Creating a functional air compressor from an old but working refrigeration unit is a classic project for the home workshop, which allows you to get a powerful tool practically free. Refrigeration compressor has a unique design that allows it to work in a closed circuit with freon, but with proper modification it also copes well with pumping air. Unlike store-bought counterparts, a homemade unit is often quieter, cheaper to maintain and easier to repair, making it an ideal choice for inflating tires, working with an airbrush or blowing out parts.
However, despite its apparent simplicity, the conversion process requires strict adherence to safety precautions and an understanding of the physical processes of compression gas. Sealed housing The factory engine is not designed to work with atmospheric air containing moisture, so ignoring the preparation steps can lead to rapid corrosion and failure of the unit. You will need not only the motor itself, but also a number of additional components, such as a receiver, filtration elements and a pressure control system.
Before you begin welding or connecting electrical equipment, you need to assess the condition of the source material. If your old refrigerator stops freezing, this does not always mean the death of the compressor - often the problem lies in a freon leak or a clogged capillary tube. Diagnostics performance at this stage will save you hours of useless labor, so make sure that the motor starts and creates pressure, even if it makes unusual sounds without refrigerant.
Preparation of necessary materials and tools
The success of the entire enterprise directly depends on the quality of the selected “donor” and components. The base will be compressor unit, which is most often located in the lower rear part of the refrigerator. For homemade installations, models from Soviet refrigerators (for example, series Biryusa or Zil) are best suited, as they are known for their reliability and maintainability, although modern imported analogues are also quite applicable provided they are in good working order.
In addition to the motor itself, you will need a container for compressed air, called a receiver. Old gas cylinders, fire extinguishers, or even cases from the refrigerators themselves are often used as a reservoir, if they are made of durable metal. Receiver performs the function of a pressure stabilizer and air cooler, so its volume should be sufficient for your tasks - usually from 10 to 50 liters.
- 🛠️ Toolkit: grinder, welding machine (or powerful clamps for seamless connections), drill, set of wrenches and screwdrivers.
- ⚙️ Accessories: high pressure hoses, clamps, adapters, pressure reducer, pressure gauge and check valve.
- 🧪 Consumables: oil (if replacement is required), sealant, degreaser, sandpaper for cleaning surfaces.
Pay special attention to finding a check valve and pressure gauge. These elements can be purchased at specialized pneumatic stores or removed from other faulty equipment. Check valve is critically important, as it prevents compressed air from returning to the compressor after it stops, preventing the motor from spinning in the opposite direction and damaging the system.
⚠️ Attention: When using old gas cylinders as a receiver, make sure that they are completely emptied of gas and, if possible, washed with water. Remaining gas even in small quantities during welding can lead to an explosion!Dismantling and initial diagnostics of the motor
The process of removing the compressor begins by disconnecting the refrigerator from the power supply. You need to gain access to the rear lower part of the unit, where the motor is usually covered by a casing. Carefully remove the protective cover by unscrewing the mounting bolts and inspect the condition electrical part. Often this is where the reasons for the silence of the device lie - a burnt-out starting relay or a broken wire.
To check the functionality, connect the motor directly to the network, using extreme caution. Contacts for connection are usually indicated on the case or in the wiring diagram. If the motor hums but does not start, the piston group may be jammed or the starting device has failed. Starting relay This is a small unit that can be temporarily replaced or “ringed” with a tester for the integrity of the windings.
If the motor starts, check whether it creates pressure. To do this, put a piece of hose on one of the fittings (usually they are located on the top of the body) and lower its end into a container of water. The appearance of air bubbles will indicate that discharge capacity saved. It is important to determine which of the three fittings is output and which are suction, since the connection diagram of the entire system depends on this.
How to determine the input and output without a diagram?
Connect the motor to the network for a short time. Place your finger on each of the three fittings. Air will blow forcefully from the outlet fitting, and a slight suction will be felt at the input fitting. Usually there is one output fitting, and two input fittings (for different circuits or modes).
When dismantling, be prepared for the fact that residual oil may leak out of the system. It has a specific smell and is often colored dark. Oil collection it is mandatory to place it in a separate container, since its disposal requires compliance with environmental standards, and reuse in a new compressor is possible only after careful filtration.
Selecting and preparing a receiver for the system
The receiver is the heart of your pneumatic system, providing a supply of air and dampening pulsations from the operation of the piston. The ideal candidate for homemade compressor often is the body of an old fire extinguisher with a volume of 10-20 liters. The metal of such cylinders is designed for high pressure, which guarantees safe operation, unlike canisters or thin-walled containers.
Before installing the fittings, the internal surface of the receiver must be thoroughly cleaned of rust and dirt. If you use a fire extinguisher, cut off the top part (neck) with a grinder, if the design allows, or carefully drill holes for the fittings. Corrosion The inside of the cylinder is the main enemy, so after mechanical cleaning it is recommended to treat the walls with a rust converter and cover them with anti-corrosion primer.
Receiver type Advantages Disadvantages Recommended pressure Fire extinguisher High strength, ready-made form Small volume (several pieces needed) up to 15-20 atm Propane cylinder Large volume, thick walls More difficult to process and welding up to 15 atm Auto-chamber Cheap, large volume Low operating pressure, bulky up to 2-3 atm Large diameter pipe Any volume can be welded Requires professional welding of the ends depends on the wall thickness After preparing the body, it is necessary to weld or secure fittings to threaded connections. You will need at least three holes: one for air supply from the compressor, one for air intake to the consumer and one at the lowest point for draining condensate. The use of high-quality threads and sealant (for example, FUM tape or anaerobic sealant) is a prerequisite here.
