Owners of Soviet and post-Soviet equipment are often faced with the need to manually adjust the climate inside the chambers, since the automation here works on a different principle than in modern models. Old refrigerators Biryusa, produced in the 80s and 90s, are highly maintainable, but require careful attention to mechanical control units. Incorrect settings can lead to damage to food or excessive energy consumption, so it is important to understand the physics of the thermostat.
The main difficulty is that these models do not have a digital display, and all adjustments are made “by eye” or by the characteristic click of a relay. You will have to focus on the behavior of the compressor and the temperature of the food to find the “golden mean”. In this article we will analyze the design of a mechanical thermostat and methods for calibrating it without calling a technician.
The design of the refrigeration system of old models
The heart of the temperature control system in old models Biryusa (for example, series 6, 8, 10) is a mechanical thermostat. This device is a relay that closes and opens an electrical circuit depending on the gas pressure in the sensing element. The capillary tube coming out of the regulator body is attached to the evaporator inside the freezer chamber and reacts to temperature changes.
When the air in the chamber is cooled to a set value, the gas in the tube is compressed, the pressure drops, and the contacts open - the compressor stops. As the temperature rises, the process goes in the reverse order. The key element here is precisely the accuracy of the setting of this mechanism, since over time the springs can get tired and the contacts can burn.
Unlike modern inverter systems, there is no smooth change in power. The compressor is either running at full capacity or completely switched off. Therefore, correct adjustment of the on and off range is critical to the longevity of the unit.
⚠️ Attention: Before any manipulations with the electrical part of the refrigerator, be sure to unplug the power cord from the outlet. Working with 220V current in humid conditions can be deadly.
Location and types of thermostats
Depending on the year of manufacture and modification, the temperature regulator in refrigerators Biryusa may be located in different places. In most older models, the control knob is located on the front panel inside the refrigerator compartment, usually in the upper right corner. However, in some designs it may be hidden behind a decorative overlay or located on the outside of the housing.
The thermostat (mechanism) itself is attached to the inner wall of the chamber or to the evaporator body. To access the adjustment screws, you often have to remove the plastic switch handle and decorative panel. Inside you will see a shaft with a slot for a screwdriver and, possibly, a second screw under the seal.
- 🔧 T-110, T-111, T-112 —the most common models of thermostats installed in single-chamber refrigerators.
- ❄️ T-130, T-132, T-133 —often found in two-chamber models, have a wider range adjustments.
- ⚙️ TAM-112, TAM-133 - analogues from other manufacturers that could be installed during factory repair or replacement.
Determine the type of your thermostat by the markings on the metal case. This knowledge will help you find accurate technical documentation if standard adjustment does not produce results.
Diagnostics of problems with temperature conditions
Before turning the screws, it is necessary to accurately determine the nature of the malfunction. Users often confuse thermostat failure with a freon leak or loss of seal tightness. If the refrigerator Biryusa stops freezing, but the compressor works continuously, the problem is most likely not in the adjustment, but in the refrigerant.
If the unit turns off too early, without gaining the required cold, or, conversely, works without interruption, turning food into ice, then intervention is required settings. It is important to conduct a preliminary diagnosis so as not to aggravate the situation.
Use the following testing algorithm:
- 🌡️ Water test: Place a glass of water and a thermometer in the center of the refrigerator for 6-8 hours. Normal temperature should be in the range of +2...+5°C.
- 👂 Listen to the cycles: in normal mode, the compressor should work for about 10-15 minutes, then rest for 20-30 minutes (depending on the load and ambient temperature).
- 🧊 Checking the evaporator: if a “fur coat” forms on the back wall of the refrigerator compartment unevenly or only in the corner, this is a sign of problems with the system, and not with the regulator.
Only after making sure that the problem is the incorrect operation of the thermostat, you can start setting it up. If the refrigerator operates non-stop, this can quickly damage the motor-compressor due to overheating.
Instructions for adjusting the mechanical thermostat
The adjustment is made using a special screw that changes the tension of the spring inside the mechanism. This screw is often protected by a control seal that will have to be broken. There are usually two holes on the thermostat body: one for setting the temperature range (accessible through the handle), the second for setting the differential (the difference between turning on and off).
First, remove the switch handle and the decorative trim. You will see an adjustment screw for a slotted screwdriver. Turning clockwise usually increases the spring tension, which causes the contacts to open at a lower temperature (the refrigerator will freeze harder and take longer). Turning counterclockwise weakens the spring, increasing the shutdown temperature.
