When you hear a quiet hum in the kitchen, you probably don’t think about what complex mechanism provides cold in your cell. However, if the refrigerator stops working or you decide to recycle the old unit, the question of what the engine is made of becomes extremely relevant. The internal structure of the compressor is an engineering marvel hidden behind a sealed casing.
The refrigerator engine, technically called hermetic compressor, is a monoblock where the electric motor and the mechanical part of gas compression are combined in a single housing. This design eliminates refrigerant leakage, but makes simple repairs at home without special equipment impossible. Understanding the materials and structure helps to assess the weight of the device and its value when delivered to non-ferrous metal collection points.
The design is based on two main elements: an electric motor that creates a rotational movement, and a compressor unit that converts this movement into freon compression. All this is immersed in oil and sealed in a steel casing. It is important to notethat absolute cleanliness reigns inside, since even a microscopic speck of dust can damage the mechanism.
Materials of the housing and external protection
The outer shell of the compressor - this is the first thing that catches your eye. It is made of durable sheet steel, often coated with black enamel to protect against corrosion. This casing is welded from two stamped hemispheres using the contact welding method, which ensures complete tightness. An excess pressure of inert gas is created inside the housing, which prevents oxidation of parts even in the presence of microscopic moisture residues.
Tubes for connection to the refrigeration system are welded to the bottom of the steel housing. They are usually made of copper or copper-plated steel, as these materials are easy to solder and resistant to vibration. There are also three mounting studs on the bottom through which the motor is attached to the refrigerator frame using rubber shock absorbers that dampen vibration.
⚠️ Attention: Under no circumstances try to saw or open the steel compressor casing with a grinder or a hacksaw! There may be compressed gas inside, and vapors from oil and varnish insulation of the windings, when heated by the friction of the tool, can ignite or cause poisoning.
The weight of the empty steel case is relatively small compared to the internal contents, but it is this that gives the device its characteristic shape. The steel used for stamping has a certain thickness to withstand temperature changes and external mechanical stress during transportation.
Electric motor design
The heart of the compressor is an asynchronous AC motor. Its rotor is mounted directly on the shaft of the crank mechanism. The motor stator is assembled from electrical steel plates, which minimizes eddy current losses. It is this part that makes up a significant part of the weight of the entire unit.
The stator windings are made of copper wirecoated with special heat-resistant varnish insulation. In older Soviet-made models, you can sometimes find aluminum windings, but modern standards require the use of copper due to its better electrical conductivity and ability to withstand high temperatures without destroying the insulation.
A starting winding and a starting relay are used to start the engine. At the moment of switching on, the rotor is stationary, and a phase shift is required to create the initial torque. As soon as the engine picks up speed, the centrifugal relay or electronic circuit turns off the starting winding, and the motor runs on the main winding.
The insulation of the wires can withstand temperatures up to 150-180 degrees Celsius, since the engine is cooled due to refrigerant and oil vapors circulating inside the casing. Overheating of the windings is one of the common causes of failure, so modern models have a built-in thermal protection relay.
Mechanical part: pistons and shafts
The mechanical part of the compressor is responsible for direct compression of the refrigerant. Household refrigerators most often use a crank mechanism, similar to that used in internal combustion engines of cars, but in miniature. The engine shaft goes into the crankshaft, which drives the piston.
Pistons in modern compressors are made of special aluminum alloys or cast iron. Aluminum is preferred because of its light weight, which reduces inertial load on bearings and reduces noise. However, the surface of the piston must be perfectly polished to minimize friction.
The cylinder in which the piston runs is also made of high-strength metal, often cast iron or special steel. The gap between the piston and the cylinder wall is measured in microns. Any damage to the cylinder surface leads to a drop in compression and the inability to build up pressure.
☑️ Signs of wear on the mechanical part
The valve system located above the cylinder controls the gas flow. Reed valves are made of thin elastic steel. They open and close hundreds of times per minute, allowing gas to flow in the desired direction. The quality of steel for valves is critically important, since their failure leads to instant failure of the compressor.
The role of oil and lubrication system
There is always oil inside the sealed casing, at the bottom. It is necessary to lubricate rubbing pairs: shaft, piston and cylinder bearings. The oil in refrigeration compressors is not an ordinary automobile engine analogue, but a special synthetic liquid with properties.
