How to replace the capillary tube in the refrigerator

Failure of the cooling system often puts the owner of household appliances in front of a difficult choice: call a technician or try to solve the problem on their own. If diagnostics have shown that the reason for the lack of cold lies in a blockage or mechanical damage to a thin copper pipeline, then replacing the capillary tube in the refrigerator becomes an inevitable procedure. This element is the heart of the hydraulic system, providing the necessary throttling of the refrigerant.

This process is technically complex and requires not only specific tools, but also a deep understanding of the operating principles. refrigeration circuit. Any mistake in soldering or calculating the length can lead to repeated breakdown of the compressor or complete failure of the unit. In this article we will analyze in detail all stages of work, from preparation to final filling.

It is worth noting right away that working with refrigerants and evacuation of the system falls into the category of professional repairs. However, for those who have experience working with metals and understand the physics of the processes, this instruction will become a detailed guide. It is important to act consistently, without skipping a single stage of preparation.

Diagnostics of the malfunction and preparation of tools

Before proceeding with the dismantling of old components, you need to make sure that the problem lies precisely in the capillary. Most often, this is indicated by a characteristic picture: the compressor operates continuously, but the temperature in the chambers does not drop below room temperature, and there is no characteristic uniform frost on the back wall or evaporator.

To carry out high-quality repairs, you will need specialized equipment. Without it, it is impossible to ensure tight connections and proper operation of the system after assembly. The main tool is a brazing torch, since soft tin solder will not withstand pressure and temperature changes.

It is also critical to have a pressure gauge station on hand to monitor the pressure in the circuit. A vacuum pump is necessary to remove moisture and air, which, if introduced into the system, can cause ice blocking or corrosion.

⚠️ Attention: Before starting any work on the pipes, make sure that the refrigerant is completely vented in a well-ventilated area. Residual pressure in the system can lead to oil splashing or eye injury.

List of necessary equipment and consumables:

• 🔥 Gas torch with a cylinder (propane-butane or MAPP gas)
• 🔧 Set of rolling tools and pipe cutter
• 📏 Manometric manifold with vacuum pump
• 🧵 Copper tube with a diameter of 0.66 mm or 0.77 mm (depending on the model)
• 🛠️ Flux and solder containing silver (L-Ag 30-40%)

Removing the old capillary tube

The process of removing the faulty element begins with access to the technical compartment and freezer chamber. In modern models Indesit, Atlant or Beko the capillary is often sealed inside the thermal insulation on the back wall of the cabinet or built into a foamed evaporator. This greatly complicates the task.

If the tube passes inside the housing, it is not recommended to carefully open the foamed circuit, as this will break the thermal insulation. Experienced craftsmen often resort to the “pulling out” method: they cut off the old tube at the filter-drier and at the entrance to the evaporator, and then unwind it and pull it out. A new one is subsequently inserted into the vacated space.

When working with solder joints, use a damp rag to cool adjacent areas so as not to damage the varnish coating of the compressor winding or plastic structural elements. Heating must be local and strictly controlled.

The old filter drier must be replaced. It is a disposable element and, after depressurization of the system, instantly absorbs moisture from the air. Installing an old filter will reduce all efforts to zero, since moisture will quickly block the operation of the new capillary.

Why can’t you heat the filter for a long time?

Prolonged heating of the filter-drier leads to burnout of the sieve filler (molecular sieve). This turns the filter into an ordinary empty flask, which will not be able to retain moisture, which will cause freezing of the capillary tube from the inside in a short time.

Calculating the length and preparing a new tube

The key point of repair is the correct selection of the length of the capillary tube. This is not just a piece of copper, but a precision choke. The length and internal diameter determine the throughput and pressure drop between the (high) and bottom (low) circuits.

Using a tube of arbitrary length will lead to an imbalance: if it is too short, the refrigerant will not have time to evaporate completely and will enter the compressor in liquid form, causing water hammer. A tube that is too long will create excess resistance, the compressor will work with overload, and the cooling capacity will drop.

For replacement, tubes of standard diameters are usually used: 0.66 mm, 0.71 mm or 0.77 mm. The length is selected experimentally or according to reference data for a specific compressor model. The standard length range for household refrigerators is from 2.5 to 4.5 meters.

⚠️ Attention: The exact length depends on the type of refrigerant (R134a, R600a) and compressor power. isobutane (R600a) requires tubes of longer length and smaller diameter compared to freon R134a due to the different physical properties of gases.

Recommended parameters for selection (reference data):

Technology for soldering connections

Soldering copper pipes requires skill and adherence to temperature conditions. Copper oxidizes when heated, so it is important to use flux or work in a nitrogen environment, although in domestic conditions it is often possible to get by with careful cleaning and a quick operation.

First, the tube is inserted into the filter drier. The planting depth should be 15-20 mm to ensure a reliable connection and no swirls. The tube is then carefully inserted into the evaporator or condenser. The gap between the tube and the wall of the hole should be minimal.

