Using an old but still working refrigerator to create a useful tool is a great idea for a home workshop. Compressor from a refrigerator has a unique advantage: it operates almost silently and does not require complex maintenance, unlike its loud piston counterparts. Such devices are ideal for airbrushing, inflating tires, blowing electronics, and even for working with pneumatic tools such as impact wrenches or spray guns.
The remodeling process does not require a professional engineering education, but will require you to be careful, have a minimum set of tools, and understand the basic principles of operation pneumatics. Refrigeration compressor is sealed and filled with oil, which makes it durable, but requires the correct approach during installation. In this article we will analyze the entire cycle of work from dismantling the unit to launching the finished product.
The main goal of the modification is to maintain the tightness of the system and ensure the correct outlet pressure. The standard operating pressure of a household refrigeration compressor is from 2 to 6 atmospheres, but with proper piping it can be raised to 8-10 bar. This is more than enough for most household needs. It is important to understand that we are not creating an industrial unit, but are designing a reliable assistant for the garage.
Preparation of tools and selection of source material
The first step is to find a suitable donor. Soviet-made refrigerators (for example, ZIL, Biryusa, Saratov) are best suited for these purposes, since their compressors are made in the form of a black metal “barrel” and are highly reliable. Modern units often use tapered compressors, which are also suitable, but may be less durable under heavy use. Make sure that the motor is in good working order: when connected to the network, it should hum confidently and create a noticeable air flow at the outlet pipe.
For assembly you will need not only the compressor itself, but also a number of additional materials. The basis of the design will be a receiver - a container for storing compressed air. Old fire extinguishers, gas cylinders or even housings from car shock absorbers are often used as a receiver. Receiver volume directly affects the stability of the pressure: the higher it is, the less often the engine will turn on.
Gather the necessary tools in advance so as not to be distracted during the work process. You will need:
- 🔧 A set of wrenches and screwdrivers for dismantling and assembling components.
- 🛠️ Drill or screwdriver for drilling holes in the receiver.
- ⚡ Soldering iron or welding machine (if you plan to weld brackets).
- 📏 Tape measure, marker and level for marking.
⚠️ Attention: It is strictly forbidden to use containers of flammable liquids (gasoline, diesel fuel) as a receiver without prior thorough cleaning and calcination. Residual vapors may ignite from a spark or heat during welding.
Removing the compressor and preparing components
The process of removing the compressor from the refrigerator requires caution. Do not saw through copper tubes with a hacksaw, as metal shavings can get inside the mechanism and damage it. It is better to use a pipe cutter or carefully cut the pipes with side cutters, retreating 10-15 cm from the motor housing. This will leave you with a reserve for later connecting the hoses.
After removal, you need to determine the purpose of the pipes. Usually there are three of them: two short and one long. To avoid confusion, briefly plug in the compressor (observing safety precautions!). The pipe from which air blows is discharge outlet. The pipe that sucks in air is the inlet. The third, often sealed or the thinnest, serves for the defrost system and is not used in our design; it must be carefully plugged or clamped.
It is important to check the condition of the oil. If you plan to use the compressor in a horizontal position (as it was in the refrigerator), there will be no problems. However, if installed vertically or at a strong tilt, oil may enter the air system. To protect the tools, it is better to immediately provide installation oil separator or use a system of several filters.
☑️ Check before assembly
Manufacture and preparation of the receiver
The receiver is the heart of your pneumatic system, providing air supply and smoothing pressure pulsations. As mentioned earlier, an old 10-50 liter fire extinguisher is an ideal candidate. Before starting work, make sure that the cylinder is completely empty and not under pressure. Remove the shut-off valve if it is in the way, and thoroughly rinse the container with water and detergent to remove any powder or rust.
The top of the receiver must be drilled and tapped to install the 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 for installing the safety valve and pressure gauge. It is better to cut the thread with a tap of the appropriate diameter, having previously lubricated the drilling area with oil.
To securely fix the compressor on the receiver or common frame, use metal corners and clamps. Vibration When the engine is running, it is quite strong, so all fastenings must be tightened through rubber gaskets or washers. This will reduce noise and prevent connections from loosening over time.
| Component | Material | Function | Requirements |
|---|---|---|---|
| Receiver | Steel (fire extinguisher) | Air accumulation | Tightness, pressure > 15 atm |
| Pipelines | Copper / Steel | Gas transportation | Resistance to oil and temperature |
| Filter | Replaceable cardboard/mesh | Air purification | Protection from dust and moisture |
| Pressure switch | Plastic/Metal | Automatic | Accuracy |
Assembling the pneumatic circuit and electrical circuits
Assembling the system begins by connecting the compressor to the receiver. It is necessary to install check valvebetween the outlet pipe of the motor and the inlet to the cylinder. It prevents compressed air from escaping back into the compressor after it stops, which protects the mechanism from turning in the opposite direction and makes restarting easier.