The main feature of refrigeration oil is its ability to dissolve in the refrigerant (freon) and not freeze at low evaporator temperatures. If the oil solidified, it would clog the thinnest capillary tubes of the system, and the refrigerator would stop working.
| Refrigerant type | Compatible oil type | Features |
|---|---|---|
| R12 (Freon-12) | Mineral (MO) | Mixes well, but is harmful to the environment |
| R134a | Polyester (POE) | Hygroscopic, afraid of moisture |
| R600a (Isobutane) | Alkylbenzene (AB) | Used in modern models |
Lubrication is carried out by splashing. Rotating parts are immersed in an oil bath or capture oil through special channels, scattering it over the internal walls and parts. The oil level is strictly regulated by the manufacturer: its excess can cause hydraulic shock, and its deficiency can cause jamming.
What will happen if you mix different types of oils?
Mixing mineral and synthetic oils can lead to the formation of sediment, which will clog the capillary tube and damage the refrigerator.
Colored metals and recycling value
The question of what the engine is made of often arises when you want to sell it for scrap. The main mass is black steel (body and stator plates), but it is of the greatest value copper. It is the copper content that determines the price of the compressor upon delivery.
Copper in the compressor is located in the stator windings. On average, one standard compressor weighing about 10-12 kilograms can contain from 1 to 1.5 kilograms of pure copper. However, it can only be removed by burning the insulation or mechanical disassembly, which is dangerous and environmentally harmful to do at home.
The device also contains a small amount of aluminum (pistons, casings of some components) and brass (connecting tubes, bushings). Steel parts make up up to 85-90% of the total weight of the unit. When scrapped, compressors are often assessed as a “complete electric motor” or copper is released at the output.
⚠️ Attention: When scrapping a compressor, make sure that it is completely free of refrigerant. Piercing the housing should only be done in a well-ventilated area or outdoors, since the release of gas under pressure can spray the oil.
There are special lines for processing refrigeration equipment, where the body is crushed and non-ferrous metals are separated by separation. This is the most effective method of recycling, allowing up to 95% of materials to be returned to the production cycle.
Types of compressors and their differences in composition
Not all refrigeration engines are the same. In addition to classic linear compressors, inverter units are increasingly found in modern models. Their internal structure is more complex, and the composition of materials may differ in the presence of more powerful magnets and electronics.
Linear compressors, popularized by the brand LG, operate on the principle of reciprocating movement of a piston, which is driven by a linear electromagnet. They do not have a crank mechanism, which reduces the number of rubbing parts and noise. The composition of their windings and cores is similar to the classic ones, but the geometry has been changed.
Inverter models contain a built-in control board that smoothly regulates the shaft rotation speed. This avoids constant inrush currents. These motors use higher quality bearings and rare earth magnets inside to improve efficiency.
Differences in design also affect maintainability. Classic compressors are easier to diagnose by sound and vibration, while inverter compressors require connecting a special tester to check the electronics.
Frequent misconceptions about the composition of the motor
There is a myth that there is a vacuum inside the compressor. This is wrong. Inside there is oil and refrigerant vapor under a certain pressure. A vacuum is created only during the operation of the system in the evaporator circuit, but not in the engine compartment itself.
Another misconception concerns the “eternal” resource. Many people believe that if a motor is made of metal, it cannot wear out. However, constant friction, thermal expansion and chemical reactions of oil with freon eventually lead to the production of friction pairs and loss of valve tightness.
Some are sure that the heavier the compressor, the better it is. Although weight does correlate with the amount of copper and the thickness of the metal, modern technology allows for lightweight and efficient units. Weight is not the only indicator of quality.
Understanding what your refrigerator engine is made of helps not only with recycling issues, but also with proper operation. Taking good care of the equipment, avoiding frequent switching on and ensuring good ventilation of the rear wall will prolong the life of this complex mechanism.
Can a compressor from a refrigerator be used for other purposes?
Yes, compressors are often used to create homemade airbrushes, inflate tires or pneumatic tools. However, it is necessary to remove the filter drier and properly organize the removal of oil, which will be ejected along with the air.
Why can’t you turn on the compressor outside the refrigerator without a system?
Without a heat exchanger and the correct outlet pressure, the compressor will quickly overheat, since the gas will not have time to cool, and the oil will lose its properties. A thermal protection relay may also operate.
How much does a standard compressor weigh?
The weight of an average compressor for a household refrigerator varies from 9 to 12 kilograms, depending on the model and manufacturer. Industrial units can weigh significantly more.
Are there precious metals in the compressor?
Precious metals (gold, silver, platinum) are not used in ordinary household compressors. The basis is copper, aluminum, steel and technical alloys. The content of precious metals is negligible and cannot be extracted.