The question of what exactly is put into the refrigerator often arises among users who are faced with loss of cold or leakage of the working fluid. Many people mistakenly believe that ordinary air or water gets inside the system, but technically this is a complex chemical process that requires the use of specific substances. Refrigerant This is precisely the substance that circulates in a closed circuit, changing its state of aggregation and transferring heat from the chamber to the outside.
Modern refrigeration units are sealed systems into which a gas mixture or pure gas is pumped under pressure. Freon is the most common name for a whole group of such substances, although chemically these are different compounds with unique properties. Understanding what exactly is inside your equipment is critical for proper maintenance and safety.
In addition to the gas itself, the system always contains a special oil that lubricates the compressor and partially circulates along with the refrigerant. Incorrect selection of components during repairs can lead to failure of an expensive compressor or even an explosive situation. In this article, we will analyze in detail which substances are used in different generations of refrigerators and why they cannot be mixed arbitrarily.
Main working gas: types of refrigerants
The main component that is charged into the refrigerator is the refrigerant. It is a volatile substance with a low boiling point that allows heat to be removed from foods. Over the decades, the industry has used a variety of chemical formulas, and today a few basic types dominate the market. Freon R134a Became the standard for most household refrigerators manufactured after the mid-90s, replacing ozone-damaging predecessors.
In older models manufactured before 2000s, was often used R12, which had excellent cooling performance, but was prohibited by international protocols due to environmental harm. Modern trends dictate the use of even more environmentally friendly, but flammable gases, such as R600a (isobutane). This gas is highly efficient and can be filled in smaller quantities, but requires special care when carrying out repair work.
⚠️ Warning: Never try to determine the type of gas by smell or appearance alone. R600a is odorless but highly explosive when concentrated in air. Working with it requires non-sparking tools.
The choice of the correct type of refrigerant depends on the design of the evaporator and condenser, as well as the type of compressor used. Filling with the wrong gas will cause the refrigerator to simply stop freezing, and the pressure in the system may exceed critical values. Below is a table that helps identify the main types of gases by markings on the compressor.
| Marking | Chemical name | Danger | Years of use |
|---|---|---|---|
| R12 | Dichlorodifluoromethane | Toxic, harmful to the environment | until 1995-2000 |
| R134a | Tetrafluoroethane | Safe, does not burn | 1995 - present |
| R600a | Isobutane | Explosive | 2000 - present |
| R404a | Mixture of gases | Under pressure | Prom. refrigerators |
Lubricants for the compressor
The second critical component that is charged into the system along with gas or located in the compressor crankcase is oil. It is necessary to lubricate the rubbing parts of the piston group and remove heat from the engine. Unlike automobile engines, in refrigeration compressors the oil is partially dissolved in the refrigerant and circulates throughout the entire circuit, so its chemical composition must strictly correspond to the type of gas.
For old freons, the R12 series was traditionally used mineral oils. They have good lubricity, but do not mix well with modern refrigerants. With the transition to more environmentally friendly gases such as R134a and R600a, the industry has switched to the use synthetic oilsparticularly polyester (POE) and polyvinyl ether (PVE). These liquids are hygroscopic, that is, they actively absorb moisture from the air, which requires special care when refueling.
Mixing mineral and synthetic oil is strictly prohibited. If a system that had mineral oil is filled with synthetic oil (or vice versa), a dense sediment or “gel” may form, which will clog the capillary tube and cause the unit to fail. When replacing a compressor, you should always fill in the type of oil specified by the manufacturer, or completely flush the system with special nitrogen and a new type of oil.
The process of evacuation of the system
Before the refrigerant is charged into the refrigerator, the system must undergo a mandatory evacuation procedure. This is the stage in which all air and, more importantly, moisture are removed from the circuit. Residual air in the system creates an “air lock”, which increases the condensation pressure, causing the refrigerator to overload and freeze poorly.
Moisture is the main enemy of the refrigeration circuit. At low temperatures in the evaporator area, water freezes, forming an ice plug in the capillary tube, which blocks gas circulation. In addition, water reacts with oil and refrigerant, forming aggressive acids that destroy the motor windings and metal parts from the inside. Vacuum pump allows you to reduce the pressure in the system to a level at which water boils and evaporates even at room temperature, after which it is removed.
The vacuum process usually takes from 15 to 30 minutes, depending on the power of the pump and the volume of the system. Control is carried out using a vacuum gauge: the needle should go into the “green zone” (usually below -1 bar or -76 cm Hg) and remain stable there after the pump is turned off. If the pressure begins to increase, it means that there is a leak in the system, and gas filling is prohibited until the leak is eliminated.
