The compressor is the heart of any refrigeration unit, circulating the refrigerant in a closed circuit. The internal mechanisms of this unit are subject to enormous mechanical stress and heat during operation. It is oil in the refrigerator compressor that performs the critical function of lubricating rubbing surfaces, preventing rapid wear of the piston group and bearings.
However, the role of the lubricant is not limited to reducing friction. In the sealed systems of modern units, it also serves as a coolant that removes excess heat from the windings of the electric motor and the compressed gas. Without high-quality lubrication, the temperature inside the compressor housing would reach critical values in a matter of minutes, which would lead to jamming of the shaft.
Many owners of household appliances do not think about the condition of the lubricant until the refrigerator stops freezing or begins to make strange sounds. Understanding the operating principles of the oil system helps to avoid costly repairs or complete replacement of the unit. In this article we will analyze in detail the types of oils, their properties and maintenance nuances.
The main functions and operating principle of the lubrication system
The principle of operation of the compressor is based on the reciprocating movement of the piston, which compresses the gaseous refrigerant. At this moment, intense friction of metal on metal occurs. Engine oillocated in the crankcase is sprayed or supplied under pressure to the rubbing parts, creating a protective film. This film minimizes contact between metal surfaces, significantly extending the life of the device.
In addition, the lubricant acts as a sealant. It fills the microscopic gaps between the piston rings and the cylinder walls, preventing compressed gas from leaking back into the suction chamber. This directly affects refrigerator performance the ability to maintain the set temperature in the chambers.
The third most important function is the removal of wear products. The circulating liquid washes away metal shavings and carbon deposits, holding them in suspension or precipitating them in special filter-driers. If you ignore the need for replacement or topping up, abrasive particles will begin to destroy the mechanism from the inside.
⚠️ Attention: An attempt to start the compressor without oil or with a critically low oil level will lead to instant jamming of the piston and burning of the electric motor windings. As a rule, such a unit cannot be restored.
It is important to understand that the lubrication system in household refrigerators most often splashes. When the shaft rotates, an eccentric mechanism or a special blade captures oil from the lower part of the housing and scatters it onto the cylinder walls and connecting rod-piston group. The effectiveness of this process depends on the viscosity and level of the liquid.
Types of compressor oils and their features
In the refrigeration equipment industry, oils have historically been divided into two main groups: mineral and synthetic. The choice of specific type depends on the refrigerant used and the design of the compressor. Mineral oils obtained by deep purification of oil have traditionally been used with group refrigerants CFC and HCFC (for example, R12, R22).
With the transition of industry to environmentally friendly refrigerants such as R134a i R600a, oils with other chemical properties were required. Synthetic oils, in particular polyester (POE) and polyvinylbenzene (PVB), have excellent solubility in new freons and high thermal stability. However, they are hygroscopic, that is, they actively absorb moisture from the air.
Mixing different types of oils is strictly prohibited. A chemical reaction between the mineral and synthetic base can cause sediment to form, which will clog the capillary tube and filter drier. This will cause an increase in pressure in the system and failure of the compressor.
Is it possible to mix oils of different brands?
Mixing oils from different manufacturers, even of the same chemical base, is not recommended. Additives and additives from different brands can conflict, losing their lubricating and anti-corrosion properties. Always use the product specified in the technical documentation or its complete analogue.
When choosing an oil to replace, you must pay attention to the viscosity. A liquid that is too thick will not have time to rise through the oil line to the upper lubrication points, and a liquid that is too thin will not create the necessary protective film under high loads. The viscosity is selected strictly in accordance with the compressor model.
Signs of the need to replace or add oil
The need for intervention in the oil system can be determined by a number of indirect signs. First of all, the owner should be alert to the changed nature of the unit’s operation. If the refrigerator begins to operate with increased noise, hum or vibration, this may indicate “oil starvation” of the rubbing parts.
The second sign is overheating of the compressor. If, when touched with your hand (being careful), the motor body is hot to the point where it is impossible to hold your hand for more than 2-3 seconds, this indicates a violation of the heat dissipation. Often the cause is the loss of lubricant properties or its leakage through leaky seals.
- 🔊 The appearance of a metallic knock or grinding sound when starting and operating the motor.
- 🔥 Critical heating of the compressor housing above 90-100 degrees Celsius.
- 📉 Reduced refrigerator performance with a working thermostat.
- 💧 Presence of oily smudges around the compressor rod or on the tubes.
It is also worth paying attention to the color of the oil if it is possible to visually control it (for example, during repairs). A blackened liquid with a burning smell indicates thermal decomposition and the presence of insulation combustion products. Such oil must be urgently removed from the system.
