Has your old refrigerator stopped freezing, but you don’t want to throw it away entirely? Many home craftsmen know that the heart of the unit - compressor - often remains fully operational even after the cooling system fails. This is a reliable electric motor that is capable of creating pressure and vacuum, which opens up wide possibilities for its secondary use.
Using a removed unit allows you to save significant money on the purchase of new equipment for a garage or workshop. In skillful hands, this unit turns into the basis for creating a compressor, an aquarium aerator, or even a vacuum sealer. The main thing is to understand the principles of its operation and observe safety precautions when altering.
In this article we will look in detail at how to properly remove the device, connect it to the power supply and assemble a functional tool based on it. You will learn what Additional elements required for stable operation and how to avoid typical mistakes when assembling homemade structures.
Removal and initial diagnostics of the unit
The first step is to carefully remove the compressor from the refrigerator body. To do this, you need to cut the copper tubes at a distance of 10-15 cm from the motor housing in order to leave convenient “tails” for later connection. It is important not to damage the fittings themselves, since hoses or fittings will be attached to them.
After dismantling, check the integrity of the motor windings using a multimeter. The resistance between the starting and operating terminal contacts should be within normal limits, usually from 10 to 30 Ohms, depending on the model. If the device shows an open or short circuit, further operation electric motor is impossible and dangerous.
It is also worth paying attention to the condition of the oil inside the housing. If, when tilting the unit, a strong splash is heard or a black viscous liquid with a burning smell flows out of the tubes, there may be a breakdown or burning of the windings inside. In this case, it is better to find another donor, since repairs are often not economically feasible.
Connection diagram for a 220V power supply
To start the motor, it is not enough just to apply voltage on two wires. The refrigerator uses a starting relay that briefly connects the starting winding to create torque. Without this element, the engine will only hum, but will not start.
You can determine the purpose of the contacts by the markings on the body or by dialing. Typically, the pair of contacts with the highest resistance is the run and start windings, and the third contact is common. The relay is placed directly on the motor terminals in a certain orientation, indicated by the arrow UP.
It is best to assemble an electrical circuit in a separate housing with a power button and a fuse. This will ensure safety and ease of use. Do not forget that starting relay is sensitive to its position in space, so fasten it securely.
- 🔌 Find three terminals on the compressor body: common, starting and working.
- 🔌 Connect the phase wire of the network to one the end of the starting winding through a relay.
- 🔌 Connect the second end of the starting winding to the working terminal of the motor.
- 🔌 Connect the neutral wire of the network to the remaining free terminal of the working winding.
Why does the compressor hum, but does not start?
Most often the problem lies in a stuck piston group or a faulty start relay. If the relay is working properly, try briefly applying voltage to the starting winding manually, but do it extremely carefully.
Creating a full-fledged air compressor
The most popular application is creating a compressor for painting or pneumatic tools. However, the performance of one refrigeration unit may not be enough for continuous operation of the spray gun, so the key element becomes receiver. Its role is often played by an old fire extinguisher or a gas cylinder.
The receiver is necessary to accumulate air and smooth out pressure pulsations, which are inevitable during the operation of a piston unit. Without a buffer tank, the air stream will come in jerks, which is critical for high-quality painting or working with an airbrush. The volume of the receiver is selected individually, but 20-50 liters is considered optimal.
To assemble the structure, you will need to connect the compressor outlet tube to the receiver inlet through a check valve. This element will prevent the backflow of air into the engine when stopped, which will facilitate the next start and protect the mechanism from overload. A gearbox and moisture-oil separator are installed at the outlet of the receiver.
Use as a vacuum pump
Few people know that a refrigeration compressor is excellent at not only pumping, but also pumping out air. If you connect a hose to the inlet pipe (where the low-pressure refrigerant was in the refrigerator), you can get an effective vacuum pump. This opens up opportunities for vacuuming product packaging or conducting experiments.
To operate in vacuum mode, it is important to ensure the purity of the intake air. If moisture or dust gets into the system, this can quickly damage the rubbing pairs. It is recommended to install a fuel filter or a special filter element on the inlet pipe.
