An old refrigerator that has failed is often sent to a landfill, although his heart - compressor - can get a second life. This unit is capable of creating pressure up to 10 atmospheres, which makes it an ideal basis for creating a compact air compressor. Such devices are widely used in garages for inflating tires, blowing out electronics, or working with an airbrush. A home-made design is much cheaper than factory-made analogues, and with proper assembly it is not inferior to them in reliability.
However, the conversion process requires not only technical skills, but also strict adherence to safety rules. Freon compressors are not initially designed to work with atmospheric air in a continuous mode, so it is necessary to take into account the features of lubrication and cooling. Improper assembly may result in equipment failure or even personal injury. In this article we will analyze in detail each stage of the transformation, from dismantling to launching the finished device.
Before starting work, it is important to understand the principle of operation of the unit. Unlike open-type piston compressors, the refrigeration unit is sealed, and the oil is under pressure in the crankcase. Air injection occurs due to the movement of the piston inside the cylinder, but the cooling and lubrication system here is tied to the circulation of the refrigerant. When pumping air, these processes are disrupted, which requires the introduction of additional elements, such as receiver and a cut-off system.
⚠️ Attention: Before starting any work, make sure that the compressor is completely disconnected from the electrical network and The refrigerant has been safely removed from the system by professionals. Independent release of freon into the atmosphere is prohibited by environmental standards.
Necessary tools and materials for assembly
To successfully implement the project, you will need to assemble a certain set of components. The basis is already there - the compressor itself, but the rest will have to be purchased or found in the garage. The key element will be receiver a container for accumulating compressed air. They often use old fire extinguishers, freon gas cylinders, or receivers from truck brake systems. The main requirement for a container is the ability to withstand high pressure without the risk of rupture.
In addition to the capacity, the correct one is critically important accessories. You will need adapters, hoses, check valves and pressure gauges. Hoses must be designed for pressure above the working pressure, usually these are reinforced tubes. To control the pressure, you need pressure switch (pressostat), which will automatically turn off the motor when a given threshold is reached and turn it on when it drops.
- 🔧 Compressor from the refrigerator (with a capacity of 100 W).
- 🛢️ Receiver (metal cylinder with a volume of 10-50 liters).
- ⚙️ Pressure switch (pressostat) with upper and lower threshold adjustment.
- 📏 Pressure gauge for visual monitoring of pressure in the system.
- 🔌 Check valve that prevents air from escaping back into the compressor.
Don't forget about fasteners and tools. You will need wrenches, a drill, a set of drills, as well as sealant or FUM tape to seal the threaded connections. If you are planning a mobile device, immediately provide a wheelbase or a convenient handle for carrying. Stationary models can be mounted on a wall or shelf, but vibration will require reliable fastenings.
Removing and preparing the compressor
The first step is to remove the compressor from the refrigerator body. It is usually located at the lower rear. Carefully disconnect the tubes going to the condenser and evaporator. It is important not to damage the copper pipes, especially if you plan to use them for connections. After removal, the unit body should be cleaned of dust and old paint to prevent future corrosion.
The next step is to determine the purpose of the tubes. When the compressor is turned on for a short time, one of the three tubes will begin to blow out air - this is discharge pipe. The second, which will suck in air, is the input. The third tube is often sealed and serves for technological purposes (filling with freon); during modification, it can be used as an oil drain or plugged. Marking the tubes will facilitate further assembly.
Pay special attention to the condition of the electrical part. Start relay and the capacitor must be in working condition. If oxide or carbon deposits are visible on the contacts, they must be cleaned. Check the integrity of the motor windings using a multimeter. If the resistance between the contacts tends to zero or infinity, the motor is faulty and requires replacement.
Preparation and modernization of the receiver
The receiver is a buffer zone that stabilizes the pressure and cools the compressed air. Using an old fire extinguisher is a popular option, but it requires careful preparation. First, make sure the cylinder is empty and not under pressure. Then remove the bell and shut-off valves. The inner surface must be washed with hot water and detergent to remove any remaining powder that can clog the pneumatic lines.
After drying, holes must be drilled in the receiver body to install fittings. Typically, three holes are required: for air inlet from the compressor, for air outlet to the consumer, and for installation drain valve at the lowest point. Draining is necessary to remove condensate, which inevitably forms when humid atmospheric air is compressed. Ignoring this element will lead to corrosion of the cylinder from the inside.
| Component | Function | Installation location |
|---|---|---|
| Inlet fitting | Air supply from the compressor | Upper part of the cylinder |
| Outlet fitting | Air intake to the tool | Middle or upper part |
| Drain faucet | Removal of condensate and oil | The lowest point of the bottom |
| Hole for pressure gauge | Pressure control | Upper part, next to the outlet |
When drilling, use cooled metal drills so as not to overheat the material. The edges of the holes should be processed by removing burrs. To insert fittings, use threaded connections, sealing them with FUM tape or anaerobic sealant. The reliability of these connections is critical, as they are under constant pressure.
