Violation of the tightness of the circuit is one of the most unpleasant breakdowns that the owner of household appliances may encounter. If you notice oily stains on the walls of the unit or ice has stopped forming, and the compressor is running non-stop, most likely a microcrack has formed in the line. In such a situation, the question arises: is it possible to restore the system yourself, or is it better to call a specialist? The answer depends on your equipment and skills in working with metal.
The process restoring tightness requires not only physical accuracy, but also an understanding of the physics of the refrigeration cycle. The copper from which the tubes are made has excellent thermal conductivity, but is also highly sensitive to overheating. Incorrectly selected temperature conditions can lead to burning of the wall or the formation of oxides inside the channel, which will subsequently cause blockage of the capillary system.
Before taking active steps, you need to objectively assess your strengths and the availability of the necessary equipment. Soldering of refrigeration tubes is carried out only in the absence of freon in the circuit. If you are simply planning “fix the hole” without first pumping out the refrigerant and evacuating the system, such repairs will be ineffective and short-term. Next, we will analyze in detail the technological process that will allow you to do the job professionally.
Diagnostics of the leak location and surface preparation
The first step is always to search for damage. A visual inspection does not always give results, since microcracks can be hidden under insulation or factory paint. Leakage often occurs at solder joints or bends, where the metal experiences the greatest thermal and mechanical stress. To detect a problem, you can use a soap solution applied to suspicious areas of a working compressor, or a special electronic leak detector.
After detecting a defect, you must carefully prepare the surface. Copper oxidizes in air, forming a layer that prevents solder from spreading. Mechanical cleaning is carried out until the metal shines using fine-grained sandpaper or a needle file. It is important not to thin the tube wall with excessive pressure, especially when it comes to thin-walled evaporator elements.
- 🔍 Degrease the cleaned area with acetone or a special solvent to remove residual oil and dust.
- 🔍 Make sure that there is free space around the damaged area for working with the burner, so as not to melt adjacent plastic elements.
- 🔍 If the crack is in a hard-to-reach place, you may need to partially disassemble the case or bend the thermal insulation.
The quality of surface preparation directly affects the adhesion of solder. Dirty or oxidized copper will not allow a solid connection to be created, and gas will begin to escape again. Some craftsmen recommend using flux already at the preparation stage, but for primary mechanical processing this is unnecessary. The main thing is to achieve a perfectly clean and smooth metal surface.
⚠️ Attention: If a leak is found in the foamed part of the housing (the evaporator inside the wall), independent soldering without opening the thermal insulation is impossible. In such cases, it is often easier to install an external evaporator (“crying” on the back wall) than to open the factory foam.
Necessary tools and consumables
For high-quality work, a conventional soldering iron for electronics will not be enough. The melting point of copper and brazing alloys requires the use of an open flame. The main tool is a gas burner. At home, hand torches that run on a mixture of propane-butane or MAF gas are most often used. For professional repairs, oxygen-acetylene equipment is also used, but it is bulky and requires special storage conditions.
The second critical element is the choice of solder. For refrigeration circuits, where the pressure can reach 10-15 atmospheres and higher, soft tin-lead solders (POS) are not recommended, although in emergency cases at low suction pressure this is allowed. The optimal choice is hard copper-phosphorus solders (for example, PMF-7, PMF-9) or silver alloys. They provide high weld strength and do not require the use of aggressive fluxes.
| Material | Melting point | Application | Necessity flux |
|---|---|---|---|
| Tin-lead (POS) | 183–220°C | Low pressure, temporary repair | Required |
| Copper-phosphorus (PMF) | 650–750°C | Soldering copper-copper, main circuit | Not required |
| Silver (PSr) | 600–700°C | High-strength connections, vibration units | Desirable |
| Brass (L63) | 880–900°C | Rarely, for steel elements | Required (borax) |
In addition to the torch and solder, you will need additional tools. This can be a pipe cutter for an even cut of metal, rolling (if a section of the tube needs to be replaced) and a reamer for deburring. Also, do not forget about personal protective equipment: gloves and goggles, since the work is carried out with an open flame and hot metal.
Technology for soldering copper tubes
The process of joining metals itself requires compliance with a certain sequence of actions. First you need to warm up the joint. The torch flame should be aimed at the tube and not directly at the solder. The copper must be heated to a temperature at which the solder begins to draw itself into the gap due to capillary effect. If you heat only the solder, it will melt, but will not “stick” to the cold tube, forming an unreliable ball.
When using copper-phosphorus solders, flux is usually not required, since phosphorus acts as an oxide reducer. However, if you are working with brass or steel, or using silver solder without phosphorus, applying flux is a must. Flux protects the surface from oxidation during heating and improves the fluidity of the molten metal. Excess flux can cause plugs to form in narrow channels, so apply it sparingly.
☑️ Soldering algorithm
It is important to control the heating time. Overheating of copper leads to its annealing - the metal becomes soft and loses its strength, which can lead to rupture of the tube under pressure in the future. In addition, with severe overheating, zinc burns out (if brass is soldered) or phosphorus from the solder, which worsens the properties of the seam. As soon as the solder has filled the joint, the flame must be removed immediately.
The connection should cool naturally. It is not recommended to speed up the process by cooling with water or a damp cloth. A sharp temperature change will create thermal stress in the metal, which can lead to the appearance of microcracks in the seam itself or near it. Only after complete cooling can you check the quality of the connection.
Replacing a section of the line and rolling
In situations where the damage is serious or the tube has rotted over a long distance, simple soldering is not enough. Requires insertion of a new section copper tube. To do this, the damaged segment is cut out and the ends are cleaned. The new piece should be of the same copper as the main circuit to ensure the same coefficient of thermal expansion.