Heat the joint evenly, moving the flame around the joint. When the copper reaches the desired temperature (cherry red color), bring in a solder rod. The solder should melt from the heat of the metal, not from the flame of the torch. The molten solder will be drawn into the gap under the action of the capillary effect.

Pay special attention to the quality of the seam. It should be smooth, without shells and sagging. Excess solder can clog the thin capillary channel from the inside, which will be fatal to the system. Immediately after soldering, allow the connection to cool naturally, without blowing on it or wiping it with a wet rag, to avoid microcracks.

Evacuating and charging the system

After installing all elements, it is necessary to remove air and moisture from the circuit. Vacuuming is a mandatory step. The remaining moisture at low temperatures will freeze and block the capillary, and the air will increase the condensation pressure, increasing the load on the compressor.

Connect the vacuum pump to the service fitting (or soldered Schrader valve). Turn on the pump and monitor the pressure gauge. The needle should drop below zero, into the blue zone (vacuum). The process should last at least 30-40 minutes for domestic refrigerators.

After achieving a deep vacuum, close the valve on the manifold and turn off the pump. Leave the system under vacuum for 15-20 minutes. If the pressure gauge needle does not rise, then the system is sealed. If the pressure increases, there is a microcrack or poor-quality soldering somewhere.

⚠️ Attention: It is forbidden to turn on the compressor to “press” air. This will lead to moisture and dust getting inside the system, and can also cause breakdown of the winding insulation when operating in a vacuum without cooling.

Refrigerant charging is carried out only after successful evacuation. For R600a (isobutane), the procedure requires special care due to the explosive nature of the gas. It is better to refill using scales, monitoring the exact weight indicated on the refrigerator nameplate.

Checking tightness and starting

The final stage is a performance check. After refueling, turn on the refrigerator and let it run for 15-20 minutes. At this time, all solder joints should be carefully checked for leaks. Use a soap solution or a special leak detector.

Pay attention to the operation of the capillary tube. It should be warm in the area after the filter and before entering the evaporator. Immediately after the entrance to the evaporator (at the exit from the seal) intense cold and frost should begin to appear. Suberization (freezing) should proceed evenly from beginning to end.

If the capillary is frozen only 10-20 cm, and then it is warm, there may be more air or moisture left in the system than normal. If the tube is warm along its entire length, but there is no cold, there is probably a blockage or insufficient amount of freon.

After making sure there are no leaks and normal operation, bite off the filling tube and solder it. This place also requires high-quality soldering. After cooling, wipe the compressor and pipelines from oil and flux.

Frequent errors when replacing yourself

Independent repair is often accompanied by typical errors that reduce the result to zero. One of the most common is neglecting to replace the filter drier. An old filter that has been exposed to air for more than 15-20 minutes is already saturated with moisture and requires replacement or regeneration in an oven at 200°C, which is difficult to do at home.

Another mistake is using steel tubes instead of copper or soldering without flux/solder with a low silver content. Steel rusts from the inside, and soft solder flows when vibrated. Rolling technology is also often violated, creating cracks at the ends of the tubes.

Incorrect calculation of the length of the capillary leads to the fact that the refrigerator either “does not draw” cold, or the compressor works non-stop, overheats and burns out.

Is it possible to use a longer capillary tube if a short one is not enough?

Using a longer tube is acceptable in extreme cases, but this will change the characteristics of the system. The pressure drop will increase, which can lead to lower boiling and evaporator freezing, but the load on the compressor will increase. It is best to follow the factory parameters or carry out an accurate calculation of performance.

What is the danger of moisture getting into the refrigerator circuit?

Moisture in the refrigerant circulation system leads to the formation of ice plugs in the narrowest place - the capillary tube. This causes periodic shutdown of the cold (thaw) and subsequent freezing. In addition, water reacts with oil and freon, forming acids that destroy the compressor windings from the inside.

Is it necessary to flush the system with nitrogen?

Rinsing with nitrogen under pressure is necessary if a “pop” (compressor combustion) has occurred in the system and soot has formed, or if the system has been open for a long time. Nitrogen blows out combustion products and oxides. In simple cases of replacing the capillary, high-quality evacuation is sufficient.

Why, after replacing the capillary, does the refrigerator freeze but does not turn off?

Most likely, the length of the capillary tube is chosen incorrectly (too long) or there is an excess of refrigerant in the system. Also, the reason may be the thermostat, which does not sense the required temperature due to incorrect placement of the sensor. Check the length of the tube and the amount of freon.

Is it possible to solder the capillary with soft solder?

Absolutely not. Soft tin-lead solder has a low melting point and strength. Compressor vibration and system pressure will quickly destroy such a connection, leading to freon leakage. Use only hard silver solder (L-Ag).