Modern tools and devices require a source of compressed air, but buying expensive industrial equipment for rare tasks in a home workshop is not always rational. Many craftsmen find the ideal solution in the form of converting an old refrigeration compressor into a full-fledged air blower. This saves the budget and allows you to get a quiet, compact unit that can cope with painting, blowing and inflating tires.
The main advantage of this design is the low noise level and lack of vibration, which is critical for working in a garage or residential area. Unlike bulky piston models, refrigeration motor works smoothly and does not require maintenance for a long time. However, for the successful implementation of the project, you will need not only the motor itself, but also a number of additional components that will turn it into a safe system.
Before you begin assembly, you need to clearly understand the operating principle and limitations of such a device. Refrigeration compressors are not designed for constant operation under high pressure, so their use requires the installation of additional safety elements. In this article we will analyze in detail the process of creating a reliable and efficient compressor.
Preparation of tools and selection of motor
The first step is to find a suitable donor. Compressors from Soviet refrigerators, such as ZIL or Biryusaare best suited, as they are known for their reliability and durability. Modern imported models are also suitable, but often have a shorter service life when working with air. It is important that the motor is sealed and has no external damage to the housing.
To work, you will need a standard set of plumbing tools, which any home craftsman will have. Do not forget to prepare personal protective equipment, since working with metal and electricity requires caution. Tightness of connections is a key success factor, so pay attention to the quality of soldering or threaded connections.
The list of necessary materials includes not only the engine itself, but also elements for creating an air storage and distribution system. Without a high-quality receiver (tank) and filters, the device will work unstably or quickly fail. Prepare all components in advance so as not to interrupt the assembly.
- 🔧 Compressor from the refrigerator (whole, without cutting the housing)
- 🛢️ Receiver (fire extinguisher, gas cylinder or receiver from a truck)
- ⚙️ Pressure switch (pressostat) for automation of work
- 🔌 Electrical cable with plug and power button
- 🔩 Fittings, hoses, check valve and pressure gauge
Dismantling and initial check of the engine
The process of removing the compressor from an old refrigerator requires care. It is not recommended to cut the tubes with a hacksaw, as metal shavings can get inside the mechanism and cause fatal damage. It is best to cut the copper tubes with wire cutters at a distance of 5-10 cm from the body, leaving the “tails” for further work.
After removal, it is necessary to determine the purpose of the pipes. Turn on the motor (briefly) and place your finger near the holes in the tubes. Where the air blows is the discharge outlet, and where it sucks in is the inlet. The third pipe is usually sealed or serves for filling with oil; it is rarely used. Freon compressors They often have a specific body shape, which must be taken into account when fastening.
Check the condition of the oil inside. If, when tilted, black liquid with a burning smell flows out of the tubes, it is better not to use such a motor. Ideally, the oil should be light and transparent. If you plan to use the unit for airbrushing or painting, make sure that it does not “spit” oil, as this will ruin the coating.
⚠️ Attention: It is strictly forbidden to open the sealed compressor housing with a grinder or a hacksaw! There may be gas under pressure inside, and dust getting inside the mechanism is guaranteed to disable it.
Manufacturing a receiver for compressed air
The receiver functions as a pressure stabilizer and air storage device. Without it, the compressor will operate in constant mode, quickly overheating. Old fire extinguishers with a volume of 10-50 liters or propane cylinders are ideal as containers. Before use, make sure that the container is free of corrosion and mechanical damage.
If you are using a fire extinguisher, you must remove the shut-off and trigger device and thoroughly rinse the inside with water and detergent. This will remove any remaining powder that may be abrasive to the compressor mechanism. After washing, the container must be completely dried to prevent moisture from entering the system.
For a gas cylinder, the preparation procedure is more complicated. The remaining gas must be released by unscrewing the valve, and be sure to fill the cylinder with water to the brim to force out all the propane. Only after this can you start drilling holes and welding fittings. Safety when working with gas cylinders comes first.
| Receiver type | Volume (l) | Max. pressure (atm) | Features of preparation |
|---|---|---|---|
| Fire extinguisher | 10-50 | 10-15 | Rinsing from powder |
| Propane cylinder | 20-50 | 15-25 | Full steaming with water |
| Receiver from KAMAZ | 20-40 | 10-12 | Minimum preparation |
| Air suspension tank | 15-30 | 10-14 | Corrosion check |
Assembling the pneumatic system
Installation of the entire system begins with installing the fittings on the receiver. You will need at least three holes: for air inlet from the compressor, for air outlet to the consumer and for installing a pressure gauge. Threaded connections must be sealed with fum tape or thread to prevent leaks under pressure.
