Availability of compressed air in garage or home workshop significantly expands the craftsman's capabilities, allowing him to use pneumatic tools, paint parts, or simply blow off dust. However, buying a new factory compressor often costs a pretty penny, and cheap models are famous for their intolerable noise. The ideal solution to this problem is to convert an old but working compressor from a household refrigerator into a full-fledged air blower.
Such a homemade product has a number of undeniable advantages, the main one of which is almost complete silent operation. Unlike industrial analogues, which roar like tractors, unit based on a refrigerator it works quietly, which allows you to be comfortable indoors while painting or delicate work. In addition, the cost of implementing the project is minimal if you have access to decommissioned household appliances.
In this article we will analyze in detail the entire process of creating a device, from choosing the source material to the final pressure setting. You will learn how to properly prepare compressor unit, which receiver to choose and why a filtration system is needed. The finished product will become a reliable assistant, capable of providing pressure up to 6-8 atmospheres, which is quite enough for domestic needs.
Preparation of the necessary materials and tools
Before starting assembly, you need to assemble all the components. The basis will be itself refrigeration compressor, which can be removed from an old non-working refrigerator or purchased used at a disassembly. It is important to choose units of domestic production or trusted brands, as they are often more repairable and have standard fastenings.
In addition to the motor itself, you will need a container for the receiver. Fire extinguishers with a volume of 10-50 liters, old gas cylinders or receivers from trucks are excellent as air storage. Also stock up on copper or brass fittings, high-pressure hoses, an oil-water separator and a pressure switch (pressostat).
For tools, you will need a drill or screwdriver, a set of wrenches, a soldering iron or welding machine (for mounting fittings on the receiver), and a hacksaw. Don't forget about thread sealant and hose clamps.
Selecting and preparing a compressor unit
The first step is to remove the compressor from the refrigerator. Carefully saw off the tubes, moving 5-10 cm away from the body, so as not to damage the insides and maintain the possibility of a sealed connection. Before starting, be sure to check the operation of the unit: connect it to the network via an extension cord and make sure that it sucks in air through one tube and blows out the other.
Determine where the inlet and outlet are located. Typically the tubes are located on one side of the housing. Connect the power briefly (literally for a couple of seconds) and bring your finger to the ends of the tubes - where the air blows, there will be discharge valve. The third, sealed tube, usually located in the middle, does not need to be touched; it is used for charging freon and will remain sealed in our design.
Can No Frost compressors be used?
Compressors from No Frost systems often have increased performance, but they are more sensitive to overheating. When using them, be sure to monitor the case temperature and install more efficient cooling.
It is important to understand that the refrigeration compressor is not designed to constantly operate under load in the same mode as in factory compressors. It requires good cooling, so ventilation or a radiator must be provided in the design. If you plan on intensive use, it makes sense to remove the casing from the motor for better heat dissipation, but this will increase the noise level.
Manufacture and preparation of the receiver
The receiver is the heart of your pneumatic system, responsible for stabilizing pressure and accumulating air. The safest and most affordable option is to use an old fire extinguisher. Before starting work, make sure that the cylinder is empty and is not under residual pressure.
The process of preparing the container includes drilling holes for fittings. You will need at least three holes: one for the air inlet from the compressor, the second for the air outlet to the consumer, and the third (at the lowest point) for draining the condensate. If you are using a gas cylinder, the procedure for preparing it is much more complicated and requires complete removal of gas residues and odorant additives.
⚠️ Attention: When working with metal containers that previously contained gas or were under high pressure, strictly follow safety precautions. Make sure there are no sparks when drilling and carry out degassing according to the official instructions for such containers.
It is best to use welding to insert fittings, as this guarantees the tightness and strength of the connection under pressure. If there is no welding, you can use epoxy glue with fiberglass reinforcement or special threaded adapters, but the reliability of such a connection will be lower. After installing all fittings, the receiver must be painted to protect it from corrosion.
