The refrigerator is an integral part of the modern kitchen, and its continuous operation is often taken for granted until a failure occurs. The heart of any refrigeration system is compressor, which is responsible for circulating the refrigerant and maintaining the required temperature in the chambers. Understanding exactly how this unit functions helps owners quickly respond to malfunctions and avoid costly repairs.
The work is based on a continuous cycle of compression and movement of gaseous freon, which, changing its state of aggregation, takes heat from the internal space of the refrigerator. Compressor circuit may vary depending on the models, be it a classic piston unit or a modern inverter engine, but the physical principle remains unchanged. It is the mechanical compression of the gas that allows it to effectively cool in the condenser and boil in the evaporator, creating cold.
To diagnose problems or just for general development, it is important to know that motor-compressor is a complex electromechanical unit, hermetically sealed in a metal casing. Inside it are electrical windings and a mechanical part that operates in an oil environment. Any disturbance in the operation of this system, be it knocking, humming or a complete lack of startup, requires a careful analysis of the operating diagram.
The basic principle of operation of the refrigeration unit
Fundamental working diagram the refrigerator is based on thermodynamic cycle where the refrigerant constantly changes from liquid to gas and back. The compressor in this chain acts as a pump, which creates the pressure necessary to move freon through the system pipes. Without this element, heat exchange would be impossible, since the gas would not be able to circulate at the required speed.
The process begins with liquid refrigerant under low pressure entering into evaporator, located inside the chambers. There it boils at very low temperatures, actively absorbing heat from food and air. Having turned into gas, freon enters the compressor, where it is compressed. When compressed, the temperature of the gas increases sharply, and it is sent under high pressure to the condenser.
In the condenser, which is usually a grate on the back wall, the hot gas gives off heat to the environment and condenses, becoming a liquid again. The cycle is closedwhen the liquid passes through a capillary tube or choke, where the pressure drops sharply and it is ready to evaporate again. This closed circuit operates until the thermostat detects that the set temperature has been reached.
⚠️ Attention: Attempts to independently depressurize the system to check the pressure without special equipment will lead to freon leakage and moisture entering the circuit, which will irreversibly damage the refrigerator.
Internal structure and types of compressors
Most household refrigerators are equipped piston compressorswhere the movement of the refrigerant is ensured by the reciprocating movements of the piston inside the cylinder. However, technological advances have brought more sophisticated and effective solutions to the market. Understanding the differences between types of motors helps to correctly assess the energy consumption and noise level of the equipment.
Modern models are increasingly equipped inverter compressors, which are able to smoothly regulate the engine rotation speed depending on the thermal load. Unlike classic models that operate in an “on-off” mode, inverters do not stop completely, but only reduce speed, maintaining the temperature. This reduces wear of mechanical parts and noise levels.
There are also rotary and linear compressors, each of which has its own design features. In rotary models, compression occurs due to the rotation of the rotor, and linear ones use electromagnetic forces for the linear movement of the piston without rotational mechanisms. Linear compressor features a smaller number of rubbing parts, which theoretically increases its reliability.
Electrical connection diagram motor
To start the compressor motor, a special one is used start-up protection equipment, which includes a starting and operating relay, as well as thermal protection. The electrical circuit ensures that voltage is supplied to the stator windings in the correct sequence, which allows the rotor to reach the required speed. Without a starting relay, the engine would only hum, but would not be able to start rotating.
When the refrigerator is turned on, current passes through the starting winding, creating the necessary torque. As soon as the engine reaches a certain speed, the centrifugal mechanism or relay opens the starting winding circuit, and the engine continues to operate on the working winding. Thermal relay Constantly monitors current consumption and opens the circuit when overloaded or overheated, protecting the motor from combustion.
In inverter models, the electrical circuit is much more complex and includes inverter control unitwhich converts the alternating current of the network into direct current, and then again into alternating current, but with a variable frequency. This allows you to smoothly regulate the compressor power. Diagnostics of such systems requires special knowledge and instruments, since the standard continuity test of the windings here is often uninformative.
Refrigerant circulation and heat exchange
The efficiency of the refrigerator directly depends on the quality of heat exchange, which occurs in two main units: the evaporator and the condenser. The evaporator hidden inside the case (often behind a plastic panel in the freezer) and is directly responsible for cooling the products. It is on its tubes and plates that frost can form, which is then removed by the No Frost system or defrost cycles.
Condenser, on the contrary, is located outside and must be freely washed by air. If dust or pet hair accumulates on the rear grille, heat output will be impaired and the compressor will have to work longer and harder. This leads to increased energy consumption and a reduction in the service life of the unit.
