Many car enthusiasts and home craftsmen are faced with the need to use compressed air to operate pneumatic tools, inflate tires or carry out painting work. Buying professional equipment often costs a pretty penny, so compressor from an old refrigeratoris an excellent solution. This device is characterized by quiet operation, accessibility of components and ease of assembly, which makes it an ideal choice for a garage workshop.
The basis of such a unit is a standard motor-compressor, which is removed from broken household appliances. Unlike noisy piston analogues, the refrigeration unit is capable of pumping up pressure to 10-15 atmospheres, although 6-8 atmospheres is sufficient for most household tasks. It is important to understand that remodeling requires a careful approach to electrical safety and tightness of connections.
In this article we will analyze in detail the entire process of transforming an old household appliance into a functional tool. You will learn how to choose the right receiver, change the oil and assemble a reliable control system. Compliance with the technology will allow you to create a device that will last for many years.
Necessary materials and tools for assembly
Before starting work, it is necessary to prepare all the components so that the assembly process is not interrupted while searching for missing parts. The basic element, of course, is the refrigerator itself. Units from Soviet refrigerators are best suited, as they are considered more reliable and repairable, although modern models also cope with the task quite well. motor-compressor from the refrigerator. Units from Soviet refrigerators are best suited, as they are considered more reliable and repairable, although modern models also cope with the task.
In addition to the engine, you will need a container for storing compressed air, known as a receiver. Old fire extinguishers, gas cylinders or even housings from (air conditioners) are often used as a receiver, but the most popular are fire extinguishers with a volume of 10-50 liters. You will also need fittings: copper tubes, hoses, clamps, tees and check valves.
- 🔧 Motor-compressor from the refrigerator (whole, with sealed tubes).
- ⚙️ Receiver (fire extinguisher, freon cylinder or gas cylinder).
- ⚡ Starting relay and capacitor (usually included with the motor).
- 🛠️ Pressure gauge, pressure relief valve, safety valve.
- 🔩 High pressure hoses, clamps, bolts, nuts.
Tools are required a drill, a set of metal drills, a hacksaw or a grinder for cutting pipes. To seal the connections, you will need adjustable wrenches and, possibly, a welding machine if you decide to weld the frame or weld fittings to the receiver. Don't forget about soldering iron to connect copper tubes if fittings are not used.
⚠️ Attention: It is strictly forbidden to use containers of flammable liquids (gasoline, solvents) as receivers without prior long-term treatment with steam and chemicals. Residual vapors can ignite from a spark or heat during welding.
Removing the compressor and preparing the receiver
The process begins with carefully removing the compressor from the refrigerator. Disconnect all pipes, moving about 10 cm away from the motor body so as not to damage the fittings. The tubes need to be cut with nippers, and not sawed, so that the chips do not get inside the mechanism. After removal, check the operation of the motor by connecting it to the network via the standard starting relay.
The next stage is preparing the receiver. If you use a fire extinguisher, make sure it is empty. Unscrew the top bell and thoroughly rinse the inner surface with water and detergent. This will remove any remaining powder that can have an abrasive effect on the compressor parts or clog the spray gun.
It is necessary to drill holes in the receiver body to install fittings. Usually there are three of them: for air inlet from the compressor, for air outlet to the consumer, and for installing a pressure gauge. The holes need to be threaded or ready-made bosses welded. It is important to observe tightness systems, so all threaded connections are sealed with FUM tape or anaerobic sealant.
☑️ Preparation for assembly
Connection and electrical diagram part
The electrical circuit of the compressor is quite simple, but requires precision. Refrigerator motor compressors are usually equipped with a start relay that briefly supplies current to the start winding to start the motor. On the relay body there are terminal markings: “C” (mains), “R” (working winding) and “S” (starting winding). An incorrect connection can burn the winding or cause a short circuit.
To automate the operation of the system, a pressure switch (pressure switch) is included in the circuit. It opens the contacts when the pressure in the receiver reaches a preset value, and closes them when the pressure drops below the threshold. This prevents the receiver from rupturing and the motor overheating. It is also advisable to include a thermal protection relay in the circuit, which will turn off the power in case of overcurrent.
Nuances of the starting relay
The starting relay works on the principle of heating a bimetallic plate or electromagnet. When starting, the current is high, the relay closes the starting winding. When the engine picks up speed, the current drops and the relay opens the starting winding circuit. If the relay sticks, the motor will burn out.
All electrical connections must be reliably insulated and protected from moisture. The wires should be laid in a corrugation or cable duct. For ease of use, a power switch and an indicator lamp are installed on the housing. Remember that you are working with voltage 220 V, so mistakes are unacceptable here.
- ⚡ Connect the phase and zero to the corresponding terminals of the starting relay.
- 🔌 Be sure to connect the grounding wire to the housing compressor.
- 🛡️ Install a circuit breaker to protect against power surges.
- 📉 Set the pressure switch to turn off at 6-8 atmospheres.
Modernization of the compressor lubrication system
One of the main problems homemade compressors have a lubrication system. Standard refrigeration compressors operate in a closed circuit and do not consume oil. However, when working for injection into the atmosphere, the oil begins to be carried away along with the air. Over time, the oil level drops and the motor may seize due to dry friction.
