Repair of the refrigerator cooling system Atlant is a process that requires not only theoretical knowledge, but also strict adherence to technical parameters. One of the most critical elements in the refrigerant circuit is the capillary tube, which is responsible for creating a pressure difference between high and low pressure zones. It is its geometry that determines how efficiently the compressor will operate and whether the unit will be able to reach the specified temperature conditions.
Many amateur craftsmen often mistakenly believe that the length of the tube is only a reference value that can be adjusted “by eye.” However, in modern models, such as Atlant MXM 1700 or newer series with linear compressors, an error of even 5 centimeters can lead to the refrigerator stopping freezing or, conversely, operating in constant overload mode. Understanding the physical principles of the throttle operation is necessary for successful restoration of equipment. Atlant MHM 1700 or newer series with linear compressors, an error of even 5 centimeters can cause the refrigerator to stop freezing or, conversely, to operate in constant overload mode. Understanding the physical principles of throttle operation is essential to successful vehicle restoration.
In this article we will look in detail at how the required length is calculated, what factors influence this parameter and why you can’t just take the tube from another refrigerator. You will learn about the specifics of working with different types of refrigerants, such as R134a and R600a, which require a fundamentally different approach to installing a throttling device.
The role of the capillary tube in the cooling system
Capillary tube performs the function of a throttle in the refrigeration system contour. Its main purpose is to create hydraulic resistance to the flow of liquid refrigerant coming from the condenser. Due to the narrow internal diameter (usually from 0.6 to 1.0 mm) and significant length, a high pressure is created at the entrance to the tube, and a sharp drop at the outlet, which leads to the boiling of freon and its transition to a gaseous state.
If the length is chosen incorrectly, the balance of the system is upset. If the tube is too short, liquid freon does not have time to completely evaporate in the evaporator and enters the compressor, causing water hammer. In case of excessive length system performance falls, since the compressor cannot push a sufficient amount of refrigerant through the high resistance.
It is important to note that in refrigerators Atlant a scheme is often used where the capillary tube is glued to the back side evaporator or inserted into the duct. This is done for heat exchange: the cold gas leaving the evaporator cools the liquid freon going into the evaporator, increasing installation efficiency.
⚠️ Attention: An attempt to replace the factory tube with one of a similar length, but with a different internal diameter, will lead to complete inoperability of the refrigerator. The flow resistance depends on the fourth power of the diameter, so replacing the diameter is unacceptable without complex length recalculations.
Modern models, for example Atlant XM 4000, may have a dual-circuit cooling system that uses two capillaries. One works for the freezer compartment, the other for the refrigerator compartment. Violation of the length proportions in one of the circuits will lead to temperature imbalance.
Factors influencing the calculation of length
Determining what length of capillary tube is needed in a particular refrigerator Atlant is based on several physical variables. You cannot simply copy the size from a faulty part, since it may have been replaced earlier or deformed. The main parameter is compressor power: the more efficient it is, the more resistance the throttle should provide.
The second critical factor is type of refrigerant. Freon R134a, which was widely used in models of past years, has different physical properties of viscosity and boiling pressure than modern R600a (isobutane). For isobutane, as a rule, tubes of a smaller diameter and a different length are required due to the greater specific refrigeration capacity.
⚠️ Attention: When switching from one type of freon to another (for example, when remaking the system), the length of the capillary tube changes dramatically. Using a tube from the R134a system in the R600a circuit without recalculation will lead to instant failure of the compressor.
Calculations are also affected by:
- 🌡️ Boiling point — target temperature regime that the refrigerator must maintain.
- ❄️ Heat exchange area —dimensions evaporator and condenser directly correlate with the required volume of circulating freon.
- 💨 Internal diameter —standard values vary, and the slightest change in diameter requires a proportional change in length.
Engineers The plant Atlant conducts thousands of hours of testing to select the ideal combination of these parameters for each series, be it budget MHM 1600 or premium XM 6000.
Standard sizes for different Atlant models
Although each repair case is unique, there are averages factory data on which service centers rely. For popular series of refrigerators Atlant standard sizes of capillary tubes have been developed. However, you should always remember that compressor modification within one model may vary depending on the year of manufacture.
Below is a table systematizing data on the most common models. These values are the starting point for the initial installation, but the final setting often requires pressure adjustment.
| Refrigerator model | Refrigerant type | Inner diameter (mm) | Recommended length (cm) |
|---|---|---|---|
| Atlant MKhM 1700 | R134a | 0.71 | 280 - 300 |
| Atlant XM 4008 | R134a | 0.66 | 320 - 340 |
| Atlant XM 6021 | R600a | 0.80 - 0.85 | 240 - 260 |
| Atlant MKhM 2808 | R134a | 0.71 | 290 - 310 |
As can be seen from the table, the transition to R600a in the model XM 6021 requires the use of a tube with a larger diameter, but shorter length compared to analogues on R134a. This is due to the different density and fluidity of gases.
If you cannot find accurate information on your model, the marking on the capillary itself often helps, if it has been preserved, or consultation with the technical documentation for the specific compressorinstalled in the unit.
