Repairing a refrigeration unit often requires a hermetically sealed connection of copper tubes, and choosing the right heat source plays a decisive role here. An error in the selection of equipment can lead to burnout of thin-walled tubes or, conversely, to insufficient heating of the solder, which will cause a refrigerant leak in the future. Professional craftsmen use a specialized tool that allows them to control the temperature of the flame and the heating zone.
In domestic conditions and small workshops, the range of equipment used is wide: from simple portable devices to complex supercharged systems. Flame temperature It should be sufficient for melting copper-phosphorus or silver solders, but should not oxidize the metal excessively. It is important to understand that standard household burners for tourist stoves are often not suitable for high-quality soldering due to the low temperature and soft flame.
In this article we will take a detailed look at the types of burners, their advantages and disadvantages, and also analyze the technical nuances of working with them. You will find out why acetylene-oxygen systems are considered the standard, and in what cases they can be replaced with more affordable analogues. The correct choice of tool is half the success in restoring the tightness of the refrigeration circuit.
Requirements for temperature and type of flame
The main task when soldering a refrigerator is to create conditions under which the solder will melt and fill the gap by capillary effect, and the base metal (copper or steel) did not melt. For copper-phosphorus solders, which are most common in the repair of refrigeration equipment, a temperature in the soldering zone of about 700-750°Cis required. However, the burner flame itself must be significantly hotter to compensate for the heat dissipation of the metal mass.
A critically important parameter is heat concentration. The flame must be focused to heat a specific section of the pipe without affecting adjacent elements, such as thermal insulation materials or plastic parts of the compressor. Soft, diffuse flame a conventional lighter or candle is not able to provide the necessary localization of heat, which leads to overheating of long sections of pipe.
⚠️ Attention: Using an open flame near the compressor requires special care. In older models of refrigerators, dust and oil deposits can accumulate in the engine compartment, which are easily ignited by a spark or sudden burst of flame.
The material of the pipes being connected should also be taken into account. If you work with a connection copper-copper, the process is easier, since the thermal conductivity of the materials is the same. When soldering copper-steel (for example, a compressor discharge tube), heat is dissipated unevenly, and a more powerful and adjustable heat source is required to heat the steel part without burning out the copper.
Acetylene-oxygen systems: professional standard
The traditional and most effective tool for soldering refrigeration circuits is an acetylene-oxygen bond. This combination of gases ensures a flame temperature of up to 3100-3200°C, which allows you to instantly heat up connections even of large diameters. Such systems consist of two cylinders, pressure regulators and a special burner with an injection principle of gas mixing.
The main advantage of an acetylene burner is the ability to fine-tune the nature of the flame. The master can set a neutral flame, which does not oxidize copper, or a reducing flame, which is useful when working with certain types of solders. Heating rate in such systems it is maximum, which minimizes the time of thermal exposure on the metal and reduces the risk of the formation of an oxide film inside the pipe.
However, this method has significant drawbacks, limiting its use in on-site repair conditions. Gas cylinders are heavy, bulky and require strict adherence to safety regulations during transportation. Acetylene is explosive if used incorrectly, and oxygen is a strong oxidizing agent, prohibited for transportation in passenger elevators and public transport without special marking.
Despite the difficulties, for stationary workshops where the volume of work is large, acetylene-oxygen remains the uncontested leader. It pays off in speed of work and the highest quality of seam. Experienced craftsmen appreciate the opportunity to work with any type of solder, including refractory silver, which requires intense heat input.
Why is acetylene dangerous?
Acetylene is an unstable gas, which, when compressed above 1.5 atmospheres or in the presence of a spark can explode even without oxygen. That is why it is stored in cylinders filled with porous material and acetone, which stabilizes the gas. Violation of operating rules (for example, working lying down or overturning a cylinder) can lead to the release of acetone and an explosion.
Propane-oxygen burners: balance of power and mobility
Systems operating on a mixture of propane (or propane-butane) and technical oxygen have become a more modern and safer alternative to acetylene. The flame temperature here is lower, about 2500-2700°C, but it is quite sufficient for soldering copper pipes of refrigerators with a diameter of up to 22 mm. The main difference lies in the design of the burner: it is often equipped with valves for separately regulating the supply of gases.
The use of propane can significantly simplify logistics. Propane cylinders are more compact, cheaper to refill and safer to store. Oxygen in such systems is used technical, in small cylinders, which makes the kit mobile. Burners for propane-oxygen often have an ejector device that ensures stable combustion without pops and backfires.
When working with propane, it is important to consider that the heating time of the connection increases according to compared to acetylene. This requires more discipline from the master and the use of high-quality fluxess that protect the soldering zone from oxidation for a longer heating time. For large diameter pipes (more than 28 mm), the power of a propane burner may not be enough, and preheating or the use of screens will be required.
- 🔥 The high mobility of the kit allows you to easily move equipment between objects.
- 💰 The low cost of gas makes operation economical for small workshops.
- ⚙️ Ability to work with most types of hard solders used in refrigeration.
- 🛡️ Less risk of explosion compared to acetylene systems if basic rules are followed.
Portable gas burners for butane and MAPP gas
For minor repairs, replacing filter-driers or soldering in hard-to-reach places, portable burners are often used, mounted on standard collet cartridges. It is important to distinguish between fuels here: ordinary household butane-propane gives a temperature of about 1300-1400°C, which may not be enough for a high-quality connection. It is much more efficient to use gas MAPP (methyl acetylene-alladine mixture), the combustion temperature of which reaches 2200°C.
