When an old refrigerator finally breaks down, many owners think about what to do with its “heart” - the motor. The compressor is a complex technical unit, hidden behind a black metal casing, which has rarely been seen in disassembled form. Inside this sealed container is a hidden mechanism that ensures the circulation of refrigerant through the system.
Understanding this is necessary not only for those who are interested in technical curiosity, but also for craftsmen involved in repairs or disposal. Many people mistakenly believe that there is a simple pump inside, but the real design is much more interesting and complex. Studying the insides helps to understand why this unit is so critical for the operation of the entire climate system. compressor from an old refrigerator what's inside has, it is necessary not only for lovers of technical curiosity, but also for craftsmen involved in repairs or recycling. Many people mistakenly believe that there is a simple pump inside, but the real design is much more interesting and complex. Studying the insides helps to understand why this unit is so critical for the operation of the entire climate system.
In this article we will analyze in detail the design of the piston unit, consider its main components and discuss the possibilities of recycling. You will learn exactly which parts are hidden under an impenetrable case and why disassembling them yourself is often impossible without special tools.
Principle of operation and purpose of the unit
The main task of this device is to create a pressure difference in the cooling system. It compresses gaseous freon, pumping it into a condenser, where it turns into a liquid state, releasing heat to the environment. Without this mechanical compression normal operation of the refrigeration cycle is impossible, since the refrigerant will not be able to circulate in a closed circuit.
Inside the housing, a continuous process of converting electrical energy into mechanical energy occurs. The electric motor drives the crank mechanism, which causes the pistons to reciprocate. It is these movements that create the necessary vacuum at the inlet and high pressure at the outlet.
It is worth noting that most household models operate in sealed mode. This means that all rubbing parts are cooled and lubricated by oil, which is also located inside the casing. This design allows you to minimize noise and prevent leaks of working gas, but makes repairs almost impossible at home.
Design of the electric motor inside the casing
If you look inside the black casing (conditionally, since it is welded), the first thing that catches your eye is its massive electric motor. It is located vertically and mounted on springs or rubber shock absorbers to dampen vibrations during operation. The engine consists of a stator and a rotor, which are constantly exposed to freon and oil.
The stator windings are made of copper wire coated with a special heat-resistant enamel. When the motor starts, a powerful electromagnetic flux occurs, which causes the rotor to rotate. It is important to understand that the rotor here is often part of the crankshaft of the compressor part, which provides direct transmission of torque without belts and gears.
- 🔌 Start relay - a device that briefly connects the starting winding to create torque.
- ⚡ Thermal relay - overheating protection, opening circuit when the permissible temperature of the windings is exceeded.
- 🔩 Capacitor - an element necessary to shift the phase of the current in some types of motors (although in older models a circuit with a starting winding is often used).
The electrical part is immersed in oil, which requires the use of special refrigerant-resistant varnishes and insulating materials. If moisture or oil breakdown products get inside, insulation breakdown and short circuit may occur, which will lead to engine combustion.
Compressor group: pistons and valves
The compressor part is located directly above the engine or on the side of it (depending on the model). The most common units in household refrigerators are piston units. A piston mounted on a connecting rod moves inside the cylinder, alternately increasing and decreasing the volume of the working chamber.
The key element here is the valve group. It consists of intake and exhaust valves, which are thin elastic plates. Their task is to pass gas in only one direction. When the piston moves down, the intake valve opens, drawing in freon. When the piston rises, it closes, the gas is compressed, and the exhaust valve opens, pushing gas into the system.
Why do valves break?
Thin metal plates of valves can break due to water hammer (liquid freon entering instead of gas) or metal wear. This leads to the fact that the compressor hums, but does not pump pressure.
In some modern or specific models there may be rotational or spiral compressors, but in old Soviet and post-Soviet refrigerators it is the piston circuit that dominates. The manufacturing accuracy of friction pairs here is extremely high, gaps are measured in microns.
Oil system and lubrication
Inside the sealed casing there is always a certain amount of special refrigeration oil. It performs several critical functions at once: it lubricates rubbing parts, removes heat from the engine windings and provides additional sealing of the gaps between the piston and the cylinder
Lubrication occurs by splashing. At the end of the crankshaft there is often a scoop or channel system that captures oil and sprays it onto the inner walls of the housing and mechanism parts. The oil level is strictly regulated by the manufacturer.
⚠️ Attention: When storing or transporting an old compressor horizontally, oil may leak from the working chamber into the circulation circuit. This clogs the capillary tube and disables the refrigerator. Always check the oil level before restarting.