Method for selecting lengths in the absence of documentation
In a situation where the technical data sheet is lost and the factory dimensions are unknown, professionals use the selection method based on suction pressure. This method is considered the most reliable, since it takes into account the real state of the system - the degree of contamination, the residual performance of the compressor and the efficiency of heat transfer.
The process begins with installing a tube of a obviously longer length than is supposedly necessary. Then it connects to the process pressure gauge station. The compressor starts and the technician observes the (low pressure) readings.
Why can’t you immediately install a short tube?
If you install a tube shorter than necessary, the system resistance will be too low. The compressor will begin to peddle, the suction pressure will rise above normal, which will lead to freezing of the compressor housing and possible water hammer. This can destroy the motor valves in a matter of minutes.
The action algorithm is as follows:
- 🔧 A tube about 3-3.5 meters long (standard coil) is installed.
- ⏱️ The system is started for 15-20 minutes to stabilize modes.
- 📉 If the suction pressure is below normal (for example, below -0.1 bar for R134a), the tube is gradually bitten off 10-20 cm at a time.
- 📈 After each shortening, wait for the pressure to stabilize. When it reaches the passport value (usually from -0.05 to +0.05 bar), the process is stopped.
It is important not to overdo it: you can always bite off too much, but it is no longer possible to grow the tube. For models Atlant it is typical that the final length is often in the range of 2.5–3.2 meters, even if the factory one was shorter, which may indicate a loss of performance of the old compressor.
Technology for replacing and soldering the capillary
Replacing a capillary tube in a refrigerator Atlant is an operation that requires complete evacuation of the system. It is impossible to simply “bleed off the gas and digest”, since moisture and air will remain in the system, which, when in contact with oil and freon, form aggressive acids.
The first step is always the dismantling of the old capillary. Often it is glued to the evaporator, so it must be carefully peeled off, warming the joints with a hair dryer, so as not to damage the thin tubes of the aluminum evaporator. Before installation, it is recommended to blow out the new capillary nitrogen to remove possible production chips.
☑️ Checklist for preparing for replacement
Soldering is carried out with using silver solder or high temperature copper solder. The entry point of the capillary into the filter drier must be of particularly high quality, since vibration occurs there. The filter drier is changed required every time the circuit is opened.
⚠️ Attention: Never use tin or soft solders to solder copper pipes of the refrigeration circuit. The pressure in the system can reach 15-20 atmospheres, and the soft solder will not withstand the load, which will lead to a freon leak and a fire hazard.
After soldering all connections, the system is connected to a vacuum pump. The vacuuming time for refrigerators Atlant should be at least 30-40 minutes. The residual pressure should be close to absolute vacuum, which is checked by a pressure gauge (the needle should go deep into the minus).
Refrigerant charging and final check
The last stage of repair is charging. The amount of freon is indicated on a label located inside the refrigerator compartment or on the back wall. For Atlant models, this value usually ranges from 60 to 140 grams, depending on the volume of the chambers. Refilling is carried out strictly by weight, since the capillary tube is very sensitive to the amount of substance in the circuit.
An excess of freon will lead to the fact that the liquid phase will not have time to turn into gas in the evaporator, and the compressor will work with liquid refrigerant. A lack of freon will lead to overheating of the engine and insufficient cold. After refueling, the refrigerator should operate for at least 2 hours without opening the doors.
A control measurement of the temperature in the freezer is made after 6-8 hours of operation. For proper operation thermostat the temperature must drop to -18°C and below, and the compressor operating cycle (on/off) must be proportional (approximately 30-40% of the operating time).
If the refrigerator Atlant after replacing the capillary it works in cycles of 5 minutes after 5 minutes or does not turn off at all, it is necessary to double-check the length of the throttle and the tightness of the system.
Frequently asked questions (FAQ)
Is it possible to use a capillary tube from another refrigerator, for example, from Indesit or Bosch?
Theoretically, it is possible if the internal diameter and length, as well as the type of refrigerant, match. However, the geometry of the bends differs between brands. When installing a tube from Indesit to Atlant make sure that the bend radii do not pinch the tube, otherwise the resistance will change and the system will not work.
What will happen if the length of the capillary tube is 20 cm longer norms?
Increasing the length will increase the resistance. The compressor will have a harder time pumping freon, the suction pressure will drop, the evaporator will be colder at the beginning, but the overall system performance will decrease. The compressor may work longer or not turn off, trying to gain temperature.
Is it necessary to heat the capillary tube when the refrigerator is operating?
No, there is no need to artificially heat it. In some models Atlant it passes through a warm circuit zone (along the perimeter of the door), where it is heated by hot freon coming from the compressor. This prevents the formation of condensation on the housing, but it is prohibited to specifically heat it with a lamp or hairdryer during operation.
How to understand that the capillary tube is clogged?
Signs of a clog: the compressor works constantly, but there is no cold; the condenser (grid at the back) is warm only at the outlet of the compressor, and the rest is cold; when the system depressurizes, little gas or only oil comes out of the pipe with a characteristic whistle.
Is it possible to clean a clogged capillary without changing it?
Cleaning is possible only with a hydraulic press using a special solvent and nitrogen under high pressure, but in domestic conditions this is extremely difficult and risky. In 95% of cases, a clogged capillary in the system Atlant is easier and more reliable to replace with a new one, since the inner surface of the old tube is already oxidized.