Assembly and installation of the pneumatic system
Assembling the entire system into a single mechanism requires sequential connection of nodes. The compressor is installed on a frame or a solid base, often using a wooden board or metal profile lined with vibration-insulating material. Vibration When the piston unit is operating, it is significant, and without proper fastening it will quickly destroy the connections or create unbearable noise.
The connection between the compressor and the receiver is made through a check valve. Air is supplied from the motor discharge pipe to the valve inlet, and the valve outlet cuts into the receiver. This scheme ensures that when the engine is stopped, the air compressed in the cylinder will not flow back, forcing piston group to idle and creating a load at the start.
- 💨 Filtration: At the inlet of the compressor, be sure to install an air filter (you can use a car filter) so that dust does not wear out abrasively cylinders.
- 🌡️ Cooling: It is useful to install a copper coil between the compressor and the receiver to cool hot air before entering the tank.
- 🔧 Adjustment: After the receiver a pressure reducer is installed and a second pressure gauge to control the pressure at the outlet to the tool.
The electrical connection diagram also requires attention. Refrigerator motors often have a starting winding that turns off after reaching speed. If you are using a stock relay there should be no problems. However, to automate the process, a pressure switch is often included in the circuit, which will turn off the motor when a specified limit is reached in the receiver and turn it on when the pressure drops. pressostat — a pressure switch that will turn off the motor when a specified limit is reached in the receiver and turn it on when the pressure drops.
⚠️ Attention: All air line connections must be checked for leaks with a soap solution under pressure. Even a microscopic leak will eventually lead to the engine constantly turning on and overheating.Oil change and maintenance of the piston group
One of the most controversial issues in the topic of homemade compressors is whether the oil needs to be changed? In the factory version, refrigeration compressors operate in a closed circuit with freon, and the oil there serves for lubrication and heat removal. When working with air, the conditions change: the air contains moisture, which, when mixed with oil, forms an emulsion that loses its lubricating properties.
If your compressor is of the type friction (where the cylinder and piston are lubricated by splashing), replace the oil with a special compressor oil (not to be confused with a motor one for ICE!) will extend the life of the unit. To replace, you need to find a drain plug (often it is sealed and requires careful drilling) or completely dismantle the bottom cover (“glass”), drain the old fluid and fill in a new one.
The oil volume is usually about 200-300 ml, but the exact level must be checked using a dipstick or sight glass, if they are structurally provided. Oil overflow as dangerous as its deficiency: excess can get into the air line and clog the pneumatic tool or ruin the paint when working with an airbrush.
☑️ Compressor maintenance
Completed: 0 / 5There are also oil-free modification options, when the cylinder is bored for Teflon rings, but this is extremely difficult to implement at home. Therefore, for garage use, it is better to adhere to the classic scheme with oil, simply changing it more often and monitoring the cleanliness of the incoming air. Make sure all fasteners are tight, electrical contacts are insulated, and the outlet valve is closed. Turn on the compressor and monitor the pressure gauge. The arrow should creep up, and the engine should run smoothly, without strong vibrations and extraneous metal clanging. incoming air.
Launch, testing and security measures
The first launch of the assembled system is the moment of truth. Make sure all fasteners are tight, electrical contacts are insulated, and the outlet valve is closed. Turn on the compressor and monitor the pressure gauge. The arrow should creep up, and the engine should run smoothly, without strong vibrations or extraneous metallic clanging.
Having reached the operating pressure (usually 6-8 atmospheres for domestic needs), turn off the power. The system must hold pressure. If the gauge needle moves down, look for a leak. A characteristic suite will indicate the place where compressed air the exit is found. Also check the temperature of the motor housing: it will be hot, but should not become red hot or smoke.
Operation of a homemade device requires strict adherence to safety rules. Do not leave a running compressor unattended, do not direct the air stream at people and do not exceed the design pressure in the receiver. Safety valveif you managed to find and install it, it should operate when the pressure is critically exceeded, saving the cylinder from rupture.
It is possible Is it possible to use a compressor from a refrigerator for a spray gun?
Yes, you can, but with reservations. Refrigeration compressors provide a small air flow (performance), so they may not be enough for continuous operation of the spray gun - the paint will lie unevenly. However, for airbrushing or touching up small parts, this option is quite suitable, especially if a large receiver is installed.
Why does the compressor get very hot during operation?
Air compression is a physical process accompanied by the release of heat. The normal operating temperature of the case can reach 90°C. If the temperature is higher, check the oil level, cleanliness of the cooling fins and the absence of jamming of the piston group. Also, the cause may be incorrect operation of the start relay.
What oil is best to fill in a homemade compressor?
The best choice is special compressor oils (for example, KKS 19 or analogues). You can use regular motor oil (M10, M15) as a last resort, but it cokes faster and loses its properties at high air compression temperatures.
How many atmospheres can such a compressor produce?
Refrigeration compressors are capable of creating pressure up to 20-25 atmospheres and even higher, but standard electrics and The design is designed to work in a circuit with freon (where the pressure is lower). For safe operation as a pneumatic compressor, it is recommended to limit the pressure to 6-10 atmospheres.
Is it necessary to change freon to air?
Yes, during the conversion, all freon is removed, and the system begins to work on atmospheric air.
In conclusion, it is worth noting that creating a compressor with your own hands is not only saving money, but also gaining valuable experience. You will know exactly how your tool works and will be able to fix any malfunction. With the right approach, such a unit will serve in the garage for many years, becoming an indispensable assistant in solving various technical problems.