The key here is to prepare the joints. If the diameters of the tubes allow, one end can be flared, making it a little wider in order to insert the second tube there overlapping. The gap between the walls should be minimal (0.05–0.1 mm) for high-quality capillary filling with solder. For rolling, a special tool is used - rolling, which allows you to make an even “skirt” without cracks.
⚠️ Attention: When rolling, do not overtighten the tool. The thin wall of the copper tube breaks easily when the cone is pressed too hard. Do this smoothly, with a little effort at each turn.
If it is impossible to flare the tube, a connection through a coupling or butt soldering is used (although butt soldering of small-diameter pipes requires high qualifications). In domestic conditions, the “pipe to pipe” method works most reliably. The inserted part must be at least 10-15 mm in length to ensure sufficient contact area for solder.
What to do if you do not have a copper tube at hand for insertion?
As a last resort, you can use a piece of capillary tube from an old refrigerator, choosing the diameter. However, it is strictly forbidden to use steel or aluminum tubes for inserts into a copper circuit due to electrochemical corrosion and the difficulty of soldering dissimilar metals.
Evacuating and charging the system
After soldering is completed, you cannot just start the refrigerator. Air and possibly flux combustion products remained in the system. The air contains moisture, which when the refrigerator operates will turn into an ice plug in the capillary tube, completely stopping the circulation of the refrigerant. In addition, the air increases the condensation pressure, which leads to overload of the compressor.
To remove air and moisture, the system must be evacuated. To do this, a vacuum pump is connected to the service pipe. The pumping process lasts at least 15-30 minutes, depending on the volume of the system and the power of the pump. The residual pressure should be about 5-10 Pa (microns). Only after creating a deep vacuum, the system is ready for refilling.
- ❄️ Refilling is carried out strictly according to the weight indicated on the nameplate of the refrigerator, using electronic scales.
- ❄️ Liquid freon is charged through the condenser, and gaseous freon is charged through the suction tube, but it is better to follow the instructions for the specific type refrigerant (R134a, R600a).
- ❄️ After filling, it is necessary to seal the filling pipe by bending it at the base and sealing the end.
Particular attention should be paid to the type of refrigerant. Modern refrigerators often operate on isobutane (R600a), which is explosive. Soldering in the presence of isobutane vapor in the circuit is prohibited. Before starting work, such systems must be purged with nitrogen or simply make sure that all the gas has been vented, and soldering should be carried out with the utmost care, ensuring the room is ventilated.
⚠️ Attention: Technical parameters of refilling (type of freon, quantity, type of oil) are individual for each model. Always check the label on the back of your refrigerator. Using the wrong refrigerant will lead to compressor failure.
Typical errors and safety measures
Independent repair of refrigeration equipment is fraught with risks. One of the most common mistakes is insufficient heating of the soldering area. The technician is afraid of overheating the tube and moves the burner too quickly. As a result, the solder is applied only superficially, forming a “drip” rather than penetrating into the gap. Such a connection will burst at the first vibration of the compressor.
Another common problem is oxides getting inside the tube. If you heat copper without protection (flux or inert gas) or with excess oxygen, scale will form inside. Over time, it breaks off and clogs the filter drier or capillary. To avoid this, experienced craftsmen recommend blowing the tube with a small stream of nitrogen when soldering, although this is difficult to do at home, so it is important not to overdo it with the temperature.
Safety also comes first. Working with open flames and flammable gases requires caution. There should be no flammable objects in the room, and the gas cylinder should be in an upright position and at a safe distance from the heat source. Do not forget that some refrigerants, when in contact with an open flame, decompose to form toxic substances (phosgene).
The result of proper soldering is a smooth, shiny seam without cavities and pores. If the surface is matte, grainy or cracked, the work needs to be redone. Tightness is the main requirement for the refrigeration circuit, and compromises here are unacceptable. If you doubt your abilities at any stage, it is better to entrust the repair to professionals licensed to work with ozone-depleting substances.
Is it possible to solder aluminum tubes?
Aluminum is extremely difficult to solder at home due to instant oxidation. For this you need special fluxes (for example, F59A) and zinc-based solders. Aluminum cannot be soldered with ordinary tin or copper-phosphorus solder. Most often, aluminum sections are simply replaced with copper ones using butt welding or special adapters.
Is it possible to solder the tube with ordinary tin solder?
Technically this is possible, but it is not recommended for high-pressure areas (injection). Tin has a low melting point and strength. On a suction tube, where the pressure is low, such soldering can last a long time, but for reliability it is better to use hard solders (copper-phosphorus or silver).
Is it necessary to nitride the tube when soldering at home?
Under ideal conditions - yes, blowing with nitrogen prevents oxidation of copper from the inside. However, in domestic conditions, if you work quickly and carefully, avoiding overheating, the formation of oxides is minimal. The main thing is not to heat the tube longer than necessary and immediately cool the joint after soldering.
What to do if after soldering the refrigerator does not cool?
Most likely, an ice plug has formed due to moisture in the system (poor vacuum) or the capillary tube is clogged with scale/solder. It is also possible to underfill or overfill freon. Repeated pumping, replacement of the filter-drier and proper refilling are required.
Is it dangerous to independently repair a refrigerator using isobutane (R600a)?
Isobutane is explosive when concentrated in air. Soldering can only be done after the gas has been completely removed from the circuit and the room has been thoroughly ventilated. A spark from the piezo ignition of the burner can ignite residual gas if there is any in the work area. Use extreme caution.