Instructions for changing the oil in the compressor yourself
The oil change procedure requires a certain set of tools and skills in working with refrigeration equipment. Before starting work, it is necessary to turn off the power to the refrigerator and provide access to the compressor. It is usually located at the lower rear of the unit.
The first step is to dismantle the compressor or, in some cases, disconnect the suction and discharge tubes. To completely remove the old liquid, it is recommended to turn the compressor over and let it stand so that all residues drain. Then the internal cavity is washed with a special solvent or nitrogen.
⚠️ Attention: When working with the compressor, it is strictly forbidden to use open fire. Refrigerant and oil vapors mixed with air can be explosive. Carry out all work in a well-ventilated area.
Filling of new oil is carried out through the process pipe or through the hole after removing the valve group. It is important to fill in exactly as much oil as indicated in the specification (usually from 150 to 300 ml, but the exact volume varies from person to person). Overfilling is just as dangerous as underfilling, since a liquid plug can destroy the valves.
☑️ Checklist for preparing for an oil change
After pouring, it is necessary to carefully seal the system. To do this, the tubes are sealed and the circuit is evacuated for 15-20 minutes. This will remove any remaining moisture and air that may have gotten inside during replacement. Only after evacuation is the system charged with refrigerant.
Compatibility table of oils and refrigerants
The correct selection of lubricant is impossible without taking into account the type of refrigerant used. Below is a table to help determine the required oil base for different types of freons. The use of incompatible components will lead to rapid equipment breakdown.
| Refrigerant type | Recommended oil | Base | Note |
|---|---|---|---|
| R12, R22, R502 | Mineral Oil (MO) | Mineral | Standard for older systems |
| R134a | Polyol Ester (POE) | Synthetic | Hygroscopic, keep closed |
| R600a (Isobutane) | Mineral / Alkylbenzene | Mineral/AB | Often used in everyday life |
| R404A, R407C | Polyol Ester (POE) | Synthetic | For industrial refrigeration |
| R410A | Polyol Ester (POE) | Synthetic | High operating pressure |
When replacing the entire compressor, the new unit may already be filled with transport oil or preservation fluid. In some cases, the manufacturer recommends draining it and refilling it with a working one, in others it is working. Always check the instructions on the label new compressor.
Frequent errors when servicing the compressor
One of the most common mistakes is an attempt to add oil into a working system through a puncture of the tube without evacuation. This leads to the entry of moisture and air, which causes oxidation of the oil and the formation of acids that corrode the engine windings from the inside.
Another mistake is the use of automotive motor oils. They contain additives that, at high temperatures inside the refrigeration compressor, can precipitate or coke. This is guaranteed to disable the equipment in the shortest possible time.
Some technicians neglect to replace the filter drier when changing the oil. An old filter, saturated with moisture and decay products, will quickly contaminate a new portion of lubricant. Saving on this part often leads to repeated repairs.
⚠️ Attention: The characteristics of oils and the requirements of equipment manufacturers may change. Before carrying out work, be sure to check the current specifications in the official service manual of your refrigerator model.
It is also important not to exceed the soldering temperature of the tubes when dismantling the compressor. Overheating can damage the internal insulation of the windings, even if the oil itself has been changed correctly. Work should be carried out quickly and using heat-dissipating clothespins.
Questions and answers (FAQ)
How often should you change the oil in a refrigerator compressor?
In domestic refrigerators, the oil is designed for the entire service life of the unit and is not subject to scheduled replacement. It is changed only in case of repair, depressurization of the system or moisture ingress. In industrial installations, the regulation may be 1-2 years.
Is it possible to use gear oil instead of compressor oil?
No, it is not possible. Transmission oils have a different additive package and viscosity; they are not designed to work in a refrigerant environment and at freon boiling temperatures. This will lead to rapid wear of the compressor.
What to do if there is more oil in the system than needed?
Excess oil sharply reduces the efficiency of heat transfer in the condenser and evaporator, since oil occupies useful volume. It is necessary to pump out the excess amount through the service port or vacuum pump so that the level corresponds to the norm.
Why should synthetic oil not be left open?
Synthetic oils (POE) are highly hygroscopic. Outdoors, they absorb moisture in minutes. Water in the cold system forms ice plugs in the capillary and acids that destroy the metal.
Is it possible to determine the type of oil by color?
It is impossible to accurately determine the chemical composition by color. Fresh mineral oil can be clear or light yellow, while synthetic oil varies. The type of oil is indicated on the label of the canister and in the documentation for the compressor.