Independent production of an air compressor from an old refrigerator is a popular solution for the home workshop, allowing you to save significant money on the purchase of factory equipment. Old Soviet refrigerators Atlant, Biryusa or ZIL brands are often thrown into landfills, although they compressor units are able to work for many years as air blowers. The main task of the master is to correctly adapt the freon compression unit to work with atmospheric air, which requires replacing working fluids and installing a filtration system.
Many people mistakenly believe that the process comes down to simply connecting a hose to the outlet pipe, but this operation will quickly disable the mechanism. Compressor unit must have a receiver to stabilize pressure, a safety valve for safety and a system for purifying air from moisture and oil emulsion. In this article we will analyze in detail all stages of the remodeling, from dismantling to the final configuration of the equipment.
The advantage of home-made devices is their low noise level and the ability to operate for a long time without overheating, which distinguishes them from cheap piston analogues. Sealed housing factory version already contains all the necessary lubricant elements, which, however, will have to be replaced with more heat-resistant analogues. A correctly assembled unit will become an indispensable assistant when painting cars, working with pneumatic tools or inflating tires.
Selecting a suitable compressor and preparing tools
First you need to find a suitable donor unit. They are best suited Soviet-made refrigeratorsas they are equipped with reliable motors designed for long-term operation. Modern imported models often have aluminum windings or less efficient units that may not be able to cope with the load when air is compressed to 6-8 atmospheres. Before dismantling, make sure that the compressor is in good working order: when plugged in, it should hum, and there should be a flow of air from the tubes.
You will need to assemble a certain set of tools and materials, without which remodeling is impossible. The base will be itself compressor unit, which must be carefully removed from the refrigeration chamber, maintaining the integrity of the copper tubes. You will also need a metal container for the receiver, which can be made from an old fire extinguisher or gas cylinder.
- 🛠️ A set of wrenches and screwdrivers for dismantling and assembling components.
- ⚙️ Pressure gauges for monitoring pressure in the system and receiver.
- 🔧 Pipe bender and cutters for working with copper tubes.
- 🔩 Sealant, clamps and fittings for connecting elements of the pneumatic system.
Pay special attention to the search pressure switch (pressostat), which will automatically turn off the motor when a specified limit is reached. Without this element, the system will operate in a dangerous mode, which can lead to rupture of the receiver. All components must be selected with a margin of safety, since air pressure creates a significant load on the connections.
Removal of the compressor and initial diagnostics
The removal process begins by disconnecting the refrigerator from the power supply and removing all internal shelves. Compressor unit usually located in the lower rear part of the case and attached to frame using four shock-absorbing springs or rubber pads. Carefully cut through the copper tubes at a distance of 15-20 cm from the motor housing to leave enough margin for subsequent insertion of fittings.
⚠️ Attention: It is strictly forbidden to cut through the tubes or open the compressor housing if there is still freon under pressure in the system. Although in old refrigerators its quantity is minimal, it is necessary to ventilate the room and avoid open fire, since upon contact with a flame, the refrigerant can release toxic substances.
After removing the motor, it is necessary to carry out its initial diagnostics. Connect the device to the network via an extension cord and run it briefly to determine the direction of rotation of the shaft and the functionality of the starting relay. Start relay is a black plastic block attached to the side, which is responsible for starting the engine; its condition is critical for stable operation.
Check the condition of the electrical contacts and the integrity of the windings using a multimeter. The resistance between the contacts must be within certain limits specified in the technical documentation for a specific model. If electric motor it hums, but does not start, the piston may be jammed or the starting device has failed, which will require replacing the relay with a similar one.
Modernization of the lubrication system and oil change
One of the most common errors is using a compressor with factory-made oil designed to operate in a freon environment. Mineral oil, poured into the refrigerator, does not have sufficient temperature stability to compress air and quickly oxidizes, forming carbon deposits on the piston group. In addition, when air is compressed in the crankcase, condensate forms, which, when mixed with freon oil, turns into an emulsion that loses its lubricating properties.
For a converted unit, it is necessary to use special synthetic oils for air compressors, such as KS-19 or its modern analogues. The replacement process requires care: you need to cut off the sealed tube through which the compressor was charged and completely drain the old liquid. Then the system is washed with a solvent to remove remnants of the old composition.
Refilling with new oil is done through the same pipe using a syringe or funnel. The oil volume is usually about 300-400 ml, but the exact amount is better determined by the sight glass (if there is one) or the level specified in the instructions for a specific motor model. Level lubricants must be strictly observed: a deficiency will lead to scuffing, and an excess will lead to the release of oil into the pneumatic system along with air.
Why can’t you use regular motor oil?
