Rinsing the capillary tube of a refrigerator: a complete guide

If your refrigerator is humming, but does not produce cold, or the compressor runs continuously, but it is still warm inside, the problem often lies in a clog in the refrigeration system. In such cases, craftsmen talk about the need circuit purging, and the key element here is the capillary tube. This thinnest element, the diameter of which is a fraction of a millimeter, is the “bottleneck” of the entire system, where the refrigerant is throttled. This is where oil oxidation products, moisture in the form of ice, or mechanical particles that have entered the system during poor-quality repairs most often accumulate.

Independent rinsing the capillary tube is a complex technical operation that requires not only theoretical knowledge, but also specialized equipment. You will have to deal with nitrogen, vacuum pumps and harsh chemical solvents. Errors at any stage can lead to failure of an expensive compressor or complete replacement of the circulation system. Therefore, before you take up the tool, evaluate your strength and the availability of the necessary arsenal.

In this article we will analyze in detail the physics of the clogging process, consider the available cleaning methods - from professional nitrogen purge to chemical flushing. You will learn how to diagnose the type of blockage, which solvents are effective for removing paraffin plugs, and which ones can only worsen the situation. We will also discuss safety precautions and nuances that even experienced craftsmen often miss.

Diagnostics of a blockage: signs and methods of determination

Before starting disassembly, you need to make sure that the problem is really in the capillary tube, and not in a freon leak or a compressor malfunction. The main symptom capillary blockage is the compressor operating in normal mode (or overheating), while the condenser (grid at the back) remains cold or barely warm. The evaporator inside the chamber is also not cooled. If the suction pressure is lower than atmospheric pressure, and the discharge pressure is higher than normal, the diagnosis can be considered confirmed.

There are two main types of blockages: oil-paraffin and ice. The first occurs due to the use of low-quality oil or mixing of different types of oils, which leads to sedimentation at low temperatures. The second type is the freezing of moisture that has entered the system. Ice plug often behaves cyclically: the refrigerator either cools or stops, as a plug either forms or melts. To accurately determine the location of the blockage, experts use the method of local heating or tapping, but instrumental control is more reliable.

For diagnostics, the method of shooting the capacitor is often used. If, when the filter-drier is turned off or the circuit is depressurized, oil comes out of the system under pressure or a whistle of escaping gas is heard, it means that the circulation has been disrupted precisely at the outlet of the condenser or in the capillary itself.

Required tools and consumables

High-quality cleaning of the system is impossible without specialized equipment. Attempts to solve the problem with improvised means, such as a car compressor or a syringe, are doomed to failure, since they are not able to create the necessary pressure or vacuum. To work, you will need a professional one nitrogen cylinder with a reducer that allows you to regulate the pressure up to 30-40 atmospheres. It is the inert gas nitrogen that is the standard for purging, since it does not react with oil and does not contain moisture.

You will also need a vacuum pump to remove moisture and solvent residues, a pressure gauge station to control pressure and a torch for soldering copper tubes. Particular attention should be paid to the choice of solvent if chemical washing is planned. Often used R141b or special liquids for cleaning refrigeration circuits. The use of acetone or alcohol can be dangerous for the rubber seals of the compressor.

⚠️ Attention: Working with nitrogen under high pressure requires compliance with safety precautions. Never exceed the pressure specified in the technical documentation for a specific type of compressor, so as not to rupture the heat exchanger.

Remember to prepare a container for waste oil and solvent. Draining technical fluid into a sewer or onto the ground is prohibited by environmental regulations. All waste must be disposed of at special collection points.

Mechanical nitrogen purging: the main method

The most effective and common way to remove blockages is purging with nitrogen. This method allows you to push out mechanical particles and soften paraffin deposits due to high pressure and inertia of the gas flow. The process begins by unsoldering the capillary tube from the filter drier and condenser. The filter-drier must be replaced in any case, since its reuse is impossible - the sorbent is already saturated with moisture.

The tube is carefully inserted into the fitting of the nitrogen cylinder reducer. Pressure is supplied in pulses: a sharp increase in pressure to 20-30 atmospheres creates a water hammer, which pushes out the plug more effectively than constant pressure. If the blockage is severe, repeat the procedure on the opposite side, carefully blowing in the opposite direction. However, you should be careful: backwash can drive dirt deeper into the bends of the evaporator if they are not sealed off..

