The appearance of puddles of oil under the refrigerator or the complete absence of cold when the compressor is running often indicates a violation of the tightness of the system. In 90% of cases, the problem lies in microcracks at the joints or in the body of the copper tubes through which the refrigerant circulates. Restoring the operation of the unit in such a situation requires soldering, which is one of the most important operations in the repair of climate control equipment.
Many self-taught craftsmen are afraid to take on this stage, considering it too difficult or dangerous, but with a theoretical basis and the right tool, the task becomes completely solvable. The key here is not just joining metal, but creating a seam that can withstand internal pressure and vibration for many years. Incorrectly performed work will lead to the re-release of freon and the need for expensive refilling.
Before taking active steps, you need to understand that soldering copper tubes requires compliance with strict safety rules and technological nuances. Copper has high thermal conductivity, which makes local heating difficult, and the thin walls of capillary tubes are easy to burn through with an inexperienced hand. In this article we will analyze all stages of the process: from preparing the work site to the final tightness check of the assembled system.
Necessary tools and materials for soldering
The quality of the connection directly depends on the equipment used. To operate, you will need a high temperature open flame source. The optimal choice would be gas burner with adjustable flame, operating on a propane-butane mixture or pure propane. The use of simple lighters or candles is unacceptable, since they are not capable of creating the temperature necessary to melt refractory solders.
The second critical element is solder. For refrigeration equipment, it is strictly forbidden to use tin-lead alloys (POS), which are used in electronics. They will not withstand the pressure in the system and may enter into a chemical reaction with the compressor oil. You need silver solder (with a silver content of 15% to 45%) or a copper-phosphorus alloy. The latter is good because it often does not require the use of additional flux when connecting copper to copper.
⚠️ Attention! Phosphorus-containing solders cannot be used for soldering steel parts (for example, compressor pipes), as they form a brittle joint that will quickly collapse under vibration. For a copper-steel joint, silver solder with flux is required.
You should also have a pipe cutter in your arsenal that ensures a strictly perpendicular cut without jams, and a set of needle files or sandpaper for cleaning. Do not forget about a fireproof mat and safety glasses, as splashes of hot metal or flux can cause injury.
Preparation of the system and removal of refrigerant
The first stage of work is to completely free the refrigeration circuit from residual gas. Even if the refrigerator does not work and seems empty, excess pressure remains inside. To discharge freon, you need to cut the thickest copper tube (usually the outlet from the compressor) and vent the gas in a well-ventilated area or outside.
After relieving the pressure, the faulty section is dismantled. If the crack is found in a straight section, the tube can simply be cut. If the damage is located near the evaporator body itself or in a hard-to-reach place, it may be necessary to unsolder the entire units. It is important to act carefully here so as not to damage adjacent elements.
Particular attention should be paid to preparing the edges. The soldering area must be perfectly clean. Oxides, dirt and remnants of old solder prevent the new metal from flowing. Cleaning is carried out until a characteristic copper sheen appears. If you use copper-phosphorus solder, mechanical stripping is often the only necessary preparatory action.
Where does the old freon go?
Freon released into the atmosphere harms the environment by destroying the ozone layer. On an industrial scale, it is necessarily collected in special cylinders, but in domestic conditions, during a single repair, the gas is simply released, which is less evil than producing a new refrigerator to replace a broken one.
Technology for connecting copper tubes
The soldering process itself requires a certain skill. A common mistake newbies make is trying to melt the solder with a torch directly above the flame. This is wrong. The metal should melt from the temperature of the heated tubes, and not from direct contact with the fire. The flame should be soft, restorative (blue with a yellow cone) so as not to burn the copper.
Heating should be done evenly, moving the flame around the joint. When the metal reaches the desired temperature (cherry-red hue), a solder rod is brought to the joint. If the temperature is selected correctly, the solder will begin to melt and be drawn into the gap under the action of the capillary effect, forming a monolithic seam.
It is important not to overheat the soldering area. If you see the copper turning bright orange or starting to melt on its own, stop heating immediately. Overheating changes the structure of the metal, making it brittle (“burnt copper”), which will lead to new cracks in the future.
Features of soldering steel and aluminum elements
In modern refrigerators, especially in models Indesit or Atlant, a combination of materials is often found: a copper tube is welded to a steel one, or aluminum is used evaporator Soldering such connections requires a special approach and special materials. Steel and copper have different melting temperatures and expansion coefficients.
To join copper with steel, you need silver solder with a silver content of at least 30-40% and a special high-temperature flux. Flux is applied to the heated joint, after which solder is introduced. Here it is important to take your time and let the flux spread, removing the oxide film from the steel.
With aluminum, things are more complicated. Aluminum tubes are rarely soldered; more often they are replaced with copper inserts or special couplings are used. If soldering is necessary, zinc-containing solders and very aggressive fluxes are used, which require careful neutralization after work, otherwise corrosion will destroy the seam in a matter of months.
⚠️ Attention! Remains of active flux used for soldering steel or aluminum must be washed off with alcohol or a special solvent. An acidic environment remaining on the metal will quickly lead to through corrosion and repeated leakage.
