak or, worse, damage to the compressor. In this article we will look in detail at how to properly prepare the system, solder copper connections and carry out vacuuming to return your unit to functionality.
Diagnostics of capillary system faults
The first step in any repair is an accurate diagnosis. Clogged capillary tube or its mechanical damage manifests itself in different ways, and it is important not to confuse the symptoms with a compressor or thermostat failure. Often equipment owners are faced with a situation where the motor-compressor runs continuously, but there is no cold in the chambers. This may indicate that the refrigerant is not circulating through the circuit due to an ice or oil plug.
In the event of a leak, which often occurs at solder points or due to corrosion, the pressure in the system drops to atmospheric pressure. If you pierce the process plug and gas comes out with a hiss, the system is sealed, but clogged. If air is sucked inside or there is silence, there is a violation of the tightness. Visual inspection Often it helps to find oil stains on the inner surface of the refrigerator, which indicate the location of the freon exit.
⚠️ Attention: Never try to clean the capillary tube by blowing with your mouth or a compressor indiscriminately systems. This can drive moisture or dirt deeper into the filter drier, making repairs impossible without a complete refill.
For accurate diagnosis, technicians use a pressure gauge station. The connection allows you to see the suction and discharge pressure. If there is a blockage, the pressure on the suction side will be lower than normal, and on the discharge side will be higher. If the system is empty, the pressure gauges will show atmospheric pressure. Only after making sure of the nature of the malfunction can you plan further actions to replace the tube.
Necessary tools and materials
The quality of the work directly depends on the preparation. In order to solder the capillary tube refrigerator, an ordinary home craftsman's kit will not be enough. You will need specialized equipment for working with non-ferrous metals and refrigerants. The main tool will be a gas torch running on a mixture of propane and oxygen or acetylene, since the melting point of copper is high.
In addition to the fire source, it is critical to have a vacuum pump on hand. It is necessary to remove air and moisture from the circuit before refueling. Residual moisture in the system will turn into ice and clog the capillary again, reducing all efforts to zero. You will also need a soldering kit, including solder (usually containing silver) and flux, although for copper, flame soldering without flux is often used if the tubes are clean.
The list of required equipment is as follows:
- 🔥 Gas torch with cylinder (oxygen-propane or acetylene).
- 💨 Vacuum pump and pressure gauge station.
- ✂️ Copper pipe cutter and roller (if required).
- 🧪 New filter drier and a piece of copper pipe.
- ⚖️ Scales for weighing the refrigerant when refilling.
Don't forget about personal protective equipment. Flame temperature The burner reaches thousands of degrees, and copper holds heat for a long time. It is necessary to work in heat-resistant gloves and safety glasses. Also make sure that the room is well ventilated, as heating residual oil or flux can release harmful substances.
Dismantling the old system and preparing the tubes
The repair process begins with freeing up the workplace and access to technical components. If your refrigerator has a foamed evaporator or a back wall hidden by foam, repairs are complicated by the need to open the case. However, if we are talking about replacing a filter or a section of tube on the visible part (usually the back), the task becomes simpler. The first step is to bleed off the remaining refrigerant, if it is still there, by making a neat puncture in the process plug.
Next, you should unsolder the old filter-drier and the capillary tube itself from the condenser and evaporator. Heating the connection it should be uniform. Do not heat only one side, otherwise the solder will not spread over the entire perimeter. When the joint is heated to cherry color, gently pull the parts in different directions. It is better not to reuse an old filter-drier; it is replaced with a new one whenever the circuit is opened.
Preparation of new tubes requires special care. Copper must be clean, without oxides or dents. If you are using a coil, straighten the desired section. The ends of the tubes that will be inserted into each other must be cleaned with fine sandpaper or a special brush until shiny. The gap between the tubes When soldering, it should be minimal, but sufficient for solder to flow in (capillary effect).
⚠️ Attention: When soldering old parts, make sure that the open flame did not reach the lacquer coating of the case or plastic elements. Use a sheet of non-flammable material (asbestos, metal) as a screen.
Technology for soldering copper connections
The most critical stage is the creation of a new hermetic connection. Soldering the capillary tube performed end-to-end or in a socket. The second option is more reliable and easier to implement at home. Insert one tube into the other with a little force so that they stick to each other. The seating depth should be approximately 5-10 mm.
