How to make a powerful pump from a refrigerator compressor with your own hands

Using old household appliances to create new functional equipment is not not only budget savings, but also a fascinating engineering process. The compressor from a non-working refrigerator is ready-made piston unit, which is ideal for conversion into an air pump or vacuum unit. Unlike cheap Chinese analogues, such devices operate much quieter, have a longer service life and are capable of producing stable pressure.

Before starting to implement the project, it is necessary to clearly understand the operating principle of the original mechanism. Inside the sealed casing there is an electric motor that drives a crank mechanism that pumps refrigerant. Our task is to adapt this unit to work with atmospheric air by changing the lubrication system and connecting the appropriate fittings. This requires caution and compliance with safety precautions.

This article is an expert guide that will help you avoid common mistakes when upgrading equipment. We will consider the issues of dismantling, installing filtration, connecting the receiver and organizing the control system. A properly assembled unit will serve for many years, becoming a reliable assistant in the garage or workshop.

Preparation of tools and selection of components

The success of any technical project directly depends on the quality of preparation. To begin with, you will need one compressor, which is removed from the old refrigerator. It is best to choose units from manufacturers like Danfoss, Secop or Atlant, as they have proven themselves to be highly reliable. Make sure that the motor windings are intact and the mechanism itself has no external damage to the housing.

In addition to the main unit, it is necessary to prepare components for assembling the pneumatic system. You will need a metal container for the receiver, shut-off valves, pressure gauges and connecting hoses. Particular attention should be paid to the materials, as they will experience a constant load under pressure.

• 🛠️ Toolkit: a set of wrenches, screwdrivers, drill, hacksaw, soldering iron or welding machine (for the receiver).
• ⚙️ Consumables: copper tubes, high-pressure hoses, clamps, sealant, oil for compressors.
• 🔌 Electrics: cable with plug, circuit breaker, pressure switch (pressostat), starting capacitor (if required).

⚠️ Attention: Before starting any work to remove the compressor, be sure to disconnect the refrigerator from the power supply and cut through the copper tubes, allowing the residual gas to completely escape. The refrigerant may be toxic or flammable.

It is important to determine in advance the type of oil that will be used. Standard refrigeration oil can be hygroscopic, meaning it can absorb moisture from the air, causing corrosion of internal parts. For air pumps, it is often recommended to use special synthetic lubricants or regularly replace them to extend the life of the mechanism.

Dismantling and initial diagnostics of the unit

The process of removing the compressor requires caution. You should not saw the casing with a grinder, as metal shavings can get inside the mechanism, which will lead to its rapid failure. The best way is to carefully cut the tubes with a hacksaw or cut them with wire cutters, leaving sufficient tails for subsequent connection.

After removal, it is necessary to carry out a visual inspection and a primary diagnostics. Check the condition of the start relay and capacitor. Often these elements are the first to fail. If the relay has traces of burning or melting, it must be replaced with one of similar characteristics. Also check the integrity of the motor windings using a multimeter.

The next step is to determine the inlet and outlet holes. In a refrigerator compressor, one tube usually sucks in gas, while the other pumps it out under pressure. To avoid mixing them up when connecting to the atmosphere, briefly apply power to the motor (observing the connection diagram indicated on the relay). The tube from which air blows is a discharge tube, and the one that draws in is a suction tube.

How to connect the relay correctly?

The connection diagram is usually marked on the relay or compressor housing. The main contacts are labeled Common (C), Start (S) and Run (R). The phase is supplied to Common, zero to Run, and Start is connected through a capacitor or starting winding, depending on the type of engine. An error in connection can lead to burnout of the windings.

Do not forget to clean the outer surface of the unit from dirt and old paint if you are planning a permanent installation. This will not only improve aesthetics, but will also allow you to quickly notice oil leaks or damage to the housing during operation.

Manufacture and preparation of the receiver

The receiver is a storage tank that equalizes pressure and reduces the pulsation of air flow, characteristic of piston systems. Without this element, your pump will produce air in jerks, which is unacceptable for many tasks, for example, for painting or working with pneumatic tools. As a receiver, you can use old fire extinguishers, gas cylinders or receivers from trucks.

The main requirement for a container is the ability to withstand high pressure with a margin. Before use, the cylinder must be carefully prepared. If it is a fire extinguisher, it must be completely emptied of its contents and washed with water. The internal walls should not have traces of corrosion, which can become a source of moisture in the system.

In the receiver body it is necessary to drill holes and weld or screw in fittings to connect the inlet pipe from the compressor, the outlet pipe to the consumer, a pressure gauge and a drain valve for condensate. Welding work should be carried out only after thorough steaming and filling the container with water to prevent an explosion of residual gases.

