Refilling a refrigerator compressor is not just “topping up” a substance, but a complex technical process that requires precise understanding chemical composition of the refrigerant and properties of lubricants. In the everyday mind there is often a myth that air or some kind of universal gas is pumped into the system, but reality is dictated by the laws of thermodynamics and chemistry. The compressor, being the heart of the refrigeration machine, works in conjunction with refrigerant and special compressor oilwhich circulate in a closed circuit, ensuring heat removal from the products.
The wrong choice of components for refilling can lead to immediate failure of expensive equipment or even create an emergency. Modern environmental standards have replaced old gases, replacing them with safer, but chemically active analogues. Therefore, before talking about the repair procedure, you need to clearly understand exactly what substances are inside your system and why they cannot be mixed arbitrarily. Mixing different types of oils (mineral and synthetic) in 99% of cases leads to the formation of a dense emulsion that clogs the capillary tube.
In this article we will analyze in detail what exactly modern and old ones are filled with refrigerators, what pressure standards exist and how to distinguish one type of refrigerant from another. You will learn about the physical properties of various freons and oils, and also understand why self-refilling without evacuation and weighing is often useless.
The principle of operation and the role of the working environment in the system
The refrigeration cycle is based on the ability of substances to absorb heat during evaporation and release it during condensation. The compressor compresses the refrigerant gas, increasing its temperature and pressure, after which the hot gas enters the condenser, where it cools and turns into a liquid. It is this liquid, passing through throttle element (capillary tube or expansion valve), that expands sharply and boils, removing heat from the internal chamber of the refrigerator.
In this process, oil performs the critical function of lubricating the rubbing parts of the compressor - pistons, shafts and bearings. Some of this oil is inevitably carried away by the gas flow into the system, so it must have a certain solubility in the freon used. If the oil is too viscous or, conversely, does not dissolve in the refrigerant, it will either settle in the heat exchangers, disrupting heat transfer, or return to the compressor, causing water hammer.
Modern systems are designed for a strictly defined type working pair: freon plus oil. Replacing one component without taking into account the properties of another is unacceptable. For example, switching from mineral oil to synthetic oil requires a complete flushing of the system, since the remnants of the old lubricant may react with the new oil or seal material.
Main types of refrigerants (freons)
The question “what is used for refilling” most often concerns the type of gas. Over the decades, the industry has evolved from toxic and flammable substances to compounds that are safe but potentially harmful to the ozone layer, and then to environmentally friendly but flammable alternatives. Today, you can find several main types in household refrigerators.
The most common in older models (produced before 2010-2012) is R12 (Difluorodichloromethane). This is an inert, non-flammable gas that worked well when paired with mineral oils. However, due to its destructive effects on the ozone layer, its production was prohibited by the Montreal Protocol. Finding it on sale now is difficult and expensive, and use requires a license.
R12 has been replaced by R134a (Tetrafluoroethane). This is the most common refrigerant in middle-aged refrigerators. It is non-flammable and safe, but requires the use of synthetic oils (polyester), since it does not dissolve in mineral oils. The pressure in the system with R134a is higher than that of its predecessor, which requires more durable pipes and compressors.
The newest generation of refrigerators (especially brand Liebherr, Bosch, LG) is switching to hydrocarbon mixtures, in particular R600a (Isobutane). It is a natural gas that does not destroy ozone and has excellent cooling performance. However, it has one drawback - high flammability. Refilling R600a requires special care, non-sparking tools and precise dosage (only 30-60 grams versus 100-150 grams for R134a).
Types of compressor oils and their compatibility
Oil in a refrigeration compressor is not just a lubricant, it is part of the working environment. It must have a high flash point, low pour point and chemical stability. The choice of oil directly depends on the type of freon used.
For old freons, group R12 and mixtures based on it (R502) were traditionally used mineral oils (MO). They are made from petroleum and have good lubricity, but do not dissolve well in modern freons. If you pour mineral oil into a system under R134a, it simply will not return from the evaporator to the compressor, leaving the mechanism without lubrication. Mineral oils With the advent of R134a and R404A, the industry switched to (POE - Polyol Ester). They are hygroscopic (absorb moisture from the air), so storing such oils requires sealing. POE oils dissolve well in new freons, ensuring the return of lubricant to the compressor crankcase. Brands like
With the introduction of R134a and R404A, the industry moved to synthetic polyester oils (POE - Polyol Ester). They are hygroscopic (absorb moisture from the air), so storing such oils requires sealing. POE oils dissolve well in new freons, ensuring the return of lubricant to the compressor crankcase. Brands like Emerson i Bitzer produce special series of oils for different types of compressors.
For R600a, special synthetic alkylbenzene-based (AB) or modified POE oils are often used, which have low viscosity and adapted for working with hydrocarbons. It is important to understand that even within the same type of synthetic oils there may be differences in viscosity, as specified in the compressor manufacturer's specifications.
