Using an old refrigerator to create a homemade one An air compressor is not just a way to recycle household appliances, but also an excellent opportunity to get a powerful tool for a garage or workshop. Motor-compressor, originally intended for circulation of freon, with proper modification, it can generate pressure of up to 8-10 atmospheres, which is quite enough for painting a car, operating pneumatic tools or inflating tires. Unlike cheap Chinese analogues, the unit from the refrigerator is much quieter and has a long service life with proper maintenance.
The main advantage of this solution lies in the availability of components and simplicity of design. Sealed compressor does not require a complex lubrication system, since the oil is located inside the crankcase, and the electrical circuit connection is elementary. However, in order to turn a household appliance into a full-fledged air blower, it is necessary to replace the refrigerant with atmospheric air and install a compressed gas purification and preparation system. Without these modifications, the device will quickly overheat and throw out oil along with air.
Before proceeding with dismantling, it is important to make sure that the engine itself is in good condition. If the old refrigerator was still working, but stopped cooling due to a freon leak, its motor is most likely fully functional, so even after 10 years of service in a kitchen cabinet, it can serve for many more years in a new role. The main thing is to correctly select the remaining equipment that will work in tandem with the engine. The service life of motor-compressors from refrigerators often exceeds 20,000 hours of operation, so even after 10 years of service in a kitchen cabinet, it can serve for many more years in a new role. The main thing is to correctly select the rest of the equipment that will work in tandem with the engine.
Necessary tools and components
To assemble a high-quality unit, it is not enough just to find an old refrigerator. You will need a number of additional elements that will ensure the safety and functionality of the system. Receiver (the air storage tank) is the heart of the system, smoothing out pressure pulsations. You can use an old fire extinguisher, a gas cylinder, or a specially welded container made of a thick-walled pipe.
In addition to the main tank, the filtration and adjustment system is critically important. The air leaving the compressor is saturated with oil mist and moisture, which is categorically unacceptable for working with a spray gun or pneumatic tools. Therefore, the scheme must include oil separators and fine filters. You also cannot do without a pressure gauge to control pressure and a reducer if you plan to connect tools that require less pressure than the pump creates.
- 🛠️ Tools: Set of wrenches, pliers, screwdrivers, hacksaw or grinder, drill with a set of drills.
- 🔧 Consumables: Copper tubes or high-pressure hoses, clamps, sealant, electrical tape, adapters and fittings.
- ⚙️ Components: Pressure switch (pressostat), reverse valve, safety valve, hoses for connecting tools.
⚠️ Attention: When using gas cylinders or fire extinguishers as a receiver, make sure that they are completely empty and have no residual pressure. Cutting or drilling a cylinder in which gas remains can lead to an explosion.
☑️ Preparation for assembly
Dismantling and preparing the motor-compressor
The first stage of work is careful removing the compressor unit from the refrigerator. Do not rush to cut the tubes with wire cutters, as metal shavings may get inside the mechanism. It is best to use a pipe cutter or carefully saw through the tubes with a hacksaw, leaving a margin of length for later connection. On the motor body you will see three copper tubes: two are usually located on one side, and one on the opposite or side.
It is important to correctly determine the purpose of the pipes. To work with air, we need to know where the entrance is and where the exit is. In the factory version, freon is sucked in through one tube and pumped under pressure through the other. The third pipe (often sealed) is used to fill the system and will not be needed in our design. To avoid guessing, turn on the motor (being careful!) and place your finger near the holes in the tubes.
Where the air blows with noticeable pressure is outlet hole. Where the finger sucks is the entrance. Marking the tubes often helps: the discharge tube may have a mark on it or is visually thicker. After identification, plug the inlet by installing an air filter on it. This will prevent dust from getting inside the crankcase, which is critical for the durability of the piston group.
How to distinguish the input from the output without connecting to the network?
If it is not possible to turn on the engine, you can try blowing into the tubes. From the outlet side it will be difficult to blow due to the resistance of the valves, and from the inlet side the air will flow freely. However, the most reliable method is short-term connection to the network.
Manufacture and preparation of the receiver
The receiver functions as a buffer, accumulating compressed air and stabilizing the pressure in the system. Without it, the compressor will work in constant on and off mode, which will quickly lead to overheating. The optimal tank volume for garage needs is from 20 to 50 liters. A smaller volume will lead to frequent engine starts, and too large will take up a lot of space.
The most popular and safest option is to use a discarded propane cylinder or a fire extinguisher cylinder. The walls of these containers are designed for high pressure, which guarantees safe operation. Before installing the fittings, the cylinder must be thoroughly cleaned of rust inside and out, and also rinsed with water to remove residual contents.