The performance in pumping mode for household models is lower than that of specialized industrial analogues, but for domestic needs it is quite sufficient. You can vacuum jars for storing bulk products or remove air from systems before charging with refrigerant.
☑️ Check before starting the vacuum generator
Features of working with oil and lubricant
Inside the compressor housing there is oil, which is sprayed by the crankshaft to lubricate the bearings and cylinders. When working in an inverted or inclined position, or when actively pumping air, oil may be thrown out along with the air flow. This is unacceptable when painting, as it will ruin the coating.
To solve this problem, it must be built into the system oil separator. The simplest design is a sealed container into which a mixture of air and oil is supplied. Due to changes in flow speed and inertia, the oil settles at the bottom, and the air moves on. This container needs to be emptied periodically.
Monitor the oil level in the compressor crankcase. Although the system is considered sealed, during long-term operation some of the lubricant may burn away or be carried away into the receiver. (checking) the level through an inspection window or dipstick (if the design allows) will extend the life of the device.
Technical characteristics and compatibility table
When When choosing a compressor for a specific task, it is important to focus on its markings. Different models have different performance and pressure generated. Below is a table with approximate characteristics of popular series of compressors often found in household refrigerators.
| Marking | Manufacturer | Refrigerant | Power (W) | Features |
|---|---|---|---|---|
| NKF 6.5 | Atlant | R12 / R600a | 130-150 | High reliability, quiet operation |
| QD35Y | Secop (Danfoss) | R134a | 100-120 | Compact size, low power consumption |
| FG 10 | Embraco | R134a | 180-200 | High performance, suitable for receivers |
| Aspera (Tecumseh) | Aspera | R404a | 250+ | Powerful, requires good cooling |
Please note that compressors designed for different types of refrigerants may have different oil requirements. Mixing different types of oils (mineral and synthetic) can lead to the formation of clots and clogged passages. If you are not sure about the type of oil, it is better to completely replace it with a compatible one.
Problems, noise and operational safety
Home-made designs often operate louder than their factory counterparts due to the lack of a noise-insulating casing. To reduce the noise level, the unit can be placed in a wooden box, covered vibration-insulating material. However, it is necessary to ensure an air flow to cool the motor, otherwise it will quickly overheat.
⚠️ Attention: The compressor housing heats up to 80-90°C during operation. When designing an enclosure or enclosed volume, ensure that there is ventilation and that flammable materials are not in contact with hot tubes.
The pressure generated by a refrigeration compressor is limited by the design of the piston group and valves. Usually it is 10-15 atmospheres, but for domestic needs 6-8 atmospheres are sufficient. Exceeding the permissible pressure can lead to rupture of the pipes or housing, so installing a safety valve on the receiver is mandatory.
Regularly check the tightness of the bolts and nuts. Vibration during operation can loosen connections, leading to air or oil leaks. Also monitor the condition of the electrical wires - they should not touch hot metal parts.
What to do if the compressor vibrates strongly?
Check the condition of the rubber feet. If they dry out, replace them with new ones or use automotive silent blocks. Vibration can also be caused by the contact of the tubes with the body or the walls of the box.
FAQ: Frequently asked questions
How long can the compressor from the refrigerator work in continuous mode?
In normal mode, the refrigerator operates cyclically. When converted to a compressor, continuous operation is possible for 30-60 minutes, after which it is recommended to rest for 15-20 minutes to cool down. Forced air cooling of the housing can increase this time.
Can such a compressor be used for car air springs?
Yes, this is a popular application. However, the performance of one unit may not be enough to quickly pump large volumes. Often, two compressors are installed in parallel or a more powerful unit from an industrial refrigerator is used.
Is it necessary to change the oil in the compressor during refurbishment?
If the compressor was taken from a working refrigerator and has not been opened, changing the oil is not necessary. But if you plan to use it for food products or demanding pneumatics, it is better to replace the oil with fresh oil corresponding to the type of refrigerant.
What is the maximum pressure that such a compressor can produce?
Theoretically, the piston group can create a pressure of up to 20-25 atmospheres, but in reality, in conjunction with the receiver, a range of up to 10 atmospheres. A further increase in pressure sharply reduces performance and increases the risk of breakdown.