When the refrigerator stops freezing or makes strange sounds, the owner’s first thought is often related to a “liquid” leak. However, technically, substances circulate in the system in different states of aggregation, and they cannot be confused. The basis of the cooling cycle is refrigerantwhich, depending on pressure and temperature, can be gas or liquid, as well as special compressor oilnecessary for lubricating the rubbing parts.
Many are mistaken It is believed that ordinary water or antifreeze is filled inside the system, as in car radiators. This is a dangerous misconception. Modern household appliances use complex chemical compounds known collectively as freons. Understanding what exactly is in the pipes of your unit is critically important when trying to independently diagnose or call a technician.
In this article we will analyze in detail the chemical composition of the working fluid of the refrigeration machine, consider the properties of lubricants and explain why a simple “topping up” of liquid is impossible without professional equipment. You will learn the difference between old and new types of refrigerants, and what safety measures must be observed.
Nature of refrigerant: gas or liquid?
Inside the sealed circuit of the refrigerator, the substance is constantly changing its state. It is more correct to call it refrigerant or carrier refrigerant. In the evaporator, where food is cooled, it boils at very low temperatures, turning from liquid to gas and absorbing heat. The compressor then compresses this gas, increasing its pressure and temperature.
In the condenser (grid on the back wall), the hot gas releases heat into the room and condenses, becoming a liquid again. It is at this moment, at the exit from the condenser in front of the capillary tube, that the substance is in the liquid phase under high pressure. A critical property of modern freons is the ability to boil at temperatures below -30°C at atmospheric pressure.
The amount of substance in the system is strictly regulated by the manufacturer. Typically, residential models circulate between 30 and 150 grams of refrigerant. A lack or excess of “liquid” disrupts the thermodynamic cycle, leading to compressor failure or lack of refrigeration. Therefore, the concept of “liquid in the refrigerator” refers more to the physical state of the substance at a certain point in the cycle, and not to the type of material poured.
It is important to understand that the system is completely sealed. If you hear gurgling or hissing sounds, this is normal; this is a mixture of oil and refrigerant leaking. But if you see a puddle under the refrigerator, it is most likely water from defrosting or condensation, and not technical fluid from the circuit.
Types of freons: from R12 to R600a
For decades, the chemical industry has offered various formulas for refrigeration machines. The choice of a specific type depends on environmental standards and energy efficiency. Old Soviet and post-Soviet refrigerators often ran on R12 (difluorodichloromethane). It was a reliable gas, but harmful to the ozone layer, the production of which is now prohibited.
It was replaced by R134a (tetrafluoroethane). It does not deplete the ozone layer, but has a high global warming potential. In modern models, especially built-in and compact ones, isobutane (R600a)is increasingly used. This is a hydrocarbon gas that is more effective than older analogues, but is flammable.
- ❄️ R12: Used until the mid-90s, toxic upon contact with an open flame, prohibited for production.
- 💧 R134a: Standard for many models of the 2000-2010s years, requires synthetic oil, has no odor.
- 🔥 R600a: Modern eco-standard, explosive in high concentrations, requires a minimum amount of substance for refilling.
- 🌍 R407C/R410A: Mixtures more often used in air conditioners, but sometimes found in industrial refrigeration equipment.
The type of refrigerant can be determined by sticker on the compressor or on the inside wall of the refrigerator compartment. The type of gas and its quantity in grams are always indicated there. Using the wrong type of freon during repairs will result in compressor failure or an explosive situation.
Compressor oil: system lubrication
The second important “liquid” in the refrigerator is oil. It is located in the compressor crankcase and is necessary to lubricate the piston group, reduce friction and remove heat. The oil circulates along with the refrigerant throughout the entire circuit, so it must have the properties: dissolve in freon and not freeze at low temperatures.
The type of oil directly depends on the type of freon used. For mineral freons (R12) mineral oilswere used. They do not mix well with modern synthetic refrigerants. For R134a and R600a synthetic oils are used: polyester (POE) and alkylbenzene (AB).
⚠️ Attention: It is strictly forbidden to mix mineral and synthetic oil. Upon their contact, a thick emulsion or solid precipitate is formed, which tightly clogs the capillary tube. Repair in this case will require a complete flushing of the system with nitrogen.
The oil level in the compressor is also strictly standardized. Its excess leads to water hammer and increased pressure in the system, and its deficiency leads to overheating and jamming of the motor. When replacing a compressor, the technician always pours oil from the old unit into the new one or refills it strictly according to the weight specified in the technical documentation.
If you plan to replace the compressor yourself, pay attention to the color of the oil in the pumped out unit. Transparent or slightly yellowish oil indicates the normal condition of the system. If the oil is dark, black or has a burning smell, this indicates overheating. In this case, the system cannot simply be recharged - a thorough flushing is required. lubricant degradation and overheating. In this case, the system cannot simply be refilled - a thorough flushing is required.
Compatibility table of refrigerants and oils
To properly maintain the refrigerator, you need to know which pairs of substances are compatible. Below is a reference table showing the dependence of the type of oil on the brand of refrigerant.
| Refrigerant type | Recommended oil | Chemical base | Features |
|---|---|---|---|
| R12 (Freon-12) | Mineral | Petroleum products | Not hygroscopic, afraid of moisture |
| R134a | Polyester (POE) | Synthetics | Highly hygroscopic, requires vacuuming |
| R600a (Isobutane) | Mineral / Alkylbenzene | Petroleum products / Synthetics | Dissolves well in mineral oil |
| R407C | Polyester (POE) | Synthetics | Zeotropic mixture, filling only with liquid |
The table shows that that the transition to environmentally friendly freons required a change in the type of lubricant. Synthetic oils, such as POE, are highly hygroscopic - they actively absorb moisture from the air. Therefore, work on replacing a compressor or repairing a circuit with such oils cannot be carried out in rainy weather or at high humidity without using nitrogen purge.