It is important to make changes smoothly. The optimal adjustment step is 1/4 or 1/2 turn of the screw. After each change, you must allow the refrigerator to return to operating mode, which can take from 2 to 5 hours depending on the load and time of year.
⚠️ Attention: Do not try to adjust the second screw (differential) if you do not have experience. Knocking the differential will lead to too frequent starts of the compressor, which is critical for older engines.
Table of typical faults and elimination methods
For ease of diagnosis and setup, below is a summary table that will help compare symptoms with necessary actions. Remember that old refrigerators Biryusa are sensitive to ambient temperature.
| Symptom | Probable cause | Action | Standard value |
|---|---|---|---|
| The compressor does not turn on | The protection has tripped or the thermostat is faulty | Close the thermostat contacts to check | Switch-on temperature +4...+5°C |
| Continuous operation of the motor | The range is off or freon leakage | Turn the screw counterclockwise | Switch-off temperature 0...-1°C |
| Food in the refrigerator compartment freezes | Switch-off temperature is too low | Loosen the spring (counterclockwise) | Cycle duration 15-20 min |
| Short cycles (on/off) | Malfunction of the starting relay or differential | Check the starting current and relay condition | Pause for at least 10-15 minutes |
If the situation does not change after adjusting the screw, the thermostat itself may have gone out out of order and requires replacement. Mechanical wear of contacts is a common occurrence for equipment 20-30 years old.
Seasonal characteristics and external factors
The operation of old refrigerators directly depends on the room temperature. Mechanical thermostats Biryusy do not have ambient temperature compensation, so in winter and summer the settings may require correction. If the room is cold (below +16°C), the compressor may not turn on at all, since the gas in the tube does not expand to the required pressure.
In the summer, when the apartment is hot, the refrigerator is forced to work longer to compensate for heat inflows through the walls. During this period, a slight adjustment towards lower temperatures may be required, but with caution so as not to overload the motor.
It is also worth considering the loading of the chambers. An empty refrigerator cools down faster, but it also heats up instantly from the warm air when the door is opened. A full load stabilizes the temperature, acting as a cold accumulator.
When the thermostat needs to be replaced
There are situations when adjusting with screws no longer helps. If you turn the shaft in both directions and the contacts do not click, or if the refrigerator turns on only when the contacts are forcibly closed with a screwdriver, the thermostat is faulty. Also, a sign of breakdown is the absence of a characteristic click when turning the knob to maximum.
Replacing the thermostat in old ones Biryusha is a simple procedure, but requires care. The main thing is to install the capillary tube correctly. It should fit snugly against the evaporator in the same place where the original one was. The use of aluminum tape or a special clamp is mandatory for thermal contact.
When choosing a spare part, pay attention to the length of the capillary tube. If the new tube is longer, it can be carefully twisted into a ring (without bending!), if it is shorter, it will not be possible to replace it, it will not reach the attachment point.
After installing the new regulator, you will need to re-adjust the temperature using the method described above. Do not be afraid to experiment with settings within safe limits, since each piece of equipment is unique.
Frequently asked questions (FAQ)
Is it possible to completely turn off the freezer in the old Biryusa?
In most old single-compressor models Biryusa It is impossible to completely turn off the freezer, since the refrigerant circulates through both circuits. However, there are models with a “Single Compressor Mode” switch or dampers, but these are rare. Usually you can only reduce the cold in the refrigerator compartment, but the freezer will always work.
Why does the Biryusa refrigerator freeze up a lot after adjustment?
Most likely, you tightened the adjustment screw too much, shifting the shutdown point to the zone of very low temperatures. The cause may also be a loose door seal or damage to the seal, which allows moist air to enter inside. Try turning the screw counterclockwise half a turn.
What is the normal temperature in the freezer of an old refrigerator?
For old-style refrigerators with mechanical control, the normal temperature in the freezer is considered to be from -6°C to -12°C. Reaching -18°C (standard for modern models) in old Biryusa is often impossible or requires the compressor to operate in continuous mode, which is not recommended.
How to understand that the Biryusa thermostat is completely broken?
If When you turn the control knob, you do not hear a characteristic click, and the refrigerator does not turn on (or, conversely, does not turn off even when defrosting), most likely the contacts are stuck or the bellows membrane has burst. Checking with an ohmmeter (it should “ring” in one position and be silent in another) will give an accurate answer.