Understanding the structure of the refrigeration circuit is necessary for anyone who plans to independently diagnose faults in household appliances. Knowing where the discharge tubeis located allows you to distinguish normal compressor operation from critical refrigerant pressure problems. Users often confuse this element with outlet pipes, which leads to incorrect diagnosis and unnecessary costs for repairs.
In this article we will analyze in detail the physical principles of the system, visual signs of heating and methods for safely identifying circuit elements. You will learn to accurately identify the high pressure line, relying on the design features of modern models Indesit, LG i Bosch. This knowledge will become the foundation for further maintenance of the unit.
The principle of operation and the role of the discharge pipe
The refrigeration circuit is a closed system in which a gaseous or liquid working substance circulates. Discharge tube is the first section of the line through which the refrigerant leaves the compressor. At this moment, the freon is under maximum pressure and has a high temperature, since it has just been compressed by the piston or inverter group.
The main task of this section is to transport hot gas to the condenser (radiator), located usually on the rear wall or along the perimeter of the housing. This is where the primary transfer of heat to the environment occurs. If a blockage or leak occurs at this stage, the efficiency of the entire unit will drop sharply, and the compressor may overheat due to operation in constant load mode.
It is important to understand that the movement of matter in the system is cyclical. After passing through the condenser and capillary tube, where the pressure drops, the refrigerant enters the evaporator, cooling the chambers. Then it returns to the compressor again to repeat the cycle. The discharge pipe is always connected directly to the outlet of the compressor and is the beginning of the high pressure path.
⚠️ Attention: The temperature at the initial section of the discharge pipe immediately after the compressor stops can reach 70-90 degrees Celsius. Do not touch metal parts with bare hands in the first 10-15 minutes after disconnecting the device from the network to avoid burns.
Visual and tactile identification signs
The easiest way to determine which tube is the discharge tube is the tactile method used while the engine is running. When the refrigerator is turned on and reaches temperature, two copper tubes come out of the compressor. One of them will be noticeably hotter than the other. Hot tube —this is the discharge line along which the compressed gas moves.
The second tube coming out of the compressor is usually suction. It usually has a larger diameter and remains cold or slightly warm to the touch, but not hot. In some models, for example Atlant or Stinol, the suction pipe may be covered with a layer of thermal insulation (porous black or gray tube), while the discharge pipe is often left exposed copper before entering the condenser.
Pay attention to the color and condition of the metal. Copper in the injection area may darken over time due to oxidation due to high temperatures. If you see that one of the tubes has a characteristic dark coating where it exits the motor housing, this is a sure sign of a high pressure line. In addition, it is to this tube that a technological fitting for filling the system is often welded.
When diagnosing, you should also pay attention to vibration. The discharge tube may vibrate slightly in time with the operation of the piston group, transmitting pressure pulsations. However, strong vibration may indicate improper fastening or water hammer in the system, which requires immediate intervention from a specialist.
Comparison of diameters and design features
The design of the refrigeration circuit is strictly regulated by engineers to ensure proper circulation of freon. The diameters of the tubes leaving the compressor are not random. The discharge pipe, as a rule, has a smaller diameter compared to the suction pipe. This is due to the need to maintain high pressure to effectively push the refrigerant through a narrow capillary.
Let's look at the main differences in the table below to systematize the knowledge:
| Characteristics | Discharge tube | Suction tube |
|---|---|---|
| Diameter | Smaller (usually 6-8 mm) | Larger (usually 10-12 mm) |
| Operating temperature | High (hot) | Low or room |
| Internal pressure | High (up to 15-20 atm) | Low (vacuum) |
| Connection | Leads to the condenser | Comes from the evaporator |
In modern models with the system No Frost the configuration may be more complex. The discharge tube can immediately go into the foamed part of the housing, where the sealed capacitor is located. In such cases, it is more difficult to determine it visually, and you have to focus on the outlet location of the compressor and the temperature.
It is also worth noting the presence of a filter-drier. It is always installed on the high pressure line, that is, on the continuation of the discharge tube, in front of the capillary. The filter is a small copper cylinder. The presence of this element helps to finally verify the correctness of the circuit definition.
Differences in models with one and two compressors
In refrigerators with one compressor, the system is relatively simple: one motor circulates freon for the freezer and refrigerator compartments. Here there is usually one discharge tube, and it leads to a common condenser. Diagnostics in such models, such as old Biryusa or Zanussi, is most straightforward.
The situation changes in models with two compressors. Here, each motor has its own independent circuit. Each compressor will have its own discharge tube leading to its own condenser (or condenser section). It is important not to confuse the tubes of different circuits, especially if it is necessary to replace one of the units.
In systems with a full No Frost and one compressor, there may be an additional heating circuit for the door or defrost zone. However, the main feature of the main discharge line remains its direct connection to the compressor outlet and maximum heating. Additional circuits may be thinner and located in hidden cavities of the case.
