The refrigerator is one of the most important household appliances in every home, ensuring the safety of food. The heart of this complex system is invariably compressorwhich causes the refrigerant to circulate in a closed circuit. Understanding exactly how this unit works will help you better understand the causes of breakdowns and communicate more effectively with technicians during repairs.
Externally, this unit looks like a massive black or gray “pot” located in the lower rear part of the case. Inside this sealed shell lies a complex mechanical system operating under high pressure. It is the quality of operation of this mechanism that determines whether your freezer will have a stable temperature or whether the food will begin to deteriorate.
In this article we will analyze the internal structure in detail, look at different types of motors and find out what processes occur inside the metal casing when the device is connected to the network. Modern models may differ significantly in design from those produced decades ago, so it is important to understand the current technological solutions.
The principle of operation of the refrigerator compressor
The main task of the compressor is to compress and move refrigerant vapor. When you plug in the refrigerator, electrical energy is converted into mechanical movement, which operates the piston group. This process creates a pressure difference necessary for phase transitions of freon.
The refrigerant, evaporating in the evaporator, takes heat from the refrigerator chambers and enters the compressor in the form of low-pressure gas. Here it is compressed, its temperature rises sharply, after which the hot gas under high pressure is pushed into the condenser. There it cools down, turns into liquid and the cycle repeats again.
It is important to note that this entire process occurs in a closed loop. Tightness system is a critical parameter, since moisture or air getting inside can lead to the formation of ice plugs and equipment failure. The outlet pressure can reach several atmospheres, which requires high strength of all connections.
⚠️ Attention: The internal pressure in the system may remain even after the device is turned off. Do not try to depressurize the tubes without special equipment and skills, this can lead to injury.
The cyclic operation is ensured by a thermostat or an electronic control board, which gives a signal to start or stop the motor. In older models, this process was accompanied by a characteristic click and hum, while new inverter systems operate almost silently, smoothly regulating power.
Main design elements
If you look inside the casing, you can find several key components, each of which performs its own function. The design is designed to minimize vibration and noise, as well as ensure the durability of rubbing parts. The basis is an electric motor and a mechanical compressor part mounted on a common frame.
The housing is usually made of durable steel and is divided into two parts welded together. An environment saturated with oil vapor is created inside, which ensures lubrication of all moving parts. The absence of oil seals and seals on the engine shaft is a key feature of sealed units, eliminating freon leakage through the shaft.
The motor suspension system plays a crucial role. The engine is mounted on springs inside the casing, which helps dampen vibrations that occur when the pistons operate. If the springs break or jump off, the refrigerator begins to vibrate and rattle strongly.
- 🔩 Electric motor —an asynchronous motor that creates rotational motion of the shaft.
- ⚙️ Crank mechanism —converts rotation into translational motion of the piston.
- 🛢️ Oil system — provides lubrication and heat removal from rubbing surfaces.
- 🌡️ Thermal protection —relay that turns off the motor when the windings overheat.
Each element is subjected to high loads. For example, stator windings must withstand significant currents, especially at the time of startup. The oil used in the system has the following properties: it should not freeze at low temperatures and should maintain viscosity when heated.
Why is the compressor housing hot?
The housing heats up because the gas is compressed inside, which, according to the laws of physics, is always accompanied by an increase in temperature. In addition, the hot freon coming out of the discharge pipe transfers some of the heat to the walls of the casing. A normal temperature is considered to be one at which you can hold your hand, but not for long (about 50-60 degrees). If the body is hot to the point that you cannot touch it, this is a sign of a malfunction.
Types of compressors: piston and inverter
The market for household appliances is still dominated by two main types of designs, which are fundamentally different in the method of control and mechanics. Understanding the difference between them will help when choosing a new refrigerator or estimating the cost of repairing an old one.
Classic piston units work on the “on-off” principle. The motor runs at full speed, cools the chamber to the set temperature, after which the thermostat opens the circuit. When the temperature rises, the cycle repeats. This is a time-tested technology that is distinguished by its maintainability.
Inverter models are devoid of sudden starts and stops. The electronics smoothly regulate the engine speed, maintaining the temperature within a narrow range. This allows you to save energy and reduce wear on mechanical parts, since there are no starting currents.
| Parameter | Piston (Start-Stop) | Inverter |
|---|---|---|
| Operating principle | Cyclic (max. power / rest) | Smooth speed control |
| Noise level | Higher, relay clicks are heard | Low, smooth hum |
| Energy consumption | Higher due to starting currents | Lower by 20-30% |
| Resource | Less (wear during startup) | Higher (no constant starts) |
When choosing, it is worth considering that inverter systems are more sensitive to voltage drops in the network. For their stable operation, the use of stabilizers is often recommended, especially in country houses or areas with unstable power supplies.
