Looking behind the back of a working refrigerator, you will probably notice a black grille or, conversely, you will see an open system of intertwining metal lines. It is this system, hidden from view inside the housing panel or taken outside, that is the “circulatory system” of your unit. Refrigerant circulates through these channels, transferring heat from the chamber to the outside, which allows the food to remain fresh. But few people think about why engineers choose particular metals to create this complex circuit.
The materials used in the production of refrigeration circuit pipelines are not chosen by chance. The safety, durability and energy efficiency of the device are at stake. In modern models you can find both classic copper and more budget-friendly aluminum or even steel with an anti-corrosion coating. Understanding the differences between these materials will help you better understand the causes of breakdowns and the cost of future repairs.
In this article we will analyze in detail the physical properties of each metal used in refrigeration units and explain why thermal conductivity and ductility play a decisive role here. You will find out which tubes are easier to break during defrosting and why some of them are almost impossible to solder at home without special equipment.
Copper: the classic standard of reliability
Traditionally copper tubes was considered the gold standard in the production of refrigeration equipment. This metal has excellent thermal conductivity, which allows it to effectively remove heat from the evaporator. In addition, copper is highly ductile, which makes it possible to form complex coils without the risk of material rupture at bend points. That is why you will most often find this material in old Soviet-made models and expensive modern units.
However, copper also has its drawbacks, which force manufacturers to look for alternatives. The main enemy of a copper circuit is moisture combined with oxygen, which can lead to the formation of acids that corrode the metal from the inside. Copper is also susceptible to electrochemical corrosion upon contact with other metals if the system uses dissimilar solders or fittings.
- 🔸 High heat transfer ensures rapid cooling of the chambers.
- 🔸 Excellent maintainability: easily soldered with soft and hard solders.
- 🔸 Resistance to high refrigerant pressure in the system.
- 🔸 Long service life with proper use and absence of manufacturing defects.
Why does copper sometimes turn black?
A black oxide deposit can form inside copper tubes if There was a vacuum breakdown in the system and air and moisture got in. This leads to blockage of the capillary tube and requires a complete flushing of the system or replacement of the compressor.
When repairing copper sections, craftsmen use a gas-flame torch and phosphorus-containing solders. It is important to understandthat the quality of soldering directly affects the tightness of the system. Even a microscopic hole, invisible to the eye, will lead to a gradual release of freon and the refrigerator stops.
Aluminium: lightness and savings for the manufacturer
In the pursuit of reducing costs and reducing the weight of the final product, many manufacturers have begun to actively implement aluminum tubes. Aluminum is much lighter than copper and cheaper to mine, which makes it attractive for the mass segment of household appliances. Most often, evaporators are made from aluminum, which are located inside the freezer or behind the rear wall of the refrigerator compartment.
However, this material has a significant drawback - low ductility and a tendency to crack due to vibration or mechanical stress. If you carelessly picked at the ice with a knife, trying to speed up defrosting, then with a high degree of probability you damaged the aluminum evaporator. Unlike copper, aluminum does not “stretch”, but bursts, which makes such damage critical.
⚠️ Attention: Aluminum is extremely difficult to solder at home. This requires special fluxes that act aggressively on the metal and high temperatures. Unprofessional soldering often leads to repeated leaks after a short time.
Another problem is the galvanic couple that occurs when connecting aluminum to copper (for example, when installing a new compressor with a copper outlet pipe). To connect such dissimilar metals, special adapters or bimetallic inserts are required, otherwise the joint will quickly be destroyed by corrosion.
Steel and modern alloys
On the capacitors (the same grilles at the back of the refrigerator) you can often see black tubes. This copper-plated steel or a special anti-corrosion coating. Steel has high strength and resistance to mechanical damage, which is important for external parts of the system that can be touched during cleaning or transportation.
Modern chemical industry offers more complex solutions. For example, some models use tubes made of stainless steel or alloys with the addition of zinc to improve resistance to aggressive environments. However, such solutions are rarely found in mass-market household refrigerators due to the high price.
Steel tubes, as a rule, have thicker walls compared to copper counterparts. This compensates for the lower thermal conductivity of steel. To ensure effective heat exchange, the surface area of a steel capacitor is often larger than that of a copper one.
- 🔹 High mechanical strength and resistance to impacts.
- 🔹 Less susceptible to accidental damage during installation.
- 🔹 Good resistance to external corrosion due to varnish coating.
- 🔹 Difficulty in soldering: refractory solders and powerful tools are required.
