How to make a compressor from an industrial refrigerator with your own hands

Converting a decommissioned industrial refrigerator into an air compressor is a popular solution for garage workshops where a constant source of compressed air is required, but the budget does not allow purchasing factory equipment. Industrial units often thrown away or sold for pennies precisely because of leakage refrigerant, although their “heart” - a piston compressor - can last for decades. The use of such a unit allows you to obtain a device with excellent performance indicators and, what is especially valuable, a low noise level.

The main advantage of the modification is the reliability of the design. Unlike household models, industrial refrigerators (such as series Sviyaga, Pozis or imported Liebherr) are equipped with high-power motors capable of operating in more severe temperature conditions. A homemade compressor based on them is ideal for painting work, blowing systems, inflating tires, and even for working with low-power pneumatic tools, if you choose the right receiver.

Before you begin dismantling, you need to understand that you will be working with a sealed unit containing oil and freon residues. Safety —priority number one. Improper preparation may result in personal injury or equipment damage. In this article we will analyze the full cycle of rework: from selecting a donor to final setting the pressure and connecting the automation.

Selecting a suitable donor and assessing the condition of the compressor

The first step is to search and diagnose the original equipment. Not every industrial refrigerator will suit your needs. The ideal donor would be a unit that has stopped cooling due to a gas leak, but whose motor-compressor still emits a characteristic even hum when trying to turn it on. If the unit is silent or hums with strong vibration and does not start without a kick, its use is risky.

Pay attention to the type of compressor. For homemade installations, piston models are best suited, which make up 90% of all industrial refrigerators. Rotary or inverter compressors (found in more modern models) are more difficult to adapt to work with atmospheric air due to the characteristics of lubrication and valve design. Look for markings on the nameplate indicating the power and current consumption.

⚠️ Attention: Before dismantling, be sure to open the freon circulation system in a well-ventilated area. Residual gas can be a fire hazard or toxic, and a sudden release of oil under pressure can damage your eyes.

The performance check is carried out by briefly plugging it into the network. There should be a noticeable flow of air coming from the outlet tube. If the compressor “spits” oil, this is normal for older units, but requires the installation of an additional oil separator in a future design. It is also important to assess the condition of the electrical part: the starting relay and capacitor must be intact, without traces of burning or swelling.

• 🔍 Visual inspection: The tubes should not be broken, the housing without dents.
• 🔌 Electrical: Check the integrity of the cord and the absence of a short circuit to the housing multimeter.
• 🔊 Sound: An even hum without knocking or grinding is a sign of serviceable bearings.
• 💨 Pressure: Plug the outlet tube with your finger (carefully!) - you should feel a stop.

Necessary tools and components for assembly

Assembling a compressor station is not only the motor itself, but also the piping that ensures its safe and efficient operation. You will need receiver (a container for accumulating air), which smoothes out pressure pulsations and makes it possible to work with the tool. Old fire extinguishers, gas cylinders or special receivers from truck pneumatic systems are often used as a receiver.

In addition, the automation system is critically important. An industrial refrigerator does not know how to turn itself off when a certain pressure in the receiver is reached - a thermostat that reacts to temperature was responsible for this in the original system. You will need pressostat (a pressure switch), a pressure gauge for control, a check valve and a safety valve. Without these elements, operation of the installation is prohibited.

The list of tools should include a set of wrenches, a drill or screwdriver, a soldering iron for electricians, as well as sealant and fum tape for sealing threaded connections. Don't forget about high-pressure hoses - ordinary garden hoses won't work; they will burst at the first serious increase in pressure. It is better to use specialized hoses for compressors or fuel hoses with reinforcement.

Dismantling the compressor and preparation nodes

The process of removing the compressor from the body of an industrial refrigerator requires care. First, disconnect all electrical circuits, having previously photographed the connection diagram so as not to get tangled in the starting relay wires. Then, using a pipe cutter or a hacksaw, saw through the copper tubes at a distance of 10-15 cm from the compressor housing. This will leave you with “ears” for future tapping or installation of fittings.

The next step is cleaning. Over the years of operation, dust, grease and dirt accumulate on the compressor. Rinse the body thoroughly with solvent or Galosh gasoline, removing all deposits. This is necessary not only for aesthetics, but also to ensure that during further assembly, dirt does not get inside the mechanisms or onto electrical contacts.

⚠️ Attention: Never use an open flame to anneal old tubes or remove paint from the compressor. There may be oil inside, the vapors of which are explosive, as well as remnants of freon, which forms toxic compounds when heated.

After cleaning, check the condition of the oil. To do this, carefully cut one of the tubes (after disconnecting the compressor from the network and allowing the residue to drain). If the oil is black and has a burning smell, it is better to replace it, although in hermetic compressors this is difficult to do without opening the housing. Most often, technicians simply put up with the fact that the compressor will be a little oily, compensating for this by installing a high-quality oil separator at the outlet. Is it necessary to change the oil in a hermetic compressor? oil separator on the way out.

Is it necessary to change the oil in a hermetic compressor?

