Replacement shredder, or, as it is often called master dry steamer (filter-drier), is one of the key operations during the overhaul of the refrigeration system. This part is responsible for cleaning the refrigerant from moisture and contaminants, and also prevents the formation of ice plugs in the capillary tube. If you are faced with the need to replace a compressor or simply change the filter due to clogging, correct soldering of the new element becomes a critically important task.
The process of connecting metal tubes requires not only the presence of specialized tools, but also strict adherence to technology, since the system must be absolutely sealed and vacuumed. Any mistake during soldering can lead to leakage freon, air getting inside the circuit and, as a result, to the rapid failure of expensive equipment. In this article we will look in detail at how to properly prepare, install and solder the shredder to the suction pipe of the compressor.
Before starting work, you need to make sure that you understand the principle of operation of the refrigeration circuit. The shredder is installed on the suction line, immediately after the evaporator and in front of the compressor, to protect the compression mechanism from liquid refrigerant and oil. Important: work is carried out only when the refrigerator is completely defrosted and the power supply is disconnected. Failure to do so may result in electric shock.
⚠️ Attention: All work with refrigerants and soldering of copper pipes must be carried out in a well-ventilated area. When heated, copper and oil residues can release toxic substances, so the presence of supply and exhaust ventilation or work in the open air is required.
Necessary tools and materials for soldering
The quality of work directly depends on the preparation of the workplace and the availability of the right tools. To solder copper tubes with a diameter of 6, 8 or 10 mm, which are used in household refrigerators, you will need gas burner. You can use both professional installations with separate cylinders for oxygen and acetylene, as well as more affordable options with disposable cylinders of a propane-butane mixture or MAF gas.
It is most often used as a solder for copper connections in refrigeration equipment silver solder (with content silver from 15% to 40%) or copper-phosphorus solder. The latter is good because it does not require the use of flux when soldering copper to copper, but for steel (if the pipes are steel) flux is required. You will also need a pipe cutter, a rimmer (rimmer-expander) for forming a countersink and a brush for cleaning internal surfaces.
- 🔥 Gas burner with a supply of fuel (propane, butane or MAF gas).
- 🪙 Solder (silver or copper-phosphorus) and flux (if required).
- ✂️ Pipe cutter for copper and rimmer for chamfering.
- 🔧 Set of flaring tools and wrenches.
- 🧹 Cleaning brushes for pipes and rags.
Special attention should be paid to protective equipment. Working with open flames and hot metal requires the use of heat-resistant gloves and safety glasses. Copper changes color when heated, and it is difficult to visually determine the temperature of 700–800 degrees Celsius without experience, so the risk of burns is high. Safety is priority number one.
⚠️ Attention: Do not use ordinary tin-lead solder used in electronics. It has a low melting point and will not withstand pressure and vibrations in the refrigerator system, which will lead to instant depressurization.
Preparing the compressor and removing the old shredder
The first stage of work is dismantling the old filter-drier. If the compressor has not yet been removed from the refrigerator, you must carefully bleed off the remaining refrigerant. Although in modern conditions environmental standards require the collection of freon in special containers, when doing self-repairs, the gas is often simply released through a cut in the tube. After this, the tube going to the shredder is cut with wire cutters.
The process of removing the old shredder itself involves heating the soldering area. The burner flame is directed to the junction of the copper tube and the filter housing. When the solder has melted, the tube can be carefully pulled with pliers. Important: do not overheat the compressor housing itself, especially if you plan to reuse it. Local heating only in the soldering zone is the key to success.
After removing the old element, it is necessary to prepare the ends of the tubes. Copper tends to oxidize when heated, forming an oxide film (scale) inside the tube. If this scale is not removed, it can enter the compressor and cause the piston group to seize. To clean, use a special brush or blow with nitrogen. The ends must be smooth, without burrs.
Why do you need nitrogen during soldering?
Blowing with nitrogen during soldering prevents the formation of copper oxides inside the tube. If there is no nitrogen, try to heat the connection for the minimum required time and immediately after soldering, vent the system.
If you are changing the entire compressor, then on the new unit, the shipping plugs are removed only at the very last moment before soldering to prevent moisture from the air from getting into the system. The hygroscopicity of the oil in the compressor is high, and it quickly absorbs moisture, which will subsequently lead to the formation of acid and destruction of the insulation of the electric motor windings.
Soldering technology: step-by-step instructions
The soldering process requires a certain skill. First you need to insert the copper tube into the shredder pipe. The planting depth should be approximately 5–10 mm. If the tube is loose, the connection will be leaky. Ideally, the tube should fit in with a slight interference fit. Make sure both surfaces are perfectly clean before inserting. You can use fine sandpaper to clean the outer surface of the tube and the inner surface of the pipe.
Heating is carried out evenly. The burner flame should not be too narrow and “evil”; it is better to use a petal flame. The entire assembly heats up: both the tube and the pipe. When the metal is heated to the desired temperature (copper-phosphorus solder melts at approximately 700°C, silver - at 600-700°C, depending on the brand), a solder rod is brought to the joint. Solder should melt from the heat of the metal, and not from direct contact with the burner flame.
☑️ Shredder soldering algorithm
When the solder begins to melt, it is under the influence of the capillary effect will flow into the gap between the tube and the pipe. It is necessary to ensure that the solder surrounds the entire perimeter of the connection. Excess solder can flow inside the tube and block the passage for freon, so it is important not to overdo it with the amount. The seam should be smooth, without cavities or sagging.