Heat the connection with a torch flame, moving it around the tubes to heat them evenly. Do not point the flame directly at the solder - it should melt from the heat of the hot metal of the tubes. Once the copper reaches the desired temperature, touch the solder rod to the joint. If the temperature is selected correctly, the solder itself will flow into the gap, filling it completely.
For different tube diameters and types of solder, the temperature regime may differ. Below is a reference table of parameters:
| Connection type | Tube diameter (mm) | Solder type | Melting temperature (°C) |
|---|---|---|---|
| Copper-Copper | 6-10 | Phosphorus-Copper | 700-800 |
| Copper-Brass | 6-10 | Silver (30%+) | 750-850 |
| Steel-Copper | 6-10 | Silver (40%+) | 800-900 |
| Aluminum | Any | Special. solder for Al | 450-550 |
After the solder has flowed into the joint, remove the burner and let the tubes cool naturally. Under no circumstances cool the soldering area with water or a damp cloth - a sharp temperature change will create microcracks in the crystal lattice of the metal, and after a while a leak will appear here again. The seam should be smooth, without sagging or cavities.
☑️ Control of soldering quality
Evacuation and refrigerant charging
Simply soldering the tube is not enough. Air and moisture that were there during soldering and replacement of parts always remain inside the refrigeration circuit. The air contains nitrogen, which does not condense and creates excess pressure, and the moisture freezes in the capillary. Therefore, stage evacuation is mandatory. Connect the vacuum pump to the process connection and turn it on.
The pumping process should last at least 30-40 minutes, and for systems with a large volume it is better to increase the time to an hour. The low pressure gauge should show a value in high vacuum (about -1 bar or 29.9 inHg). This will allow all the moisture from the compressor oil and tube walls to boil away. Only after reaching a vacuum can you close the valve and turn off the pump.
Filling the refrigerator with refrigerant is done strictly by weight. On the back wall of the unit (on the nameplate) the number of grams required for your model is indicated. Use electronic scales, place a cylinder with freon on them and control the mass of pumped gas. Refilling or underfilling will lead to incorrect operation: the compressor will work with overload or will not be able to reach the desired temperature.
Why you can’t refill "on eye"?
The amount of refrigerant is calculated by engineers to the nearest gram. Excess freon will fill the evaporator with liquid, and the compressor may suffer a water hammer, which will lead to its instant failure. A lack of freon will cause overheating of the compressor and insufficient cooling.
Checking tightness and starting
The final stage is checking the work performed for tightness. Even a microscopic hole will cause the refrigerator to stop freezing again after a month or two. There are several verification methods. The simplest is a soap solution. Apply thick foam to all solder joints and observe. If bubbles appear, it means the connection is leaky and requires rework.
A more professional method involves using nitrogen under pressure. The circuit is filled with nitrogen to 10-15 atmospheres and left for a day, monitoring the pressure gauge readings. If the arrow does not move, the system is sealed. After checking, the nitrogen is bled off, evacuation is done again, and only then the working refrigerant is charged.
After starting the refrigerator, let it work for 2-3 hours without loading food. Check the temperature in the chambers, the absence of ice freezing in the wrong places and the uniform heating of the condenser grid. If all parameters are normal, we can consider repair of the capillary tube successfully completed.
⚠️ Attention: Technical characteristics of refrigerants and safety requirements may change. Always check the current technical documentation of the manufacturer of your refrigerator before starting work.
Is it possible to solder a capillary tube with ordinary tin solder?
No, it is not possible. Conventional tin-lead solder has a low melting point and insufficient strength. In a refrigerator system, pressure and temperature can fluctuate, causing the seam to fail. Use only hard solders (silver or copper-phosphorus).
Do you need to change the filter drier when soldering?
Yes, definitely. The filter drier is a disposable element. When the circuit is opened, it instantly absorbs moisture from the air and loses its properties. Installing an old filter will negate all evacuation efforts.
What gas is best to use for copper soldering?
For high-quality copper soldering, a mixture of oxygen and propane (or acetylene) is best suited. Oxygen-fuel burners produce a higher temperature and a cleaner flame, which ensures better weld quality compared to conventional gas cartridges.
What to do if the refrigerator does not freeze after soldering?
Most likely, there is a blockage, moisture, or a leak in the system. It is necessary to bleed off the gas again, replace the filter-drier, carry out a long evacuation and check the seams for leaks with a soap solution.