There are two ways to solve this problem. The first is to regularly add oil through a special funnel or syringe as needed. To do this, an inspection window is often made in the housing or a transparent hose is used to visually monitor the level. The second, more correct way is to install a forced lubrication system or use an oil-free compressor (although conversion to an oil-free mode is complex and reduces the service life).
To control the oil level, you can use a transparent tube connected to the bottom of the crankcase. This will allow you to see the actual fluid level. It is also important to use only the oil recommended by the manufacturer, or its modern analogues, for example, synthetic oils for compressors. Oil viscosity also plays a role: too thick oil will make it difficult to start in cold weather.
Some craftsmen implement a “breather” system, removing the breathing pipe through a fine filter. This prevents oil mist from being released into the atmosphere and dust from being sucked in during cooling. The filter can be made from a car fuel filter or simply from a piece of foam rubber in a housing.
Assembling components and sealing connections
Assembling the entire structure requires careful sealing. Any microcrack or poor connection will lead to loss of performance and constant operation of the motor, which will not be able to gain the required pressure. Copper tubes from the compressor are connected to the receiver through high-pressure hoses secured with double clamps.
A check valve must be installed at the outlet of the receiver. It prevents air from escaping back into the compressor after it stops. If there is no check valve, the compressed air will begin to rotate the engine shaft in the opposite direction, which can damage the valve plates. After the check valve, a reducer is installed, which reduces the pressure to the operating value for the tool.
| Component | Function | Material | Recommended pressure |
|---|---|---|---|
| Receiver | Air accumulation and cooling | Steel (fire extinguisher) | up to 15 atm |
| Manometer | Pressure control in system | Brass/Steel | up to 20 atm |
| Safety valve | Emergency pressure release | Brass | set to 9-10 atm |
| Oil separator | Cleaning air from oil | Glass wool/Ceramics | working |
All threaded connections must be lubricated with sealant or wrapped with FUM tape before tightening. After assembly, the system must be purged with compressed air (if available) or a soap solution, checked for leaks during the first start-up. Bubbles will indicate places where improvements are needed.
First launch and testing of equipment
The first launch is a crucial moment. Make sure all fasteners are tight and the electrical parts are assembled correctly. Plug in the compressor and note the time it takes for it to pump the receiver to the cutoff. The normal time is from 2 to 5 minutes for a receiver with a volume of 20-30 liters, depending on the performance of the motor.
During operation, listen to the sounds. Knocking, grinding, or excessive vibration indicate problems. The refrigerator motor is quite quiet, so any extraneous noise should alert you. Also control the temperature of the compressor housing: it should not heat up to the point where it is impossible to touch it with your hand (above 90°C).
Check the operation of the automation: the compressor should turn itself off when the upper pressure threshold is reached and turn on when it drops to the lower one. If the automation does not work, immediately turn off the device and adjust the pressure switch. Operation without automation is dangerous because the receiver will rupture.
Operation, maintenance and safety measures
For the long life of your creation, you must follow the operating rules. Drain condensation from the bottom of the receiver regularly. Moisture contained in compressed air settles at the bottom of the cylinder and causes corrosion, which can lead to thinning of the walls and an accident. This should be done after each work session or at least once a week during intensive use.
Keep the air filter at the inlet clean. A clogged filter causes the motor to work overload, reducing performance and increasing energy consumption. The filter element (foam rubber or synthetic padding) must be periodically changed or washed.
⚠️ Attention: Do not leave the operating compressor unattended for a long time. Despite the automation, the risk of wiring fire or failure of mechanical parts remains, especially in home-made designs.
Store the compressor in a dry, ventilated area. If the unit is used outdoors or in an unheated garage in winter, monitor the oil temperature. At low temperatures, the oil thickens and the engine may not start or may run rough. In such cases, preheating or the use of winter grades of oils is recommended.
Frequently asked questions (FAQ)
What pressure does the compressor develop from refrigerator?
The standard refrigerator compressor is capable of developing a pressure of up to 15-25 atmospheres, however, for safe operation of a homemade system, it is recommended to limit the pressure to 6-8 atmospheres using a pressure switch and a safety valve.
Can such a compressor be used for sandblasting?
For a classic pressure sandblaster with the capacity of one refrigeration compressor (usually 40-60 liters per minute) will not be enough. It is suitable only for very small work or for inflating tires, but not for active abrasive processing.
Is it necessary to change the oil in the compressor after modification?
Changing standard refrigeration oil to motor oil is not necessary and is even harmful. Refrigeration oil has specific properties and compatibility with compressor materials. Just monitor its level and cleanliness, adding the same if necessary.
Why does the compressor get very hot?
Heating up to 70-80 degrees is normal for piston compressors. If the temperature is critical, check: whether the air filter is clogged, whether the cooling fan is working correctly (if any), whether the motor turns on too often due to leaks or small volume of the receiver.
What volume of the receiver is optimal for a garage?
For periodic work (inflating tires, blowing, working with an airbrush) it is enough 10-20 liters. If you plan to paint a car or work with pneumatic tools, it is better to use a receiver with a volume of 50 liters or more to smooth out the pulsations and give the engine a rest.