During the operation of household refrigeration units and professional commercial equipment, there is often a need to clean the internal line. This may be required after the combustion of the compressor, when the breakdown products of oil and acids enter the system, or when switching to another type of refrigerant. Freon flushing is a key tool in the master’s arsenal, allowing mechanical impurities and old oil residues to be washed out of the tubes without completely disassembling the circuit.
The washing process requires strict adherence to technology and safety measures, since the work is carried out under pressure and with volatile substances. Improper use of flushing fluid can lead to repeated equipment failure or even rupture of thin-walled evaporator elements. In this article we will analyze in detail how to use flushing freon, what methods exist and what to pay special attention to.
Why is flushing the refrigeration circuit necessary
The main purpose of flushing is to remove contaminants that cannot be eliminated by evacuation or replacing filter-driers. When the compressor motor windings burn, solid soot particles are formed in the system. If they are not removed, the new compressor will burn out within several hours or days of operation. acid environment and carbon particles. If they are not removed, the new compressor will burn out within hours or days of operation.
Flushing is also necessary when the equipment is idle for a long time, when moisture could get inside the system, or when replacing the compressor with a model that works with a different type of oil (for example, switching from mineral to synthetic). In such cases flushing gas acts as a solvent and transport medium for removing dirt.
It is important to understand that conventional nitrogen purging is not always effective against viscous oily deposits. Specialized flushing compounds, such as R141b or mixtures based on R406a, have solvent properties, which makes them indispensable in case of serious contamination.
Selection of flushing agent: R141b, R406a or Nitrogen
There are several main types of substances on the market for cleaning refrigeration circuits. The choice depends on the degree of contamination and the type of equipment. The most common option is R141b -dichlorofluoroethane, which is an excellent flushing liquid, but requires caution due to toxicity.
An alternative is mixtures such as R406a or R600a (in large volumes for flushing), which often used in conjunction with nitrogen. Nitrogen itself is inert and safe, but it only blows out mechanical dust without dissolving acid residues and varnish coatings.
- 🧪 R141b - better dissolving ability, but toxic and prohibited in many countries for new equipment, ideal for flushing old systems.
- ❄️ R406a / R22 - used as a flushing gas under pressure, less effective against carbon deposits, but safer for the environment environment.
- 💨 Nitrogen —used for final purging and checking tightness, leaves no traces, but does not dissolve the oil.
When choosing a product, always pay attention to the compatibility of the materials of the seals of your refrigerator. Some aggressive solvents can damage rubber gaskets if left in the system.
⚠️ Attention: R141b, when in contact with an open flame or hot surfaces, can release phosgene, a chemical warfare agent. Work only in a well-ventilated area!
Required equipment for flushing
For high-quality cleaning of the system, one gas cylinder is not enough. You will need to assemble a special installation that will allow you to circulate the flushing liquid or supply it under high pressure. The basic set includes a cylinder with a flushing agent, a reducer and a pressure gauge station.
Another element is oxygen cylinder (used as a pressure source for nitrogen or air) or a compressor if you plan to do the flushing with your own compressed air, although the latter option is less preferable due to possible humidity. To collect waste liquid, you need special containers.
Do not forget to prepare tools for soldering, since flushing often requires temporary disassembly of the circuit or installation of process fittings. The table below shows the main components of the kit.
| Component | Purpose | Requirements |
|---|---|---|
| Gauge station | Pressure control | Two pressure gauge, high pressure hoses |
| Reducer | Flow adjustment | Brass, oil resistant |
| Collection container | Exhaust drain | Sealed, transparent preferred |
| Hoses | Connection of units | Evacuated, without cracks |
Preparing the refrigerator for the cleaning procedure
Before starting any work, it is necessary to completely empty the refrigeration circuit of old refrigerant. If there is pressure left in the system, it is released in a well-ventilated place, observing fire safety measures. After this, the compressor is usually unsoldered or disconnected, since flushing through the working compressor is prohibited.
The next stage is the vacuuming system. This allows you to remove remaining freon gas and some moisture. The vacuum pump is connected to the service fitting, and the system is pumped out until a deep vacuum is reached (about 500 microns).
☑️ Preparation for flushing
It is important to disconnect the capillary tube and filter drier before washing. These elements have a very narrow cross-section and can be tightly clogged, making flushing impossible, or the flushing liquid will wash away the dirt and clog them completely. Instead of a capillary, a copper tube of the same length is often installed to create resistance.
