Using an old one that still works refrigeration unit to create a compressor is a classic example of smart engineering improvisation. Many home craftsmen are faced with a situation where equipment breaks down, but motor-compressor the inside remains fully functional. Throwing away such a unit would be wasteful, because its potential is enormous.
A homemade installation based on a household refrigerator can provide pressure up to 6-10 atmospheres, which is quite enough for painting work, inflating tires, blowing out electronics, or working with pneumatic tools like an airbrush. Unlike cheap store-bought analogues, such a device is much quieter and has a longer service life when used correctly.
However, simple alterations require attention to detail, especially in terms of air filtration and installation receiver. Without proper preparation, condensation and oil will quickly damage not only your product, but also the instrument you plan to connect. In this article we will look at all the nuances of creating a reliable and safe system.
Preparation of tools and materials for assembly
Before proceeding with dismantling and assembly, it is necessary to prepare the workplace and purchase components. The basis of your future compressor is itself refrigeration unit, which is removed from the body of the old refrigerator. It is advisable to choose Soviet-made models or high-quality modern analogues, since they are often equipped with more reliable components.
The key element of the system will be receiver a container for storing compressed air. You can use an old fire extinguisher, a freon gas cylinder, or even a receiver from a truck as a tank. The main thing is that the container is sealed and can withstand pressure with a margin. You will also need a set fittings, hoses and shut-off valves.
For assembly and installation you will need:
- 🛠️ A set of wrenches and screwdrivers for dismantling.
- 🔧 Drill or screwdriver for drilling holes in the receiver.
- 🔩 Sealant, fum tape or thread adhesive for sealing connections.
- ✂️ Hacksaw or grinder for preparation tank.
- 🧪 Oil (if replacement is required in the compressor).
⚠️ Attention: When using old gas cylinders or fire extinguishers, make sure that they are completely empty and do not contain any residual gas under pressure. Before drilling or cutting metal, you must take all precautions.
Removing the compressor and preparing for work
The removal process motor-compressor begins by disconnecting the refrigerator from the power supply. Locate the black casing at the back where the unit is located. Carefully cut through the copper tubes running from the compressor to the condenser and evaporator, stepping back about 10-15 cm from the motor housing. This will allow you to maintain a length margin for easy connection.
It is important to determine where the inlet and outlet pipes are located. Typically, there are three terminals on the compressor housing: two short (refrigerant inlet and outlet) and one long (charging). To avoid guessing, plug in the compressor (being careful) and place your finger on the tubes - where the air is it is blown inthere will be an inlet, and where it is blown out with force there will be an outlet.
How to determine the type of compressor?
There are piston and rotary compressors. Piston engines (noisier, but more efficient) are better suited for creating compressor stations. Rotary ones are often used in small refrigerators and may not provide the required pressure for pneumatic tools.
After identifying the pipes, you need to drain the old oil if you plan to change it, or simply check its level. Standard refrigeration compressor works in a closed circuit with freon, but in our system it will pump atmospheric air, which requires the installation of high-quality filters at the inlet.
Manufacture and preparation of the receiver
The receiver serves as a buffer, equalizing pressure pulsations and accumulating air reserves. Without this element, your homemade compressor will work jerkily, and electric motor will quickly overheat from frequent switching on. The optimal tank volume for household needs is from 20 to 50 liters.
If you use a fire extinguisher, the first thing you need to do is release the remaining gas and unscrew the shut-off valve. Then holes for installation are drilled in the upper part of the cylinder (where the dome is). Typically, a minimum of three holes are required: one for the air inlet from the compressor, the second for the outlet to the consumer, and the third for installing a pressure gauge and safety valve. fittings. Typically, a minimum of three holes are required: one for the air inlet from the compressor, the second for the outlet to the consumer, and the third for installing a pressure gauge and safety valve.
For reliable fastening of fittings, it is recommended to use metal adapters with threads that are welded or screwed through a pre-cut thread. Plastic elements are unacceptable here, since when compressed, the air heats up, and the plastic may not withstand temperature expansion pressure.
The finished receiver must be secured on a stable base. Often, a wooden board or metal frame is used for this, to which the tank is screwed with clamps. The design must be stable to prevent tipping over during operation.
Assembling the system: connecting filters and valves
Assembling the pneumatic circuit is the most critical stage. The air coming from the atmosphere contains dust and moisture, therefore it must be installed at the inlet pipe of the compressor air filter. In the simplest case, this could be a zero-resistance car filter or even a carburetor filter adapted to fit the pipe.
