In a garage or at the dacha, many car owners have a situation when they urgently need to pump up a flat tire, and there is no professional equipment at hand. Buying a new compressor can be expensive, especially if you don't need it every day. In such cases, an excellent solution is compressor from the refrigerator, which can be assembled from a failed household appliance. This device is characterized by quiet operation and the ability to create the necessary pressure for inflating passenger car tires.
The main advantage of such a homemade product is the availability of components. Old refrigeration unit can be found at scrap metal collection points or obtained free of charge when disposing of old equipment. The design is simple and does not require complex engineering knowledge to assemble, making the project accessible to the home DIYer. However, in order for the device to operate safely and efficiently, it is necessary to strictly adhere to the assembly technology and take into account the technical nuances of the operation of piston systems.
In this article we will analyze in detail the process of turning an old refrigeration unit into a full-fledged tool for inflating tires. You will learn how to properly prepare components, assemble a filtration system, and ensure stable pressure in the receiver. We will also pay attention to safety measures, since working with compressed air requires care and adherence to certain rules.
Preparation of materials and tools
Before starting assembly, you must assemble all the components. The main element, of course, is itself refrigeration compressor. Units from Soviet refrigerators are best suited, as they are often equipped with copper tubes that are easy to solder. Modern imported models may have steel tubes, which will complicate the installation process, but are also quite suitable for use.
To create a compressed air reservoir, or receiver, you will need a metal container. Old freon or propane gas cylinders with a volume of 10-50 liters are ideal. You can also use the housing from an old fire extinguisher if it is in good condition without severe corrosion. It is important that the container can withstand pressure significantly higher than the operating pressure of the compressor.
- 🔧 Basic equipment: compressor from the refrigerator, receiver (cylinder), pressure gauge for pressure control.
- 🔩 Fasteners and connections: hoses (oil-resistant or for high pressure), clamps, adapters, tees, return valve.
- 🛠 Tools: drill, set of keys, soldering iron or gas torch (for copper pipes), hacksaw.
Don't forget to prepare materials for filtration. An air filter must be installed at the compressor inlet to prevent dust from getting inside the mechanism. The output will require oil separator, since compressors from refrigerators operate in an oil bath and can throw out oil along with air. The pressure control system will require a pressure switch or mechanical shut-off valve.
Dismantling and preparing the compressor
The first step is to remove the unit from the refrigerator. Carefully saw off the copper tubes at a distance of 5-10 cm from the compressor housing in order to have a reserve for connection. Important to rememberthat freon may remain inside the system, so it is better to carry out work in a well-ventilated area or outside. After removal, it is necessary to determine which of the tubes is discharge and which is suction.
To do this, connect the compressor to the network (for a short time!) and place your finger at the ends of the tubes. Air will come out of the discharge tube with strong pressure, and will be drawn into the suction tube. The third, sealed end is usually blind and serves for refilling with freon; it can be used to drain old oil or install an additional valve, but for a simple compressor it often remains unused.
⚠️ Attention: Before long-term operation, be sure to drain the old mineral oil and replace it with fresh one if the compressor has been standing for a long time. Old oil could oxidize and lose its lubricating properties, which will lead to rapid wear of the piston group.
Clean the unit body from dirt and rust. If the compressor shows signs of corrosion, treat them with a rust converter and coat them with heat-resistant paint. This will not only improve the appearance, but also extend the life of the device. Check the integrity of the electrical part: the wires should not be frayed, and the terminals should not be oxidized.
Manufacture and preparation of the receiver
The receiver serves as a buffer, accumulating compressed air and stabilizing the pressure in the system. Without it, the compressor will work in a ragged mode, constantly turning on and off every time the tap is opened. To make a receiver, it is best to use a metal cylinder. Before starting work, make sure that the cylinder is completely empty and does not contain any remaining gas.
The process of preparing the container includes several stages. First you need to remove the valve if it is in the way. Then hot water with dissolved dishwashing detergent or lye is poured into the container to remove any remaining odor and rust. After thorough washing and drying, you can begin drilling holes for welding fittings.
| Component | Material of manufacture | Function | Strength requirements |
|---|---|---|---|
| Receiver body | Steel (cylinder 10-50 l) | Air accumulation | High (design pressure > 10 atm) |
| Inlet fitting | Brass/Steel | Air supply from compressor | Medium (threaded connection) |
| Outlet fitting | Brass/Steel | Supply air to the hose | Medium (located above the bottom) |
| Drain valve | Brass | Condensate removal | Low (located at the lowest point) |
A fitting for connecting the compressor is welded into the upper part of the cylinder or screwed onto the sealant. A tap must be installed in the lower part to drain condensate, which inevitably forms when air is compressed. Also mounted in the upper part is a pressure gauge for visual control of pressure and an outlet fitting with a tap.
Why can’t you use plastic containers?
