When household appliances break down or extraneous noise appears, owners often have a question about what exactly circulates inside the system and ensures a low temperature. Many people mistakenly believe that this is ordinary water or some kind of special coolant, similar to antifreeze in a car. In fact, the operating principle of a household refrigeration unit is based on the physical process of changing the state of a substance under the influence of pressure.
A gaseous or liquid substance constantly circulates in a sealed circuit, which, when evaporated, takes away heat, and when compressed, releases it. It is this cycle that keeps food fresh. Understanding what is poured into the refrigeratoris necessary not only for general development, but also for competent operation, as well as to understand the risks of mechanical damage to the tubes.
The main working fluid is refrigerantwhich in everyday life is most often called freon. This substance has the unique ability to boil at very low temperatures even at normal atmospheric pressure. It is under pressure in the system, which allows it to condense into liquid, after which, passing through the capillary tube, it expands sharply and boils, cooling the walls of the evaporator.
In addition to the refrigerant itself, the system contains technical oil, which lubricates the rubbing parts of the compressor. These two liquids never mix with food, as the circuit is completely sealed. However, when depressurizing, it is important to know what exactly you are dealing with so as not to harm your health or the environment.
Main working substance: refrigerant
The main component that provides cold is refrigerant. In technical documentation and among repairmen it is often called the working fluid. Historically, the most common name has become “freon,” although this is only a trademark of the DuPont company, which has become a household name for a whole group of chlorofluorocarbons. Modern household refrigerators use various types of these gases, each of which has its own chemical formulas and physical properties.
The principle of operation is based on a cyclic change in the state of aggregation. The compressor compresses the refrigerant gas, heating it. As the gas passes through the condenser (the black grill at the back), it cools and turns into a liquid. Next, the liquid enters a narrow capillary tube, where the pressure drops sharply and the substance boils, turning into steam and absorbing heat from the fridge compartment. This steam is again sucked in by the compressor, and the cycle repeats.
Modern requirements for environmental safety dictate the abandonment of old compounds containing chlorine, which destroy the ozone layer. Therefore, in new models you will more often find mixtures that are safe for the atmosphere. It is important to understand that Freon has no color and is generally odorless (except for some brands with an added odorant to detect leaks). This makes it invisible to humans during normal operation of the equipment.
The amount of refrigerant in the system is strictly regulated by the manufacturer. A lack of gas leads to the fact that the refrigerator stops freezing, and an excess can cause water hammer in the compressor and its breakdown. That is why independent refueling without special weighing equipment and a vacuum sealer is impossible and ineffective.
Types of freons in household refrigerators
Over the decades of development of the refrigeration industry, the chemical composition of working substances has changed. If in the old Soviet models, which still work for many grandmothers, R-12was used, then the modern industry has switched to safer analogues. R-12 (difluorodichloromethane) did an excellent job of cooling, but was recognized as hazardous to the environment due to the high potential for depleting the ozone layer, and its production was prohibited by the Montreal Protocol.
It was replaced by R-134a (tetrafluoroethane). This substance does not destroy the ozone layer, but has a high global warming potential. It is non-toxic and non-flammable, making it safe for household use. Most refrigerators produced between the late 90s and mid-2010s are filled with this gas. Its characteristics require the use of synthetic oil to lubricate the compressor.
The most modern and environmentally friendly solution at the moment is R-600a (isobutane). It is a hydrocarbon refrigerant that does not affect the ozone layer and has minimal global warming potential. It has excellent refrigeration properties and allows you to make appliances more energy efficient and quiet. However, it has a significant drawback - flammability. At concentrations in air from 1.3% to 8.5%, the mixture with air becomes explosive.
- 🧊 R-12: obsolete, toxic at high concentrations, destroys the ozone layer (used until the 2000s).
- ❄️ R-134a: safe for ozone, does not burn, but requires synthetic oil (main standard 2000-2015).
- 🔥 R-600a: environmentally friendly, efficient, but flammable (standard for most new models).
