A modern refrigerator is a complex unit, where each component performs a critical function for maintaining food freshness. When it comes to the failure of the cooling system, craftsmen often mention the abbreviation TRV, which raises many questions among equipment owners. Thermostatic valve is a key element that ensures proper circulation of the refrigerant in the freon circuit.
Understanding In addition, what is a expansion valve in a refrigeratorwill help you quickly diagnose the problem and avoid unreasonable expenses for repairs. In this article, we will analyze in detail the device, purpose and common malfunctions of this component, so that you can confidently conduct a dialogue with a specialist or independently assess the scale of the problem.
It is worth noting that not all household models use a expansion valve; often its role is played by a capillary tube, however, in powerful and two-compressor systems, the valve is indispensable. The difference between these elements is significant and affects energy efficiency and temperature stability.
The main purpose of a thermostatic valve
The main task of this device is to regulate the flow of liquid refrigerant into the evaporator. TRV in the refrigerator reacts to changes in temperature at the outlet of the evaporator, automatically changing the throughput. This allows you to maintain an optimal level of steam superheat, preventing liquid cutters from entering the compressor, which could lead to water hammer and breakdown.
The principle of operation is based on balancing the forces acting on the valve. On one side, a spring and pressure in the evaporator press on the valve needle, and on the other, pressure in a thermal cylinder, which is filled with the same medium as the system, or an analogue gas. Thermostatic valve is constantly in dynamic equilibrium, opening and closing thousands of times a day.
It is important to understand that the correct operation of the valve directly affects energy consumption the refrigerator. If the valve opens too much, excess liquid enters the evaporator, which does not have time to evaporate. If the throughput is small, the compressor runs idle, not creating sufficient cold.
Design features and types of expansion valves
The thermostatic valve device includes several main components: a housing with inlet and outlet pipes, a nozzle, a needle (spool), spring and thermal bulb with capillary tube. The thermal cylinder is tightly attached to the outlet pipe of the evaporator and transmits temperature changes to the sensitive element.
Depending on the design and method of balancing pressure, there are several types of valves. In domestic refrigerators, internal balanced expansion valves are most often found, where the pressure in the evaporator is transferred directly under the diaphragm. There are also external balanced valvesused in industrial installations where the pressure drop is too high.
Difference between internal and external balancing
Internal balancing is used when the pressure drop in the evaporator insignificant. External requires a separate tube for transmitting pressure from the outlet of the evaporator, which makes it possible to compensate for large pressure losses in the refrigerant.
The materials used in production must withstand the aggressive effects of freons and oils. Brass, stainless steel and special alloys ensure the durability of the unit. However, even high-quality materials are not immune from wear or mechanical damage during careless transportation.
Difference between expansion valve and capillary tube in household refrigerators
Many users confuse expansion valve with a capillary tube, believing that they are the same thing. In fact, these are fundamentally different throttling devices. A capillary tube is simply a long tube with a very small internal diameter that has no moving parts and does not regulate flow depending on the load.
Whereas TRV is an active regulator, a capillary operates on the principle of constant resistance. This makes the capillary system cheaper and more reliable in terms of the absence of moving parts, but less efficient when external conditions change. That is why most modern household refrigerators (Indesit, Bosch, LG) use a capillary, and TRV is found in powerful models or old Soviet units.
Below is a table demonstrating the key differences between these elements:
| Characteristics | Thermostatic expansion valve (TEV) | Capillary tube |
|---|---|---|
| Flow control | Automatic, dynamic | None (constant throttling) |
| Presence of moving parts | Yes (needle, membrane, spring) | No |
| Reaction to load | Instant adaptation | Works as designed mode |
| Cost and complexity | High | Low |
| Application | Industrial and high-power household systems | Standard household refrigerators |
The choice between these systems depends on the manufacturer’s task. For a standard kitchen, the reliability of a capillary is sufficient, while for blast freezing chambers it is necessary to have thermostatic valve.
Typical malfunctions and symptoms of failure
Despite the reliability, Refrigerator expansion valve may fail. The most common problem is the loss of seal of the thermal bulb. If the gas has evaporated from the cylinder, the pressure on the membrane disappears and the valve closes completely under the action of a spring. As a result, freon stops flowing into the evaporator, and the cold disappears.
