When an old refrigerator finally breaks down, many people wonder about its disposal or recycling. The most valuable part of the unit is often called compressor, which in everyday life is mistakenly called simply the engine. It is this unit that is responsible for circulating the refrigerant through the system, creating the necessary pressure to cool the chambers. But what exactly is hidden under the metal casing of this unit?
Having understood the what's inside refrigerator engine, you can understand the reasons for its breakdowns or identify opportunities for creative use in other projects. Inside the sealed case lies a complex mechanical system that works in tandem with the electrical part. Understanding these processes is necessary not only for craftsmen, but also for technology enthusiasts who want to save on repairs or make a compressor for airbrushing.
In this article we will take a detailed look at the internal structure of the compressor, analyze the principle of operation of the piston group and find out why the housing is sealed tightly. You will learn about the role of oil, start relay and thermal protection, and also get answers to questions that arise when you first try to look “under the hood” of a refrigeration motor.
Design of a sealed casing and principle of operation
Visually, the compressor is a massive black or gray “tank” welded to the frame. This is not just a decorative element, but sealed casingthat isolates working units from the external environment. Inside this housing there is a vacuum or pressure, depending on the phase of operation, as well as the refrigerant and oil vapor. This design was not chosen by chance: it allows minimizing leakage of the working fluid and reducing the noise level, since the sound of the mechanism is damped by the walls and oil.
The engine inside the casing is suspended on special springs. This damper systemis critical for stable operation. When starting and stopping the motor, vibrations occur, which without shock absorption would quickly destroy the tubes or the housing itself. The springs take on these loads, ensuring smooth operation of the piston group. Access inside is only possible by carefully sawing the housing, which is an irreversible procedure.
⚠️ Attention: It is strictly forbidden to open the compressor if there is still pressure in the system or the refrigerant has not been removed. Older models may use ammonia or freon, which are dangerous if inhaled, as well as oil under pressure.
The operating principle is based on the conversion of electrical energy into mechanical energy. The rotor of the electric motor rotates, driving the crankshaft, which in turn pushes the pistons. These pistons compress the refrigerant gas, forcing it into the condenser. The whole process occurs in a closed circuit, where each element plays a strictly defined role.
Electrical part: stator, rotor and starting equipment
The basis of the power unit is electric motor, which is structurally reminiscent of washing machine motors, but has its own characteristics. It operates from a single-phase network and consists of a stator with windings and a rotor. The stator is rigidly fixed to the inner surface of the casing, and the rotor is placed on the crankshaft of the compressor. The windings are made of copper wire coated with insulation varnish, which must withstand high temperatures and exposure to oil.
A special circuit is used to start the motor. starting winding. Since single-phase current does not produce a rotating magnetic field on its own, a phase shift is necessary. This task is performed by the starting relay, which briefly connects the additional winding. As soon as the rotor reaches the required speed, the relay opens the starting winding circuit, and the engine continues to operate on the main one.
The most important element of electrical protection is thermal relay. It monitors the winding temperature and current consumption. If the compressor overheats or the rotor jams, the current increases sharply. The bimetallic strip inside the relay heats up, bends and opens the contacts, de-energizing the motor. This prevents the insulation from melting and a fire.
Mechanical part: piston group and crank mechanism
The heart of mechanics is crank mechanism. It converts the rotational motion of the rotor into the reciprocating motion of the piston. The compressor shaft has an eccentric (crank) onto which a connecting rod fits. When the shaft rotates, the connecting rod describes a circle, pushing the piston up and down inside the cylinder.
The piston itself is made of a special alloy that is wear-resistant. It moves inside the cylinder with minimal clearance. At the end of the piston there are valves (petal) ones, which work as a one-way gate for gas. When the piston is lowered, the suction valve opens and gas from the evaporator enters the cylinder. When the piston rises, this valve closes, the discharge valve opens, and the compressed gas goes into the condenser.
The manufacturing accuracy of these parts is extremely high. Any play or scuffing on the surface of the cylinder leads to a drop in performance or complete failure of the unit. It is the wear of the mechanical part that most often causes the refrigerator to “not freeze,” although the motor is humming.
☑️ Signs of mechanical wear
The role of oil and the lubrication system
It is located inside the compressor special refrigeration oil. It performs several critical functions at once: it lubricates rubbing parts, removes heat from the engine windings, and seals the gaps between the piston and cylinder. Unlike automobile oils, it should not freeze at low temperatures and should be chemically inert with respect to the refrigerant.