Assembling a pneumatic circuit and connecting
Assembling the system begins with installing the compressor on the frame or directly to the receiver. It must be installed between the compressor outlet pipe and the receiver. check valve. It prevents the reverse flow of air from the receiver into the compressor after it stops, which protects the mechanism from overload the next time it starts and maintains pressure in the system.
Next, the automation unit is mounted. The pressure switch (pressostat) is connected to the receiver via a tee. Electrical wires from the network and from the compressor motor are supplied to the relay itself. The principle of operation is simple: when the pressure in the receiver drops below the set minimum, the relay closes the circuit and starts the motor. When the maximum is reached, it opens. The thresholds are adjusted using screws under the relay cover.
⚠️ Attention: The electrical circuit must be assembled taking into account the engine power. Use wires with a cross-section of at least 1.5 mm² and be sure to install a circuit breaker to protect against short circuits.
The final stage of assembly is connecting the outlet hose with a quick-release connection. This will allow you to quickly change tools (airbrush, tire gun). All connections should be checked for leaks. To do this, pump the system to operating pressure and cover the joints with soapy water. The appearance of bubbles will indicate a leak that needs to be repaired.
☑️ Checking the assembly
Features of lubrication and system maintenance
One of the main problems of converted compressors is oil carryover. Since refrigeration compressors operate in an oil bath, part of the lubricant, along with the air, enters the receiver and then into the pneumatic tool. For spray guns or airbrushes, this is a disaster, as the oil will ruin the coating. The solution is to install an oil-moisture separator at the outlet of the receiver.
A homemade filter can be made by filling a container with expanded clay or activated carbon, but it is better to use ready-made industrial designs. Regular maintenance also includes checking the oil level in the compressor crankcase (if there is a sight glass or dipstick) and periodically replacing the air inlet filter. A clogged filter increases the load on the motor and reduces performance.
Why does the compressor heat up?
When air is compressed, the gas temperature rises sharply. In refrigerators, heat is removed through the casing and natural convection. In homemade conditions, especially during intensive operation, the compressor may overheat. To solve this, you can install an additional fan or take breaks in operation every 20-30 minutes.
Do not forget about draining the condensate. Moisture accumulating at the bottom of the receiver causes metal corrosion. Weakening the walls of a cylinder under pressure is a recipe for explosion. Therefore, the rule is simple: after each use, open the drain valve and completely bleed out any remaining air and water.
Safety precautions and precautions
Working with high pressure requires discipline. Never exceed the maximum permissible pressure for which your receiveris designed. If you are using a fire extinguisher, find out its operating pressure (usually indicated on the body, for example, 1.5 MPa or 15 bar) and set the shutdown relay with a margin of 10-15%. Excessive pressure can lead to depressurization.
It is prohibited to use containers containing flammable gases (propane, butane) for receivers without special preparation and cleaning, since gas residues can ignite from a spark or heat. It is also not recommended to use plastic or glass vessels - they will not withstand the load. Only metal with a safety margin.
- 🔥 Do not smoke or use open fire near the operating compressor.
- 🛡️ Use safety glasses when working with pneumatic tools.
- 🔌 Ground the compressor and receiver housing to protect against static electricity.
- 🚫 Do not direct a jet of compressed air at people or animals.
If you notice vibration, unusual noise or a burning smell, immediately disconnect the device from the network. Diagnostics malfunctions should only be carried out on de-energized and completely discharged equipment. Regular visual inspection of the receiver's welds for cracks and corrosion is mandatory.
Possible problems and ways to solve them
During operation, you may encounter a number of typical problems. For example, the compressor may not reach the required pressure or may run for too long. This is often due to wear on the piston group or leaks in the connections. Another common problem is that the engine starts frequently, which indicates a small reservoir volume or a malfunction of the check valve.
If the compressor vibrates strongly, check the fastenings and condition of the rubber shock absorbers. Vibration is transmitted to the receiver and can lead to fatigue failure of the metal. To reduce noise and vibration, you can place the unit in a soundproofing box, but it is necessary to ensure an air flow to cool the motor.
What to do if the compressor hums, but does not start?
Most likely, the thermal protection relay has tripped or the starting device is faulty. Let the engine cool down. If the problem persists, check the mains voltage and the condition of the capacitor. Also, the cause may be jamming of the piston due to thickened oil or lack of lubrication.
Is it possible to use such a compressor for painting a car?
Only if you have a high-quality oil and moisture separator and a receiver of sufficient volume (from 50 liters). Refrigeration compressors often produce pulsating flow, which can create defects on the surface being painted. For professional painting, it is better to use specialized models.
How often do you need to change the oil in a converted compressor?
In hermetic compressors, the oil is rarely changed, but when converted to air, it oxidizes faster. It is recommended to replace or top up every 100-200 operating hours, using special compressor oil, not engine oil.
Why does oil fly from the outlet pipe?
This is a design feature of oil compressors. The oil level in the crankcase may be too high or the piston rings may be worn. Installing a high-quality separator at the outlet will solve the problem of oil getting into the pneumatic line.
What is the maximum service life of such a compressor?
With careful operation and timely maintenance, a home-made unit can last 5-7 years or more. The resource depends on the intensity of the load: continuous operation reduces the service life faster than short-term pumping cycles.