Using an old but still working one refrigerator to create air compressor is a popular way to save money and get a useful tool for your garage or workshop. Such units are ideal for inflating tires, working with a spray gun or blowing out mechanisms where industrial performance is not required. The main advantage of a homemade design is that the motor-compressor from a household refrigerator is capable of creating high pressure, while operating much quieter than its industrial counterparts.
Before you start disassembling household appliances, you need to make sure that motor-compressor is working and capable of starting. If your old refrigerator is still humming and freezing, its heart will work for years in a new role. It is important to understand that the remodeling process requires not only technical skills, but also compliance with safety rules, since you will be working with electricity and compressed air.
In this article we will analyze in detail the entire process of creating a mini-compressor station, from dismantling to commissioning. You will learn what additional components are required to assemble the receiver and filtration system, and also consider typical mistakes that beginners make when starting up for the first time.
⚠️ Attention: Before starting any work, be sure to disconnect the refrigerator from the electrical outlet. Residual voltage in the starting capacitors can be dangerous, so let the equipment stand turned off for at least 15-20 minutes.
Preparation of tools and necessary materials
To create a high-quality compressor, a motor alone is not enough. You will need to assemble a number of components that will ensure stable operation of the system and air purification. The basis of the future station will be receiver a container for accumulating compressed air, which is often used as old fire extinguishers or gas cylinders. Also indispensable elements will be hoses, clamps, a pressure gauge and a check valve system.
Particular attention should be paid to the selection of hoses and fittings. Cheap PVC pipes may not withstand the pressure and burst, so it is better to use specialized pneumatic hoses or high-pressure fuel hoses. To connect all the nodes you will need brass fittings, tees and adapters, which can be purchased at specialized plumbing stores.
- 🛠️ Motor-compressor from the refrigerator (power from 100 to 200 W).
- ⚙️ Receiver (fire extinguisher, gas cylinder or freon canister).
- 📏 Pressure gauge for monitoring the pressure in the system.
- 🔌 Pressure switch (pressostat) for automatic on/off.
- 🧴 Oil and moisture separator and air filter.
Don't forget to prepare the tools: a hacksaw, a drill, a set of keys, a soldering iron or a screwdriver for electrical connections. To seal threaded connections, be sure to use FUM tape or anaerobic sealant, since air leaks will reduce the efficiency of the entire structure to zero.
Dismantling the compressor and initial inspection
Extraction process compressor installation begins with carefully removing the rear panel of the refrigerator. Find a black cylindrical or pear-shaped unit to which copper tubes fit. Motor-compressor attached to the frame of the refrigerator on four shock-absorbing bushings, which must be carefully disconnected, being careful not to damage them, as they dampen vibration.
Copper tubes, coming from the compressor, you need to bite with wire cutters at a distance of 10-15 cm from the body. This is necessary to prevent chips and debris from getting into the tubes. After removing the unit, plug it into the network to check its functionality. At this stage, it is important to determine which of the tubes is dischargeand which is suction.
To check, place your finger on the ends of the cut tubes while the engine is running. From the tube where the air is blown out with force, air will come out - this is the exit. The second tube will suck in air, creating a vacuum. Remember this location, since when connecting to the receiver, mixing up the inputs and outputs will lead to system breakdown.
⚠️ Attention: When first started outside the refrigerator, the compressor may become very hot, since in normal mode it is cooled by air flows inside the refrigerator body. Do not keep it turned on for more than 2-3 minutes without connecting to the cooling system or receiver.
☑️ Check before assembly
Manufacture and preparation of the receiver
The receiver is the heart of your compressor station, acting as a buffer. It stabilizes pressure, removes air pulsations and allows moisture to condense. The most affordable and safe option for beginners is to use fire extinguisher a volume of 10-20 liters. Aluminum or steel fire extinguisher bodies are initially designed for high pressure, which makes them ideal candidates.
Before use, the container must be carefully prepared. If it is a former fire extinguisher, remove any remaining powder, wash the insides with detergent and water, and dry. In the upper part of the cylinder you need to drill holes and weld or screw two fittings onto the sealant: one for air inlet from the compressor, the other for outlet to the consumer.
