When an old refrigerator stops working or makes suspicious sounds, the owner is often faced with the question: what to do with the unit? Many people simply call a specialist, but curious craftsmen prefer to look inside on their own. If you have ever wondered what is hidden under the black casing on the back wall, then this article is just for you.
The motor-compressor is the heart of the refrigeration system. It is this unit that causes the refrigerant to circulate through the tubes, creating cold. Hidden inside this metal ball are complex mechanics operating under high pressure. Understanding how the compressor workswill help not only in repairs, but also in proper disposal of equipment.
Inside the sealed housing there is vacuum and oil. There is no place for dust or moisture from outside. All components are immersed in a special oil medium, which lubricates rubbing parts and removes heat. That is why opening a working unit without special equipment is a dangerous and often pointless undertaking.
General design and sealed housing
Externally, the compressor is a painted metal cylinder or sphere, usually black. This housing serves not only as protection, but also as a noise suppressor. Inside there is electric motor the compressor unit itself, combined into a single system on a spring suspension. Such a suspension is necessary to dampen vibrations that occur during operation of the piston group.
All internal components are connected to the outside world only through three contact tubes: two copper (suction and discharge) and one electric. Tightness is a key parameter. If the integrity of the casing is compromised, oxygen and moisture get inside, which instantly oxidizes the windings and destroys the properties of the refrigerant. Therefore disassembling the case is possible only with the help of a special tool and an angle grinder, after which re-sealing at home is impossible.
In the lower part of the case, at the bottom, there is always oil. Its level is strictly regulated by the manufacturer. If there is too little oil, the rubbing parts will wear out quickly. If there is too much, water hammer will occur and the compressor will jam. It is the oil that often leaks when the refrigerator is transported incorrectly, which is one of the common causes of breakdown.
⚠️ Attention: Residual pressure may remain inside the case even after many years of inactivity. When you try to cut the casing, a sudden release of oil and freon vapors is possible. Work only in a ventilated area and wear safety glasses.
There is also start-protective equipment inside, which is often mounted outside on the terminal box, but the electrical circuits lead inside. Starting relay and thermal relay are the first elements that technicians check during diagnostics, since they fail more often than the motor itself.
Electrical part: stator and rotor
The motor that rotates the compressor shaft is asynchronous. It consists of a stationary stator and a rotating rotor. The stator is a set of metal plates with copper windings wound on them. Usually there are two of them: working and starting. Working winding creates the main magnetic field, and the starting one helps to accelerate the rotor at the moment of switching on.
The rotor, or “squirrel cage”, is mounted directly on the compressor shaft. It does not have any brushes or commutators, which makes the design very reliable. Friction here occurs only in the plain bearings. The motor windings are impregnated with a special varnish that is resistant to freon and oil. If you see blackened wires inside, this is a sure sign of an interturn short circuit.
Electric current is supplied through a sealed input that passes through the housing wall. This unit is insulated with glass or special ceramics to prevent voltage breakdown on the metal case. Violation of the input insulation is a common reason why the circuit breaker in the panel “knocks out” when the refrigerator is turned on.
It is important to note that in modern inverter models the design of the electric motor may differ. More complex control circuits are used there, and the motor itself can be three-phase. However, the principle of operation remains similar: electrical energy is converted into rotational movement of the shaft.
Mechanical part: piston group
The heart of mechanics is the crank mechanism. The engine shaft, which passes into the crankshaft, rotates and transmits movement to the piston through the connecting rod. The piston, in turn, moves inside the cylinder, compressing the refrigerant gas. This part experiences enormous loads and requires perfect lubrication.
An eccentric is often installed at the upper end of the shaft, which drives the connecting rod. Some designs use an oscillating connecting rod, which reduces the number of parts and improves reliability. All rubbing surfaces are made of high-strength alloys with minimal clearances. Wear of these parts leads to a drop in compressor performance. compressor performance.
- 🔩 Piston: is made of cast iron or steel, has high precision surface treatment.
- 🔩 Valves: thin metal plates that regulate gas flow. They open and close under pressure.
- 🔩 Cylinder: working chamber in which freon is compressed.
The valve group is the thinnest mechanism inside the motor. Reed valves are made of resilient steel. If solids or water (turned to ice) enters the system, the valves may become distorted. This will lead to the fact that the compressor will work, but will not create cold, since the gas will simply be passed back.
Lubricating system and oil
Special compressor oil circulates inside the engine. It differs from automobile or machine oil in its chemical properties. The main requirement for it is complete miscibility with the refrigerant and the ability to return to the compressor from the piping system. If the oil settles in the radiator, the compressor will be left without lubrication and will burn out.