At the outlet of the compressor, in front of the receiver, a check valve is often installed. It prevents air flow in the opposite direction when the engine is stopped, which protects piston group from water hammer and makes restarting easier. It is also advisable to install a shut-off valve between the compressor and the receiver.
The connection diagram is as follows:
- 🌬️ Atmospheric air ➔ Filter ➔ Compressor inlet.
- 💨 Compressor outlet ➔ Check valve ➔ Receiver.
- 📊 Receiver ➔ Pressure gauge + Safety valve.
- 🔌 Receiver ➔ Outlet tap ➔ Hose to tool.
All threaded connections must be carefully sealed. Use fum-tape or anaerobic thread sealant. This is critically important, since even a microscopic leak during prolonged operation of the compressor will lead to a drop in performance and constant turning on of the motor.
Electrical circuit and automation
To control the compressor, it is not enough to simply plug it into an outlet. You will need an automation system that will turn off the motor when the set pressure in the receiver is reached and turn it on when it drops. The main element here is pressostat (pressure switch).
The pressure switch has electrical contacts for breaking the power circuit and a pneumatic input connected to the receiver. When the pressure reaches the upper limit (for example, 6 atmospheres), the contacts open and electric motor stops. When the pressure drops to the lower limit (for example, 4 atmospheres), the circuit closes again.
☑️ Electrical check
It is also recommended to include in the circuit thermal relay engine protection, especially if you plan on long operating cycles. It will prevent the windings from burning out when overheated. Do not forget that household refrigerator compressors are not designed to operate 24/7 in pressure mode.
Test start-up and pressure adjustment
The first start-up of the assembled system should be carried out with caution. Make sure all taps are closed and the outlet hose is disconnected. Turn on the compressor and monitor the readings pressure gauge. The pressure should increase smoothly, without jerking or extraneous sounds indicating air etching.
Check the operation safety valve. It should work if the pressure exceeds the permissible norm (usually 10-15% higher than the working one). If the valve does not operate, it must be replaced or adjusted, otherwise this may lead to rupture of the receiver.
| Parameter | Normal value | Critical value |
|---|---|---|
| Working pressure | 4 - 8 atm | > 10 atm |
| Case temperature | Up to 60°C | > 90°C |
| Time continuous operation | 15 - 20 min | > 40 min |
| Noise level | 40 - 50 dB | > 70 dB |
If leaks are found in the system, they can be easily identified by ear or using a soap solution. Lather all joints and welds generously - bubbles will indicate problem areas. After eliminating the defects, retest.
Maintenance and safety measures
Operating a homemade compressor requires regular maintenance. The main enemy of the system is condensate, which accumulates in the receiver due to temperature changes during air compression. Water in the system leads to corrosion of the tank and damage to pneumatic tools.
Regularly, about once a week of active use, open the bottom drain valve (if installed) or unscrew the plug at the bottom of the receiver to remove moisture. Also monitor the oil level in the compressor if the design involves replacing or topping it up.
⚠️ Attention: Never leave a running compressor unattended for a long time. If the pressure switch or thermal sensors fail, overheating and fire of insulation or plastic elements may occur.
The device should be stored in a dry, ventilated area. If the compressor is used for painting, make sure that it is installed at the inlet oil-moisture separator, otherwise oil from the compressor may get onto the surface to be painted, ruining the result.
What kind of oil should be poured into the compressor from the refrigerator?
In most cases, special synthetic or mineral oil for refrigeration compressors is used (for example, freon oils). However, since in our system the compressor pumps air rather than freon, the requirements are less stringent. You can use motor oil or specialized compressor oil, but it is important to ensure that it is not too viscous, otherwise the compressor will be difficult to start.
Why does the compressor get very hot?
Heating to 60-70 degrees Celsius is the norm for piston compressors. However, if the housing becomes hot, there may be several reasons: valve malfunction, low oil level, too high ambient temperature or prolonged operation without a break. Allow the unit to cool before the next cycle.
Can this compressor be used for airbrushing?
Yes, you can, but only if you install a high-quality fine filter and a moisture separator at the outlet. A conventional refrigerator compressor produces pulsations that can ruin the pattern, so the presence of a receiver and a pressure regulator is critical here.
What is the maximum size of a pneumatic tool that can be connected?
The performance of a household compressor from a refrigerator is usually 30-50 liters per minute. This is enough for an airbrush, tire inflation or blowing. Such power is absolutely not enough to operate impact wrenches, grinders or sandblasters - the tool simply will not start or will work intermittently.