The movement of freon through the system is also controlled by a capillary tube, which creates hydraulic resistance and separates the high and low pressure zone. The diameter and length of this tube are calculated by engineers with high accuracy for each specific model. Impaired capillary patency (clogging) is a common cause of stopping cooling, although the compressor itself can work properly.
| System element | Function | Location | Surface temperature |
|---|---|---|---|
| Compressor | Compression and pumping of gas | Bottom rear | Hot (up to 90°C) |
| Condenser | Cooling and condensation | Rear wall | Warm |
| Evaporator | Boiling and heat absorption | Inside chambers | Very cold |
| Filter drier | Cleaning freon from moisture | At the condenser outlet | Warm |
Typical malfunctions and their symptoms
Understanding the operating pattern helps to quickly identify a breakdown by external signs. The most common problem is the failure of the start relay, when the compressor tries to start, makes a clicking sound and hums for a few seconds, then goes silent. In this case, starting winding receives power, but the engine cannot turn over, and the thermal protection emergency turns off the power.
Another common situation is the “turn-to-turn short circuit” of the motor windings. In this case, the compressor may start, but work with overheating and consume increased current. Symptom such a malfunction often occurs when plugs or circuit breakers in the electrical panel are knocked out immediately after turning on the refrigerator. Repair in this case is usually impossible; replacement of the unit is required.
If the compressor runs continuously without turning off, and the temperature in the chambers does not drop to normal, this may indicate a freon leak or loss of compression. The piston group could be worn out, and the engine pushes gas, but does not create the necessary pressure. This can only be determined accurately using a pressure gauge station by connecting it to the service fitting.
Why is the compressor knocking?
The knocking can occur due to wear of the crankshaft bearings, loosening of the shock absorbers or water hammer if the liquid fraction of freon has entered the cylinder.
Diagnostics and safety measures
Before proceeding with any diagnostics, it is necessary to completely de-energize the device. Electrical safety —priority number one, since there is oil and refrigerant inside the compressor casing, and voltage may remain on the terminal box. Checking the windings with a multimeter is the first step in troubleshooting.
To check, you need to remove the terminal box from the compressor and measure the resistance between the contacts. The normal resistance of the working winding is usually 10-30 Ohms, and the starting winding is 20-50 Ohms. The resistance between the housing and any contact must be infinite (open). If the device shows zero or a short circuit to the housing, the compressor is faulty.
It is also important to visually inspect the tubes coming out of the compressor. If they have traces of oil, this is a sure sign of system depressurization. At the point of leakage, freon carries with it droplets of compressor oil, so even a small oil stain on the motor housing requires attention.
☑️ Primary diagnostics of the compressor
⚠️ Attention: Replacing the compressor requires evacuation of the system and refilling with the exact amount Freon. Independent replacement without a vacuum sealer will lead to the rapid failure of the new compressor.
Operating life and durability of equipment
The average service life of a modern compressor is from 10 to 15 years, but the actual figures are highly dependent on operating conditions. Overheating is the main enemy of any electric motor. If the refrigerator is located close to the wall, in a niche or next to heating appliances, the life of the motor is reduced significantly due to constant operation at the limit.
Frequent power surges also negatively affect the electrical part of the motor and the starting relay. Using a voltage stabilizer or surge protector can significantly extend the life of equipment, especially in the private sector or old houses. Stable power supply ensures smooth start-up and operation without overloads.
It is also important to consider that the service life of linear and inverter compressors is declared by manufacturers to be higher, but their repair is much more expensive. In classic models, it is often economically feasible to replace the motor, while in complex systems it is sometimes easier to buy a new refrigerator.
When you need to call a technician
Despite the availability of theoretical knowledge, a number of situations require the intervention of a professional technician with a license and equipment. If you have identified a freon leak, hear extraneous metallic knocks inside the compressor housing or smell burnt wiring, further operation is dangerous. Specialist will be able to accurately determine the cause and carry out repairs in compliance with all technological standards.
Also help is needed if after defrosting, the refrigerator does not start to freeze for several hours. This may indicate a clogged capillary system or more serious circulation problems that cannot be resolved at home. Attempts to “break through” the blockage with pressure can lead to rupture of the tubes.
Remember that a modern refrigerator is a complex device where the mechanical part is inextricably linked with control electronics. Unqualified intervention can lead to damage to the control board, the cost of which is often comparable to the price of a new compressor.
Why is the compressor hot, but the refrigerator does not freeze?
This is a classic sign of a freon leak or a clogged system. The compressor continues to run and heat up, trying to pump gas, but there is not enough refrigerant in the circuit or it is not circulating. It requires searching for leaks, soldering and refueling.
Is it possible to replace a conventional compressor with an inverter one?
Theoretically it is possible, but it is technically extremely difficult and economically impractical. It will be necessary to replace the entire control system, wiring and modify the housing. It is easier and cheaper to install a conventional motor with similar characteristics.
How often do you need to defrost the refrigerator to preserve the compressor?
Models with the No Frost system do not need to be defrosted, it is enough to wash them once a year. Drip systems require defrosting when an ice coat more than 5 mm thick forms, usually 1-2 times a year, so as not to overload the motor.