Another common malfunction is the needle jamming in the open position. This occurs due to contamination of the system with compressor wear products or moisture that has turned into an ice plug. In this case, too much liquid freon enters the evaporator, which can lead to “clogging” of the compressor with liquid and its failure.
⚠️ Attention: If you notice that the tube going from the evaporator to the compressor is covered with frost or ice far from the refrigerator body, this is a sure sign that the expansion valve is leaking too much refrigerant.
It is also worth mentioning the clogged filter driers, which are often associated with the valve. Contamination of the system can simulate a breakdown of the expansion valve, so the diagnosis must be comprehensive. The technician must check not only the valve itself, but also the cleanliness of the circuit.
Diagnostics and methods for checking functionality
Checking thermostatic valve requires special equipment and skills. First of all, a visual inspection is carried out for corrosion, dents and the condition of the thermal cylinder. It is important to make sure that the cylinder fits tightly to the pipeline and is not displaced, as this distorts the temperature readings.
A pressure gauge station is used for accurate diagnosis. Having connected it to the system, the specialist measures the suction and discharge pressure. Normal readings depend on the type of refrigerant (R134a, R600a) and ambient temperature. Sudden pressure surges or their absence while the compressor is running will indicate a problem with throttling.
☑️ Diagnosis of the expansion valve by a master
In some cases, the thermal balloon heating method is used. If, when heated with a hairdryer or a warm hand, the valve begins to allow more gas to pass through (which can be heard by a change in the sound of the compressor or a change in pressure gauge readings), it means that the mobility of the needle is preserved.
Replacement of the expansion valve and repair features
Repair TRV in a service center is usually not carried out, since the device is considered non-separable. If a malfunction is detected, the unit is completely replaced with a similar one. This requires evacuation of the system, refilling with freon and checking for leaks.
Independent replacement is highly not recommended due to the risk of damaging thin tubes or incorrectly calculating the amount of refrigerant. Additionally, soldering copper tubing requires a torch and skills in working with non-ferrous metals. Incorrect installation of the thermal bulb will also reduce the effectiveness of the new valve to zero.
⚠️ Attention: When replacing the expansion valve, it is critical to use a valve with exactly the same markings and performance as the original. Installing an unsuitable model will disrupt the balance of the cooling system.
The cost of the work consists of the price of the valve itself, the cost of the refrigerant and the labor costs of the technician. In some cases, if the refrigerator is old, replacing the expansion valve may not be economically feasible compared to purchasing new equipment.
Frequently asked questions (FAQ)
Is it possible to travel with a refrigerator if a expansion valve is installed in it?
Transporting refrigerators with a expansion valve requires special care. Unlike capillary systems, the valve is position sensitive. It is recommended to transport the unit strictly vertically. If this is not possible, then after horizontal transportation it is necessary to allow the refrigerator to stand in a vertical position for at least 12-24 hours before turning it on, so that the oil flows into the compressor.
How often do you need to change the expansion valve in the refrigerator?
Service life thermostatic valve is calculated for the entire service life of the refrigerator, which is usually 10-15 years. No scheduled replacement required. Failure occurs either due to a manufacturing defect, or due to contamination of the system or mechanical damage during transportation.
Why does the expansion valve freeze?
Freezing of the valve itself or a section of pipe immediately after it often indicates the presence of moisture in the system. The water circulating along with freon freezes at the throttling point, where a sharp drop in temperature occurs. This requires a complete recharge of the system with replacement of the filter-drier.
Does a breakdown of the expansion valve affect electricity consumption?
Yes, a faulty one TRV directly affects energy consumption. If the valve does not hold pressure or does not work correctly, the compressor is forced to work longer and more often to reach the set temperature, which leads to an increase in energy bills.
Where is the expansion valve located in the refrigerator?
In household models where it is used, the expansion valve is usually located inside the housing, often hidden by thermal insulation or plastic panels in the freezer compartment or behind the back wall. Access to it is possible only after partial disassembly of the unit.