Diagnostics of faults in refrigeration equipment often begins with a visual inspection of the motor-compressor, which is the heart of the entire system. Understanding what what kind of pipes comes from the unit and what role they play in the refrigerant circulation cycle is necessary for an initial assessment of the condition of the equipment. To a non-professional it may seem that all pipes are the same, but their purpose is strictly regulated by the design features of the sealed unit.
In this article we will analyze in detail the functionality of each line, explain the physical principles of their operation and point out the critical differences between high and low pressure lines. Knowing these nuances will help you avoid gross mistakes when trying to independently service or replace the unit. Correct identification elements are the key to successful repairs.
Before delving into technical details, it is worth noting that modern refrigerators, be it Indesit, Atlant or LG, use similar principles of compressor operation. The differences may only relate to the location of the pipes on the body, but their physical essence remains unchanged. Let's look at the main elements of the system.
Functional purpose of compressor pipes
The compressor in a household refrigerator is a sealed block, inside which there is an electric motor and a piston group. Three main tubes approach and depart from this block, each performing a unique task in the thermodynamic cycle. Two of them are intended for refrigerant circulation, and the third serves for technological needs during factory charging.
The first and most important for understanding the operation of the system is discharge tube. It is through it that hot gaseous freon, compressed by a piston, is released under high pressure into the condenser (a heat exchanger, usually located on the rear wall). The diameter of this tube is usually the smallest among all three, due to the need to maintain high flow pressure.
The second line is known as suction tube. It has the largest diameter, since low pressure and low temperature refrigerant vapors from the evaporator enter the compressor through it. Unlike the discharge line, this pipe is often covered with a layer of frost or condensation during operation of a working refrigerator, which is a normal physical process.
⚠️ Attention: Never pinch copper pipes with pliers or other tools with sharp edges. Deformation of the lumen can completely disrupt the circulation of freon, which will lead to instant failure of the compressor due to overheating.
The third tube, often called filling station or technological, is sealed from the factory. It is used exclusively for evacuation of the system and injection of refrigerant during production or professional repairs. During operation of the refrigerator, it does not participate in circulation and must remain hermetically sealed.
How to visually distinguish pipes from each other
For a master diagnostician or equipment owner who decides to conduct an inspection, it is important to be able to distinguish pipes without connecting pressure gauges. There are several visual and tactile signs that make it possible to determine with a high degree of probability the purpose of each line. These signs are based on the laws of physics and design refrigeration units.
First of all, pay attention to the diameter. As already mentioned, the suction tube always has a larger diameter compared to the discharge tube. This is due to the fact that the density of freon gas at the compressor inlet is lower, and a wider cross-section is required to ensure the required mass flow. The discharge line, where the gas is compressed, may be thinner.
The second important criterion is the location on the housing. In most models, such as Beko or Samsung, the suction tube is often (but not always) connected to the compressor housing through a filter muffler or has a more complex bend shape to reduce noise. The discharge tube usually comes straight out of the top of the compressor dome and goes directly to the condenser.
The third method is a temperature test, which can only be done with the refrigerator running. Be careful not to get burned. The discharge tube becomes hot in the first minutes of operation, sometimes up to 70-80 degrees Celsius. The suction tube, on the other hand, remains cold or becomes covered with dew. The technological tube usually has an ambient temperature.
Connection diagram and refrigerant movement
Understanding how the compressor tubes are connected to the rest of the refrigerator elements helps to present a complete picture of the operation of the device. The cycle begins with cold freon gas from the evaporator entering the compressor through the suction line. Here it is compressed, its temperature and pressure increase sharply.
Next, through the discharge tube, the hot gas is supplied to the condenser located on the outside of the housing. There it gives off heat to the environment and condenses, turning into a liquid. The liquid refrigerant passes through a filter drier and a capillary tube, where its pressure drops and it enters the evaporator inside the chamber, starting the cycle again.
