Using an old but serviceable refrigerator does not necessarily end with scrapping it. Compressor, which is the heart of the refrigeration unit, has a colossal service life and is capable of creating pressure sufficient for many household needs. Many home craftsmen prefer not to throw away equipment, but to give it a second life by creating effective air blowers.
A homemade unit often surpasses cheap Chinese analogues in terms of noise and durability. Piston group household refrigerators are designed for round-the-clock operation for decades, which guarantees high reliability of the design. Unlike industrial models, such a compressor operates almost silently and does not require complex maintenance.
The main task during remodeling is to properly prepare system and equip it with additional safety elements. You don’t need rare tools, just a basic home craftsman’s kit and an understanding of the principles of pneumatic operation. The receiver in this design is an old fire extinguisher or a gas cylinder with a volume of 10–50 liters.
⚠️ Attention: Before starting any work, make sure that the refrigerant (freon) is completely removed from the system. Opening sealed tubes should only be done in a well-ventilated area, away from open fire.
Operating principle and advantages of a homemade design
A refrigeration compressor is a sealed unit, inside which an electric motor operates in an oil bath, driving a piston group. Unlike open models, where the motor and cylinder are separated, here all components are located in a single housing. This provides minimum level of vibration and noise, which is critical for working in a garage or workshop.
The main advantage is the ability to (long-term) maintain stable pressure without overheating. If a conventional construction compressor requires periodic stops to cool down, then refrigeration analogue can work for hours. However, it has a maximum pressure limitation, which is usually 6–8 atmospheres, which is quite enough for airbrushing, inflating tires or pneumatic tools.
- 🔧 Low noise level - the operation of the unit is barely audible even in a small room.
- 🔧 No vibration - does not require a massive foundation or anchorage.
- 🔧 Cost-effective - energy consumption is minimal compared to industrial analogues.
- 🔧 Availability - the basis is equipment that is often available or purchased for pennies.
The design makes it easy integrate automation, which will turn off the motor when the specified pressure in the receiver is reached. This makes operation safe and convenient, eliminating the need for the user to constantly monitor the pressure gauge. The system is easy to upgrade and repairable.
Necessary materials and tools for assembly
To create a full-fledged pneumatic system, a compressor alone is not enough. You will need receiver a container for storing air, which smoothes out pressure pulsations and allows the pump to rest. Steel cylinders from fire extinguishers OU-5, OU-10 or small propane containers are ideal. They already have the necessary threads and are designed for high pressure.
In addition to the container, you will need the following accessories: a check valve that prevents the reverse flow of air into the compressor, and a pressure switch (pressostat). Pressure switch automatically opens the power circuit when the pressure in the system reaches the upper limit, and closes it when it drops to a minimum. You will also need a pressure gauge, shut-off valves and fittings to connect the elements.
☑️ List of required materials
It is important to prepare tools: an angle grinder for cutting metal, a drill with metal drills, a set of wrenches and screwdrivers. To seal threaded connections, be sure to use FUM tape or plumbing flax with paste. Do not skimp on the quality of the hoses - they must withstand pressure with a margin.
⚠️ Attention: It is strictly forbidden to use plastic containers, glass bottles or cylinders of flammable liquids (gasoline, solvents) as a receiver without careful preparation. Only steel!
Preparing the compressor and removing freon
The first step is to remove the compressor from the refrigerator. Carefully cut the copper tubes at a distance of 5–10 cm from the body to leave lengths for later connection. Electrical diagram usually simple: two wires go to the starting relay, which is mounted on the side of the motor.
If the compressor has not been opened before, there may be residual freon pressure and vapor. When biting the tubes, a hissing sound may be heard - this is normal. To be completely sure, you can drill the upper part of the case (in the area where the tubes are soldered) with a thin drill, after putting on safety glasses to release any remaining gas.
The next step is to determine the inlet and outlet holes. Insert the hose into the suction tube (usually thicker) and blow through your mouth. The air must come out of the pressure tube. Third tube, often sealed or short, is technological and is used for filling oil at the factory; in homemade conditions, it is better to plug it or use it to control the oil level, if the design allows it.
Is it necessary to change the oil in the compressor?
Changing the oil in a sealed refrigerator compressor is not recommended and is often impossible without violating the integrity of the housing. Factory oil is designed to last a lifetime. If the compressor runs quietly and does not heat up excessively, there is no need to interfere with the lubrication system. An attempt to replace mineral oil with synthetic oil can lead to destruction of the rubber seals inside the unit.
Check the operation of the unit by connecting it to the network via an extension cord. Make sure it starts up confidently and produces a noticeable blast of air. At this stage, you can assess the level of noise and vibration in order to plan further installation.
