Use using old household appliances to create new useful devices is not just a way to save money, but also an excellent method for deeply understanding the principles of operation of mechanisms. Compressor, extracted from a failed refrigerator, has enormous hidden potential, which often remains unclaimed in a landfill. This unit is capable of creating pressure up to 10 atmospheres and above, which makes it an ideal basis for creating a full-fledged air compressor or pump for aeration.
Self-assembly of such a device requires certain technical knowledge and skills in working with tools, but the result is worth it. You will receive a reliable, quiet and durable device that can be used for painting cars, inflating tires, operating pneumatic tools, or even organizing an aeration system in a large aquarium. The main thing is to approach the modernization process correctly and not ignore safety precautions.
In this article we will analyze in detail the entire transformation process, from dismantling to the first launch of the finished product. You will learn what additional components are required, how to calculate the volume of the receiver and why you can’t just plug the old motor directly into the network without modifications. The critical point is to preserve the lubrication and filtration system, since a violation of the crankcase seal will lead to instant failure of the device.
Operation principle and choice of source material
Before you begin disassembling, you need to understand exactly how the sealed unit you plan to use functions. Unlike open piston compressors, refrigeration units operate in an oil bath, where freon and the oil are in a closed circuit. The engine and compressor part are located in a single housing, which ensures a low noise level, but creates difficulties during modification.
To create an efficient pump, compressors from Soviet-made refrigerators or more modern models with a high energy efficiency class are best suited. It is important to pay attention to the condition of the housing: it should not have dents, signs of corrosion or visible damage to the welds. If you hear a metallic knock when the internal pendulum swings, it is better not to use such a unit.
- 🔍 Power: It is optimal to choose models with a power of 100 to 200 W, they provide the best balance between performance and energy consumption.
- 🔍 Refrigerant type: Units operating on R12 or R134a, are structurally similar, but require thorough flushing of the system from residual oil.
- 🔍 Tube integrity: Incoming and outgoing copper tubes must be intact, without creases, since their cutting and soldering require care.
It is worth noting that modern inverter compressors can also be used, but starting them requires a special controller, which significantly complicates the design. For beginners, it is recommended to start with classic linear models, where control is carried out through a start relay.
Removing and preparing the compressor unit
The process of removing a compressor from an old refrigerator requires caution and precautions. First of all, you need to disconnect the device from the power supply and let it cool down if it has been running recently. Then the copper tubes going to the condenser and evaporator are carefully cut, leaving “stumps” 5-10 cm long on the compressor for the convenience of further work.
The most crucial moment is dismantling the start relay and thermostat. On the compressor housing there is an electrical box, inside of which there is a start relay. It must be carefully removed, remembering or photographing the connection diagram of the motor windings. Often the relay is attached to latches or screws, which may be rusty.
⚠️ Attention! There may be residual pressure inside the sealed housing. Under no circumstances try to drill the housing or cut the tubes under load, this may lead to splashing of the technical oil.
After removing the electrics, it is necessary to drain the old mineral oil. To do this, turn the compressor over and make a neat hole at the lowest point of the housing or bite off one of the lower tubes. The drained oil is disposed of in accordance with environmental standards, as it contains wear products and possibly refrigerant residues.
The next step is the flushing procedure. A special flushing solvent or new oil is poured into the housing through the free holes, after which the compressor is briefly started to circulate the liquid. This helps remove slag and metal shavings accumulated over years of operation.
Selection and preparation of a receiver (receiver)
A receiver is a container for accumulating compressed air, which stabilizes the pressure and allows the compressor to operate in intermittent mode, extending its service life. Without a receiver, the pump will turn on every time you open the tap, which will quickly lead to overheating of the windings. Old gas cylinders, fire extinguishers, or specially prepared metal containers are most often used as a receiver.
The ideal option is a 50-liter propane cylinder or an OU-5 fire extinguisher. Before use, the container must undergo mandatory testing for leaks and corrosion resistance. The inner walls are cleaned of rust mechanically or chemically, after which they are coated with an anti-corrosion compound.
| Tank type | Working pressure (atm) | Advantages | Disadvantages |
|---|---|---|---|
| Fire extinguisher (5-10 l) | 15-20 | Compact, threaded | Small volume, frequent starts |
| Propane cylinder (50 l) | 15-25 | Large volume, rare starts | Dimensions, difficulty of transportation |
| Receiver from KAMAZ | 10-15 | Ready fittings, reliability | Heavy, requires cleaning from the inside |
It is important to equip the receiver with a safety valve that bleeds air when critical pressure is exceeded. You also need a pressure gauge for visual control and a drain valve at the bottom to remove condensate, which inevitably forms when air is compressed.
Assembling the pneumatic system and piping
Assembling the pneumatic part is the process of connecting the compressor, receiver and output line into a single system. For this purpose, copper or steel tubes, high-pressure hoses and fittings are used. All connections must be tight, so it is recommended to use thread sealant or FUM tape designed for high pressures.
An air filter must be installed at the inlet of the compressor. It protects the piston group from dust and abrasive particles, which can quickly damage the unit. At the outlet of the compressor, in front of the receiver, it is advisable to install a check valve. It prevents the reverse flow of air from the receiver to the compressor when the engine is stopped, which makes restarting easier.