Over time, the oil can oxidize, especially if there was a freon leak in the system and air got into it. Oxidation products form acid, which destroys the insulation of the windings. That is why when replacing a compressor, a complete flushing of the system and replacement of the filter-drier are always required.
Table of characteristics of internal components
For a better understanding of the scale and materials used in production, let’s consider the main parameters of the elements hidden inside the housing. Data may vary slightly depending on the manufacturer (Atlant, Danfoss, Secop).
| Component | Material | Function | Wear criticality |
|---|---|---|---|
| Piston | Aluminum alloy / Steel | Refrigerant compression | High (scuffing) |
| Valve plates | Elastic steel | One-way gas circulation | Critical (fragility) |
| Motor windings | Copper with enamel | Creating a magnetic field | Medium (insulation breakdown) |
| Shaft (crankshaft) | Steel | Rotation transmission | Low |
As can be seen from the table, the most vulnerable elements are thin valve plates and winding insulation. It is their condition that determines the life of the entire assembly. Metal parts, if lubricated, can work for decades.
Recycling possibilities
Many home craftsmen are wondering: if compressor from an old refrigerator it still works, where can it be used? Most often it is used to create homemade compressors for airbrushing, inflation of tires or pneumatic tools. However, there are some nuances here.
Firstly, such units are not designed for continuous operation in air injection mode. They are designed for cyclic operation of the refrigerator (works for 10 minutes, rests for 20). During constant operation, they quickly overheat.
- 🎨 Airbrush - requires the installation of a moisture separator, since there will be a lot of oil mist at the output.
- 🔧 Pneumatic tools - low productivity (usually 30-50 liters per minute) allows you to pump only small tools.
- 💨 Blowing —great for creating an air flow for cleaning electronics or starting a fire.
Therefore, when creating a home-made installation, it is necessary to provide forced cooling of the housing or an operating time limiter.
Diagnostics of faults without opening
Since the housing is welded, diagnosis of internal failures is carried out by indirect methods. The first sign of trouble is often the nature of the sound. If the unit hums but does not start, the piston may be jammed or the starting winding has burned out.
If the motor runs but there is no cold, most likely the problem is in the valve group. The piston moves, but does not create the required pressure due to broken plates or loss of tightness. You can check this by connecting a pressure gauge to the service fitting (if there is one) or by ear - when the valves break, the sound of operation changes and becomes more “empty.”
⚠️ Attention: Never try to open the welded compressor housing with an angle grinder at home! Freon vapor under pressure may remain inside, and if it comes into contact with sparks, it can ignite or cause poisoning. In addition, it is impossible to weld it back properly without vacuum equipment.
It is also worth checking the resistance of the windings with a multimeter. Normal values vary for different models, but usually the starting winding has a higher resistance (20-40 ohms) than the working winding (10-20 ohms). If the device shows an open circuit or a short circuit to the housing, the compressor is faulty.
☑️ Compressor diagnostics
Disposal and environmental safety
An old compressor is not just a piece of metal, but an object that requires proper disposal. Technical oil remains inside the casing, which pollutes the soil and water. In addition, in older models (manufactured before the 2000s), freon R12 could circulate in the system, which destroys the ozone layer.
Modern units are filled with safer gases, but oil is still dangerous. Therefore, it is strictly forbidden to throw compressors into a regular trash can. They should be taken to special collection points for scrap metal or household appliances, where they will pump out the refrigerant and dispose of the oil.
Compliance with recycling rules helps preserve the environment and gives materials (copper, steel, aluminum) a chance to get a second life in the form of new products. Recycling one compressor saves a significant amount of energy compared to mining and processing ore.
Is it possible to change the oil in a refrigerator compressor?
Theoretically, it is possible, but only if you are a professional craftsman with vacuum equipment. At home, it is impossible to completely drain the old oil and fill in new oil without moisture and air getting in. Moisture will lead to the formation of acid and rapid failure of the unit.
Why does the compressor get very hot?
Heating up to 80-90 degrees is the norm for some models. However, if the housing is hot to the point that you cannot touch it with your hand, this may indicate an interturn short circuit, a lack of refrigerant, or problems with ventilation around the motor.
How much does a refrigerator compressor weigh?
Weight depends on power and dimensions. A standard household compressor weighs from 8 to 12 kilograms. This weight contains a significant amount of non-ferrous metals (copper in the windings), which makes them a valuable raw material for delivery.
The compressor hums, but does not start - what to do?
Most often the starting relay is to blame. You can replace it yourself by choosing an analogue. If replacing the relay does not help and a humming sound is heard, it means that the mechanical unit is jammed or the winding is burned out. In this case, the entire unit must be replaced.