In a situation where the refrigerator stops cooling or makes strange sounds, there is often a need for replacement or repair compressor. Carrying out such work on your own requires an accurate understanding of the unit’s structure, and the first critical step is identifying the pipes coming out of the motor housing. An error in the connection can lead to instant failure of expensive equipment or even to an explosion of the system.
For an amateur craftsman or a novice specialist, the visual difference between the tubes is not always obvious, since they are all made of copper and may look the same. However manufacturers even experienced repairmen use a number of physical principles and design features that allow them to accurately determine the purpose of each output. In this article, we will analyze in detail diagnostic methods that will help you carry out high-quality work.
It is worth noting right away that modern refrigeration units may have different layouts, but the basic physical laws of compressor operation remain unchanged. Understanding how refrigerant flows and where pressure is created is key to a successful repair. Let's begin a detailed examination of each element of the system.
The principle of operation of the compressor and the movement of freon
To understand where each tube is, it is necessary to clearly understand the refrigerant circulation cycle. Compressor in this system it acts as a heart that pumps freon gas, creating a pressure difference. The gas enters the motor from the evaporator, is compressed and released under high pressure into the condenser, where it cools and turns into liquid.
It is important to know that suction occurs directly into the engine cavity, so the inlet tube always leads inside the housing. The escaping gas, already compressed, first passes through the muffler (if it is external) or exits directly, but under significant pressure. It is the difference in pressure and temperature that is the main marker for determination.
⚠️ Attention: Never try to determine the purpose of the tubes by simply blowing into them with your mouth. The system may contain oil under pressure or freon residues, which is dangerous to health.
In addition, most household models use a sealed casing, inside which the electric motor is located. Suction pipe often passes through the internal cavity of the casing to cool the motor windings before the gas enters the cylinder. This is an important nuance that distinguishes it from the discharge one.
Visual methods for identifying pipes
The first and easiest way to determine the purpose of the tubes is a careful visual inspection. Typically, on the back wall of the refrigerator where the unit is located, you can see three copper outlets. Two of them have different diameters, and the third, the so-called “blind” tube, is often sealed from the factory and has the smallest diameter.
The diameter of the pipes is important. indicator. The tube through which freon is sucked into the compressor always has a larger diameter. This is due to the fact that the gas at the inlet has a lower density and volume, and requires more space for free passage. The discharge tube, on the contrary, is thinner, since the gas is compressed there.
The third outlet, which is often called technological, is used at the factory to charge the system with freon and evacuation. It is sealed in the finished product and its diameter is usually minimal. Do not confuse it with working outputs when planning cuts.
Also pay attention to the location. In the classic scheme discharge pipe it is often located on top or on the side, and the suction is located below or also on the side, but on the opposite side from the technological one. However, you cannot rely only on the location, since different brands, such as Indesit, Atlant or Bosch, the layout may differ.
Purge method and tactile diagnostics
If Visual inspection did not give a clear answer; the blowing method can be used. To do this, you will need to remove the compressor from the frame of the refrigerator, cutting through the tubes, and turn it over. By carefully blowing into one of the open pipes (after making sure that there are no toxic substances inside), you can feel resistance.
Into the pipe that is suction, air will enter freely and with minimal resistance, since it leads directly into the engine volume. If you try to blow into the discharge outlet, you will feel noticeable resistance or will not be able to push air at all, since the valves will prevent reverse flow.
⚠️ Attention: Be extremely careful when tactile testing. Compressor oil may remain in the system, which can enter the lungs if you exhale forcefully. Use a rubber bulb for safe blowing.
There is also a method of testing your hearing when turned on for a short time (only for experienced ones!). During a short start (literally for 1-2 seconds), air will begin to flow out of the discharge tube with force, and, on the contrary, it will be drawn into the suction tube. To do this, you can bring your finger to the hole: where it blows is the exit, where it sucks is the entrance.