- 🔧 Pipelines: Use copper tubes with a diameter of 6-10 mm to connect the compressor to the receiver, they are easily bent and soldered.
- 🔧 Hoses: For connection Reinforced polyurethane hoses that can withstand up to 20 bar are suitable for pneumatic tools.
- 🔧 Accessories: Quick-release connections such as Camozzi or Festo will greatly simplify the work with the tool.
The connection diagram is as follows: air enters the compressor through the filter, is compressed, passes through the check valve and enters the receiver. From the receiver, through a reducer (if the pressure needs to be reduced) and a moisture separator, air is supplied to the consumer. The reducer allows you to regulate the output pressure regardless of the pressure in the tank.
☑️ Checklist for pneumatic system assembly
Electrical circuit and automatic starting
To automate the operation of the compressor, it is necessary to assemble an electrical circuit that will turn the engine on and off depending on the pressure in the receiver. The main element here is the pressure switch (pressure switch). This device has a mechanical contact that opens the circuit when the upper pressure limit is reached and closes it when it drops to the lower value.
The connection is made through the start relay of the compressor itself. The pressure switch breaks the phase wire going to the relay. It is also recommended to include a thermal motor protection relay in the circuit, which will turn off the power in case of overheating of the windings or jamming of the piston. This is especially important during long-term operation.
Connection diagram:220V network -> Pressure switch -> Start relay -> Motor windings
|-> Thermal relay (in the gap)
If you use three-phase motor (which is rare, but happens in powerful models), the circuit will include a magnetic starter. In this case, the starter coil is controlled through a pressure switch. It is important to select the correct cross-section of wires so that they can withstand motor starting currents, which can be 5-7 times higher than the rated current.
⚠️ Attention! Carry out all work on the electrical part only with the power completely turned off. Incorrect assembly of the circuit may result in a short circuit or electric shock.
First start-up and testing of the system
Before the first start-up, it is necessary to conduct a thorough visual check of all connections. Make sure that the receiver drain valve is open so that the compressor does not immediately pump air into the enclosed volume. Also check the oil level in the compressor crankcase - it should be in the middle of the sight glass or at the mark specified in the instructions.
Turn on the device and monitor the process of pressure build-up. Listen carefully to the operation of the engine: unusual knocks, squeaks or vibrations indicate a malfunction. After the pressure reaches the maximum value (when the pressure switch is activated and the engine turns off), close the outlet valve and leave the system for 15-20 minutes.
What to do if the compressor hums, but does not start?
If the engine hums, but the shaft does not spin, the piston group may be jammed or the starting relay is faulty. Try to carefully rotate the shaft by hand (with the power off!). If the shaft does not turn, mechanical repairs are required. If it turns, replace the starting relay or capacitor.
During this time, the pressure should not drop by more than 0.5 atmospheres. If the pressure gauge needle creeps down, it means there is a leak in the system. Locate the leak using a soap solution (bubbles will indicate the problem) and fix it. After successful testing, the pump can be considered ready for operation.
Regular maintenance includes draining condensate from the receiver after each operation and checking the oil level. Every six months, it is recommended to change the air filter and check the belt tension if a belt drive is used (in modified versions).
Safety precautions and operating restrictions
Despite its apparent simplicity, a homemade compressor is a source of increased danger. Compressed air has enormous energy, and rupture of the receiver or hose can result in personal injury. Therefore, never exceed the design pressure for which your receiver and connecting elements are designed.
It is strictly forbidden to use homemade compressors to inflate tires if pure oxygen or other active gases are used as the working medium. Oil mist from the compressor mixed with oxygen can cause an explosion. For such purposes, only special oil-free compressors are needed.
- 🛡️ Eye protection: Always use safety glasses when working with pneumatic tools or blowing parts.
- 🛡️ Temperature conditions: Do not allow the device to operate at temperatures below +5°C, as the oil thickens and lubricates deteriorates.
- 🛡️ Ventilation: Ensure good air flow to the compressor to cool the engine during operation.
Remember that the service life of a household refrigeration compressor in pump mode is lower than in normal operation of the refrigerator, due to higher temperatures and loads. Let the device rest: an operating mode of 10 minutes after 10 minutes or 15 after 15 will be optimal for extending its service life.
Is it possible to use a compressor without a receiver?
Theoretically it is possible, but this is highly not recommended. Without a receiver, the compressor will turn on instantly whenever the tap is opened, which will lead to rapid wear of the starting equipment and overheating of the engine. The receiver also dries the air and evens out flow pulsations.
What kind of oil should be poured into a converted compressor?
It is best to use special compressor oil (for example, KS-19 or analogues). You can use high-quality motor oil, but it can coke at high temperatures. The main thing is not to mix different types of oils (mineral and synthetic).
Why does the compressor get very hot?
Heating up to 80-90 degrees is normal for piston compressors. If the temperature is higher, check the ventilation, oil level and air leaks that are causing the engine to run continuously. Also, the reason may be the wrong direction of shaft rotation (for three-phase motors).
Is it necessary to change the starting relay when remaking?
If the old relay is working properly and corresponds to the engine power, it does not need to be changed. However, if you notice that the relay often clicks or burns out, it is better to replace it with a new one, selected exactly for the power of your motor.