Coolant in the refrigerator: name, types and features of refrigerants

The question of what exactly is the name of the liquid circulating inside the cooling system of a household refrigerator often confuses equipment owners who are faced with the need for repair or maintenance. In everyday life, this substance is mistakenly called “freon,” although this is only a trade name for one of the classes of refrigerants, and not a universal name for all types. In fact, it is more correct to use the term refrigerant or refrigerant gas, since in a closed circuit of the unit the substance constantly changes its state of aggregation from gas to liquid and back.

Understanding the chemical composition and physical properties of this substance is critical for the safe operation of the device. Different models of refrigerators, released in different decades, use fundamentally different substances: from explosive hydrocarbons to inert fluorine-containing compounds. Incorrect identification can lead not only to compressor failure, but also to serious health consequences or even fire, so knowledge of the markings and properties of the refrigerant is a basic requirement for any master.

In this article we will analyze in detail what substances are used in modern and old refrigerators, how they differ from each other and why you cannot simply “add” any liquid from a cylinder. You will learn about labeling R134a, R600a and outdated R12as well as how to correctly identify the type of gas in your specific device without resorting to complex chemical reference books.

Correct terminology: refrigerant or freon?

The first thing you need to understand is this confusion in names. The technically correct name for the working fluid in the refrigeration cycle is refrigerant. This is the term used in technical documentation, GOSTs and operating instructions. A refrigerant is a substance that, when boiling and condensing at low temperatures, removes heat from objects being cooled. In everyday life, the word “freon” has taken root, which is not the name of a specific element, but a trademark of the DuPont company (now Chemours) for a whole group of haloalkanes.

The use of the term “freon” is acceptable when talking about old Soviet or early imported models where chlorofluorocarbons were actually used. However, modern environmental standards dictate their own rules, and manufacturers are massively switching to hydrocarbon compounds that are not chemically freons. Calling isobutane freon is a technical error, although it constantly slips into colloquial speech. It is important to distinguish between these concepts, especially when searching for materials for refilling.

⚠️ Attention: Never try to determine the type of gas only by smell or color (if it suddenly leaks). Most refrigerants are colorless and odorless, and some, when mixed with air, form explosive concentrations. Always rely on the manufacturer's labeling.

To accurately identify the substance in your refrigerator, you must look for the information sticker. It is usually located on the rear wall of the cabinet, inside the refrigerator compartment on the side wall, or on the plinth panel at the front. It is there that the manufacturer indicates the type and amount of refrigerant charged in grams. Ignoring this information when attempting repairs may cost you a new compressor, since different gases require different types of oils to lubricate the mechanism.

Main types of refrigerants: from R12 to R600a

The history of the development of refrigeration technology goes back more than a century, and during this time humanity has come from the use of ammonia and sulfur dioxide to modern safe mixtures. There are three main groups of substances most common in residential refrigerators, each with its own unique characteristics and maintenance requirements. Understanding the differences between them will help you better navigate the characteristics of your equipment.

The first mass refrigerant was R12 (difluorodichloromethane). For a long time it was considered ideal: non-flammable, non-toxic, with excellent cooling properties. However, in the late 20th century, R12 was discovered to destroy the Earth's ozone layer. As a result of the Montreal Protocol, the production of this substance was almost completely stopped, and modern refrigerators using R12 are no longer produced, although it is still found in older models.

R12 has been replaced by R134a (tetrafluoroethane). This substance no longer harms the ozone layer, but has a higher global warming potential. R134a requires the use of synthetic oils (polyester), which are very hygroscopic, that is, they actively absorb moisture from the air. This makes the system sensitive to the quality of vacuuming during repairs. Most refrigerators produced from the late 90s to the mid-2010s operate on this gas.

The de facto modern standard has become R600a (isobutane). This is a hydrocarbon gas that is natural and absolutely safe for the environment. Its main advantage is high energy efficiency and low noise level when the compressor operates. However, R600a has a serious drawback: it is extremely flammable. That is why, when repairing such refrigerators, it is prohibited to use tools that produce a spark, and the amount of gas in the system is strictly limited (usually up to 150 grams) so that in the event of a leak, a flash does not occur.

• 🧪 R12 - outdated freon, prohibited for production, destroys the ozone layer.
• 💧 R134a - is safe for ozone, but requires ideal dryness of the system and synthetic oils.
• 🔥 R600a - environmentally friendly isobutane, economical, but flammable when concentrated in the air.
• 🌍 R290 (propane) - an analogue of isobutane, more often used in industrial installations or air conditioners, less often in household refrigerators.

