The second wind of an old refrigerator: 5 best ways to use the motor

Many owners of summer cottages or home craftsmen have an old, no longer working refrigerator in their garage. It's a shame to throw it away, but it takes up space. However, inside this bulky box hides a real technical “gold bar” - compressor. It is this unit, created for pumping refrigerant, that has amazing versatility and can become the basis for dozens of useful homemade products.

Before you start disassembling the equipment, it is important to understand what kind of device you are dealing with. Modern models often use inverter systems, which are more difficult to adapt for simple tasks, while classic piston engines from the times of the USSR or the early 2000s are the standard of reliability. Engine from refrigerator capable of creating pressure up to 6-10 atmospheres and vacuum up to 0.5 atmospheres, which opens up wide horizons for creativity.

In this article we will look in detail at how to safely remove the unit, prepare it for work and turn it into a functional tool. We will consider not only obvious options like tire inflation, but also more specific applications that require minimal modifications. The main thing is to follow safety precautions and clearly understand what result you want to get.

Preparation and safe removal of the compressor

The first step should always be a complete decompression system. Even if the refrigerator has not been working for years, residual pressure of freon or oil may remain in the pipes. Never cut through copper tubing with wire cutters or a hacksaw until you are sure that the system is sealed and empty. It is best to carefully file the tube away from the body and allow the remaining gas to escape.

After this, you need to disconnect the entire unit from the frame of the refrigerator. It is usually mounted on four spring suspensions that dampen vibration.

⚠️ Attention: The springs are under tension. When cutting the fasteners, the compressor may jerk sharply, so hold it with your hand or loosen the tension first.

It is also important to preserve the starting relay and thermal relay if they are in a separate casing, since without them starting the engine is impossible.

Pay special attention to the condition of the electrical part. The wires should not be chafed and the contacts should not be oxidized. If you plan to use the motor in a stationary workshop, it makes sense to immediately replace the old power cord with a new one with high-quality insulation. This will reduce the risk of short circuit and electric shock in the future.

During long-term storage or improper transportation (if the refrigerator was lying on its side), oil could leak into the outlet pipes. Before starting a new device for the first time, it is better to blow out the system with compressed air to prevent water hammer.

Connection diagram and starting the engine

Starting refrigeration compressor is different from starting a conventional electric motor. It requires a starting winding, which is turned on only at the time of start, and a working winding, which powers the motor constantly. The starting relay, which is usually mounted on the side or bottom of the case, is responsible for this process. If the original relay is working properly, the task is greatly simplified.

The connection diagram, as a rule, looks like this: the phase goes to one terminal, the zero to the other, and the starting winding is switched through the relay. On older models, the relay can be a posistor or inductive. Posistor heats up with current and opens the starting winding circuit, and the induction relay reacts to an increase in current in the working winding.

Connection diagram (simplified):
L (Phase) --> Terminal 1 (Working winding)
N (Zero) --> Terminal 2 (Start winding) --> Starting relay --> Terminal 3 (Common)

If the original relay is burned out or lost, it can be replaced with a universal one, selected for power engine. The compressor housing is often stamped with markings, for example QD35 or SC15CL, according to which it is easy to find an analogue in the correspondence table.

⚠️ Attention: Do not try to start the compressor directly, bypassing the relay. This will lead to overheating of the starting winding and combustion of the engine in a matter of seconds.

What to do if the compressor hums, but does not start?

If you hear a hum, but the shaft does not spin, the piston may be stuck or the starting relay has failed. Try gently tapping the housing with a wooden handle (sometimes it helps to wedge it) or replace the relay. If it doesn’t help, the engine is most likely mechanically faulty.

Idea No. 1: Compressor for airbrushing and painting

One ​​of the most popular applications is creating a quiet and efficient compressor for airbrushing. Unlike noisy industrial counterparts, the refrigerator operates almost silently, which is critical for working at home. The pressure it produces (usually 2-4 atmospheres in static conditions) is quite enough for working with water-based paints and varnishes.

To implement this idea, you will need a receiver. Old fire extinguishers, gas cylinders, or even thick plastic canisters are excellent as containers for storing air (although metal is more reliable). The receiver is necessary in order to smooth out the pulsations of the air flow and give the engine the opportunity to rest, turning on only when the pressure drops.

• 🎨 Flow uniformity: The receiver provides stable pressure, which eliminates “spitting” of paint.
• 🔇 Silence: The noise level of such a compressor does not exceed 40 dB, which comparable to a quiet conversation.
• 💧 Moisture separation: When air is compressed, condensation is formed, so you definitely need a filter-moisture separator in front of the spray gun.

The assembled system is connected through a gearbox, which allows you to fine-tune the operating pressure. For airbrushing, 1.5-2 atmospheres is usually sufficient. The key point here is to install a check valve between the compressor and the receiver so that air does not flow back into the engine when it stops.

Idea No. 2: Vacuumator for packaging and experiments

Few people know that a compressor from a refrigerator is also excellent vacuum pump. If you switch the hose from the discharge pipe to the suction pipe, the device will begin to pump out air from the sealed container. This property is widely used for vacuum packaging of products, which significantly extends their shelf life.