A mandatory element of the system is check valve. It is installed between the compressor and the receiver and prevents air from escaping back into the engine after stopping. This protects the piston group from overload when restarting. Without this valve, the motor may simply not start under pressure.
To drain condensate, a drain valve is installed at the bottom point of the receiver. Moisture contained in compressed air will settle at the bottom of the tank and must be removed periodically. If this is not done, water will get into the pneumatic tool or paint sprayer, which will lead to their breakdown.
☑️ Assembling the pneumatic system
Electrical circuit and automation
For automatic control of the engine operation pressure relay (pressostat). This device opens the electrical circuit when the pressure in the receiver reaches a predetermined maximum, and closes it when the pressure drops to a minimum. The connection is made through the relay contact group, which is designed for the motor current.
The connection diagram is quite simple: phase and zero from the network go to the relay input, and from the output to the compressor windings. If the engine power is high, it is better to use an additional contactor or starter controlled by a pressure switch. This will extend the life of the contacts and protect the wiring from overheating.
Do not forget to ground the compressor and receiver housing. Static electricity from air movement and the possibility of insulation breakdown make grounding a mandatory safety requirement. All electrical connections must be reliably insulated and protected from oil.
How to set the pressure switch?
There are two adjusting nuts inside the pressure switch. The large nut (usually on a large spring) is responsible for the switching pressure, and the small one (on a small spring) is responsible for the delta (difference) between switching on and off. Rotate them carefully, monitoring the readings of the pressure gauge.
Startup, configuration and maintenance
The first launch of the assembled system must be carried out under careful supervision. Turn on the compressor and listen carefully: there should be no extraneous knocks, vibrations or air hissing. Check all connections with a soap solution - the appearance of bubbles will indicate a leak that needs to be repaired immediately.
During operation, monitor the temperature of the engine housing. Refrigeration compressors they heat up more when working with air than with freon, so they may require additional cooling or breaks in operation. Do not allow overheating above 90-100 degrees Celsius.
Regular maintenance includes changing the oil (if the design allows) or monitoring its level, as well as draining condensate from the receiver. Periodically check the tension of the belts (if a belt drive is used) and the cleanliness of the air inlet filter. Clean air is the key to a long life of the piston group.
⚠️ Attention: Never leave a running compressor unattended for a long time. The automation may fail, which will lead to excess pressure and rupture of the receiver.
Possible problems and ways to solve them
During the operation of a homemade compressor, typical malfunctions may occur. For example, if the engine hums but does not start, the piston may be stuck or the start relay may be faulty. In this case, you will need to replace the relay or repair the mechanical part, which is difficult to do at home.
If the compressor does not gain pressure or gains it too slowly, check the integrity of the valves and the presence of leaks in the system. Worn plate valves inside compressor heads may not provide the desired compression. Also, the cause may be a clogged air filter at the inlet.
Strong vibration often indicates that the compressor is poorly secured to the frame or receiver. Use rubber pads or shock absorbers to reduce noise and vibration. This is especially important if you plan to use the device for painting, since vibration can ruin the quality of the coating.
Frequently asked questions (FAQ)
Can such a compressor be used for airbrushing?
Yes, you can, but only if you install a high-quality moisture and oil separator. Refrigeration compressors often “spit” oil, which will ruin the design. You will also need a reducer for precise adjustment of low pressure.
What is the maximum pressure you can get?
Standard refrigeration compressors are designed for pressures up to 10-15 atmospheres. Exceeding this value may result in housing rupture or engine combustion. For most tasks in the garage, this pressure is sufficient.
Is it necessary to change the oil in the compressor?
In hermetic compressors, changing the oil is difficult and is often not provided for by the design. If the compressor is new, the oil does not need to be changed. If it is old and makes a lot of noise, change the oil through the drilled hole, but this is risky.
Why does the compressor get very hot?
When pumping air, the efficiency of a refrigeration compressor is lower than when working with freon, so more energy goes into heat. In addition, the lack of freon cooling (which in the refrigerator also cools the motor) leads to heating. Breaks from work are necessary.