Table of differences between compressor tubes
To systematize the knowledge gained, it is convenient to use a summary table. It will help you quickly navigate the characteristics of each output by comparing them with each other. Remember that the combination of features gives a 100% guarantee of correct identification.
| Characteristics | Suction tube | Discharge tube | Technological (blind) |
|---|---|---|---|
| Diameter | Largest | Medium | Smallest |
| Location | Often below or on the side | Often on top or side | In the middle or on the side |
| Condition during operation | Getting cold | Getting very hot | Not used |
| Purge resistance | Minimum | High | Soldered |
As can be seen from the table, diameter is the most reliable visual indicator. However, in some rare compressor models, the diameters may be selected differently, so it is always recommended to double-check the diagnosis by purging or short-term starting.
The process tube, in turn, almost never participates in the working cycle after the factory. It is used only if it is required refilling with freon or a complete recharge of the system after replacing the compressor. During normal diagnostics, it can be ignored, unless you plan to solder.
Why is the suction tube thicker?
This is due to the physics of gases. At the entrance to the compressor, freon is in a state of low pressure vapor and has a large specific volume. To ensure the necessary performance and not create excessive resistance, the cross-section of the pipe is made large. At the outlet, the gas is compressed, its volume has decreased significantly, so a thin tube is enough for transportation.
Instructions for safe dismantling and replacement
After you have managed to determine which tube is responsible for what, you can begin preparing for replacement. This process requires care, as copper is a soft metal and is easily deformed. Incorrect dismantling can damage the internal partitions of the compressor.
For work you will need a set of tools: a pipe cutter, a rolling machine (if you plan on rolling), a soldering torch, solder and flux. Also, do not forget about personal protective equipment, especially glasses and gloves, since the work involves open fire and chemicals.
☑️ Preparing to replace the compressor
The tubes should not be cut to the very root, but leaving a “stump” 10-15 mm long. This is necessary so that during subsequent soldering, the high temperature from the burner is not transferred to the compressor housing itself, which can melt the internal insulation or seals.
If you are replacing a compressor, the new unit is often supplied with the pipes already plugged. They should be opened at the very last moment, immediately before soldering, so that moisture and air do not have time to get inside. Moisture in the system it is the main enemy, leading to the formation of acids and capillary blockage.
Frequent errors and important nuances
One of the most common mistakes made by beginners is confusion between the discharge and suction tubes when installing a new compressor. If you confuse them and start the system, the refrigerator will not cool, and the compressor may fail in a matter of minutes due to operation in vacuum mode at the outlet or overload.
Another mistake is ignoring the condition filter drier. When replacing a compressor, the filter drier must be changed. The old filter is already saturated with moisture and will not be able to effectively clean the refrigerant, which will lead to a quick re-repair.
⚠️ Attention: Technical characteristics of compressors may vary depending on the specific model and year of manufacture. Always check the technical documentation or the markings on the device nameplate before starting work.
It is also important to keep the system clean. When soldering, be sure to use nitrogen purging or at least carefully monitor the absence of oxides inside the pipes. Getting microscopic chips or solder inside the system can clog capillary tube, and the refrigerator will stop working again.
Questions and answers (FAQ)
Is it possible to start a refrigerator without sealing the process tube?
Theoretically, you can start it, but you absolutely cannot do this. Moisture and air will enter the system through an open pipe, which will lead to the formation of an ice plug in the capillary and oxidation of the oil. The system must be sealed.
What to do if all three tubes are the same diameter?
In modern compressors this is rare, but possible. In this case, the only reliable way is to start it briefly (for 1-2 seconds) and check with your finger where the air is blowing from. Where it blows there is discharge, where it sucks there is suction.
Is it necessary to flush the system when replacing a compressor?
Yes, if the old compressor burned out, acidic oil and combustion products could remain in the system. Flushing with a special solvent or nitrogen under pressure is mandatory, otherwise the new compressor will burn out in a short time.
What solder is best to use for copper tubes?
For copper-copper connections, silver solder (with a silver content of 5% to 15% and above) is best suited. It provides a strong and flexible connection that is resistant to vibration. The flux should also be designed for soldering copper.