MAP gas burners are equipped with a turbocharger or a special mouthpiece design that creates a vortex flame. This allows heat to be concentrated in a narrow area. Such tools are ideal for soldering capillary tubes, suction lines and other thin-walled elements. They do not require hoses and bulky cylinders, which makes them indispensable for service engineers.
The limitation of portable systems is the short time of continuous operation. When working intensively with a powerful burner, a 500 ml can can be empty in 15-20 minutes. In addition, at low ambient temperatures (below +5°C), the pressure in the cylinder drops and the flame becomes weak. In such cases, the cylinder has to be warmed, which is inconvenient in field conditions.
| Burner type | Flame temperature | Set weight | Operating cost |
|---|---|---|---|
| Acetylene-oxygen | ~3100°C | High (>20 kg) | Average |
| Propane-oxygen | ~2600°C | Medium (~10 kg) | Low |
| MAPP gas (portable) | ~2200°C | Low (<1 kg) | High |
| Butane-propane (portable) | ~1350°C | Low (<1 kg) | Low |
Soldering technology and choice of solder
The choice of torch is directly dictated by the type of solder used. To connect copper pipes in refrigerators, they are most often used copper-phosphorus solders (for example, brand BCuP). They have the property of self-fluxing when soldering copper to copper, that is, they do not require additional flux, since phosphorus itself reduces copper oxides.
If you need to connect copper to steel (for example, a compressor discharge tube), copper-phosphorus solder cannot be used - the connection will be fragile and will be destroyed by vibration. In this case, they are used silver solders (with a silver content from 15% to 45%) in combination with active fluxes. To melt such solders, a higher temperature and uniform heating are required, which only gas burners with good heat transfer can do.
☑️ Checking readiness for soldering
The soldering process is as follows: first, the entire joint area is heated, moving the flame along the pipes. When the metal reaches the desired temperature (determined by the glow color or melting of the solder rod when touched), solder is injected into the area. It is important not to heat the solder itself with a flame, but to heat the metal so that it melts the solder with its heat. This ensures that the solder flows into the joint.
⚠️ Attention: When using fluxes, after the joint has cooled, be sure to remove any remaining flux with warm water or solvent. Flux residues are hygroscopic and over time can cause corrosion of the metal at the soldering site, leading to fistulas.
Safety precautions and workplace preparation
Working with open flames and flammable gases requires strict adherence to safety rules. Before starting work, you must make sure that there are no gas leaks from the burner itself and the hoses. The test is carried out with a soap solution: the appearance of bubbles indicates a violation of the tightness of the connections. Backfire - a dangerous phenomenon when the flame jumps inside the burner. Modern burners are equipped with flame arresters, but if there is a bang, work should be stopped immediately.
The room where soldering is performed must be well ventilated. When gases burn and fluxes evaporate, harmful substances are released. In addition, in a confined space, a concentration of gas is possible in the event of an accidental leak, which creates an explosive mixture. It is critically important to keep a fire extinguisher in close proximity to the soldering area, and also remove all flammable materials (alcohol, oil, rags) at a safe distance.
When working with cylinders are prohibited:
- 🚫 Place cylinders in a horizontal position or heat them with an open fire.
- 🚫 Use tools contaminated with oil to service oxygen equipment (oxygen reacts violently with oil).
- 🚫 Leave a burning burner without supervision even for a short time.
- 🚫 Carry out work in clothes soaked in oil or grease.
Common mistakes when choosing and using a burner
Beginners often make the mistake of trying to solder refrigeration pipes with a hair dryer or too weak turbocharged lighters. The temperature of a construction hair dryer rarely exceeds 600°C, which is not enough to melt hard solders. As a result, the solder either does not flow or falls in clumps, not providing a tight seal. An attempt to increase the heating time only leads to oxidation of copper and burning through the thin walls of the tubes.
Another common mistake is using too powerful a flame on small diameters. If you direct a powerful stream of acetylene at a thin capillary tube, it will instantly melt. The master must be able to adjust the length of the torch and the intensity of the flame using nozzles of different diameters. For delicate work, nozzles with a small hole are used, creating a soft but hot flame.
It is also worth mentioning the problem of “cold soldering”. This happens when the master is afraid of overheating the pipe and removes the flame ahead of time. In this case, the solder flows only superficially, forming a visible bead on the outside, but not penetrating into the gap. Such a connection will not withstand refrigerant pressure and compressor vibration. High-quality soldering requires confidence and understanding of the thermal processes of metal.
Is it possible to solder a refrigerator with a regular gas burner for stoves?
Theoretically, it is possible if you use special turbo attachments, but this is extremely inconvenient and ineffective. The flame from the stove has a low temperature and a large area, resulting in overheating of large areas of insulation and difficulties with local heating. This is not recommended for professional repairs.
Which solder is best for a novice master?
It is best to start with copper-phosphorus solders (for example, P-14 or their imported analogues with a phosphorus content of 5-8%). They are cheaper than silver ones, do not require flux when soldering copper to copper and have a wide melting temperature range, which forgives small errors in heating temperature.
Is it necessary to nitride pipes when soldering with a torch?
Ideally, yes. Purging with nitrogen during soldering prevents the formation of an oxide film (scale) inside the pipe, which can subsequently clog the capillary or filter drier. However, when using high-quality fluxes and fast work in domestic conditions, this is sometimes neglected, although nitrogen protection is mandatory for the long life of the refrigerator.