Manufacture and preparation of the receiver
The receiver serves as a buffer that accumulates compressed air. The most affordable option is a fire extinguisher. Before use, you must make sure that it is free of corrosion and mechanical damage. Cleaning The internal surface is required: pour a hot solution of alkali or a special product inside, shake and rinse thoroughly with water.
After washing, the container must be completely dry. To do this, you can leave it in the sun for several days or use a hair dryer. The inner walls are coated with an anti-corrosion primer so that rust does not get into the pneumatic tool. Receiver volume affects the frequency at which the compressor is turned on: the larger the volume, the less often the motor will start.
| Receiver type | Volume (l) | Working pressure (atm) | Weight (kg) |
|---|---|---|---|
| Fire extinguisher OU-5 | 6.5 | 150 | ~10 |
| Fire extinguisher OU-10 | 13.5 | 150 | ~18 |
| Propane cylinder (50 l) | 50 | 16 | ~22 |
| Receiver from KAMAZ | 20 | 20 | ~12 |
In the receiver body it is necessary to drill holes and weld (or screw into sealant, if the pressure allows) bosses for connecting the compressor, air outlet, pressure gauge and drain valve. Drain valve at the lowest point is required to remove condensate, which inevitably forms when air is compressed.
Installation of the pneumatic system and electrics
Assembling the system begins by installing the compressor on a frame or wooden stand. To reduce vibration, use rubber pads or old car tires. The compressor is connected to the receiver via check valve. It allows air to flow only in one direction - into the cylinder, preventing it from returning back when the engine is stopped.
Next, a pressure switch is mounted. Its input is connected to the receiver (after the check valve), and the output is connected to the compressor. The electrical diagram for connecting the relay assumes a break in the phase wire running from the outlet to the compressor. Inside the relay there are contacts that open when the upper pressure threshold is reached.
Connection diagram:220V network --> Pressure switch --> Compressor
|
+--> Grounding (required)
Don't forget install pressure gauge at the outlet of the receiver to visually monitor the pressure. All threaded connections are sealed with FUM tape. The hoses are connected using quick-release connections, which is convenient for connecting tools.
After assembling the entire pneumatic part, perform a test run. Carefully inspect all joints for air leaks. A soap solution will help identify even microscopic fistulas - bubbles will inflate at the leak sites.
Setting up, testing and safety
The final stage is adjusting the pressure switch. There are usually two springs on the relay body: the large one is responsible for the switching pressure, the small one is responsible for the delta (difference). By rotating the nuts, achieve the desired values, for example, turning on at 4 atmospheres and turning off at 6.
Check the operation of the system under load. Connect an air tool or simply bleed the air through the valve. The compressor should automatically turn on when the pressure drops and turn off when it builds up. Operation cycle It should be smooth, without jerking or extraneous sounds.
- 🛡️ Install a safety valve in case of relay failure to avoid rupture receiver.
- 🛡️ Regularly (once a week) drain the condensate through the bottom tap of the receiver.
- 🛡️ Monitor the temperature of the compressor housing - it should not get hot.
- 🛡️ Use hoses designed for the pressure is at least 1.5 times higher than the working pressure.
Compliance with safety precautions when working with compressed air is the key to the long service life of your device. Do not direct the air stream at people or animals, as even slight pressure can cause injury.
⚠️ Warning: If you notice that the compressor runs continuously and does not turn off, stop it immediately. This may indicate a malfunction of the pressure switch or a leak in the system, which can lead to an emergency.
Frequently asked questions (FAQ)
Can such a compressor be used for a spray gun?
Yes, it is possible, but with reservations. For high-quality painting, stable pressure and the absence of oil in the air are required. You will definitely need to install oil separator a moisture separator at the outlet of the receiver. Also, the power of the compressor must correspond to the consumption of the spray gun.
What kind of oil should be poured into the compressor from the refrigerator?
In hermetic compressors, the oil is not filled by the user, it is located inside in the crankcase. If a leak occurs or replacement is required, you need to use only special synthetic or mineral oil for refrigeration compressors (for example HF12-16 or analogues), ordinary motor oil can cause coking and breakdown.
Why does the compressor hum, but not starts?
Most often the problem lies in the starting relay or capacitor. It is also possible for the piston group to jam due to lack of oil or prolonged parking. In some cases, gently “swinging” the shaft when the power is off helps, but this is a temporary measure.
Is it necessary to cool the receiver?
Special cooling is not required, since when air passes through the receiver it already cools, giving off heat through the walls. However, you should not place the installation in direct sunlight or near heat sources.
What is the maximum pressure you can get?
A standard household refrigerator is designed for a circuit pressure of about 9–12 atmospheres, but 6–8 atmospheres is considered a safe operating pressure for a homemade system. Exceeding this value can lead to rupture of the compressor seals or damage to the connections.