Lubrication is carried out by splashing. At the bottom end of the crankshaft there is often a scoop or screw thread that, when rotated, captures oil from the crankcase and feeds it up the shaft bore. From there it is sprayed onto the bearings, piston and cylinder walls. The oil level is strictly regulated: its excess can cause water hammer, and its lack can cause instant jamming.
⚠️ Attention: During long-term storage or transportation of the compressor in the wrong position, the oil can drain into the refrigerant circuit. This creates an “oil plug” that prevents the normal operation of the system.
Over time, the oil oxidizes and loses its properties, especially if there was moisture in the system or overheating occurred. In such cases, it can turn into a thick mass or acid, corroding the insulation of the windings. Changing the oil at home without vacuuming the system is practically impossible and ineffective.
Table: Main components of the compressor and their functions
To systematize knowledge about the internal structure, it is convenient to use a summary table. It will help you quickly navigate the purpose of various components hidden under the metal case.
| Component | Location | Main function | Material |
|---|---|---|---|
| Stator | Fixed on the casing wall | Creation of a magnetic field | Electrical steel, copper |
| Rotor | On the shaft engine | Rotation and torque transmission | Steel, copper/aluminium |
| Piston | Inside the cylinder | Refrigerant compression | Aluminum alloy |
| Spring suspension | Inside the casing | Vibration damping | Steel |
| Valve plate | At the end of the cylinder | Gas flow adjustment | Elastic steel |
Each of these components operates under extreme conditions. High pressure, temperature changes from -30°C to +100°C and constant friction require the highest reliability from materials. Malfunction of any element leads to an imbalance of the entire system.
Is it possible to repair a compressor with your own hands?
Many enthusiasts are wondering about repairing the “internals” of the engine. Theoretically, this is possible: replace the valve, re-weld the windings or replace the bearings. However, in practice repair of hermetic compressors in everyday conditions it is impractical. Specialized equipment is required for welding, evacuation and refrigerant charging.
In addition, after opening the casing, the tightness is broken, and it is almost impossible to assemble it back to factory quality. Even a microscopic refrigerant leak will cause a breakdown within a month or two. Therefore, most experts recommend not to go inside the motor, but to replace the entire unit when internal faults are identified.
Exceptions to the rules
Repair makes sense only if the starting relay, thermal relay or external capacitor is replaced. These elements are located outside the casing and are often the first to fail.
However, if your goal is not to restore the refrigerator, but to use the compressor for other needs (for example, as a pump for an airbrush or inflating tires), then opening and reworking is completely justified. In such cases, the tightness of the refrigerant circuit is no longer important, and you can use the motor as a regular air compressor.
Recycling and safety measures
An engine from an old refrigerator is an excellent donor for a home workshop. A power of 100-200 watts is enough to create a compressor capable of delivering pressure up to 6-10 atmospheres. Such devices are used by artists, car modelers and pneumatic tool makers.
When using an old compressor, you need to remember safety. First, be sure to remove any remaining coolant and oil if you plan to use it to inject air into breathing masks or for painting. Secondly, monitor the temperature: without freon circulation to cool the windings, the compressor may overheat faster, so it is recommended to install additional fans or thermal relays.
⚠️ Attention: Never connect the compressor to the network without a starting relay and a capacitor (if provided by the circuit). A direct connection will lead to the windings burning out or the plugs being knocked out in the very first seconds.
Proper operation and understanding of the internal structure can extend the life of the equipment or give it a second life in a new project. Knowing what's inside helps you make informed decisions about repair or disposal.
Why can't you open the compressor if the refrigerator is still running?
Opening it will break the seal of the system, The refrigerant will evaporate and oil will come out. Without them, the refrigerator will stop cooling, and restoration will require expensive equipment for evacuation and refilling.
What is the service life of the refrigerator engine?
The average service life of modern compressors is 10-15 years or about 80-100 thousand operating hours. However, the resource greatly depends on operating conditions, voltage stability and room temperature.
Is it possible to use a compressor from a refrigerator to inflate tires?
Yes, you can. Refrigerator compressors (especially piston ones) do an excellent job of creating high pressure. The main thing is to ensure heat removal and air filtration from oil residues, if any.
What to do if the compressor hums but does not start?
Most often the problem is a start relay or a jammed piston. Try replacing the relay (it's cheap). If it doesn’t help, you probably need professional “unclipping” with an electric current or replacement of the unit.