When repairing equipment, it is critical to know what type of gas was originally used. Replacing one type of refrigerant with another without completely re-soldering the system and changing the oil is prohibited, since they have different chemical compatibility and require different types of compressor oils.
Is it possible to mix different types of freon?
It is absolutely not possible. Mixing R-134a and R-600a will lead to changes in pressure in the system, unstable operation of the compressor and possible failure of the piston group. In addition, different freons require different types of oils (mineral, alkylbenzene, polyester), and mixing them creates an acid that corrodes the motor windings.
Compressor oil: a hidden component of the system
When talking about what is inside the refrigerator, we must not forget about the second important component - compressor oil. It is necessary to lubricate the moving parts of the compressor motor, which is the “heart” of the refrigerator. Without oil, the pistons would quickly wear out from friction, and the device would overheat and fail within a matter of minutes of operation.
Oil circulates through the system along with the refrigerant, but in very small quantities. The special design of the compressor and the presence of an oil separator minimize the entry of liquid into the circuit, but it is impossible to completely eliminate this process. Therefore, the oil must have the following properties: it should not freeze at low temperatures in the evaporator and should not enter into a chemical reaction with the refrigerant or tube materials (copper, aluminum, steel).
There is a direct relationship between the type of freon and the type of oil used. For the old freons of the group R-12 mineral oils were used. They mixed well with the refrigerant and returned to the compressor. For R-134a mineral oils are no longer suitable, since this gas does not dissolve the mineral base well. Synthetic oils based on polyesters (POE) are used here. They are hygroscopic (absorb moisture), so they cannot be stored in open containers.
⚠️ Attention: If a technician replaces a compressor when repairing a refrigerator, he must use oil that strictly matches the type of refrigerant. Filling with the wrong oil will lead to the formation of an acidic environment, clogging of the capillary tube with decomposition products and repeated breakdown of the compressor in a short time.
In modern gas systems R-600a special oils are also used, often with additives that improve their return to the compressor crankcase, since Isobutane does not carry oil well with it through the pipes. The amount of oil in the system is also strictly regulated: usually from 150 to 300 grams, depending on the power of the unit.
Comparative table of refrigerant characteristics
For a better understanding of the differences between the substances used, it is worth referring to the technical characteristics. This data helps technicians select the correct refueling equipment and diagnose problems. Below is a table comparing the main parameters of the most common refrigerants.
| Parameter | R-12 (Freon-12) | R-134a (Freon-134a) | R-600a (Isobutane) |
|---|---|---|---|
| Chemical formula | CCl2F2 | CH2FCF3 | C4H10 |
| Boiling point (1 atm) | -29.8 °C | -26.3 °C | -11.7 °C |
| Impact on the ozone layer | High (destroys) | None | Absent |
| Flammability | Does not burn | Does not burn | Flammable (explosive) |
| Type of compatible oil | Mineral | Synthetic (POE) | Mineral / Synthetic |
As can be seen from the table, R-600a has a higher boiling point at atmospheric pressure, which means that it operates at a lower system pressure than its predecessors. This reduces the stress on the tube walls and the compressor, reducing noise and vibration. However, its flammability requires manufacturers to use explosion-proof electrical equipment and seal all contacts.
Use R-134a requires a higher condensation pressure, which makes the system more demanding on cleanliness. Any moisture that gets into the circuit with this gas can turn into an ice plug in the capillary tube, stopping circulation completely. Therefore, when repairing such systems, a vacuum procedure is required.
Old R-12 had excellent dissolving ability, washing out contaminants from the system, but its environmental harm outweighed all the advantages. Today it is impossible to find a new refrigerator with this gas; they remain only in rare models.
☑️ Signs of a refrigerant leak
Danger and safety in case of leakage
The issue of safety in the event of a refrigerant leak worries many users. It’s worth noting right away: if depressurization occurs in your refrigerator, there is no need to panic. The amount of gas in a household appliance is negligible (usually from 30 to 150 grams), and it is not capable of causing poisoning or suffocation in a standard kitchen with a volume of several tens of cubic meters.