Flushing technology: step-by-step instructions
There are two main methods: pressure washing and circulation washing. The first method is more common in household repairs. Connect a cylinder with flushing agent (for example, R141b) through the reducer to the condenser inlet. At the outlet of the evaporator, install a hose to drain the waste liquid into a container.
Supply gas or liquid under pressure sufficient to push the flow, but not exceeding 15-20 barto avoid damaging the heat exchangers. The process is repeated several times, changing the direction of flow (countercurrent) in order to most effectively wash out contaminants from all corners of the system.
Connection diagram: Cylinder -> Reducer -> Input to the Condenser ->... -> Output from the Evaporator -> CapacityIf the circulation method is used (more often for large systems), the flushing liquid is pumped into the system, allowed to “acidify” to dissolve contaminants, and then pumped out through a trap filter. The cycle is repeated until the escaping liquid becomes clear.
What to do if the liquid does not flow?
If the flushing liquid does not pass through the circuit, the capillary tube or filter is probably clogged. Try applying nitrogen at high pressure (up to 30 bar) in short bursts. If this does not help, the section of pipe with the blockage will have to be cut out and cleaned separately or replaced.
After completion of flushing, the system must be thoroughly purged with dry nitrogen. This is a critical step to remove any remaining flushing fluid and vapors. Blowing is carried out until the escaping air stream no longer smells like a solvent.
⚠️ Attention: Remaining R141b flushing fluid in the system may react with the new oil, changing its viscosity, or cause hydrolysis, which will lead to the formation of new acid.
Completing work and starting the system
After the circuit is washed and purged, it is necessary to restore the integrity of the circuit. A new one is soldered in, which cannot be opened in advance - it absorbs moisture from the air in seconds. Then a capillary tube or expansion valve is mounted, and the compressor is sealed. filter-drier, which cannot be opened in advance - it absorbs moisture from the air in seconds. Then a capillary tube or expansion valve is installed and the compressor is sealed.
The next step is to re-evacuate the assembled system. The pumping time should be at least 30-40 minutes for household refrigerators. This is necessary to evaporate microscopic moisture residues that may have settled on the walls of the tubes.
- 🔧 Check the tightness with nitrogen under pressure before filling.
- 🌡️ Fill the system with refrigerant in accordance with the weight indicated on the nameplate.
- 🔌 Start the compressor and monitor currents and pressure during the first hour of operation.
Successful completion of work is considered to be a stable temperature in the chambers and the absence of extraneous noise. If the system has been heavily contaminated, it is recommended to replace the filter-drier again after 2-3 weeks of operation, as it can absorb residual dirt washed from hard-to-reach places.
Frequent errors when flushing
One of the most common mistakes is neglecting to replace the filter drier. Many technicians try to “blow out” the old filter, which is absolutely useless. The cement inside it is already saturated with moisture and acid, and it is impossible to restore its properties.
Another mistake is the use of flushing freon through a running compressor. This is strictly prohibited, since flushing fluids (especially R141b) do not have lubricating properties and have a different viscosity. The compressor will jam or the winding will burn due to lack of lubrication.
The stage of long-term nitrogen purging is also often ignored. The “chemistry” remaining in the system mixes with the working fluid, changing the thermodynamic properties of the cycle. This leads to increased condensation pressure and overload of the compressor.
Is it possible to flush the system with regular R134a freon?
Theoretically, it is possible, but this is extremely ineffective and expensive. R134a does not have the solvent properties of R141b. To flush the system with R134a, you will need a lot of it, and it will not be able to remove acid residues and varnish deposits from a burnt out motor. Saving on flushing fluid will lead to the purchase of a new compressor.
How many times should the flushing cycle be repeated?
The number of cycles depends on the degree of contamination. Typically, 2-3 cycles of supplying flushing fluid followed by purging are sufficient. The stopping criterion is the visual cleanliness of the escaping liquid and the absence of mechanical suspensions in it.
Is it necessary to change the oil in the compressor after flushing?
If the flushing was carried out correctly (without including the compressor in the flushing circuit), then the oil in the new compressor does not need to be changed. In old compressors that are decided to be left behind, the oil is changed by squeezing out through the service pipe before installation in the system.
Is R141b dangerous for humans?
Yes, R141b vapors are heavier than air and displace oxygen, which can cause suffocation. The substance is also toxic if inhaled in high concentrations. Work should be carried out wearing a respirator and with active ventilation of the room.