Features of inverter compressors
In inverter models (for example, LG Linear Compressor), the tubes can be arranged asymmetrically, and the compressor itself operates without characteristic vibrations, which makes the tactile method less effective. In such cases, it is better to focus on the diagram on the label on the back of the refrigerator.
Table of symptoms of discharge line faults
Incorrect operation of the discharge pipe often indicates serious problems within the system. If you notice deviations from the norm described below, this is a reason for a more in-depth diagnosis.
Clogging of the capillary tube or filter-drier leads to the fact that the pressure in the discharge section increases and the temperature becomes extremely high. In such conditions, the compressor operates with overload and can be switched off by a thermal relay. Ignoring these symptoms leads to costly engine failure.
The table shows typical symptoms and their probable causes:
| Symptom | Probable cause | Necessary actions |
|---|---|---|
| The tube is cold when the engine is running | Freon leak or compressor breakdown | Checking leaks, measuring pressure |
| Excessive heating (>90°C) | System clogged or air in circuit | Blowing with nitrogen, replacing the filter |
| Whistling or hissing | Microcrack or poor-quality soldering | Searching for leaks using a leak detector |
| Oil stains at the base | Depressurization at the soldering point | Re-soldering of the connection |
⚠️ Attention: If you find oily traces in the area where the discharge tube exits the compressor, this is almost guaranteed to indicate a refrigerant leak along with compressor oil. Operation of such a refrigerator is prohibited.
Instructions for safe diagnostics
To independently determine the discharge tube, follow the algorithm that minimizes the risks of equipment damage and injury. Before starting any work, make sure that you understand the structure of your specific refrigerator.
☑️ Discharge tube search algorithm
The first step is to ensure access. Remove the cardboard or metal cover covering the compressor compartment. It is usually secured with latches or several screws. Let the unit stand turned off so that the pressure in the system equalizes if it was just running.
Plug in the refrigerator. Wait 5-10 minutes for the compressor to reach operating mode. At this time, you can use an infrared thermometer (pyrometer) for non-contact temperature measurement. Point the device at the copper tubes at the very outlet of the black barrel of the compressor. A tube with readings above 50-60 degrees is what you are looking for.
If there is no thermometer, use the back of your hand (the skin there is less sensitive to burns, but feels heat well). Briefly touch the handsets. Remember safety precautions: no metal objects (screwdrivers, knives) should touch live tubes or near electrical contacts.
Frequent errors in determining the circuits
Beginners often make typical mistakes when trying to understand the structure of the refrigerator. One of the most common is confusion between the defrost zone heating tubes and the main discharge pipe. In some schemes, the tube from the compressor first goes to the defrost and then to the condenser, which can be confusing.
Another mistake is ignoring thermal insulation. There is often porous material on the suction tube. People mistake this as a sign of a "cold" pipe, forgetting that the main function of insulation is to prevent condensation and freezing, not to indicate the direction of flow. The discharge tube does not require insulation, since it is hot.
It is also worth mentioning the error of visual search for “beginning” and “end”. In foamed refrigerators, the condenser is hidden in the walls. Users look for the radiator at the back, do not find it and think that the system is designed differently. In such models, the discharge tube simply goes into the polyurethane foam of the housing, and you need to focus solely on the outlet from the compressor.
Do not try to bend the copper tubes for a better view. Copper is a soft metal and will break easily if subjected to repeated bending or strong pressure. Repairing such damage will require soldering and vacuuming the system, which is extremely difficult to do at home.
Is it possible to determine the discharge tube without turning on the refrigerator?
Without turning on the unit, it is impossible to do this with a 100% guarantee, since the main sign - temperature - is absent. However, you can focus on the diameter (the discharge is thinner) and the presence of a process fitting (often, but not always, located on the high pressure line next to the filter). The diagram on the label will also help if it is readable.
Why might the discharge tube be cold?
If the refrigerator is turned on, but the tube is cold, this indicates a lack of refrigerant circulation. Reasons: freon leak (gas escaped), compressor breakdown (valves do not create pressure) or complete blockage of the system. When turned off, the tube should be at room temperature.
Is it dangerous to touch the discharge tube?
The copper tube itself is not under electrical voltage. However, it can reach high temperatures, causing burns. In addition, next to it are the electrical contacts of the compressor and the starting relay, which are energized at 220V. Be extremely careful and do not use wet hands or metal tools.
Does the discharge tube need to be painted or insulated?
No, the discharge tube cannot be insulated. Its task is to release heat to the environment. If it is wrapped, the efficiency of condensation will decrease, the pressure in the system will increase, and the refrigerator will work worse or fail. Painting is also not recommended, as this will worsen heat transfer.
What to do if a crack has formed on the pipe?
The refrigerator cannot be used. The freon will leave, and moisture and air will get inside the system, which will cause corrosion and blockage of the capillary with ice. It is necessary to call a specialist to trim the cracked area, solder a new connection, vacuum and charge with refrigerant.