Technology for soldering copper pipes of a refrigerator with your own hands

Repairing the refrigerant circulation system is a complex procedure that requires not only theoretical knowledge, but also practical skills in working with the tool. Soldering copper tubes is a key step in restoring the tightness of the circuit, be it replacing a compressor, filter drier or eliminating a freon leak. Errors at this stage can lead to repeated equipment failure or even an explosive situation, so the preparation and process should be taken with the utmost seriousness.

Before heating the metal, it is necessary to completely evacuate the refrigerant from the system. Freon it should not remain under pressure in the tubes, since when heated it will react with oil and oxygen, forming aggressive acids. To safely release the gas, you should pierce the filling fitting or carefully saw off the tube away from open fire, ensuring good ventilation of the room. Ignoring this rule can lead to poisoning by combustion products of fluorine-containing compounds.

The quality of the connection directly depends on the cleanliness of the surfaces and the correct selection of consumables. Copper has high thermal conductivity, which requires rapid and uniform heating of the joint area. In this article we will analyze in detail how to properly prepare pipes, which solder to choose for a specific type of connection and how to avoid common mistakes, such as the formation of an oxide film inside the line.

Necessary tools and consumables

To perform high-quality soldering, it is not enough just one gas burner. You will need a specialized set of tools that will ensure accuracy and safety. The main element is an open fire source: this can be a propane-oxygen burner for professionals or a more affordable option with a can MAPP gas or a propane-butane mixture for the home craftsman. The melting point of copper is about 1083°C, but hard soldering requires heating to 600-750°C.

The most important consumable material is solder. For copper-copper connections, silver or phosphorus-copper rods are traditionally used. Phosphorus-copper solder (for example, PMF brand) has the property of self-fluxing, that is, it does not require the mandatory use of flux when joining homogeneous metals. If you connect copper to steel (for example, a compressor discharge tube), the use of flux becomes mandatory, since phosphorus-copper alloys cannot be soldered with steel.

Do not forget to prepare auxiliary tools, without which the process will be difficult:

• 🔥 Pipe cutter - provides ideal an even cut without the formation of chips that could get inside the system.
• 🧹 Brush and rags —necessary for mechanical cleaning of surfaces from oxides and contaminants before heating.
• 🧊 Wet rags or thermal protective gel —used for cooling adjacent units, so as not to damage the plastic parts or the varnish coating of the compressor.
• 🧤 Safety glasses and gloves - mandatory equipment to protect against splashes of molten metal and UV radiation of the flame.

⚠️ Attention: Never use lead-tin solders (PLS), which are used in plumbing or electronics, for soldering refrigeration systems. They have a low melting point and insufficient strength to work under pressure and vibration of the compressor.

Particular attention should be paid to the choice of flux if the type of connection requires it. Flux promotes the spread of solder and protects the metal from oxidation during heating. However, its excess can lead to corrosion of the system from the inside, so it should be applied in the minimum required amount, strictly at the joint, avoiding getting inside the tube.

Preparation of copper pipes for soldering

The success of soldering depends 80% on the quality of surface preparation. Oxide filmformed in air prevents the adhesion of solder, so the metal must be cleaned to a shine. First, the pipe is cut strictly perpendicular to its axis. Using a hacksaw for metal is strictly prohibited, since metal dust will inevitably get inside, which will subsequently clog the capillary tube or expansion valve.

After cutting, the edges of the pipe must be treated with a rimmer (chamfer). This action removes the inner and outer edges (burrs). If the internal chamfer is not removed, it will create resistance to refrigerant flow and cause noise. An external chamfer is needed so that when inserting one pipe into another (into a socket or fitting), all the applied flux or solder does not come off on the sharp edge.

The stripping process is as follows:

• 🔪 Cut the pipe with a pipe cutter, making several full turns around the axis for an even cut.
• 🌀 Remove the internal and external chamfer with a rimmer using rotational movements.
• ✨ Clean the outer surface of the inserted pipe and the inner surface of the socket with fine-grained sandpaper or a special brush until a uniform copper shine appears.
• 🚫 Do not touch the cleaned surfaces with your hands, since grease stains will also worsen the quality of soldering.

If you are forming a socket (increasing the diameter of the end of a pipe to insert another pipe) using an expander, make sure that the seating depth is not less than the diameter of the pipe itself. This will provide enough contact area for a strong connection. A connection that is too short may come apart under pressure or vibration.

Soldering technique: step-by-step instructions

The joining process itself requires coordination of movements and an understanding of the physics of heat propagation. Copper heats up quickly, but the heat is distributed unevenly if you heat only one point. Your task is to heat the entire joint evenly so that the solder melts from the heat of the pipes, and not from direct contact with the burner flame.

Here is the algorithm for creating a reliable seam:

1. Insert one pipe into the other (or into the fitting) until it stops. The gap between the walls should be minimal (capillary effect).
2. If flux is used, apply it in a thin layer to the joint before heating.
3. Point the burner flame to the joint area. Keep the torch in motion, moving the flame around the pipe to heat it in a circle.
4. When the copper reaches operating temperature (determined by color or using a thermal marker), bring the solder rod to the joint on the side opposite the flame.
5. The solder should melt from the hot pipe and be drawn into the joint by capillary action strength.

It is important not to overheat the soldering area. If you see the copper starting to melt or the solder balling up and not flowing into the gap, the temperature is too high or the surfaces are dirty. Let the metal cool a little and try again, adding a little flux.