For clarity, consider the main parameters of the lines in the table below. This data will help systematize knowledge about the hydraulic system refrigerator.
| Tube type | Pressure | Temperature during operation | Diameter |
|---|---|---|---|
| Suction | Low | Low (cold) | Highest |
| Discharge | High | High (hot) | Small |
| Technological | Depends on the cycle | Environment | Medium/Small |
| Capillary | Difference (High -> Low) | Different (heat transfer) | Minimum |
It is worth noting that in some modern inverter models, for example, from Whirlpool or Haier, the circuit may have additional elements, such as “pipe-in-pipe” heat exchangers, but the basic principle of connecting to the compressor remains the same. Violation of the connection sequence during repair will lead to the impossibility of creating the required pressure drop.
Why can’t you swap tubes?
If you mix up the input and output of the compressor, the system will not work. The compressor will not be able to create a vacuum in the evaporator, and the refrigeration cycle will not start. The pressure in the system will equalize and cooling will not occur.
Technological tube: features and purpose
The third tube deserves special attention, which often raises questions among novice craftsmen. This filling fittingis used at the factory to connect a vacuum pump and a freon filling station. After filling the system with refrigerant and checking the tightness, this tube is cut and sealed.
In everyday life, the need to intervene in this tube arises only in two cases: when the compressor is completely replaced or in case of a serious leak that requires evacuation and new filling. It is categorically not recommended to open this line on your own without a pressure gauge station and scales for freon, since it is impossible to accurately dose the amount of refrigerant.
When replacing a compressor with a new part, a small piece of copper tube is often already welded on. If it is not there, the technician welds a new fitting.
⚠️ Attention: When biting off a sealed process tube on a working (or recently working) refrigerator, a sudden release of oil may occur along with freon residues. Be sure to make sure that the unit is unplugged and cooled down.
Diagnostics of faults based on the condition of the tubes
The condition of the compressor tubes can tell a lot about the health of your refrigerator. Experienced professionals use these signs to make a preliminary diagnosis. For example, if the suction tube is covered with a layer of ice (“shubby”), this may indicate an excess of freon in the system or a malfunction of the thermostat.
If the discharge tube is barely warm or cold, and the refrigerator does not freeze, this is a sure sign that the compressor is not creating the necessary pressure. The reasons may lie in a freon leak, blockage of the capillary system or mechanical wear of the piston group of the unit itself unit.
You should also pay attention to vibration. Excessive vibration of tubes, especially at solder joints, can lead to the formation of microcracks and subsequent leaks. In some models, such as old ZIL or Minsk, the tubes are fixed rigidly, which over time leads to their breaking off due to metal fatigue.
☑️ Signs of proper operation of the tubes
Questions and answers on the design of the compressor
At the end of the article, we will consider the most frequently asked questions questions that users have when studying the design of refrigeration equipment. These clarifications will help avoid common misconceptions.
Can I replace the compressor myself if I know what kind of pipes it has?
Theoretically, yes, if you have the skills to solder copper pipes, a vacuum pump and a freon refill station. However, simply knowing the location of the tubes is not enough. It is necessary to accurately calculate the amount of refrigerant, use the correct oil and follow the soldering technology in a nitrogen environment to avoid oxidation within the system.
Why is the suction tube sometimes hot?
This is an abnormal situation. If the suction tube is hot, this may mean that there is not enough cold gas entering the compressor due to a freon leak, or the compressor is idling without load. Also, the cause may be a malfunction of the motor itself, which overheats and transfers heat to the housing and pipes.
What are the differences between the tubes of an inverter compressor?
In principle - nothing. Inverter models, for example, from Electrolux or Boschalso have an inlet, an outlet and a process pipe. The difference lies in the electronic control of the engine speed, but the physical connection of the copper lines remains standard for hermetic compressors.
What to do if a compressor tube breaks off?
If a tube breaks off, the system is depressurized, and air and moisture get inside. Simply soldering the tube will not help - the refrigerator will stop freezing after a short time due to the ice blockage. A call to a technician is required to purge the system with nitrogen, replace the filter-drier and refill.