When malfunctions of the cooling system occur or when planning independent maintenance of a refrigeration unit, owners often wonder about the materials used in production. Historically, classic models of household appliances were equipped with copper lines, but modern realities dictate their own conditions. Manufacturers are actively introducing new alloys and technologies in pursuit of cost reduction and environmental friendliness, which leads to confusion among consumers.
Understanding what what kind of tubes are in the refrigerator is installed in your model is critical to the correct selection of repair tools and soldering methods. An error in identifying the metal can lead to a poor connection and re-leakage of the refrigerant after a short time. In this article we will analyze in detail the evolution of materials, methods of their visual identification and technical features of operation.
It must immediately be noted that there is no universal answer for all models. Design features depend on the year of manufacture, price segment and specific brand of device. Below we will provide comprehensive information that will help you accurately determine the composition of the circuit and make the right decision regarding further maintenance of the equipment.
Evolution of materials in refrigeration technology
At the dawn of mass production of household refrigerators, engineers used mainly copper tubes to create a closed refrigerant circulation loop. This metal had excellent thermal conductivity, high ductility and, most importantly, was easy to solder with soft solders. Copper is chemically inert to many types of freons and oils, which ensured a long service life without the risk of corrosion from the inside.
The situation changed dramatically in the late 1990s and early 2000s, when prices for non-ferrous metals increased sharply on the world market. Manufacturers were forced to look for alternatives to reduce the final cost of the product. As a result, aluminum and steel elements appeared in the designs. Aluminum is attractive for its lightness and low price, but it is much more difficult to process and requires special equipment for joining.
Why was copper replaced?
Copper has better thermal conductivity (about 400 W/m K) compared to aluminum (about 230 W/mK). However, the difference in the cost of raw materials reached three times, which became a decisive factor for the mass market.
Modern models are often hybrid structures, where different sections are made of different metals depending on their function. For example, the discharge line may be steel, but the evaporator may be aluminum. It is important to understand that the transition to new materials does not always mean a deterioration in quality, but it changes the approach to repair and maintenance.
How to visually distinguish copper from aluminum
Primary diagnosis of the material is often possible without the use of complex equipment, a fairly careful visual inspection and simple physical tests. Color is the first indicator: copper has a characteristic reddish-orange hue that can oxidize to a dark brown or greenish color over time. Aluminum always remains silver-gray, matte or slightly shiny.
The second important parameter is weight and magnetic properties. Copper is significantly heavier than aluminum for the same volume, which is noticeable if you hold a cut piece of tube in your hands. Also, neither copper nor aluminum are magnetic, but steel, which is also often used in circuits, will respond to a magnet. This allows you to quickly cut off the third version of the material.
It is also worth paying attention to the nature of the break or cut. Copper is a very soft and tough metal; when cutting, it can be slightly deformed, but does not break. Aluminum is more fragile and can crack if not handled carefully. When soldering, copper retains heat for a long time, while aluminum quickly removes it, which requires a more powerful burner flame.
Technical characteristics: comparison of metals
For a deep understanding of the processes occurring inside the refrigerator, it is necessary to compare the physical properties of the materials. Thermal conductivity is a key parameter for the evaporator and condenser, since it determines the efficiency of heat transfer. Mechanical strength is important for areas exposed to compressor vibration, and corrosion resistance determines the durability of the entire system.
Below is a comparative table of the main parameters used in refrigeration production:
| Parameter | Copper (Cu) | Aluminum (Al) | Steel (Fe) |
|---|---|---|---|
| Thermal conductivity | High (~390 W/mK) | Medium (~230 W/mK) | Low (~50 W/mK) |
| Density | 8.9 g/cm³ | 2.7 g/cm³ | 7.8 g/cm³ |
| Ductility | High | Medium | Low |
| Soldering difficulty | Low | High | Medium |
The table shows that copper tubes lead in heat transfer, which theoretically makes the refrigerator more energy efficient. However, aluminum compensates for its lower thermal conductivity by increasing the area of the heat exchanger (fins). Steel is used where strength is important, for example, in high-pressure injection lines, despite low thermal conductivity.
Where the tubes are located in different models
The location of the pipelines depends on the type of defrosting system and the design of the refrigeration chamber. In classic models with a weeping evaporator, the tubes are often sealed into the back wall or attached to the outside. In modern systems No Frost the evaporator is hidden behind a plastic panel in the freezer, and it is impossible to get to it without partial disassembly.
The condenser (heat exchanger that gives off heat) in older models was a black wire coil on the back wall of the case. In new refrigerators, the condenser is often integrated into the sides or bottom, making it visually invisible. In such cases, the tubes pass inside the thermal insulation layer, and their material can only be determined by the areas near the compressor.