Starting system and starting relay
The unit responsible for starting the engine deserves special attention. The asynchronous motor of the refrigerator cannot start on its own; it needs an initial push. This function is performed by a starting relay, which briefly connects the starting winding.
In older models, relays with a posistor (thermistor) were used. When voltage is applied, the posistor is cold and passes current through the starting winding. It heats up quickly, its resistance increases, and the circuit opens. More modern systems use electromagnetic relays.
If you hear a click, a hum from the motor for a couple of seconds, and then another click and silence, this is a classic sign of a starting problem. The motor tries to gain speed, but cannot, and the thermal protection emergency turns off the power to prevent the windings from burning out.
- 🔌 Posistor - an element that changes resistance when heated, opening the circuit.
- ⚡ Starting winding - creates an initial torque.
- 🛡️ Thermal relay - a bimetallic plate that opens the circuit when overloaded.
Replacing the starting relay is one of the simplest and cheapest procedures in repairing refrigerators. However, it is important to select an element with exactly the same characteristics, otherwise the engine will either not start or burn out.
⚠️ Attention: Frequent attempts to start a faulty compressor (when it hums and clicks) can lead to an interturn short circuit of the windings. If the refrigerator does not start 3-4 times, unplug it and call a technician.
Diagnostics of faults by sound and external signs
An experienced technician can determine the nature of the breakdown even before opening the casing, simply by listening to the operating unit. Beeps are often the first indicator of mechanical or electrical problems.
If the compressor runs continuously without turning off, this may indicate a freon leak or a leak in the circuit. The motor tries to compensate for the lack of cold by working at its limit, which ultimately leads to its overheating and failure.
A knocking, clanging or metallic grinding sound indicates mechanical wear. This could be a broken shaft bearing, damage to the piston group, or a torn off valve. In such cases repair often it is not economically feasible, and replacement of the entire unit is required.
☑️ Symptoms of a faulty compressor
Also You should pay attention to the smell. If there is a smell of burning or burnt insulation coming from the back wall, this is a sure sign of electrical problems. The insulation of the windings may have melted or the start relay has burned out.
Maintenance and extending service life
Although the compressor is a sealed unit and does not require regular lubrication or replacement of filters by the user, its operating conditions directly affect its durability. Proper care of the refrigerator can significantly extend the life of this expensive unit.
First of all, it is necessary to ensure good ventilation of the back wall. Dust, animal hair and fluff settling on the condenser (the black grille at the back) create a “thermal coat”. It becomes more difficult for the motor to release heat, it works with increased load and overheats more often.
It is also important not to place the refrigerator close to the wall. A minimum gap of 10-15 centimeters will ensure natural air circulation. Built-in models require special attention to the ventilation system of the furniture box.
- 🧹 Regularly (once every six months) vacuum the condenser at the back.
- 🌡️ Do not load hot products into the chamber, this increases the load.
- ❄️ Make sure the seals are in good condition doors so that the cold does not escape.
Another factor is level installation. If the refrigerator is tilted, the oil in the compressor may be unevenly distributed, which will lead to dry operation and jamming of the mechanism. Adjust the legs so that the doors close by themselves under the influence of gravity.
FAQ: Frequently asked questions
Why does the refrigerator compressor get very hot?
Heating the case to 50-70 degrees is a normal operating process, as it happens inside gas compression. However, if the housing is so hot that it is impossible to touch it, or only one part of it is heated, this may indicate an interturn short circuit, a jammed mechanism, or problems with the heat removal system (the capacitor is clogged).
Is it possible to replace the compressor yourself?
Theoretically, it is possible, but this requires special equipment: a vacuum pump, pressure gauge station, burner and freon cylinder. You cannot simply “re-solder” the pipes - the system must be evacuated and charged with the exact amount of refrigerant. Without experience and tools, there is a high risk of damaging a new unit.
How long does a compressor last on average?
The service life of modern compressors ranges from 10 to 15 years or more. Inverter models, due to the absence of constant starts and stops, often last longer than their piston counterparts. However, the resource greatly depends on the quality of the voltage in the network and operating conditions (room temperature, dustiness).
What to do if the refrigerator is humming, but not cooling?
This may mean that the compressor is working, but does not create the necessary pressure (compression). Reasons: valve breakage inside, freon leak or capillary tube clogged. Diagnostics by a technician with a pressure gauge is required to measure the pressure in the system.