Compatibility table of refrigerants and oils
To avoid fatal mistakes during repairs, it is necessary to strictly adhere to the compatibility of materials. Below is a reference table to help determine what the compressor is charged with depending on the brand of refrigerant.
| Refrigerant type | Chemical group | Type of oil required | Features |
|---|---|---|---|
| R12 | Chlorofluorocarbon (CFC) | Mineral (MO) | Prohibited, high inertness |
| R134a | Hydrofluorocarbon (HFC) | Polyester (POE) | Hygroscopic oil, non-flammable |
| R600a | Hydrocarbon (HC) | Synthetic (AB/POE) | Flammable, small filling (up to 60 g) |
| R404A | Hydrofluorocarbon (HFC) | Polyester (POE) | Used in freezers |
⚠️ Attention: Never try to replace R12 with R134a or R600a without complete re-soldering the system and replacing the compressor. These gases operate at different pressures and require different oils. An attempt to “just refill” with another gas will lead to compressor breakdown or fire.
Refilling technology and necessary tools
The process of refilling a refrigerator compressor is not just connecting a cylinder to a tube. This is the sequence of operations: evacuation, oil filling (if the compressor has been changed) and refrigerant dosage. To work, the master needs a set of manifold, a vacuum pump, electronic scales and a burner.
The first step is always removing air and moisture from the circuit. Moisture in a system with R134a freon turns into ice plugs or reacts with oil, forming acid that corrodes the motor windings. Evacuation should last at least 30-40 minutes until the residual vapor pressure reaches below 50 microns.
Refrigerant charging is carried out strictly by weight. The nameplate of the refrigerator (usually inside the chamber or on the back wall) indicates the exact weight of the charge, for example 65 g ± 5 g. Filling “by eye” or by pressure (especially for R600a) is unacceptable, since pressure depends on the ambient temperature and is not a direct indicator of the amount of substance.
☑️ Checklist for preparing for refilling
Pressure standards and diagnostics malfunctions
The pressure in the system is a variable value that depends on the boiling point of the refrigerant and the ambient temperature. For R134a at an ambient temperature of +25°C, the pressure in the system after turning off the compressor (static pressure) will be about 4-5 bar. For R600a it will be significantly lower - about 2-3 bar.
During the operation of the compressor, the pressure on the suction (low) and discharge (high) sides changes. If you connect the pressure gauge and see that the suction pressure is lower than normal, this may indicate a leak or blockage in the capillary tube. If the pressure is too high, there may be an excess of freon or the presence of air in the system.
The compressor current consumption, the temperature of the condenser housing and the evaporator temperature give a more complete picture. For example, if there is a shortage of freon, the current will be low, and the compressor will work continuously without shutting down.
Why can’t you refill a refrigerator “by eye”?
If freon is insufficient, the compressor will work without interruption, trying to gain temperature, which will lead to overheating and burnout of the windings. When overflowing, liquid freon can enter the compressor, causing water hammer and mechanical destruction of the valves. Accurate dosage is the key to durability.
Safety and environmental aspects
Working with refrigerants requires compliance with strict safety measures. Although R134a is considered safe, when exposed to an open flame, it decomposes to form phosgene, a chemical warfare agent. Therefore, any soldering work in the refrigerator system is carried out only after complete removal of freon and purging with nitrogen.
R600a (isobutane) is explosive. A gas concentration in the air of only 1.3% already creates an explosion spark. When repairing such refrigerators, it is prohibited to use sparking tools, and the room must be equipped with forced ventilation. Workshops working with R600a are required to have gas analyzers.
From an environmental point of view, the release of freons into the atmosphere is unacceptable. R12 depletes the ozone layer, and R134a and R404A are potent greenhouse gases whose global warming potential (GWP) is thousands of times higher than CO2. Professional disposal or (refrigeration) of refrigerant is a legal requirement in many countries.
⚠️ Attention: Specifications, filling standards and safety requirements may vary depending on the specific refrigerator model and year of manufacture. Always check the technical documentation (service manual) of the manufacturer, located on the product nameplate.
Frequently asked questions (FAQ)
Is it possible to fill a refrigerator with regular car freon?
No, absolutely not. Automotive air conditioners operate on R134a (less commonly R1234yf), but the requirements for gas purity, amount of oil and additives in automotive and refrigeration equipment differ. Using automobile gas can lead to clogged capillary or destruction of the compressor.
How to determine what kind of freon is in my refrigerator if the nameplate is not readable?
Focus on the year of manufacture. Until 2000-2005, R12 was most often used. From 2005 to 2015 - massively R134a. Modern models (after 2015), especially those labeled "Green" or "Eco", are most likely filled with R600a. Only a gas analysis or studying the compressor model will give an exact answer.
Why does the refrigerator freeze after refilling, but the compressor is hot?
This may indicate several problems: the presence of air in the system (air lock), an excess of refrigerant, or the use of inappropriate oil, which is poorly drained from the compressor. Also, the cause may be a malfunction of the compressor itself (interturn short circuit).
Is it necessary to change the oil when filling with freon?
When simply refueling due to a leak, the oil does not need to be changed, since the system is sealed and the oil remains inside. The oil is changed only when replacing the compressor or if moisture/dirt has entered the system and requires flushing.