- 😎 Rear wall: classical arrangement of an open condenser, often steel with copper inserts.
- 🧊 Inside the chamber: evaporator, which in budget models is almost always aluminum.
- 🔧 Compressor compartment: here are the connecting points where copper can be connected to steel or aluminum.
It is important to consider that in dual-circuit systems (separate evaporator for refrigeration and freezers) materials can be combined. One circuit can be made of copper, and the other of aluminum, depending on the year of production and logistics of the manufacturer.
Features of soldering and repair of the circuit
Repair of the cooling system directly depends on what metals need to be connected. Soldering copper to copper is a standard procedure, accessible even to a novice craftsman using a gas torch and phosphorus-containing solder. However, if in the refrigerator aluminum tubes, the situation becomes much more complicated. Aluminum instantly oxidizes in air, forming a refractory film that prevents jointing.
⚠️ Attention: Soldering aluminum requires special fluxes (for example, F-59A) and zinc-based solders. Conventional PIC (tin-lead) solder will not take aluminum, and the use of aggressive fluxes without neutralization will lead to rapid corrosion of the soldering site.
There is often a need to connect dissimilar metals, for example, a copper outlet of a compressor and an aluminum evaporator. For such cases, there are special adapter sleeves or bimetallic solders. The technology requires careful cleaning, degreasing and precise temperature control: aluminum melts at 660°C, while copper melts at 1083°C, so you need to heat the joint carefully so as not to burn through the soft metal.
☑️ Preparation for soldering dissimilar metals
If you do not have sufficient experience, an attempt to solder an aluminum circuit may result in damage to an expensive unit. In such cases, professionals often resort to installing a “weeping” evaporator - a mounted aluminum radiator that is mounted externally, which eliminates the need for soldering inside the chamber.
Problems of corrosion and leaks
The most vulnerable point of refrigerators with aluminum tubes is corrosion. Aluminum is an electrochemically active metal, and in the presence of moisture and contact with other metals (galvanic couple) it is destroyed. This happens especially often at soldering points, if the technology has been broken, or at points of contact with thermal insulation, which can accumulate condensation.
Copper is susceptible to corrosion to a much lesser extent, but it is not immune from problems. When using refrigerants containing chlorine (which is now rare, but found in older equipment), or when moisture gets into the system, acid can form inside, corroding the walls of the tubes from the inside. Steel tubes are susceptible to rust if the outer varnish coating is damaged.
- 🔍 Visual inspection: look for white oxides on aluminum or a greenish coating on copper.
- 👃 Smell: a freon leak is often accompanied by a specific smell of oil that comes out along with the gas.
- 🧼 Soap solution: The easiest way to find a fistula is to apply foam to suspicious areas while the compressor is running.
Why do Indesit and Ariston refrigerators leak?
In a row models of these brands used an aluminum evaporator sealed in foam. When the metal expanded and contracted due to temperature changes, the tube inside the housing chafed or ruptured, which made repairs economically unfeasible.
To extend the service life, it is important to ensure good ventilation of the compressor compartment and avoid mechanical damage to the rear wall during defrosting. Any scratch on the evaporator tube can be the beginning of the end for the entire refrigeration system.
Frequently asked questions (FAQ)
Is it possible to completely replace aluminum tubes with copper ones during repairs?
Theoretically it is possible, but this requires complete re-welding of the circuit, which is not economically viable and technically difficult. Usually, only the damaged section of the evaporator is replaced with a mounted aluminum radiator, preserving the rest of the system.
Does the material of the tubes affect energy consumption?
Yes, copper has better heat transfer, so the refrigerator can work a little more efficiently. However, in modern models the difference is leveled out by the thickness of the walls, the quality of the insulation and the power of the compressor, so this is practically not reflected in the light bills.
How to determine a leak if the tubes are hidden in the housing?
If there are no external signs, technicians use leak detectors that react to freon vapor, or plug the circuit and check the pressure drop with a pressure gauge. Sometimes you have to open the thermal insulation in places of probable damage.
Why is there almost no pure copper in new refrigerators?
The main reason is the cost of raw materials. Copper is rising in price faster than aluminum and steel. In addition, modern technologies make it possible to create effective heat exchangers from aluminum, making its use justified.
Is it dangerous to breathe vapors when soldering aluminum tubes?
Yes, fluxes for aluminum often contain aggressive chemicals, and when heated, harmful compounds can be released. It is necessary to work in a well-ventilated area and use personal respiratory protection equipment.