B In classic hermetic compressors from refrigerators, changing the oil without opening the housing (cutting and subsequent welding) is impossible. Attempts to freeze or shake out old oil rarely give 100% results. If the compressor runs smoothly, leave the oil as is, but install an oil separator filter at the air outlet. If there is a suspicion of water hammer or severe wear, it is easier to find another compressor than to open this one.

Modernization and installation of automation

The most important part of the project is the implementation of a control system. In the original refrigerator, the compressor was controlled by a thermostat, but now we need it to respond to pressure. For this purpose it is installed pressostat. The connection diagram is simple: phase and zero go to the relay input, and from the output to the compressor start relay. The pressure switch opens the circuit when the upper limit is reached (for example, 6 atmospheres) and closes when it drops to the lower limit (4 atmospheres).

A non-return valve is a mandatory element. It is installed between the compressor and the receiver. Its task is to prevent compressed air from the receiver from escaping back into the compressor after it stops. Without this valve, it will be extremely difficult for the motor to restart, since it will have to overcome the pressure in the entire system from scratch, which will lead to overload and burning of the windings.

It is also necessary to provide for condensate drainage. During the process of air compression, water is formed from atmospheric moisture, which accumulates at the lowest point of the receiver. At the bottom of the receiver (fire extinguisher) you need to weld or screw in a fitting with a ball valve. By periodically opening this tap, you will drain the accumulated liquid, preventing corrosion of the tank from the inside.

• 🔧 Installation: Fix the pressure switch on the frame in an accessible place for adjustment.
• 📉 Setting: Adjust the pressure differential (the difference between switching on and switching off).
• 🛡️ Protection: Install a safety valve that will bleed air if the pressure switch jams.
• 🔌 Electrical: Make all connections through terminal blocks, twists are unacceptable.

Assembling the system: connecting the nodes into a single mechanism

When all components are prepared, it is time for assembly. It is best to place the compressor and receiver on a common frame. To do this, you can use a wooden board, a sheet of plywood, or weld a simple metal frame from a corner. The main requirement is stability and the presence of vibration supports. Compressors from refrigerators vibrate during operation, and if they are tightly screwed to the frame, the vibration will be transmitted to the floor and can cause resonance.

The connections are made using copper tubes or special high-pressure hoses. It is advisable to install a small section of air cooling tube between the compressor and the check valve, since at the outlet of the piston group the temperature can reach 100-120 degrees. After the check valve, air enters the receiver.

A critically important point: the compressor inlet (suction tube) must be protected by an air filter. In the factory version there is a small “jar”, but for work in the workshop it is better to install a car air filter or at least tightly fill the inlet pipe synthetic padding so that dust from the air does not get inside the cylinders and cause abrasive wear.

The final stage of assembly is connecting the outlet fitting. From the receiver, air goes to the reducer (if you need to reduce the pressure for the tool) and then to the hose. Don't forget to install a pressure gauge at the outlet of the receiver to visually monitor the pressure in the system.

First start-up, testing and safety precautions

Before connecting to the 220V network, carefully check the entire electrical circuit again. Make sure the ground connection is secure. The first launch is best done away from people and under constant supervision. Turn on the compressor and note the time it takes for it to pump the receiver to operating pressure. Assess the heating of the case - it should not be critical (more than 90 degrees).

Be sure to conduct a leak test. Pump the system to maximum, unplug and leave for several hours. If the pressure drops, look for leaks using soapy water - bubbles will indicate problem areas. Most often, threaded connections or poorly welded seams on the receiver are etched.

During operation, remember that receiver is a pressure vessel. Although homemade systems usually operate at 6-8 atmospheres (which is safe for fire extinguishers rated at 15 atmospheres), safety precautions cannot be neglected. Regularly check the condition of the hoses and the integrity of the electrical insulation.

Can this compressor be used for airbrushing?

Yes, but with reservations. Refrigerator compressors produce a pulsating air flow. For airbrushing, which requires a stable thin torch, you need a high-quality moisture-oil separator and, preferably, an additional small-volume receiver directly in front of the spray gun. It is also important that the compressor does not overheat during prolonged operation.

What kind of oil should you pour if the compressor starts knocking?

Hermetically sealed compressors are usually filled with special refrigeration oil (mineral or polyester, depending on the type of freon with which it worked). You cannot pour regular motor oil - it can foam or coke when it comes into contact with residual refrigerant and high temperatures. It is better to use original oil for refrigeration compressors.

Why does the compressor hum but does not pump?

Most likely, the plate valves inside the compressor head are broken or the connecting rod is cracked. In sealed housings, repairs are extremely difficult and require cutting the housing, which disrupts the geometry and balancing. It is easier to replace the entire assembly.

Do I need to change the starting relay?

If the old relay is intact and corresponds to the motor power (indicated on the nameplate), there is no need to change it. However, when assembling a new system, they often install an external starting relay or leave the standard one, but provide it with good cooling, since operating modes may differ from refrigeration ones.

What maximum pressure can be achieved?

Single-stage compressors from household and industrial refrigerators are usually designed for an operating pressure of up to 10-12 atmospheres. Exceeding this value may cause the housing or gaskets to rupture. For higher pressures, two-stage compressors are needed.