Motor oils for internal combustion engines contain detergents and additives, which at high air compression temperatures can form hard deposits on valves and piston rings. This leads to loss of compression and jamming of the mechanism. Use only specialized compressor oils with a high flash point.
Manufacture and preparation of the receiver
The receiver functions as a compressed air storage device, smoothing out pressure pulsations and allowing the compressor to operate in cyclic mode. The best option for a homemade installation is to use an old propane tank 50 liter capacity or fire extinguisher. These tanks are made of thick steel and have the necessary certification to work under pressure, unlike thin-walled tanks from water heaters.
Before use, the container must be thoroughly cleaned of rust and remaining contents. If you use a fire extinguisher, make sure it is not critically expired, although this is less important for a static receiver than for a mobile device. It is necessary to weld or embed several fittings into the cylinder body: for air inlet, outlet to the consumer, installation of a pressure gauge and drainage of condensate.
| Receiver element | Purpose | Installation requirements |
|---|---|---|
| Input branch pipe | Air supply from the compressor | Must have a check valve |
| Outlet pipe | Connecting the tool hose | Threaded connection with tap |
| Drain tap | Condensate removal | Located at the lowest point |
| Hole for pressure gauge | Pressure control | Installed in a visible place |
It is important to provide an installation safety valvethat bleeds air if the pressure exceeds the safe limit (usually 8-10 atmospheres). Ignoring this safety element can lead to an explosion of the receiver if the automatic shutdown fails.
Assembling a pneumatic circuit and installing automation
Assembling the system begins by connecting the compressor to the receiver through a check valve. Check valve prevents compressed air from returning back to the compressor after it stops, which prevents turning the shaft in the opposite direction makes the next start easier. It is recommended to install a small cooling radiator between the compressor and the receiver or extend the connecting copper tube so that the air enters the tank already cooled.
The key control element is pressostat (pressure switch). It is mounted on the receiver or on the output line and has electrical contacts to break the compressor power circuit. The pressure switch is adjusted using an adjusting nut: the upper limit is set at 6 atmospheres, and the delta (the difference between turning on and off) is usually 2 atmospheres.
☑️ Checking the system assembly
The electrical connection circuit must be assembled in compliance with all safety standards. Start relay The compressor is connected in series with the contacts of the pressure switch. It is also advisable to include a thermal protection relay in the circuit, which will turn off the motor in case of current overload, preventing the windings from burning out.
⚠️ Attention: All electrical connections must be reliably insulated and protected from moisture. The use of twists instead of terminal blocks is unacceptable, since vibration from a running compressor can weaken the contact and cause sparking or fire.Starting, testing and troubleshooting
The first start-up of the assembled unit should be carried out with caution. Turn on the compressor without connecting to the receiver (or with the outlet valve open) to check the direction of rotation of the shaft and the absence of extraneous noise. If the motor is hummingbut does not start, check the starting relay and the presence of voltage on the windings.
After a successful idle start, connect the system to the receiver and start pumping. Monitor the pressure gauge readings: when the set pressure is reached, the compressor should automatically turn off. If this does not happen, immediately stop the system manually and reconfigure pressure switch. Check all connections for leaks using a soap solution - bubbles that appear will indicate leaky joints.
During operation, monitor the temperature of the compressor housing. Heating up to 90 degrees is considered acceptable, but if metal housing it gets hotter, the oil circulation may be impaired or the air filters are clogged. Regular replacement of filter elements and draining of condensate will extend the life of your installation.
Frequently asked questions (FAQ)
Is it possible to use a compressor from a refrigerator for a spray gun?
Yes, you can, but with restrictions. Refrigerator compressors produce a relatively small air flow (performance), so they are suitable for working with low-power spray guns (HVLP type with low pressure). For professional pneumatic tools that require a large volume of air, the performance may not be enough.
How often do you need to change the oil in a converted compressor?
It is recommended to make the first oil change after 50 hours of running-in in order to remove the products of grinding in parts. In the future, the oil is changed every 200-300 hours of operation or once a year, depending on the intensity of use. If the oil has darkened or become viscous, it must be replaced immediately.
Why does the compressor get very hot during operation?
Strong heating can be caused by several reasons: low oil level, operation at maximum pressure, faulty valves or poor ventilation. Make sure that the compressor is installed in a ventilated place and is not covered by foreign objects.
What is the maximum pressure that can be obtained from such a compressor?
Standard household compressors from refrigerators are designed for operating pressures of up to 6-8 atmospheres. Exceeding this threshold is dangerous for the integrity of the housing and requires the installation of a more powerful engine and a reinforced piston group, which is difficult to do at home.