Lubrication is carried out by a centrifugal pump located at the lower end of the shaft, immersed in an oil bath. When the shaft rotates, the oil rises upward along the spiral grooves, reaching the bearings and piston group. After lubrication, it flows back to the bottom of the housing. This cycle is repeated thousands of times per hour.
⚠️ Attention: It is strictly forbidden to mix different types of oils (mineral and synthetic). When replacing a compressor, you must use only the type of oil that is specified in the specification, otherwise the mixture will coagulate (curdle) and clog the capillary tube.
The oil service life is practically unlimited if the tightness of the circuit is maintained. However, when the engine overheats, the oil can coke, turning into tar. This clogs the thin lubrication channels and leads to a wedge of the mechanism. Dark color of the oil When opened, this is a clear sign of overheating or moisture entering the system.
Table of main components and their functions
For a better understanding of the structure of the device, consider the main components in the form of a table. This will help systematize knowledge about what is inside the black “barrel”.
| Unit | Material | Function | Frequent malfunction |
|---|---|---|---|
| Stator | Copper, electrical steel | Creation of a magnetic field | Open or short circuit of the winding |
| Piston | Cast iron, steel | Refrigerant compression | Ring wear, scuffing on the cylinder mirror |
| Valves | Elastic steel | Gas flow adjustment | Deformation, breakage of the petal |
| Bearings | Babbitt, bronze | Shaft support | Workout, shaft jamming |
Each of these nodes is critical. Failure of any element requires either a complex overhaul (which is almost impossible under domestic conditions) or a complete replacement of the unit. Modern compressors are often made non-separable, which simplifies production but complicates repair.
Why can’t you repair the compressor yourself?
In factory conditions, assembly occurs in a vacuum. This cannot be repeated at home. The ingress of even a microscopic amount of moisture or dust will lead to the rapid death of the new compressor.
Why motors stop working
Knowing the device, it is easier to understand the causes of breakdowns. The most common problem is piston group wedge. This happens when the oil loses its properties or its level drops. Metal parts begin to rub “dry”, heat up and expand until movement becomes impossible.
The second reason is electrical breakdown. Voltage surges in the network can damage the insulation of the windings. Particularly dangerous is an interturn short circuit, in which the engine hums, but cannot start, quickly overheating. In this case, the thermal relay should turn off the power, but if it is faulty, the windings burn to the ground.
- 💥 Hydraulic hammer: liquid freon enters the cylinder instead of gaseous. The liquid does not compress, which leads to the destruction of the valves or connecting rod.
- 💥 Relay malfunction: if the starting relay does not open the starting winding circuit, it burns out in a matter of seconds.
- 💥 Clogged system: increases the load on the compressor, forcing it to work at its limit.
It is also worth mentioning natural wear and tear. The service life of a household compressor is on average 10-15 years. After this period, the metal gets tired, the gaps increase, and efficiency decreases. During this period, the motor may work louder than usual or keep it on longer.
Disposal and recycling
If you have disassembled an old refrigerator, you have valuable non-ferrous scrap in your hands. There is a lot of copper inside the motor. The stator windings are high quality pure copper. The rotor also contains non-ferrous metals. The weight of the copper component can reach 1-1.5 kg, depending on the power of the model.
The steel case and internal mechanical parts are sold as scrap. However, you can’t just throw away the compressor. Oil may remain inside, which is a hazardous waste. It must be drained into a separate container and handed over to special collection points.
☑️ What to do with an old compressor
Some craftsmen use old compressors to create homemade devices: spray guns, pumps for aerating ponds or vacuum pumps. However, this requires alteration of the lubrication system and valves, since the standard compressor is designed to operate in a closed circuit, and not to pump air from the atmosphere.
Is it possible to restore a compressor if it is jammed?
In 99% of cases, no. A wedge means physical destruction of friction pairs (piston-cylinder or bearings). Attempts to “unwedge” by hitting or twisting usually lead to permanent shaft breakage. It’s easier and cheaper to buy a new unit.
Why is the splashing of oil inside the compressor heard?
This is normal when the unit is not working. The oil is located at the bottom of the housing. However, if a splashing sound is heard while the refrigerator is running, this may indicate wear on the internal shock absorbers of the motor suspension.
Is it dangerous to open the compressor with an angle grinder?
Yes, it is dangerous. In addition to the risk of flying sparks and debris, there is a risk of ignition of oil vapors when in contact with an open flame or high cutting temperatures. Be sure to use a respirator and safety glasses.