TRV in the refrigerator: purpose, principle of operation and signs of failure

Have you ever wondered how the refrigerator maintains the same temperature in the freezer and main chamber, despite different loads? Or why do some models begin to act up after defrosting? The culprit (or savior!) often turns out to be TRV the thermostatic valve. This small but critical part is responsible for the correct distribution of refrigerant throughout the cooling systems.

In modern refrigerators with No Frost, two-compressor or multi-zone models (for example, Samsung RB37J5240SA or LG GA-B459SQDL) The expansion valve plays the role of a “dispatcher” who decides where and how much freon to send. Without it, the compressor would run idle, and the temperature would change every hour. But how exactly does this happen - and what to do if the valve fails? Let's figure it out in order.

What is a TRV in a refrigerator: a simple explanation

TRV (thermostatic valve) is a mechanical or electronic device that controls the flow of refrigerant (freon) into the evaporator of the refrigerator. Its main task is to maintain the optimal temperature difference between boiling freon and the air in the chamberso that the compressor is not overloaded, and the products are cooled evenly.

Imagine the expansion valve as a valve on a pipe: it can open or close depending on how much the chamber needs to be cooled. Unlike a conventional capillary pipeline (which is used in budget models), TRV reacts to temperature changes in real time. This is especially important for refrigerators with:

• 🔹 Two compressors (for example, ATLANT XM 6025-031), where each is responsible for its own zone;
• 🔹 No Frost System, where the evaporator is hidden behind the panel and requires precise control;
• 🔹 Zones freshness (as in Liebherr CPesf 4023), where different temperature conditions are needed.

Without a TRV, the refrigerator will either freeze the food or not cool it to the required temperature. And in the worst case, the compressor will burn out from constant overloads.

Device and principle of operation TRV

Structurally, a thermostatic valve consists of several key elements:

• 🔧 Case with a seat and a needle — regulates the flow area for freon;
• 🔧 Thermal cylinder —a sensor filled with gas or liquid that responds to temperature;
• 🔧 Capillary tube - connects the thermal cylinder to the valve membrane;
• 🔧 Membrane and spring - converts pressure from the thermal cylinder into mechanical movement of the needle.

The principle of operation of the expansion valve is based on thermodynamic balance:

1. The thermocylinder is attached to the outlet of the evaporator and “feels” the temperature of the freon.
2. If the freon is too warm (which means the evaporator cannot cope), the pressure in the thermal cylinder grows, the membrane bends, and the needle opens the valve slightly - more freon comes in.
3. If the freon is too cold (risk of evaporator freezing), the pressure drops, the needle closes the valve - refrigerant flow decreases.

Thus, the expansion valve maintains overheating of freon at the outlet from the evaporator within 4–8°C (depending on the model of the refrigerator). This ensures that the compressor will not “swallow” liquid freon, which is fraught with water hammer.

What is water hammer in a compressor?

If liquid freon (and not gas) gets into the compressor, this will lead to a sharp jump in pressure and valve or winding failure. The expansion valve prevents this situation by maintaining proper overheating.

TRV vs. capillary tube: what is the difference?

Many budget refrigerators (for example, Biryusa 106 or Indesit DF 4180 W) instead of expansion valves use capillary tube a thin copper pipeline of a fixed diameter. It is cheaper, but has a number of disadvantages:

The main advantage of the TRV is adaptability. For example, if you have loaded hot food into the refrigerator, the valve will temporarily increase the supply of freon to cool the chamber faster. The capillary tube is not capable of this: it either passes too much refrigerant (risk of freezing) or too little (prolonged cooling).

Signs of a malfunctioning expansion valve in a refrigerator

The failure of a thermostatic valve is not as obvious as, for example, the failure of a compressor. However, there are several “symptoms” that should alert you:

• ❄️ Evaporator freezing (especially in models No Frost), while the fan can touch ice and make a grinding noise;
• 🔥 The compressor works without stopping, but the temperature in the chamber does not drop to the desired level marks;
• 💧 Condensation on the back wall (in drip refrigerators) or puddles under the drawers;
• 📉 Sudden temperature changes (for example, in the freezer then -24°C, then -10°C).

The most dangerous malfunction is TXV jammed in the closed position. In this case, freon stops flowing into the evaporator, and the refrigerator simply stops freezing. If the valve, on the contrary, is “stuck” in the open state, the compressor will work for wear, trying to compensate for the excess. refrigerant.

Check the temperature of the condenser (should be hot)|Measure the compressor current (the rating is indicated on the nameplate)|Inspect the evaporator for ice and frost|Listen to the valve for extraneous sounds (clicks, hissing)-->

How to check the expansion valve yourself?