⚠️ Attention: It is strictly forbidden to use containers containing flammable liquids (gasoline, diesel fuel) as a receiver without professional chemical cleaning and degassing. Residual vapors can ignite from a spark during welding or static electricity.

Assembling a pneumatic system and filtration

Assembling the system begins by installing the compressor on a frame or wooden base with vibration insulation. Then the receiver is mounted. The connection between the compressor and the receiver is made through a check valve, which prevents air from escaping back into the compressor after it stops. This is a critical element for the operation of automation.

The air entering the system contains dust and moisture. To protect the compressor mechanism and pneumatic tools, it is necessary to install air filteron the inlet pipe. You can use a car fuel filter or a special air vent. It is also recommended to install a moisture-oil separator at the outlet of the receiver, especially if you plan to use a pump for airbrushing.

• 💧 Moisture removal: Be sure to install a tap at the lower point of the receiver to regularly drain condensate. Moisture inside the tank leads to corrosion and destruction of the metal from the inside.
• 🌡️ Temperature conditions: When compressed, the air heats up. If long-term operation is planned, provide additional cooling of the tubes between the compressor and the receiver (for example, a copper coil).
• 🔒 Security: A safety valve should be installed on the receiver, set to a pressure slightly higher than the operating one, to prevent rupture of the container.

All connections must be tight. Use FUM tape or anaerobic sealant for threaded connections. After assembly, carry out a test run, using a soapy solution to check all joints for air leaks.

Electrical circuit and automation

For comfortable operation, the pump requires an automatic control system. The main element here is pressostat (pressure switch). It automatically turns off the engine when the set pressure in the receiver is reached and turns it on when the pressure drops to a minimum threshold. This relieves the operator of the need to constantly monitor the pressure gauge.

Connecting the electrical part requires care. The pressure switch breaks the engine power supply circuit. It is also advisable to include a thermal protection relay in the circuit, which will turn off the unit in case of overcurrent or overheating of the windings. For engines with a power of more than 1 kW, an additional starting capacitor may be required.

Connection diagram (simplified):
220V network -> Automatic -> Pressostat (contacts 1-2) -> Compressor motor
|-> Pressostat (contacts grounding) -> Earth

If your compressor is equipped with a starting relay, it must be connected strictly according to the markings on the case. An error in phasing can lead to engine humming and eventual combustion. For models with capacitor starting, make sure that the capacitor capacity corresponds to the motor power.

Startup, testing and safety measures

The first launch of the assembled device is a crucial moment. Make sure that the receiver drain valve is open so that the compressor does not immediately pump air into the enclosed volume. Turn on the power and check the direction of shaft rotation (if there is a cooling fan, it should blow in the right direction).

Let the unit idle for a few minutes. Pay attention to noise and vibration levels. If everything is normal, close the drain valve and check the process of pressure build-up. The pressure gauge needle should move smoothly, without jerking. When operating pressure is reached, the pressure switch should click and turn off the engine.

During operation, remember the following rules:

• 👁️ Visual inspection: Regularly inspect hoses and connections for cracks and abrasions.
• 🛢️ Oil level: Monitor the lubricant level in the compressor crankcase, if the design provides for its replacement or topping up.
• 🌡️ Overheating: Do not allow the compressor to operate in a mode where the housing is heated to temperatures dangerous for the wire insulation.

⚠️ Attention: Compressor specifications may vary depending on the model and year of manufacture. Always check the passport data of a particular device before changing the electrical circuit or increasing the operating pressure.

Frequently asked questions (FAQ)

Can such a pump be used for a spray gun?

Yes, it is possible, but with reservations. Refrigerator piston compressors produce a small volume of air (performance), so they are only suitable for small spray guns with low air consumption. You definitely need a good moisture-oil separator to prevent oil from getting onto the surface to be painted.

What oil is best to fill into the compressor?

Ideally, special synthetic compressor oil. However, many mechanics successfully use regular motor oil with a viscosity of 10W-40, changing it more often. The main thing is not to mix different types of oils and monitor the level.

Why does the compressor get very hot?

Heating up to 70-90 degrees is normal for such units, since they are designed to work in a closed circuit with freon, which cools the motor. When working with air, cooling is worse. If the heating is critical, check the ventilation, oil level and the absence of pressure leaks.

Is it necessary to change the starting relay during modification?

If the original relay is working properly and matches the mains voltage, it does not need to be changed. However, if you change the electrical circuit or motor, the relay must be selected again based on the starting current and power.