In addition to the kitchen, such a vacuumizer is useful in the workshop. It can be used to remove air bubbles from epoxy resin before pouring, impregnate wood, or assemble simple vacuum presses for gluing furniture. The pumping performance of household models is about 150-200 liters per minute, which is quite enough for volumes up to 50 liters.

For working with a vacuum, it is important to take into account the design features. Oil compressors can eject microscopic drops of oil along with the pumped air.

⚠️ Attention: When pumping wet products or liquids, be sure to use a trap (flask) between the container and the compressor, otherwise water will get into the oil and damage the mechanism.

Upgrading to a vacuum often requires replacing the oil with a more viscous one or installing an additional fine filter on the inlet pipe. This will prevent clogging of the internal channels with dust and small particles that can get from the packaged products.

Idea No. 3: Pneumatic tools and equipment cleaning

Although the performance of a household compressor is inferior to industrial models, it is quite enough to work with some types pneumatic tools. Drills, impact wrenches and sanders require a lot of air flow, so the refrigerator cannot cope with them. However, for blow guns, small pneumatic punches or control of pneumatic valves, its power is sufficient.

It is very useful to use such a unit for cleaning electronics and computers from dust. A jet of compressed air under a pressure of 3-4 atmospheres effectively blows dust out of radiators, keyboards and cases where a vacuum cleaner cannot reach. This is especially true for service centers and radio amateurs.

When using a compressor for a tool, it is important to monitor the body temperature. During prolonged operation without a break (more than 30-40 minutes), the motor may overheat, since its cooling system is passive (due to the housing and natural convection). Operation cycle It is better to build on the principle: 20 minutes of work, 10 minutes of rest.

Maintenance and modernization

In order for your creation to serve for a long time, you need to choose the right oil. The original uses a special refrigeration oil, which does not freeze at low temperatures and does not oxidize. For a compressor operating in a warm room, you can use conventional compressor oils, but their viscosity must comply with the recommendations of the motor manufacturer.

An oil change is rarely required, only if you notice that the unit has begun to get very hot or “spit” oil into the outlet pipe. To replace, you need to turn the compressor over, drain the old liquid through the lower hole (if there is one) or through one of the pipes, and fill in new liquid up to the mark on the dipstick or sight glass.

It is also worth thinking about sound insulation. Although the refrigerator operates quietly, the metallic clanging sound of the piston group can be annoying close up.

⚠️ Attention: Do not completely seal the ventilation holes of the casing. The engine needs an air flow for cooling, otherwise it will quickly fail.

It is better to use sound-absorbing materials with a porous structure that do not interfere with air circulation.

As an upgrade, you can install an automatic pressure switch (pressostat), which will automatically turn the motor on and off when the specified parameters are reached in the receiver. This will turn your homemade product into a full-fledged professional tool that does not require constant monitoring.

Conclusion and final recommendations

Using a motor from an old refrigerator is an excellent example of reasonable consumption and engineering creativity. Instead of sending metal to be melted down, you get a powerful and versatile tool for the workshop. Whether it’s painting a fence, vacuuming food, or simply blowing out a computer, this unit will get the job done.

The main rule when creating such homemade products is not to skimp on safety. Use high-quality hoses designed for high pressure, reliable clamps and working electrics. Pneumatics accumulates enormous energy, and rupture of the receiver or hose can lead to injury.

Experiment, improve your skills and give a second life to old equipment. Perhaps it is your version of the improvement that will become the basis for a new useful invention. Remember that the limits of application of the compressor are limited only by your imagination and the basic laws of physics.

Is it possible to use a compressor outside in winter?

You cannot use a regular refrigerator compressor in the cold. The oil will thicken and the engine will burn when you try to start it. In addition, the condensate inside the system will freeze and block the valves.

What is the maximum volume of the receiver that can be used?

Theoretically, the volume of the receiver is not limited, but for a household compressor from a refrigerator, a volume of 20 to 50 liters is considered optimal. A receiver that is too large (for example, 100+ liters) will take a very long time to fill to operating pressure, and the motor will run almost continuously, which will lead to overheating. If you need a large volume, it is better to use several compressors in parallel.

Do you need to change the oil when converting it into a compressor?

If the compressor is new or in good condition - no. Factory oil does its job perfectly. You should only change it if you suspect that there is moisture inside, or if you plan to use the unit in extreme temperature conditions that require specific lubricants.

Why does the compressor get very hot?

Heating up to 60-80 degrees for the compressor housing is the norm. It heats up due to gas compression and friction of the piston group. If the temperature exceeds 90-100 degrees and the hand cannot tolerate it, it means that the heat exchange is impaired (the casing is clogged), the valves are faulty, or the motor has been running for too long without a break.

Is it possible to pump an aquarium with this compressor?

It is absolutely not possible. The oil in the compressor crankcase is always present in the exhaust air in the form of a microscopic emulsion. Getting even the slightest amount of oil into the water will kill the fish. There are special oil-free membrane compressors for aquariums.

What pressure is considered the maximum for a household compressor?

The standard operating pressure is about 2-3 atmospheres. The maximum it can develop before stopping (cut-off pressure) is usually in the range of 6-10 atmospheres, depending on the model. Exceeding 10-12 atmospheres is dangerous: oil seals, gaskets or the body itself may not withstand it, which will lead to explosive destruction.