Understanding how a refrigerator works often begins with studying its electrical circuit, which is the “heart” of the entire cooling system. It is the electric current that causes the compressor to compress the refrigerant, starting the physical process of removing heat from the chambers. For a master or an inquisitive owner, knowledge the principle of operation of an electrical circuit is the key to quickly diagnosing breakdowns without calling an expensive specialist.
Unlike simple household appliances, the refrigerator circuit is a closed control circuit, where each element performs a strictly defined function. The stability of temperature maintenance depends on how exactly the thermostat, start relay and motor windings interact. In this article we will analyze in detail wire switching the operating logic of each node.
It is important to immediately note that modern models can differ significantly from classic Soviet units in the presence of electronic control boards. However basic principle the voltage supply to the compressor has remained unchanged for many decades. Having understood the basics, you will be able to understand the essence of the operation of even complex No Frost systems.
The main elements of the electrical circuit of a refrigerator
The electrical circuit of any refrigerator, be it Atlant or Indesit, is built around several key components. The first and main element is the compressor, which is essentially an electric motor enclosed in a sealed housing. It is this that consumes the bulk of the electricity and requires the most complex connection circuit.
The second critical element is the thermostat (thermostat), which acts as the “brain” that makes the decision to turn the system on or off. When the temperature inside the chamber rises above the set point, the thermostat contacts close and electric current flows to the starting device. Without this element, the refrigerator would operate continuously, which would lead to freezing of food.
The third link in the chain is often a thermal protection relay, which monitors the current consumption of the motor. If for some reason the compressor jams or the current increases to critical values, bimetallic plate the inside of the relay will heat up and open the circuit, preventing the windings from burning out. This is a simple but ingenious security system.
- 🔌 Compressor - converts electrical energy into mechanical energy to compress freon.
- 🌡️ Thermostat - mechanical or electronic sensor that opens the circuit when the desired value is reached temperature.
- ⚡ Starting relay —supplies a pulse to the starting winding to start the engine.
- 🛡️ Thermal relay —protects the motor from overloads and overheating.
All these elements are connected by wires, the cross-section of which is designed for certain current loads. In older models, switching was often done through terminal blocks, which made it easier fault diagnosis. In new models, the wires may be soldered or connected with permanent connectors, which requires a more careful approach during repairs.
⚠️ Attention: Before any manipulations with the electrical circuit, be sure to disconnect the refrigerator from the network! The 220V voltage is dangerous to life, and capacitors in some circuits can retain charge.
The principle of operation of a single-phase asynchronous motor
The heart of the refrigerator is a single-phase asynchronous motor, and understanding its operation is necessary to read the electrical circuit. The peculiarity of such an engine is that in order to start it, it needs to create a rotating magnetic field, since one working winding is capable of creating only a pulsating field, which is insufficient to start the rotor.
To solve this problem, the engine design provides two windings: the main (working) and auxiliary (starting) windings. The working winding has a larger wire cross-section and lower resistance; it is constantly involved in the operation of the engine. The starting winding turns on only at the moment of start and has a higher resistance.
The key point here is the phase shift of the current between the windings, which creates the necessary torque. Once the rotor reaches about 75% of its rated speed, the starting winding should be disconnected. If this does not happen, the engine will burn out due to overheating.
Why does the refrigerator hum when starting?
If the starting relay is stuck and does not open the starting winding circuit, the engine will hum, but will not start, or will start, but will quickly overheat. This is a classic symptom of a faulty starting device.
The starting relay is responsible for the process of turning the starting winding on and off. Classic circuits use a relay with a series coil, which, when current is injected, draws in the core and closes the contacts of the starting winding. When the operating mode is reached, the current drops, the core drops, and the circuit breaks.
The role of the thermostat and defrosting system in the electrical circuit
The temperature regulator in the electrical circuit of the refrigerator serves as the main switch. It opens or closes the compressor power circuit depending on the temperature in the evaporator or air damper. In the electrical circuit, it always stands “at the beginning” of the circuit, immediately after the mains connection plug.
In refrigerators with the No Frost system, the circuit is complicated by the presence of a defrost timer or an electronic control module. In such systems, the compressor and fan are periodically switched off, and voltage is applied to Defrost heating element. This process is critically important, since without it the evaporator will become overgrown with ice and stop cooling.
The electrical defrosting circuit usually includes:
- ❄️ Heating element defrost —a heating element that melts the ice.
- 💧 Defrost sensor —a thermostat that opens the heating element circuit when a certain temperature is reached (usually +10...+15°C).
- ⏱️ Timer or module —switches the "Cooling" and "Defrost" modes.
It is important to understand that when the heating element is operating, the compressor and fan must be de-energized. The electrical circuit is designed in such a way that the timer contacts cannot physically close the heating circuit and the cooling circuit at the same time. This prevents the system from working in reverse.
Diagnostics of faults using an electrical circuit
Knowledge of the electrical circuit allows diagnostics to be carried out by elimination. If the refrigerator does not turn on at all (no sound, no light), the problem is most likely in the supply cable, socket, or internal open circuit to the lamp. If the light is on, but the compressor is silent, the malfunction lies in the engine control circuit.