In the lower part of the receiver it is necessary to provide drain valve (tap). During the process of air compression, condensate is formed from atmospheric moisture, which accumulates at the bottom of the tank. If it is not drained, water will enter the pneumatic tool or spray gun, ruining the work or painting.
| Receiver type | Volume (liters) | Working pressure (atm) | Complexity of preparation |
|---|---|---|---|
| Fire extinguisher | 10-20 | up to 15 | Low |
| Propane cylinder | 20-50 | up to 16 | High (welding required) |
| Freon canister | 10-12 | up to 10 | Medium |
Assembling the electrical circuit and connecting the automation
For automatic operation of the compressor, it is necessary to install pressure relay (pressostat). This device opens the electrical circuit when the pressure in the receiver reaches a predetermined maximum, and closes it when the pressure drops below the minimum. The connection diagram is simple: phase and zero from the network go to the relay input, and from the output to the compressor motor windings.
It is important to take into account the starting currents of the motor. Refrigeration compressors have high inrush currents, so a regular relay can burn out quickly. It is recommended to use a relay with a current reserve or add it to the circuit capacitor to facilitate starting if the engine does not start under load. All electrical connections must be securely insulated and placed in a protective box.
Don't forget about grounding. The compressor housing and receiver must be grounded to prevent electric shock in the event of a breakdown of the winding insulation. This is a critical safety point that cannot be neglected.
What to do if the pressure switch clicks, but the motor does not start?
Most often the problem lies in the starting capacitor or the starting relay of the compressor itself (the black box on the side of the motor). Try replacing the start relay with a similar one or checking the capacitor with a multimeter. The cause may also be a jammed piston due to thickened oil.
Filtration system and air preparation
The air exiting the refrigeration compressor contains oil vapor and moisture. If you plan to use a compressor for painting or working with pneumatic tools, it is air purification required. Oil escaping from the compressor can ruin the paintwork or damage an expensive tool.
The purification system usually consists of two stages. The first stage is a filter at the compressor inlet that traps dust. The second stage is an oil and moisture separator, installed after the receiver before exiting to the hose. As simple filters, you can use housings from automobile fine fuel filters or special modules for pneumatics.
For serious work, it is recommended to assemble cyclone filter or use ready-made air preparation units (FRL groups). They not only clean the air, but also allow you to regulate the outlet pressure and add oil to the air mixture to lubricate pneumatic tools.
Starting, setting up and troubleshooting
After assembling all the components, the moment of truth comes - the first launch. Plug in the compressor and observe the pressure gauge readings. The arrow should confidently creep up. When the pressure reaches the cut-out value on the relay, the engine should stop. If this does not happen, check the settings pressostat or the tightness of the system.
Check the system for leaks. Apply soapy water to all connections, pipe joints and threads. The appearance of bubbles will indicate the location of the leak. Even small leaks over time lead to the compressor turning on more often than necessary, wearing out the motor.
During operation, monitor the temperature of the compressor housing. If it heats up above 90 degrees, the cooling system may be broken or the cut-off pressure may be too high. In this case, it is worth increasing the volume of the receiver or installing additional cooling.
⚠️ Attention: Never exceed the maximum operating pressure indicated on your receiver or pressure switch. Excessive pressure may cause container rupture and serious injury. Always use a safety valve.
Frequently asked questions (FAQ)
How long can a homemade compressor operate without interruption?
Refrigeration compressors are not designed for long-term continuous operation (100% duty cycle). They can usually work for 15-20 minutes before needing a rest to cool down. For long-term operation, it is necessary to install a forced cooling system (fan) or increase the volume of the receiver in order to turn on the motor less often.
What kind of oil should be poured into the compressor from a refrigerator?
In most cases, compressors from refrigerators are already filled with oil at the factory and do not require replacement. If the oil level drops, you need to add special synthetic oil for refrigeration compressors. Regular motor oil cannot be used, as it can foam or freeze.
Can this compressor be used for airbrushing?
Yes, you can, but only if you install a high-quality oil-moisture separator and a receiver of sufficient volume (minimum 20-30 liters). Without good filtration, oil will get into the paint, leaving defects on the surface.
Why does the compressor hum but not pump?
This may indicate a broken valve group inside the compressor head or that the inlet and outlet are mixed up. Another possible cause is the lack of oil or its thickening. In some cases, replacing the valve plate helps.