In some cases, craftsmen use the “pressure test” method, leaving nitrogen in the circuit under a pressure of 10-15 atmospheres for several hours. If the pressure drops, it means there are microcracks in the system or poor-quality soldering. If the pressure is maintained, but there is no cold, the blockage remains, and more aggressive chemical flushing or replacing the capillary tube with a new one is required.

Why can’t you blow with your mouth or a compressor?

Exhaled air and air from household compressors contain moisture. If even a microscopic amount of water gets into the refrigeration circuit, it will lead to the formation of an ice plug and corrosion of internal parts, which will completely destroy the equipment.

Chemical flushing of the refrigerant system

If nitrogen purge does not produce results, resort to chemical flushing. This method is necessary when so-called “acid” or persistent paraffin deposits have formed in the system, which do not dissolve under gas pressure. For flushing, a special solvent is used, which is poured into the system, left for a certain time, and then purged with nitrogen. It is important to use only those liquids that completely evaporate and do not leave a film.

The process is as follows: cleaning liquid is poured into the circuit, after which the tubes on both sides are pinched. The unit is left for several hours (sometimes up to a day) to dissolve deposits. The solvent is then pumped out with a vacuum pump, and the system is thoroughly purged with nitrogen to remove chemical vapors. You can repeat the procedure several times until a clean solution appears at the outlet.

There is a compatibility table for solvents and oils that must be strictly observed:

After chemical washing, it is necessary to install a new filter-drier and long-term evacuation of the system. Remaining solvent may react with the new oil, so you cannot save time at this stage.

Replacing the capillary tube: when cleaning is pointless

There are situations when flushing the capillary tube is inappropriate. If the tube is damaged by corrosion, has creases, or the internal diameter has changed due to deposits on the walls (which often happens in older systems), it must be replaced. The new tube is selected strictly according to the internal diameter and length, since these parameters determine the performance of the system and the boiling point of the refrigerant.

Selecting an analogue is a complex process. If you take a tube with a smaller diameter or longer than required, the compressor will work with overload, trying to push through the freon, which will lead to its combustion. A tube that is too short or wide will not provide the necessary throttling and the refrigerator will not freeze. Craftsmen often use universal tubes with a large margin of length, which are then extended or shortened by trial method, controlling the compressor current and temperature.

The process of soldering a new tube requires accuracy. Copper is easy to burn, so use a soft flame and fluxed solder. The entry point of the capillary into the evaporator often requires special attention, since a blockage from solder can form there if the technology is not followed.

Evacuating and filling the system

After successful washing and removing the blockage, the assembly and evacuation stage begins. This is a critical step that determines the longevity of the repair. The vacuum pump should run for at least 30-40 minutes, and ideally an hour, to remove any moisture that may have entered the system with solvent or during repairs. The residual pressure should be close to zero.

Then the system is charged with refrigerant. The type and quantity of freon are indicated on the label located on the back wall of the refrigerator. Refilling is carried out with the compressor running, monitoring the suction pressure and the electric motor current. Refilling is just as dangerous as underfilling: excess freon can lead to water hammer and destruction of the compressor valves.

⚠️ Attention: Refrigerant characteristics and safety requirements are subject to change. Always check the current technical documentation of the manufacturer of your refrigerator before refueling.

After refueling, solder joints must be checked for leaks using a soap solution or a leak detector. If there are no bubbles and the refrigerator has begun to gain temperature, the repair can be considered complete.

Frequently asked questions (FAQ)

Is it possible to flush capillary tube without unsoldering it?

Theoretically, you can try to blow through the fitting if the design allows it to be connected, but the effectiveness of this method is extremely low. For high-quality cleaning, the tube must be dismantled or soldered on one side to ensure free passage of gas or liquid flow.

What is dangerous about using acetone for flushing?

Acetone is an aggressive solvent that can damage the varnish insulation of compressor windings and rubber seals. In addition, it does not evaporate well at low temperatures and can remain in the system, disrupting heat transfer.

How do you understand that the filter drier needs to be changed?

The filter drier is always changed when the circuit is opened. This is a one-time item. If you have unsoldered the tube, it means that air and moisture have entered the system, and the old filter will no longer be able to retain them.

How much does it cost to replace a capillary tube in the service?

The price consists of the cost of materials (pipe, freon, filter, oil) and the complexity of the work. On average, repairs cost 30-50% of the cost of a new refrigerator, which often makes it worthwhile.