The situation when the refrigerator stops freezing and the compressor hums, but does not start, often confronts the owner with a difficult choice: call a technician or try to figure it out on your own. One of the common reasons for the failure of a motor-compressor is a violation of the circulation of the refrigerant or loss of the lubricating properties of the working fluid. Oil change in a refrigerator compressor is a complex technical procedure that requires not only accurate knowledge of volumes, but also an understanding of the chemical properties of the materials used.
Many households Craftsmen mistakenly believe that it is enough to drain the old fluid and fill in new fluid “by eye”. However compressors modern refrigeration units, whether Atlant, Indesit or Boschare high-precision sealed units, where every drop of liquid matters. An incorrect level of lubrication can lead to jamming of the piston group or, conversely, to water hammer, which will instantly disable the equipment.
In this article we will analyze in detail how much oil is needed for different types of compressors, how to correctly calculate the volume and why it is critical to use only specified brands. Accuracy in this matter is the key to the long service of your refrigerator after repair.
⚠️ Attention: All work with the refrigeration circuit requires specialized equipment (vacuum pump, pressure gauge station) and skills. Failure to comply with the technology can lead to depressurization of the system and loss of refrigerant.
The role of lubricating fluid in the operation of the compressor
The main function of the oil in the refrigeration circuit is to provide lubrication of the rubbing parts of the compressor, such as the crankshaft, bearings and piston group. Without high-quality lubrication metal parts begin to overheat and quickly wear out, which leads to a wedge of the motor. However, unlike car engines, the oil in the refrigerator performs another critical role - it circulates along with the refrigerant throughout the system.
This means that the lubricant must have chemical properties: it should not freeze at low temperatures in the evaporator and should not foam when passing through the capillary tube. Viscosity and chemical stability are the key parameters that engineers select for a specific type of freon. If you fill in the wrong oil, it can react with the refrigerant or form acidic compounds that destroy the system from the inside.
In addition, the oil helps remove heat from the hot parts of the compressor motor. In sealed units, where there is no direct access to air, it is the circulating liquid and refrigerant that take away excess heat. Violation of the oil level leads to overheating of the windings and melting of the insulation, which often ends in a short circuit.
How much oil is needed: calculation of volume and norm
The question of exactly how much oil to pour into a refrigerator compressor does not have a universal answer “for everyone”. The volume depends on the power of the unit, the type of compressor (piston, inverter) and the recommendations of the specific manufacturer. Standard household compressors, which are most often found in models LG, Samsung or Stinol, usually contain from 180 to 350 grams of lubricating fluid.
The exact volume can be determined in several ways. The most reliable way is to find technical documentation for a specific compressor model, where the charging parameters are indicated. If the documentation is lost, which often happens, experienced craftsmen use the weighing method. The old oil is completely drained (by heating the pipes and turning the unit over), weighed, and a new volume is poured with the addition of 10-15 grams for waste and residues in the system.
Below is a table of approximate oil volumes for popular types of household compressors:
| Compressor type | Power (hp) | Approximate oil volume (g) | Application |
|---|---|---|---|
| Low temperature (LBP) | 1/6 - 1/4 | 200 - 280 | Single chamber refrigerators |
| Medium temperature (MBP) | 1/3 - 1/2 | 300 - 400 | Two-chamber models, freezers |
| High-performance | 1/2 and above | 400 - 600 | Side-by-Side refrigerators, No Frost |
| Linear / Inverter | Varies | 250 - 350 | Modern energy-efficient models |
It is important to understand that too much oil is just as dangerous as its lack. Excess lubricant leads to the fact that it begins to be actively carried away into the system, clogging the capillary tube and reducing the efficiency of heat transfer in the condenser. This phenomenon is called "oil breakdown", and it sharply reduces the cooling capacity.
Selecting the type of oil: mineral or synthetic
Choosing the right type of oil is no less important than calculating the volume. There are three main types of oils used in refrigeration technology: mineral, alkylbenzene (AB) and polyester (POE). The choice depends solely on the type of refrigerant used. Mineral oils have traditionally been used with freons of the R12 and R22 groups, which are now practically phased out, but are still found in old refrigerators ZIL or Mir.
Modern refrigerators running on environmentally friendly freons R134a, R600a or R407C require the use of synthetic oils. Polyester oils (POE) are highly hygroscopic, that is, they actively absorb moisture from the air. Hygroscopicity is a property that dictates special operating rules: an open canister of oil should not be exposed to air for more than 15-20 minutes.
Mixing different types of oils is strictly prohibited. Mineral oil does not mix with synthetic oil, forming a heterogeneous mass that can precipitate and clog the system. If you change the type of freon (for example, when retrofitting from R12 to R134a), you must completely remove the old oil and flush the system, since the remaining mineral water is incompatible with the new synthetic filler.