The electrical part requires special attention. Direct connection of the compressor to the outlet is possible, but inconvenient: you will have to constantly monitor the pressure and manually turn off the device. To automate the process, a pressure switch (pressostat) is used. It opens the circuit when the maximum pressure is reached (for example, 6 atm) and closes it when the pressure drops to a minimum (for example, 4 atm).
The connection diagram of the pressure switch is as follows: phase and zero from the network come to the input of the relay, and from the output they go to the compressor. Grounding is connected directly to the motor and receiver housing for safety. If you are using a relay with a 220V coil, no additional transformers are required.
⚠️ Attention: All electrical connections must be made in sealed boxes (IP54 and above). In a garage or workshop there is always dust and possible moisture, which creates the risk of a short circuit.
Installation of filters and moisture separators
The air leaving the compressor contains oil vapor and moisture that condenses during compression. Getting this mixture into a spray gun or pneumatic tool is unacceptable. A filtration system is installed for cleaning. The primary coarse filter is placed immediately after the compressor (before the receiver or after, depending on the design), and the final fine filter is installed before the outlet to the consumer.
The moisture separator (condensate collector) is usually a flask with a drain valve at the bottom. Passing through it, the air cools, moisture settles at the bottom and is periodically drained. For homemade systems, transparent flasks from water filters are often used, filled with silica gel or simply empty, serving as a sump.
To connect the hoses, use quick-release connections (type Quick Connect). This will allow you to quickly change tools or hoses without using wrenches. The standard diameter of pneumatic hoses for garage needs is 6, 8 or 10 mm. Polyurethane hoses are more flexible and durable than rubber ones.
Why is condensation dangerous?
Moisture in the pneumatic system causes corrosion of the metal parts of the tool from the inside. In the case of airbrushing, water spoils the paint, leaving craters. In winter, condensate may freeze in the line, completely blocking the air supply.
First start-up and testing of the system
Before the first full start, conduct a visual inspection of all connections. Soap all pipe joints, fittings and welds with soapy water. Turn on the compressor and observe: the appearance of bubbles will indicate leaks. Small leaks can be eliminated with a tightener or sealant; large ones require reworking the unit.
Start the system and wait until the pressure switch turns off the motor. Check the pressure gauge readings. If the system maintains pressure and does not “bleed” air after stopping, tests can be carried out with the instrument. Pay attention to the temperature of the compressor housing: during prolonged operation, it can heat up to 90-110 degrees, which is the norm for sealed units, but requires control.
If you plan to use the compressor for airbrushing, be sure to install an additional reducer with a pressure gauge at the outlet to accurately regulate the pressure (usually 1.5-3 atm). To inflate tires, the total pressure in the receiver is sufficient.
⚠️ Attention: Do not exceed the maximum pressure for which your receiver is designed. If you are using a fire extinguisher, its operating pressure is usually indicated on the body (for example, 1.6 MPa or 16 bar). Exceeding this value can lead to rupture of the container.
Frequently asked questions and answers
How long can a refrigerator compressor run without interruption?
Household compressors are not designed for continuous operation 24/7. The optimal operating mode is 20-30 minutes, after which it is recommended to let it cool for 10-15 minutes. When installing additional cooling (fan), the operating time can be increased.
What kind of oil should be poured into the compressor?
In hermetic compressors, the oil is poured inside the housing and does not require replacement during the entire service life, unless the system is opened. If a leak occurs, you need to add special synthetic oil for refrigeration compressors (for example Frigidaire or analogues), ordinary motor oil can coke and ruin the unit.
Can this compressor be used for sandblasting?
For classic pressure sandblasting power and The capacity (displacement) of one refrigeration compressor is usually not enough. It is suitable only for mini-sandblasting machines with a very small nozzle diameter and short-term operation.
Why does the compressor hum but not pump?
Most likely, the tightness of the valve group inside the “barrel” is broken or the tubes are clogged. It is also possible that the connecting rod may break or the piston group may jam due to lack of oil. At home, repairing a sealed case is complicated and often unprofitable.