In the upper part of the receiver, several fittings must be welded or screwed through adapters. One of them will be used to connect the compressor, the second - to take air to the consumer, the third - to install a pressure gauge and pressure switch. Also, at the lowest point of the tank, it is necessary to install drain valve to remove condensate, which will inevitably form when air is compressed.
| Component | Function | Material execution | Requirements |
|---|---|---|---|
| Receiver | Air accumulation | Steel (cylinder) | Pressure > 15 atm |
| Pipeline | Air transport | Copper / Steel | Heat resistance |
| Filter | Dust removal | Plastic / Metal | Density 5-10 microns |
| Pressure switch | Automatic | Plastic / Metal | Setting 2-8 atm |
Assembling a filtration and automation system
The air preparation system is what distinguishes a professional tool from a handicraft. The air leaving the compressor has a temperature of up to 100-120 degrees and contains a suspension of oil. For cooling and primary cleaning, a cooler is installed (often made in the form of a coil made of a copper tube), followed by a separator.
The separator (oil separator) is a container in which the air flow sharply changes direction, and the oil settles on the walls. After the separator, the air passes through fine filter, which retains the smallest particles. Only after this does clean and dry air enter the receiver. If you skip this step, oil stains will remain on the surface when painting, and the pneumatic tool will quickly fail.
The control automation is assembled on the basis of a pressure switch (pressostat). This device monitors the pressure in the receiver and automatically turns on the motor when the pressure drops below a set threshold (for example, 4 atm) and turns off when the maximum is reached (for example, 6 atm). The connection diagram is simple: phase and zero from the network go to the relay input, and from the output to the compressor motor.
⚠️ Attention: The pressure relay must be designed for the current consumed by your motor. If the engine power is high, be sure to use an intermediate electromagnetic relay or contactor so as not to burn the pressure switch contacts.
Installation and testing of the system
After preparing all components, the final assembly stage begins. The compressor and receiver can be mounted on a common frame made of a metal angle or a wooden beam. It is important to ensure vibration isolation: use rubber gaskets under the motor feet so that vibration is not transmitted to the structure and does not cause noise.
Connect all elements with hoses or tubes according to the diagram: Input filter → Compressor → Check valve → Oil separator → Receiver → Pressure switch → Output faucet. Check valve is installed between the compressor and the receiver so that air does not flow back into the motor after stopping, which could rip off the impeller.
Carry out the first start in a well-ventilated area. Turn on the unit and carefully monitor the pressure gauge readings. Check all joints for air leaks using a soap solution. If bubbles do not appear, and the pressure builds up to the cutoff and the motor stalls, the system is assembled correctly.
Frequent errors and safety rules
When assembling a compressor with their own hands, beginners often neglect the cooling system. The motor-compressor from the refrigerator is cooled by circulating freon and blowing through the housing. In air mode it heats up much more. Therefore, it is recommended to either pause work or organize forced ventilation of the housing with a fan.
Another common mistake is the use of plastic tubes or low-pressure hoses for lines after the compressor. Temperature and pressure can melt or break such connections. Use only metal tubes or specialized hoses designed for a pressure of at least 1.5-2 times higher than the working pressure.
- 🔥 Overheating: Do not allow the motor to operate continuously for more than 20-30 minutes unless a temperature sensor is installed.
- 💧 Moisture: Do not forget to regularly drain the condensate from the receiver, otherwise the tank will begin to rust from the inside.
- ⚡ Electrical: Be sure to ground the installation housing and use a circuit breaker in the power circuit.
⚠️ Attention: Technical characteristics and safety requirements for equipment may change. Before operating a homemade device under high pressure, make sure that all components (especially the receiver) have been tested for leaks and comply with safety standards for working with pressure vessels.
Frequently asked questions (FAQ)
How many atmospheres can a compressor produce from refrigerator?
A standard motor-compressor from a household refrigerator is capable of creating pressure up to 8-10 atmospheres. However, the operating pressure is usually limited by relays to 4-6 atmospheres for safety and extended service life.
Is it necessary to change the oil in the compressor during refurbishment?
Changing the oil is not necessary and is even harmful. Inside the crankcase there is a special refrigeration oil that does not evaporate and works well in conjunction with rubber seals. You cannot add regular motor oil.
Can this compressor be used for sandblasting?
For a full-fledged sandblaster, the performance of one compressor from a refrigerator will not be enough. It is suitable only for very small work or pumping, but not for active abrasive processing of metal.
Why does the compressor get very hot?
When air is compressed, heat is released. Unlike freon, air does not cool the engine. Long-term operation requires forced air cooling of the case or breaks in operation.