Plastic canisters and bottles are absolutely not suitable for the receiver. Even durable plastic, when exposed to compressed air and vibration for a long time, can become brittle and rupture into fragments. Use only metal cylinders certified for gases.
Assembling the filtration and oil separation system
One of the main problems with using a refrigeration compressor to inflate tires is the presence of oil in the exhaust air. This type of compressor sprays oil to lubricate the cylinders and some of it enters the air stream. If the air is not cleaned, oil will get inside the tire and can damage the rubber cord, and also contaminate the car's paint when pumping.
To solve this problem, a filtration system is assembled. An air filter is installed at the inlet of the compressor (you can use a zero-resistance car filter or even a padding polyester in the housing). At the outlet, immediately after the compressor and before the receiver, it is necessary to install oil separator. The simplest option is a transparent fine fuel filter with the filter element replaced with a more porous material.
- 🌬 Input filter: protects internal mechanisms from dust and abrasives.
- 💧 Oil and moisture separator: retains oil vapors and droplets that condense during compression.
- 🌡 Thermal break: it is recommended to use heat-resistant hoses, since the air leaving the compressor can heat up to 100°C and higher.
All connections must be tight. Use thread sealant (FUM tape or anaerobic sealant) for metal threaded connections. For flexible connections, select hoses with the appropriate internal diameter to minimize pressure loss. The optimal operating pressure for inflating tires is 2-3 atmospheres, but the system must withstand up to 6-8 atmospheres with a margin.
☑️ Checking the system before starting
Installation of the electrical part and automation
For convenient operation of a homemade compressor, you need to assemble an electrical circuit. The minimum option involves a wire with a plug and a switch. However, a more advanced solution is to install pressure switch. This device will automatically turn off the compressor when the set pressure in the receiver is reached and turn it on when the pressure drops below a certain threshold.
If you do not use an automatic relay, then you will have to control the pressure manually by watching the pressure gauge. In this case, it is extremely important not to leave the compressor running unattended. Electrical wiring must be made with a wire with a cross-section corresponding to the current consumption of the motor (usually 1.5-2.5 mm² for copper wire).
⚠️ Attention: Be sure to install a fuse in the electrical circuit. This will protect the wiring from overheating and fire in the event of a short circuit or jamming of the compressor motor.
For connection, use a standard socket and plug. All wire twists must be carefully insulated or, better yet, connected through terminal blocks. If the compressor has a starting relay (black box on the side), make sure that it is securely fastened and protected from moisture and mechanical damage.
Starting, testing and safety measures
After assembling all the components, the moment of truth comes - the first start. Connect the compressor to the network and let it run idle for a few minutes (if the design allows it) or immediately connect it to the receiver. Carefully monitor the pressure gauge readings and listen to the operation of the unit. There should be no extraneous knocks, air whistling from connections or strong vibration.
Check the system for leaks. Apply soapy water to all joints of pipes, fittings and connections. The appearance of bubbles will indicate a leak that needs to be repaired. Also check the operation of the check valve: when the compressor is turned off, air should not flow back out of the receiver through the compressor.
- 🔊 Noise level: compressors from refrigerators operate relatively quietly, but vibration can be transmitted to the floor. Install the device on rubber gaskets.
- 🌡 Temperature conditions: monitor the temperature of the compressor housing. During prolonged operation, it can heat up to 60-90°C, which is normal, but requires breaks in operation.
- 💨 Performance: remember that the performance of such a compressor is lower than that of professional models. Inflating a severely flat tire may take 5-10 minutes.
During operation, regularly drain the condensate from the receiver through the bottom tap. Moisture that accumulates at the bottom of the container causes corrosion of the metal, which over time can lead to a decrease in the strength of the container. Also periodically check the oil level in the compressor, if the design allows, and change the air filters as they become dirty.
Can such a compressor be used for a spray gun?
Theoretically it is possible, but with limitations. Refrigerator compressors produce low air flow (performance). For small painting jobs (touch-up of parts) this may be enough, but for painting a whole car the performance will not be enough, and the pressure will constantly drop, creating defects on the surface (shagreen).
What is the maximum pressure such a compressor can develop?
Refrigeration compressors are capable of creating pressure up to 10-15 atmospheres and even higher, since in In the refrigerator they work with freon under high pressure. However, 2-3 atmospheres are enough to inflate tires. Excessive pressure is dangerous for a poorly assembled system.
Is it necessary to change the oil in a compressor during refurbishment?
It is advisable to replace the oil with fresh oil, specifically designed for compressors, if you do not know what type of oil was filled there and for how long ago. Old oil may contain acidic impurities from the breakdown of freon and moisture, which will accelerate wear of parts.
Why does the compressor get very hot?
Heating to 70-90 degrees is normal for piston compressors when compressing air. If the heating is critical and the device turns off via a thermal relay, the ventilation may be impaired, the air filter is clogged, or the load is too high (small volume of the receiver).