Material Comparison Chart
To organize the information and help you better understand the differences between materials, we have prepared a summary table of characteristics. It will help to evaluate the pros and cons of each type of tube from the point of view of physics and operation.
| Characteristics | Copper | Aluminum | Steel (copper-plated) |
|---|---|---|---|
| Thermal conductivity | Very high | High | Medium |
| Plasticity | High (stretches) | Low (brittle) | Medium |
| Corrosion resistance | Medium (afraid of moisture) | High (oxide film) | High (coating) |
| Repair complexity | Low | High | Average |
| Material cost | High | Low | Low |
As can be seen from the table, there is no ideal material. Each manufacturer chooses a compromise between the cost of production and the expected service life of the product. In expensive premium models, copper is more often used, while in budget segments aluminum and steel.
Circuit design and arrangement of tubes
The refrigerator cooling system is a closed circuit consisting of several key sections, each of which performs its own function. Understanding where and what tubes are located will help diagnose the problem by external signs.
The first section is discharge linegoing from the compressor to the condenser. Here the refrigerant is under high pressure and has a high temperature. The tubes in this area are always hot. Next comes the condenser (grid at the back), where the gas cools and turns into liquid.
Next comes the capillary tube - a very thin copper or aluminum channel where a sharp drop in pressure occurs. After this, the refrigerant enters the evaporator located inside the chambers. It is here that the tubes are the thinnest and most vulnerable, since they are hidden behind a plastic panel or mounted in the housing wall.
☑️ Diagnostics of the condition of the tubes
In models with a system No Frost the evaporator is located in a separate block, often in the upper part of the freezer, and a complex system of aluminum channels leads to it. In “crying” refrigerators, the evaporator can simply be sealed into the back wall of the chamber, which makes replacing it almost impossible without compromising the integrity of the case.
Typical problems and causes of damage
The most common cause of tube failure is corrosion. It can be caused by both manufacturing defects (poor cleaning of the metal before soldering) and external factors. For example, if you often wash the floor around the refrigerator and water stagnates at the base, the lower part of the condenser can quickly rust.
The second enemy is mechanical stress. As mentioned earlier, using sharp objects to chip away at the ice in your freezer is a surefire way to puncture an aluminum evaporator. Also, the tubes can be damaged during careless transportation if the compressor and internal elements have not been secured.
⚠️ Attention: If you hear hissing or whistling from the tube area, immediately unplug the refrigerator. This is a sign of an active freon leak. Operation in this mode can lead to compressor combustion due to lack of cooling of the windings.
The third problem is vibration fatigue of the metal. If the compressor is installed rigidly or has defects, constant vibration is transmitted to the tubes. Over time, microcracks may appear in places where bends or soldering occur. This is especially true for copper tubes, which lose their ductility over time.
Features of repair and replacement of sections
Repairing refrigerator pipelines is a task for professionals that requires special tools. The process begins by searching for the leak, often using a leak detector or soap solution. After localizing the damage, a decision is made: solder the hole or replace the area.
For soldering copper, a propane-oxygen torch and solder containing silver or phosphorus are used. Aluminum is soldered using special high-temperature solders (for example, zinc-based) and active fluxes, which must be washed off after work, otherwise they will continue to corrode the metal.
The process of replacing a section of the tube:1. Relieving residual pressure.
2. Cutting the tube (do not saw so that there are no shavings).
3. Rolling of ends or preparation for butt soldering.
4. Purging with nitrogen during soldering (to prevent oxidation inside).
5. Evacuating the system.
6. Refilling with refrigerant.
After the tightness is restored, the system must be vacuumed to remove air and water vapor. Only after this is the refrigerant charged with new refrigerant in strict accordance with the model specifications. Using the wrong freon or oil can lead to destruction of the tubes from the inside.
Is it possible to solder a refrigerator tube at home?
Theoretically, it is possible if you have access to a gas burner and solder, and the tube is copper. However, without a vacuum pump and scales for refilling freon, a full repair is impossible. In addition, soldering aluminum at home is extremely difficult and rarely gives long-lasting results.
Why are the tubes on the back of the refrigerator hot?
This is normal. In the condenser (grid at the back), hot freon gas gives off heat to the environment and cools, turning into liquid. The temperature of the tubes can reach 50-60 degrees Celsius.
What to do if you pierce the wall with a knife during defrosting?
Immediately unplug the refrigerator from the outlet. Do not turn it on again until the technician fixes the leak and refills the system. Turning on the compressor with an open circuit will lead to its breakdown, since it is designed to work with gas, and not to pump air.
Does the material of the tubes affect the noise of the refrigerator?
Indirectly. Aluminum tubes are thinner and can resonate more strongly when vibrating, transferring sound to the body. Copper tubes are more massive and dampen vibrations better, but the main source of noise is still the compressor, not the pipeline material.
How long do the tubes last in the refrigerator?
In the absence of mechanical damage and manufacturing defects, the service life of the tubes is equal to the service life of the refrigerator itself - 10-15 years or more. The main reason for their failure is corrosion or damage due to careless defrosting.