In domestic conditions, it is impossible to check the type of oil “by eye”. It is necessary to rely on the compressor markings. For example, compressors Secop (formerly Danfoss) or Embraco have clear compatibility markings. The use of universal substitute oils is possible, but only if they are certified by the refrigeration equipment manufacturer.
Is it possible to add liquid yourself?
A frequent question from equipment owners: “Can I just buy a can of freon and add it like antifreeze in a car?” The answer is clear: no. A refrigerator is not an open system, but a closed high-pressure circuit. It does not have a filler neck with a valve.
To access the contents of the circuit you need to:
- 🛠️ Cut through the filling or suction tube of the compressor.
- 🔥 Solder the connection point burner (oxygen-propane or using solder).
- 📉 Connect a vacuum pump to remove air and moisture.
- ⚖️ Fill the system with refrigerant strictly according to the scale, using a pressure gauge station.
Attempt to fill "by eye" or through homemade adapters will result in air remaining in the system. Air contains nitrogen, oxygen and water vapor. Oxygen oxidizes the oil, water freezes in the capillary, forming an ice plug, and nitrogen creates excess pressure. As a result, the compressor will burn out in a few days or weeks.
Why can’t you refuel a refrigerator with a running compressor?
There is a myth that freon can be sucked through a bitten off tube while the unit is running. This is a big mistake. Firstly, you do not control the amount (weight) of the substance added. Secondly, air will enter the system along with the gas, which will lead to the formation of an acidic environment inside the circuit and destruction of the insulation of the motor windings.
Diagnostics of leaks and maintenance
Since in a working refrigerator the liquid does not disappear anywhere, the need to add it arises only when there is a leak. Leaks most often occur at solder joints, in the foamed part of the housing (evaporator) or in the condenser due to corrosion. Signs of a leak are: lack of cold, hot sides (instead of warm), continuous operation of the compressor.
To find leaks, technicians use leak detectors (electronic or ultraviolet) or the soap foam method. If the leak is found in an accessible location (for example, on the outer grill), it is sealed. If the foamed evaporator inside the case is poisoning, repair is often not economically feasible - it is easier to install an external evaporator (“crying” on the back wall).
⚠️ Attention: Never try to find a leak with an open flame (lighter) in places where gas may accumulate, especially if you have a refrigerator on R600a. Isobutane is heavier than air and accumulates below, near the floor. A spark can lead to a volumetric explosion.
Regular maintenance of the refrigerator does not imply replacing the liquid. The circuit is designed for 10-15 years of operation without intervention. The only thing that may be required is to clean the condenser from dust to ensure normal heat exchange. Dust on the grill at the back causes the compressor to work longer, increasing the pressure and temperature, which can lead to rupture of the tubes and leakage of freon.
☑️ Signs of a refrigerant leak
Environmental safety and disposal
Releasing freon into the atmosphere is not just a technical error, but also an environmental crime. Old freons (R12) destroy the ozone layer, while modern ones (R134a, R410A) contribute to the greenhouse effect. In addition, when freon burns in the presence of an open flame, a chemical warfare agent is formed phosgene - a chemical warfare agent.
Therefore, when decommissioning an old refrigerator or repairing it due to depressurization, you must follow the rules:
- ♻️ Do not disassemble the refrigerator yourself for the purpose of handing over the metal, unless the refrigerant is removed.
- 🚫 Do not burn elements of the refrigeration circuit (pipes, condenser).
- 👨🔧 Call specialists to pump out freon before disposal housings.
Modern gas stations are equipped with recovery systems that allow you to collect old gas into cylinders for subsequent processing or destruction. It is impossible to do this in a domestic environment, so in the event of a serious breakdown, it is better to contact a certified service center.
Conclusion
The refrigerator uses not one liquid, but a couple of substances: a refrigerant (freon), which changes the state of aggregation, and compressor oil for lubrication. The type of these substances is strictly determined by the design and year of manufacture of the model. Replacing or adding “liquid” on your own without special equipment, scales and knowledge of the chemistry of the processes is impossible and dangerous.
Understanding the principles of the system helps owners avoid common mistakes, such as puncturing tubes during defrosting or trying to “treat” a humming refrigerator using traditional methods. Careful use of equipment and timely cleaning of the condenser will extend the life of the refrigerant and the entire unit as a whole.
Frequently asked questions (FAQ)
What will happen if R12 freon is poured into a refrigerator using R134a?
This will lead to incorrect operation of the system. R12 requires mineral oil, while R134a requires synthetic oil. Mixing oils will cause sediment to form and clog the capillary system. In addition, these freons have different operating pressures and boiling temperatures, which will lead to overload of the compressor and a lack of normal cold.
Why does the refrigerator freeze after refilling, but stops after a week?
Most likely, the soldering was done poorly or a leak test was not carried out (pressure testing with nitrogen). A microcrack remained in the system through which the gas slowly escaped. Also, the reason may be the presence of moisture in the circuit, which has frozen in the capillary, creating an ice plug.
Is it possible to use car freon for a refrigerator?
No, it is not. Automotive air conditioners often run on R134a, but the oils and additives in them may differ from those needed for hermetic refrigeration compressors. In addition, automotive systems use UV dyes and additives that can be harmful to the thin capillary tube of a household refrigerator.
How do I know how much freon my refrigerator needs?
The exact amount (in grams) is indicated on the manufacturer's sticker, which is usually located inside the refrigerator compartment on the side wall or on the back panel next to compressor. Refilling "by eye" or by pressure (without scales) for household refrigerators is unacceptable due to the small volume of the system.