After filling the seam, the burner is removed and the joint is allowed to cool naturally. Do not blow on it or pour water on it to speed up the process - this can cause cracks in the still hot metal or solder. While the connection is hot, it cannot be moved or wobbled, otherwise the tightness will be broken.
| Parameter | Copper-phosphorus solder | Silver solder (15-30%) | Brass solder |
|---|---|---|---|
| Melting point | ~700-750°C | ~600-700°C | ~850-900°C |
| Do you need flux (copper-copper) | No | Advisable | Required |
| Weam ductility | Average | High | Low |
| Vibration resistance | Good | Excellent | Average |
| Recommended use | Domestic refrigerators | Professional repair | Rarely, for special tasks |
Installation and sealing of connections
After the shredder is soldered, you need to check the quality of the connection. A visual inspection allows you to identify obvious defects: lack of fusion, cracks or excessive sagging. However, visual inspection is not enough. The next step is to pressurize the system with nitrogen. This makes it possible to identify microcracks that could have formed during cooling.
For crimping, a pressure gauge station is connected to the process pipe (shredder). The system is filled with nitrogen under pressure, usually 10–15 atmospheres (for R134a and R600a). The pressure is maintained for several hours. If the pressure gauge shows a drop in pressure, there is a leak somewhere. The location of the leak can often be found by hearing (hissing) or using a soap solution that is applied to the seams.
Critical point: If the leak is found at the soldering point of the shredder, nitrogen is released and the defect site is resoldered. Re-soldering requires special care so as not to overheat the finished joint and melt the previous layer of solder. In such cases, the soldering area can be cooled with a damp rag, protecting adjacent areas.
Tightness is not just the absence of holes, it is a guarantee of long-term operation of the compressor. The entry of air (oxygen) and moisture into the system leads to oil oxidation, the formation of acids and “plugs” in the capillary tube. Therefore, the pressure test stage cannot be ignored, even if visually the seam looks perfect.
Evacuation of the system after soldering
After successful crimping and elimination of all leaks, the vacuum stage begins. This is perhaps the most important stage for the longevity of the refrigerator. The vacuum pump removes not only air from the system, but also, more importantly, water vapor. The water in the refrigerator system freezes in the area of the capillary tube, forming an ice plug that blocks the circulation of freon.
The vacuum pump is connected to the service pipe. The operating time of the pump depends on the power of the equipment and the volume of the system, but usually ranges from 15 to 30 minutes. The residual pressure should reach values of about 200-500 microns (0.2-0.5 mm Hg). A vacuum gauge is used for monitoring.
- 💨 Connect the vacuum pump to the service port.
- ⏱ Turn on the pump and monitor the pressure gauge readings.
- 🛑 Close the valve and turn off the pump, check the stability of the vacuum.
- 🔍 Make sure that the arrow does not creep up (this will indicate a hidden leak or the presence of moisture).
If, after turning off the pump, the pressure in the system begins to increase, this is a signal of a problem. Either there was a microscopic leak somewhere, or there was a lot of moisture in the compressor oil or in the new shredder that began to evaporate. In the latter case, the vacuuming procedure is repeated, sometimes with heating the compressor with a hairdryer to remove moisture.
⚠️ Attention: Never turn on the compressor to create a vacuum (“pushing”) if there is no freon in the system or it is not sealed. This is guaranteed to lead to the combustion of the motor windings due to lack of cooling and lubrication.
Filling with refrigerant and final check
The final step of the repair is filling the refrigerator with freon. The type of refrigerant and its quantity (grams) are indicated on the factory sticker, which is usually located inside the refrigerator compartment or on the back wall of the unit. For modern refrigerators, freons are used R134a or R600a (isobutane). The latter is explosive, so working with it requires special care and the absence of sparking tools.
Refilling is carried out in the liquid or gas phase, depending on the type of refrigerant and the manufacturer's recommendations. For R134a, charging is often used in the liquid phase through a filter drier, and for R600a, only in the gas phase through the suction pipe while the compressor is running. The amount of refrigerant is controlled by scales (for the liquid phase) or by the pressure and current consumption of the compressor (for the gas phase).
After refueling, the refrigerator is plugged in and allowed to operate for several hours. The uniformity of cooling of the evaporator, the temperature in the chambers, and the absence of excessive heating of the condenser are checked. The shredder should not be hot or, conversely, icy (except for the entrance area). Its temperature should be close to room temperature or slightly elevated.
If all parameters are normal, the service pipe is sealed. At this point, the work on replacing the shredder is considered complete. A high-quality repair allows you to restore the performance of the refrigerator to factory parameters.
Is it possible to use a shredder from another refrigerator?
Yes, you can, if it fits the diameter of the pipes and has a similar or larger capacity (gram). The main thing is that it is designed for the same type of freon (although most are universal) and is new. Used filters cannot be used, as they are already saturated with moisture.
What to do if the solder does not stick to the tube?
Most likely, the surface is not cleaned or heated enough. Make sure the copper is shiny and not black from oxides. Also check the temperature: if the metal is not hot enough, the solder will form balls. Add a little flux if you are using solder that requires its use.
Do you need to change the oil in the compressor when replacing the shredder?
When regularly replacing the shredder (filter), a complete oil change is usually not required if the system has not been opened for a long time and moisture has not entered it. However, if the reason for the replacement is compressor combustion or moisture ingress, then flushing the system and changing the oil are required.
Which solder is best to choose for a beginner?
For a beginner, copper-phosphorus solder with a silver content (for example, 5% or 15%) is best. It is easier to use than pure copper, has a good melting range and does not require flux when soldering copper joints, which reduces the risk of errors.