If you suspect a malfunction of the thermostatic valve, you can carry out preliminary diagnostics without disassembling the refrigerator. You will need:

• 🔧 Thermometer (preferably infrared);
• 🔧 Multimeter (to check the compressor winding);
• 🔧 Gauge manifold (optional, to check the pressure).

Step 1. Checking the temperature of the condenser and evaporator

In normal mode:

• The condenser (grid at the back of the refrigerator) should be hot (50–60°C);
• The evaporator (in the freezer) should be uniformly cold, without “spots” of frost.

If the condenser is barely warm and the evaporator is covered ice is a sign lack of freon (possibly due to a jammed expansion valve).

Step 2. Listening to the valve

With the compressor running, bring your ear to the place where the expansion valve is located (usually the tube in front of the evaporator). Normally, you should hear light hissing sound - this is freon passing through the valve. If there is no sound or clicks are heard, the valve is faulty.

Repair or replacement of expansion valve: what to do?

If diagnostics have confirmed a malfunction of the thermostatic valve, you have two options:

1. Replacing the expansion valve —the most reliable method. The new valve is selected according to the model of the refrigerator (for example, suitable for Samsung RL38*** ). The cost of the part is from 1,500 to 4,000 rubles, plus the work of a specialist (another 2-3 thousand). 6701-001605). The cost of the part is from 1,500 to 4,000 rubles, plus the work of a master (another 2–3 thousand).
2. Cleaning the system is relevant if the valve is clogged (for example, after unqualified refilling of freon). However, this is a temporary solution - worn parts will still have to be changed.

Important! It is better to entrust the replacement of the expansion valve to a professional, as it is required:

• 🛠️ Soldering work (copper tubes);
• 🛠️ Evacuating the system;
• 🛠️ Refilling freon (the dose depends on the model).

⚠️ Attention: When replacing the expansion valve, be sure to install filter drier (it costs 200–500 rubles). It protects the new valve from moisture and debris that could remain in the system after depressurization.

If the refrigerator is under warranty, do not try to repair the expansion valve yourself - this will lead to loss of warranty. In service centers LG, Samsung or ATLANT such a breakdown will be repaired free of charge (if it is not caused by mechanical damage).

Prevention of problems with expansion valves

To make the thermostatic valve last longer, follow simple rules:

• 🔄 Defrosting 1-2 times a year (even for No Frost!) prevents the accumulation of ice on the evaporator, which reduces the load on the expansion valve;
• 🚫 Do not overload the refrigerator with hot products - sudden temperature changes accelerate wear of the valve membrane;
• 🔧 Keep the condenser clean (dust worsens heat transfer and makes the compressor work harder);
• 🛡️ Use a voltage stabilizer - power surges can damage electronic expansion valves (found in models Bosh KAN92VI20R i etc.).

If your refrigerator is equipped electronic expansion valve (with sensors and control unit), avoid:

• ⚡ Connections via extension cords;
• ⚡ Independent firmware of the module (if this is not provided for in the instructions).

⚠️ Attention: In refrigerators with inverter compressors (for example, Hitachi R-WB460PUC6), the expansion valve works in tandem with a control board. When replacing the valve, it may be necessary to flash the system!

FAQ: Frequently asked questions about the expansion valve in the refrigerator

Is it possible to repair the expansion valve or only replacement?

In 90% of cases, replacement is required, since a valve is a precision device with moving parts that wear out. Repair is only possible if there is a blockage (flushing) or a slight gas leak from the thermal cylinder (which happens extremely rarely).

How to understand that it is the expansion valve that is broken, and not the compressor?

If the compressor works (hums, heats up), but the refrigerator does not freeze, either the expansion valve or a freon leak is to blame. If the compressor does not turn on at all, the problem is in it or in the start relay. Only diagnostics with a pressure gauge will show the exact reason.

How much does it cost to replace the expansion valve in a refrigerator?

The cost depends on the model:

• Budget refrigerators (Indesit, Biryusa) - 3,000–5,000 rubles;
• Middle class (Samsung, LG) - 5,000–8,000 rubles;
• Premium (Liebherr, Bosch) - 8,000–12,000 rubles.

The price includes the part, labor and refilling of freon.

Can the expansion valve fail due to improper operation?

Yes, if:

• The refrigerator is often disconnected from the network (for example, at the dacha);
• The door is left open for a long time;
• The evaporator freezes due to a faulty fan (in No Frost).

This leads to overload of the system and accelerated wear TRV.

Where is the TRV located in the refrigerator?

Usually on the tube between the condenser and the evaporator, closer to the back wall. In models with No Frost it can be hidden under the panel In two-compressor refrigerators, the TRV is installed on each circuit separately.