Assembling the pneumatic system and connecting
Assembling the system begins with installing the compressor on the frame next to the receiver. To reduce vibration, use rubber gaskets or mountings from the car engine. Connect the compressor outlet tube to the receiver inlet through a check valve. Check valve critically important: it prevents air from leaving the receiver back into the compressor after the engine stops.
Next, the control system is mounted. A pressure switch (pressostat) is installed at the receiver output, which will automatically turn the compressor on and off when the specified thresholds are reached. Standard settings for household needs: turn on at 4-5 atmospheres and turn off at 7-8 atmospheres.
After the pressure switch, an air preparation unit is installed, including a moisture-oil separator and a reducer. This ensures a clean and dry air supply to the tool, which is especially important when painting where the presence of oil or water is unacceptable. Make all connections using thread sealant.
Electrical circuit and automation
For automatic operation of the system, it is necessary to correctly connect the electric motor to the pressure switch. The connection diagram depends on the type of pressure switch you have, but the general principle is the same: the relay breaks the compressor power circuit when the upper pressure limit is reached. Usually, a capacitor is included with the relay, which must be connected according to the markings on the case.
Be sure to provide a circuit breaker with overcurrent protection in the circuit. Although the refrigerator compressor consumes little power (usually 100-200 W), the inrush currents may be higher and protection will save the wiring. It would also be a good idea to add an emergency stop button (“Stop”) to quickly de-energize the system.
☑️ Checking the electrical part
If you do not have the skills to work with electricity, it is better to invite a specialist to switch the power part. Errors in connection can lead to a short circuit or failure of the motor windings, which will be extremely difficult to restore in homemade conditions.
Testing, configuration and safety measures
The first start is a crucial moment. Turn on the compressor without connecting to the receiver (if the design allows) or with the outlet open to check the direction of rotation and operation of the valves. Then seal the system and introduce air. Listen carefully: there should be no hissing of air from the connections.
Check the operation of the automation. Bring the pressure to the upper limit - the compressor should stop. Bleed some air and the engine should start again. If the automation does not work, adjust the springs on the pressure switch or replace the unit.
| Parameter | Normal value | Critical value |
|---|---|---|
| Working pressure | 4-7 atm | > 10 atm |
| Case temperature | 40-60 °C | > 90 °C |
| Operating time | Cyclic | More than 20 minutes continuously |
| Noise level | < 50 dB | > 70 dB |
⚠️ Attention: Never exceed the pressure for which your receiver is designed. If you use an old fire extinguisher, its operating pressure usually does not exceed 15-20 atmospheres, but for safety it is better to limit it to a maximum of 8-10 atmospheres.
During operation, monitor the temperature of the compressor. If the housing gets hot, take a break. Refrigeration compressors are cooled by freon circulating inside, and in our case, cooling is only air and less efficient. Long-term work without a break can lead to jamming of the piston group.
Frequently asked questions (FAQ)
What kind of oil should be poured into the refrigerator compressor?
Refrigerator compressors use special synthetic or mineral refrigeration oil (for example, Freon-compatible). Unlike piston compressors, here the oil is in a sealed crankcase and does not require regular replacement or topping up during operation if the system is sealed.
Can such a compressor be used for airbrushing?
Yes, it is possible, but with the obligatory condition of installing a high-quality moisture-oil separator and a receiver of sufficient volume (minimum 20-30 liters) to smooth out pulsations. The pressure will have to be reduced by a reducer to 2-3 atmospheres.
Why does the compressor get very hot?
Heating to 60-70 degrees is the norm for such units. If the temperature is higher, check the ventilation, cleanliness of the cooling fins (if equipped) and the duration of continuous operation. The engine may be overloaded or the air filter at the inlet is dirty.
What is the maximum resource of such a compressor?
If the operating mode is observed (no more than 20-30 minutes continuously) and normal operating conditions, the resource can be several thousand hours. The key factor is the absence of overheating and the purity of the intake air.