After the seam is formed, let it cool naturally. Do not try to speed up cooling with water or a damp cloth - a sudden temperature change can cause microcracks in the metal crystal lattice, which will lead to a weakening of the connection. Only after complete cooling can you remove flux residues with a damp rag, since many fluxes are hygroscopic and can cause corrosion.

Soldering in a nitrogen environment: why is it necessary

When copper is heated in air, active oxidation occurs. A layer of copper oxide (black deposit) forms inside the pipe, which can fall off in the form of flakes and enter the system. For modern refrigerators with narrow capillary tubes and electronic expansion valves, this is critical. Oxide flakes can clog the system, causing an increase in pressure and failure of the compressor.

To avoid this, professionals use system purging nitrogen during soldering. Nitrogen displaces oxygen from the pipe, preventing the formation of oxides. The process looks like this: a weak stream of nitrogen (pressure about 0.5-1 atm) is supplied through one end of the system, and it flows freely at the outlet. Soldering is carried out with a continuing gas flow.

Comparison of soldering with and without nitrogen:

⚠️ Attention: The use of nitrogen requires a reducer. High pressure gas may rupture the pipe or create a hazardous situation. Always check the pressure on the pressure gauge.

If you do not have the opportunity to use nitrogen, try to minimize the heating time and thoroughly clean the system after soldering. However, for long-term repair of the refrigerator nitrogen purging is a mandatory quality standardignoring of which will shorten the service life of the equipment.

What to do if nitrogen is not at hand?

If nitrogen purging is not possible, try to keep pipe with the hole down when heated, so that convection currents of hot air go out, rather than drawing oxygen in. Inert substitute gases can also be used, but argon or helium are more expensive and heavier than air, which is less efficient at displacement. As a last resort, after soldering, be sure to replace the filter-drier, as it will absorb some of the moisture and contaminants.

Typical errors and defects in soldering

Even experienced craftsmen sometimes make mistakes that become visible only after refueling the refrigerator. One of the most common problems is the formation of a “sealed throat”. This occurs when the craftsman heats the edge of the pipe excessively and surface tension causes the molten copper to collapse, blocking the passage. You can check the permeability of the pipe by simply blowing into it before final assembly.

Another common mistake is insufficient heating. If the solder lies on top like a “sausage” and does not flow into the gap, such a connection will not withstand the pressure. Visually, a high-quality seam looks like a uniform bead around the entire circumference of the joint, without tears or sagging. The color of copper after soldering should be uniform, without rainbow or black spots indicating overheating.

List of defects that should be avoided:

• 🕳️ Fistulas and pores - arise due to dirt, moisture or sudden cooling. They appear as small holes in the seam.
• 🌊 Underheating —the solder has not spread, the connection is leaky.
• 🔥 Burn —the metal has become brittle, burning of the pipe wall is possible.
• 💧 Moisture in the system —if the pipe was not dry before soldering, the water inside will turn into steam and rupture the seam or create acid.

Particular attention should be paid to soldering in hard-to-reach places, near the refrigerator body or other pipes. Use heat-sinking clamps or just a damp cloth wrapped around adjacent elements so as not to melt their insulation or varnish coating. Local overheating of the refrigerator body can deform the plastic or damage the foam insulator.

Checking tightness and crimping

After completing all soldering work, you cannot immediately refill the refrigerator with freon. The system must be tested for leaks using a pressure test method. To do this, the circuit is filled with nitrogen at a pressure exceeding the operating pressure (usually 10-15 atmospheres for household refrigerators) and left for a day. The pressure gauge should not show a drop in pressure.

All soldering areas must be thoroughly washed with soapy water. The appearance of tiny bubbles indicates a leak. If the pressure drops, but the leak cannot be visually found, the problem may be a microcrack or a poor-quality connection that manifested itself during cooling. In this case, the nitrogen is released, the place of the suspected leak is resoldered, and the procedure is repeated.

Before filling with refrigerant, the system must be evacuated for at least 15-20 minutes until a residual pressure of 200-300 microns is reached (or according to the readings of the vacuum gauge). This will remove moisture and residual air, which are the main enemies of the refrigeration system.

⚠️ Attention: Never create excess pressure in the system using oxygen or ordinary air from the compressor. Oxygen mixed with compressor oil can cause an explosion, and the air contains moisture, which will lead to the formation of acid inside the system.

Frequently asked questions (FAQ)

Is it possible to solder refrigerator tubes without removing it from its place?

Theoretically, it is possible, but it is highly not recommended. Soldering must be done in a well-ventilated area, and access to the back wall and bottom (where the compressor is located) should be free from all sides. In addition, working with open flames near plastic elements and insulation of the refrigerator requires increased caution. It is better to take the unit out to the balcony or garage.

How to replace silver solder if it is not available?

For copper refrigerator pipes, the best alternative is phosphorus-copper solder (without silver). It is cheaper, has good fluidity and strength. However, for soldering copper to steel (for example, a steel compressor pipe), silver or special high-temperature solders are required, since phosphorus does not work with steel. They cannot be replaced with tin solders.

Why does the solder roll into balls and not stick?

This is a classic sign of insufficient heating temperature or the presence of oxides. The copper needs to be heated more strongly by moving the flame around the pipe. It is also possible that you overheated the soldering area and the flux burned out prematurely. Let it cool, clean the surface again, apply fresh flux and try to heat it more evenly, focusing on heating the pipe itself rather than the solder.

Do you need to change the filter drier after each soldering?

Yes, this is a mandatory rule. The filter drier is a disposable element. When soldering and opening the system, it absorbs moisture from the air. If you leave the old filter, moisture will enter the compressor and capillary tube, causing ice blockage or corrosion. Always install a new filter immediately before soldering the last joint.