⚠️ Attention: When working with polyester oils (POE), avoid contact with skin and moisture. Absorbed moisture can cause acid to form inside the circuit, which will destroy the motor windings.
Replacement technology: step-by-step instructions
The process of changing oil in a refrigerator compressor requires care and adherence to a sequence of actions. First you need to dismantle the old compressor or, if the design allows, gain access to its pipes. To completely remove old oil, the compressor is often heated with a hair dryer in the bottom area to reduce the viscosity of the liquid, and then turned over, draining the contents into a measuring container.
After draining, it is recommended to purge the system with nitrogen to remove any remaining old lubricant and possible dirt. Then the drained volume is weighed. Filling new oil is produced through the process pipe using a syringe or funnel, strictly observing the weight balance. It is important to prevent air from getting inside the compressor housing during the filling process.
Follow this algorithm of actions:
- ⚙️ Disconnect the suction and discharge pipes, let the oil drain into the prepared container.
- 🔥 Warm up the compressor housing with a hairdryer (not open fire!) to 50-60 degrees for better drainage.
- ⚖️ Weigh the drained oil and add 10-15% to this volume for a new refill.
- 💉 Pour new oil through a funnel or a syringe into the technological hole, avoiding contact with air.
After refueling, you must immediately plug the pipes or solder the compressor into the circuit to minimize contact of synthetic oil with the atmosphere. The following is the procedure for vacuuming the system, which is mandatory to remove moisture and air before starting.
☑️ Preparation for changing the oil
Consequences of incorrect refueling
Ignoring oil filling standards leads to serious consequences. Lack of lubrication causes dry friction, rapid heating and shaft jamming. In this state, the compressor hums, consumes increased current, and the thermal protection relay is triggered. If the process is not stopped in time, the motor windings burn out, and repairs become economically unfeasible.
Excess oil, as mentioned earlier, leads to a decrease in cooling efficiency. Oil entering the evaporator creates a film on the walls, which acts as a heat insulator. The refrigerator begins to work endlessly, trying to gain temperature, which increases energy consumption and wear on the compressor. In addition, an oil plug in the capillary tube can completely stop the circulation of freon.
What will happen if you mix mineral and synthetic oil?
The mixture will lose its lubricating properties, a solid precipitate (slag) may form, which will clog the filter drier and the capillary tube. This will lead to the need to completely flush the circuit or replace the compressor.
⚠️ Attention: The characteristics of refrigeration equipment may vary depending on the modification. Always check the data with the manufacturer's official technical documentation before starting work.
Common mistakes during self-repair
Home craftsmen often make mistakes that nullify all efforts. One of the most common is the use of motor or transmission oil. These liquids are not designed to work in tandem with freon and behave unpredictably at low temperatures. They can freeze in the evaporator or foam, causing water hammer.
Another mistake is neglecting evacuation. After opening the circuit and filling the oil, air and moisture remain in the system. Moisture upon contact with freon and oil forms an acid that corrodes the metal and insulation. Without a high-quality vacuum pump (not a car one!) it is impossible to perform this work efficiently.
Replacement of the filter drier is also often ignored. When changing the oil or compressor, the old filter is already saturated with moisture and will not be able to protect the system. Its replacement is mandatory for any opening of the refrigeration circuit.
Is it possible to add oil to a running compressor without disassembling?
Theoretically, there are methods of refueling through a puncture, but they are highly not recommended for domestic use. Without vacuuming and precise weight control, there is a high risk of introducing moisture or overdoing the volume. Professionals always prefer complete draining and filling by weight.
How often should you change the oil in the refrigerator?
In sealed household refrigerators, the oil is designed for the entire service life of the unit (10-15 years). It does not require scheduled replacement. Replacement is made only if the compressor is repaired, moisture gets into the system or when switching to another type of refrigerant.
What is the difference between oil for R134a and R600a?
Both types of freons require synthetic oils (usually polyester POE or polyvinyl ester PVE). However, viscosity and additives may vary. Using oil that is not certified for a specific freon can lead to stratification of the mixture and loss of lubricating properties.
Why does the oil in the compressor turn black?
Blackening of the oil indicates overheating of the compressor, moisture ingress (acid formation) or prolonged operation with low-quality freon. Such oil loses its properties and requires mandatory replacement along with flushing the system.
Where to buy special refrigeration oil?
Specialized oils (Emkarate, Bitzer, Mobil) are sold in refrigeration equipment and spare parts stores. As a rule, they are not available in regular auto stores. Buy oil only in sealed containers from trusted suppliers.