However, there are nuances. Freons are heavier than air and if they leak in a large volume (which is impossible in everyday life, but theoretically) they can displace oxygen. Moreover, upon contact with an open flame (gas stove, lighter), some types of freons can decompose to form phosgene a chemical warfare agent. Therefore, if you smell chemicals or see an oily stain under the refrigerator, you should ventilate the room and call a specialist.
Particular care should be taken with models on R-600a. Although the likelihood of an explosion in a domestic environment is extremely low (you need a concentration of gas in a closed cabinet and a spark), manufacturers do not recommend carrying out any repair work related to soldering tubes yourself. Craftsmen use special burners with spark extinguishing and work in ventilated areas.
⚠️ Attention: Never try to pierce refrigerator tubes or solder them yourself unless you are sure that the system is completely evacuated and does not contain gas residues. Residual pressure in combination with fire can lead to a bang or fire.
If you find that the refrigerator has stopped freezing and suspect a leak, first unplug the appliance. This will prevent the compressor from running “dry” (without oil cooling) and eliminate sparking of the relay, which is especially important for flammable refrigerants.
Refilling process and maintenance
Refueling a refrigerator is a complex technological process that cannot be done by eye. It requires specialized equipment: a vacuum pump, a pressure gauge station, electronic scales and a refrigerant cylinder. First, the system is opened, purged with nitrogen to remove moisture and combustion products (if there was soldering), and then vacuumed.
Evacuation is a critical stage. The moisture remaining in the tubes during operation will turn into ice and clog the capillary. In addition, moisture combined with oil and freon can create acid that will corrode the motor windings from the inside. The evacuation time depends on the pump power and the volume of the system, usually it is 15-30 minutes.
Gas dosage is carried out strictly by weight. The refrigerator label (usually inside the chamber or on the back) indicates the exact type of refrigerant and its mass in grams. The master connects the cylinder to the scales and releases the gas until the desired value is reached. Overfilling gas is just as dangerous as underfilling: excess pressure can rupture the evaporator tubes or damage the compressor valves.
After filling, the system is sealed and the refrigerator is left to operate for testing. The master controls the temperature of the condenser, the operation of the compressor and the absence of freezing. Only after a successful test the equipment is returned to the owner. Buying cylinders with freon on your own will not solve the problem, since without a vacuum sealer you will simply force air and moisture into the system, completely finishing off the unit.
Why can’t you fill the refrigerator “by eye”?
The pressure in the system depends on the ambient temperature and the load of the chambers. Simply connecting the cylinder all the way will reboot the system with liquid freon. The liquid is not compressible, and when turned on, the compressor will try to compress the incompressible, which will lead to mechanical destruction of the piston group or valves in the very first seconds of operation.
Can freon run out on its own?
Freon is not a consumable material, like fuel in a car. In a sealed circuit it circulates endlessly. If the gas has disappeared somewhere, it means that a microcrack has formed in the tube (often due to corrosion or mechanical damage during defrosting). Simply adding gas without eliminating the hole is a temporary measure for a couple of days or weeks.
Is it dangerous to breathe freon vapors?
Short-term inhalation of vapors from a household refrigerator is not fatal, but can cause headache, nausea or irritation of the mucous membranes. In high concentrations it displaces oxygen. The main rule: if you smell gas, open the windows and do not turn on electrical appliances if R-600a is flammable.
How often should freon be changed?
Never. With a working refrigerator, freon lasts as long as the unit itself - 10, 15 or more years. Replacement is required only in case of repair (elimination of leakage). Planned replacement or “renewal” of gas is not provided for by the design and is a sign of dishonest service.
Why is a new R-600a refrigerator quieter than the old one?
Isobutane (R-600a) has better refrigerant properties with lower pressure in the system. The compressor does not need to compress the gas to high pressures, as is the case with R-134a or R-12. Less load on the motor and the absence of vibrations from high pressure make the operation of modern equipment almost silent.