The first step in diagnostics is to check the thermostat. When cold, its contacts should be closed. If the multimeter shows a break, then the thermostat is faulty and needs to be replaced. This is the most common reason why the refrigerator does not start..
Next, the starting and thermal relay is checked. They can be “ringed” by a tester. The resistance of the series start relay coil is usually several ohms. The thermal relay in a cold state should “ring” (have zero resistance). If the relay heats up or crackles, but does not start the motor, the problem may be in the compressor itself.
☑️ Diagnostics of the electrical circuit
When checking the compressor, the resistance between the terminals of the windings is measured. It is considered normal if the sum of the resistances of the starting and working windings is equal to the resistance between the common contact and the contact going to the starting device. If the resistance tends to infinity - a break, if it approaches zero - an interturn short circuit.
Comparison of electrical circuits: Classic versus No Frost
The electrical circuits of refrigerators with a drip system and the No Frost system have fundamental differences. In classic models (“crying evaporator”) the circuit is as simple as possible: Plug -> Thermostat -> Relay -> Compressor. There is practically nothing to break in the electrical part, except for the actuators themselves.
In No Frost systems, a control circuit for the fan and heating elements is added. In older models, this was done by a mechanical timer that clicked every few hours. In modern models (LG, Samsung, Bosch), everything is controlled by an electronic module that receives signals from a variety of temperature sensors.
| Parameter | Classic system | No Frost system | Full No system Frost |
|---|---|---|---|
| Number of heating elements | 0 or 1 (for drip) | 1-2 (evaporator defrost) | 2-3 (evaporator + drainage) |
| Control | Mechanical thermostat | Timer or Electronics | Electronic module |
| Fan | Absent | Yes (in the freezer) | Yes (in both chambers) |
| Circuit complexity | Low | Medium | High |
Electronic control modules allow you to implement complex algorithms, for example, quick freezing or economical mode. However, such complexity makes repairs dependent on the availability of spare parts and the qualifications of a technician who can read error code on the display or by blinking indicators.
Frequent errors when reading diagrams and repairs
One of the most common mistakes self-repair is to ignore the color markings of the wires. Although there is a certain standard (brown - phase, blue - zero, yellow-green - earth), in reality, especially in equipment of different years of manufacture, the colors can be confused or fade over time.
The second mistake is an attempt to replace a blown fuse in the heating element circuit with a “bug” or a wire of a larger cross-section. The defrost circuit often uses fuses with a melting point of about 100-130°C. Their installation is fire protection. If they burn out, it means that the defrost sensor did not work and the temperature is out of control.
⚠️ Attention: Never close the contacts of the thermostat or sensors on a permanent basis to “check”. This can lead to failure of the compressor or defrosting of food due to continuous operation of the refrigerator.
Also, beginners often confuse the terminals of the compressor windings. In the diagram they are designated as C (Common), S (Start), R (Run). If you mix up the starting and operating windings when connecting, the engine may hum, but not rotate, or rotate in the opposite direction (which is fatal for a piston compressor).
Safety and features of modern modules
Modern refrigerators are equipped with inverter compressors, the control of which is radically different from classical schemes. There is no usual starting relay and thermostat in the classical sense. Instead, there is a frequency converter that smoothly changes the engine speed.
The electrical circuit of an inverter refrigerator includes a complex electronics unit that converts the alternating current of the network into direct current, and then again into alternating current, but with a variable frequency. Repairing such systems requires special equipment and deep knowledge of electronics, since checking with a multimeter often gives false results due to the presence of PWM signals.
When working with any electrical circuit, it is important to remember grounding. The body of the refrigerator is metal, and if the insulation breaks down, it can become dangerous. The presence of proper grounding in the outlet is a prerequisite for safe operation.
In conclusion, it is worth noting that although the electrical circuit may seem complicated, it obeys the clear laws of physics. Understanding the path of current from the outlet to the compressor and back allows you to find faults quickly and efficiently. The main thing is to follow safety precautions and take your time.
Is it possible to replace the thermostat with a universal one?
Yes, in most cases it is possible. The main thing is that the length of the capillary tube and the temperature range of the new thermostat meet the requirements of your refrigerator. It is also important to connect the contacts correctly, as their locations may vary.
Why does the refrigerator click but does not start?
The clicking sound is usually made by the start relay trying to start the engine. If it is followed by a humming sound and a second clicking sound after a few seconds, it means that the compressor cannot reach operating speed. Reasons: the starting relay is faulty, the compressor is jammed or low voltage in the network.
How to check the defrost heating element with a multimeter?
You need to remove the back panel in the freezer, find the heating element (usually a curved tube under the evaporator) and test it with the probes of the multimeter in resistance measurement mode. A working heating element should show a resistance in the range from 200 to 400 Ohms. A break (infinity) indicates a malfunction.
Is it dangerous to change the starting relay yourself?
Replacing the starting relay is technically simple (it is removed from the compressor rod), but requires disconnection from the network. The main danger is incorrect installation (upside down the relay does not work) or the use of the wrong model, which can lead to combustion of the compressor windings.