☑️ Evacuation control
Accurate dosage and weight filling
One One of the most common mistakes during repairs is filling the refrigerator by eye. The amount of refrigerant that is charged into the system is regulated by the manufacturer to the nearest gram. This information is always indicated on a special sticker located on the compressor housing or on the back wall of the refrigerator. Exceeding the filling rate leads to a sharp increase in pressure, freezing of pipelines and possible rupture of the system.
An insufficient amount of gas is also dangerous: the compressor will work without stopping, trying to increase the temperature, but will not achieve the result. This leads to overheating of the windings and thermal breakdown of the insulation. For accurate dosage, electronic scales are used, on which a gas cylinder is installed. The master refills the system, monitoring the decrease in the weight of the cylinder in real time.
It is important to consider that for different types of refrigerants the density of the substance is different. For example, R600a is significantly lighter than air and lighter than R134a, so much less of it is required (often only 50-70 grams versus 100-140 grams for R134a). The use of measuring rulers (flasks) is possible only by experienced craftsmen who understand the dependence of pressure on ambient temperature, but the weight method remains the reference.
⚠️ Attention: The pressure in the system depends on the ambient temperature. You cannot judge the amount of gas only by the pressure gauge readings if you do not know the exact temperature in the room. Use scales for accurate filling.
Nitrogen as a diagnostic and cleaning tool
Although nitrogen does not remain in the refrigerator forever, it is an essential element of the maintenance process. Before soldering new connections or after opening the system, dry nitrogen under pressure is supplied to the circuit. This is done to displace air, preventing oxidation of the copper from the inside during soldering. Copper oxides, entering a thin capillary tube, can clog the system.
Nitrogen is also used for pressure testing - checking the system for leaks. After soldering, nitrogen is pumped into the system under high pressure (usually 15-20 atmospheres for R134a and R600a) and left for several hours or days. If the pressure gauge shows a drop in pressure, it means there is a microcrack or a poor-quality seam somewhere. Filling a system with refrigerant that has not undergone long-term pressure testing with nitrogen is a waste of money and gas.
The use of oxygen or compressed air from a compressor for these purposes is strictly prohibited. Oxygen mixed with oil and when heated can cause an explosion, and ordinary air always contains moisture, which will ruin the refrigerator. Only technically pure, dry nitrogen is suitable for preparing the circuit for filling with working gas.
Why can’t you use air from a compressor?
The air compressed by a conventional compressor contains oil vapor from the compressor itself and moisture from the atmosphere. When it enters the refrigerator circuit, the oil becomes coked at high temperatures, and the moisture freezes in the capillary, causing an ice jam.
Common mistakes and myths about refilling
There are many myths around the topic “what goes into the refrigerator” that can cost the owner of the equipment money. One of the most common is the opinion that if the refrigerator has stopped freezing, you just need to “add freon.” In a working, sealed system, gas is not consumed or disappears. If there is less gas, it means there is a leak. Simply adding gas without finding and sealing the leak is a temporary solution, which in a week or month will lead to a repeat breakdown.
Another mistake is the use of universal freon substitutes sold in aerosol cans. Often these are mixtures of gases with unpredictable properties, which may contain flammable components in concentrations dangerous for a household compressor, or chemical additives that destroy seals. Original refrigerant in a pressurized cylinder is the only safe solution.
There is also a myth that the color gas matters. In fact, most refrigerants are colorless. They are painted specifically for ease of leak detection (for example, R12 was often made bluish, but not always). You cannot rely on color to determine a substance. Always look at the cylinder markings and the refrigerator label.
FAQ: Frequently asked questions
Is it possible to fill a refrigerator with freon yourself without a scale?
Theoretically, experienced craftsmen can navigate by the pressure and current consumption of the compressor, but for a beginner it is almost impossible to do this correctly. The risk of damaging the compressor or creating an explosive mixture (with R600a) is too great. Without scales, it is impossible to maintain the exact grams necessary for effective work.
What is the difference between refilling R134a and R600a?
The main differences are in volume and safety. R600a (isobutane) is charged in smaller quantities (up to 60 grams), is lighter than air and is flammable, requiring explosion-proof tools. R134a is refilled in large volumes, it does not burn, but requires synthetic oil and careful vacuuming due to its hygroscopicity.
How often does freon need to be changed or refilled?
In a normally operating refrigerator, freon never needs to be changed or refilled. The system is sealed and designed for its entire service life (10-20 years). If refueling is required, it means that a breakdown (leak) has occurred that needs to be repaired.
Is it dangerous to breathe freon vapors when refueling?
Yes, it is dangerous. Although modern freons (R134a, R600a) are considered low-toxic, in high concentrations they displace oxygen, causing suffocation. In addition, upon contact with an open flame, freons can decompose to form phosgene, a chemical warfare agent. You only need to work in a ventilated area.