Table for selecting materials for various connections
To simplify the selection of consumables, we present a summary table that will help determine the required type of solder and flux depending on the metals being connected. The use of unsuitable components is the main reason for defects.
| Type of connection | Recommended solder | Necessity of flux | Melting point |
|---|---|---|---|
| Copper - Copper | Copper-phosphorus (BCuP) | Not required (self-fluxing) | 650-750 °C |
| Copper - Brass | Copper-phosphorus or Silver | Desirable | 650-800 °C |
| Copper - Steel | Silver (Ag 30-45%) | Required (high temperature) | 700-850 °C |
| Steel - Steel | Silver or Copper | Required | 800-900 °C |
The table shows that a universal solution for a home craftsman who does not want to buy many different rods is silver solder with a silver content of about 30-40%. It allows you to solder almost any combination of metals found in a refrigerator, although it is more expensive than copper-phosphorus.
When purchasing materials, pay attention to the diameter of the rod. For thin refrigerator tubes (6-8 mm), rods with a diameter of 2-3 mm are optimal. Thick solder will take a long time to melt and may overheat the joint while you wait for it to spread.
Checking tightness and crimping
After all the seams have cooled, you cannot immediately start the refrigerator. It is necessary to ensure that there are no microscopic fistulas that could have formed due to holes in the solder. To do this, the system is pressurized with nitrogen or dry air under pressure.
In domestic conditions, a compressor from an old refrigerator connected through a filter to the system is often used. The pressure is raised to 6-10 atmospheres. If the pressure gauge holds the needle for 12-24 hours, it means the soldering is done well. A drop in pressure will indicate the presence of a leak.
To find a leak during pressure testing, use a soap solution. It is applied liberally to all soldered seams. The appearance of even small bubbles indicates a defect. The place needs to be cleaned and soldered again.
☑️ Checking the quality of soldering
Evacuating the system before filling
After successful pressure testing and before starting the refrigerant from the system needs to remove air and, most importantly, moisture. Moisture in the system is enemy number one. Freezing in the narrow opening of the capillary tube, it forms an ice plug that blocks the circulation of freon. In addition, water reacts with oil and refrigerant, forming aggressive acids.
To remove moisture, the system is connected to vacuum pump. The pumping process should last at least 20-30 minutes. The residual pressure should be about 200-500 microns (or the maximum possible vacuum that your pump can create).
Only after creating a vacuum, close the valve on the pump, turn it off and quickly open the valve of the freon cylinder, releasing the refrigerant into the system. This prevents air from getting back inside the circuit.
⚠️ Attention! Never attempt to “blow out” the system with air from the compressor to remove moisture. You will only drive moisture deeper into the pores of the metal and oil. The only effective way is a deep vacuum, in which water boils and evaporates at room temperature.
Common mistakes and how to avoid them
Analysis of unsuccessful repairs shows that most problems arise due to haste and neglect of little things. For example, insufficient stripping of pipes leads to the fact that the solder lies only on top, without penetrating into the gap. Such a connection will fall apart from the very first vibration of the compressor.
Another common mistake is the lack of nitrogen purge during soldering in professional repairs. When copper is heated, scale (copper oxides) forms inside the pipe, which then enters the compressor or clogs the filter drier. At home, it is difficult to completely avoid this, but you should try to minimize the heating time and not keep the tubes open longer than necessary.
Overheating is also common. Beginners are afraid that the solder will not flow and heat it up too much. As a result, the tube at the soldering point becomes paper thin. Remember: solder flows where it is hot, but not where the base metal is already molten.
In conclusion, it is worth noting that soldering refrigerator tubes is a skill that comes with practice. If you have the opportunity, practice first on scraps of copper pipes of different diameters before taking on an expensive unit. Compliance with the technology will allow you to extend the life of the refrigerator for many years.
Is it possible to solder the tubes of the refrigerator without removing it from its place?
Technically this is possible, but it is highly not recommended. When working with an open flame near plastic elements, wiring and thermal insulation, there is a high risk of fire or melting. In addition, for high-quality soldering you need good access from all sides, which is difficult to provide in the assembled state. It is better to roll out the refrigerator into free space.
Which solder is better: with or without flux inside?
For beginners, solder with flux inside (fluxed) is more convenient, since there is no need to separately apply paste-like flux. However, for critical copper-steel connections, it is better to use a separate high-quality flux and a silver rod, controlling its quantity manually.
What to do if the refrigerator does not freeze after soldering?
Most likely, an ice or debris plug has formed in the capillary pipe, or the dosage of freon has been violated. It is also possible that the tube was pinched during soldering. Repeated diagnostics are required, possibly with purging with nitrogen under pressure and replacing the filter-drier.
Is it necessary to change the oil in the compressor after soldering?
If the system was open for a short time (less than 15-20 minutes) and was immediately shut off or purged with nitrogen, it is not necessary to change the oil. If the compressor worked for a long time with open tubes, the oil could absorb moisture, and it is better to replace it with a similar viscosity.