The choice of a specific type of refrigerant depends not only on environmental standards, but also on the design of the compressor and heat exchangers. Engineers select the substance so that it provides maximum efficiency with minimal energy consumption. Therefore, replacing one type of gas with another (for example, filling R134a instead of R600a) is strictly prohibited without completely re-soldering the system and changing the oil, since their condensation and boiling pressures are radically different.

Chemical composition and physical properties of gases

To understand why you cannot mix different types of refrigerants, you need to look into them physicochemical properties. The main parameter here is the saturated vapor pressure. Each substance has its own pressure at a certain temperature. For example, at a boiling temperature of -26°C the pressure will be the same, and at the same temperature it will be completely different. The compressor and the entire pipeline design are designed to operate in a certain pressure range. R134a at a boiling point of -26°C the pressure will be the same, and R600a at the same temperature - completely different. The compressor and the entire piping structure are designed to operate within a certain pressure range.

The second critical parameter is compatibility with compressor oil. Older R12 systems used mineral oil. It mixes well with freon and circulates through the system. In R134a systems, mineral oil does not dissolve in the gas, which would lead to blockage of the capillary tube and jamming of the compressor. Therefore, synthetic polyester oil (POE) is used there. Isobutane (R600a) is compatible with mineral oil, which simplifies maintenance, but requires careful cleaning of the system from moisture.

⚠️ Attention: Mixing different types of oils (mineral and synthetic) leads to the formation of a solid sediment ("slag"), which tightly clogs the capillary expander. This is the most common cause of repeated breakdowns after unqualified repairs.

Heat capacity and thermal conductivity also play a role. Hydrocarbons (R600a) have better heat dissipation, allowing manufacturers to make smaller heat exchangers or place the condenser on the rear wall (grill at the back), making the refrigerator quieter. R134a freons require more efficient cooling of the condenser, so in such models you can often hear the fan running or see that the side walls of the case become very hot during operation.

Gas density also affects the performance of the compressor. Since R600a has a higher molecular weight, a lower volumetric gas flow rate is required to pump the same amount of cold. This allows the use of smaller and smaller compressors, which directly impacts your energy bill. It was the transition to isobutane that allowed modern refrigerators to achieve energy consumption class A++ i A+++.

Why can’t you mix gases?

Mixing different refrigerants (for example, R12 and R134a) leads to an unpredictable change in pressure in the system, a change in the boiling point of the mixture and, as a result, incorrect operation of the refrigerator. In addition, different gases require different oil additives. The mixture can become explosive or cause corrosion of the internal components of the system from the inside, even if individually the components were safe.

How to determine the type of refrigerant in your refrigerator

If you are planning a diagnosis or simply want to know what is inside your unit, you do not need to be a chemist. Manufacturers are required to label equipment in accordance with international standards. The most reliable way is to find the nameplate. It may look like a metal plate with embossed data or a sticker with a barcode.

Look for a line with the word Refrigerant or just a letter R followed by numbers. For example, the inscription R600a / 130g means that the system uses 130 grams of isobutane. If the weight indicated is less than 150 grams, it is almost guaranteed to be isobutane. If the weight is 200-300 grams or more, R134a is most likely used. Also, the type of gas is often duplicated in technical documentation or on the manufacturer’s website by serial number.

It is difficult to visually identify gas by the appearance of the compressor, but there are indirect signs. Compressors running on R600a are often smaller in size and are labeled with a suffix indicating the type of refrigerant (for example, the compressor model name may have a letter for Isobutane). Also, color markings are sometimes applied to the compressor pipes: blue is often used for R134a, red or green for R600a, but you should not rely on the color alone, since standards may differ between brands. C or I for Isobutane). Also, color markings are sometimes applied to the compressor pipes: blue is often used for R134a, red or green for R600a, but you should not rely on the color alone, since standards may differ between different brands.

If the sticker is missing or worn off, you can try to find information on the compressor model. The unit itself also has a nameplate with the name (for example, Secop, Aspera, Embraco) and model number. By typing this number into the search, you can find a technical datasheet that will indicate the recommended type of refrigerant. However, if the refrigerator has been repaired, the data on the compressor may not correspond to what is currently pumped into the system, so this method is less reliable.

Dangers and safety measures when working with refrigerants

Working with the refrigeration circuit requires strict adherence to safety precautions. The main danger of modern refrigerants, especially R600a, is fire hazard. Isobutane is heavier than air and, if leaked, accumulates in the lower part of the room. A single spark from a light switch or static electricity is enough to cause a flash. Therefore, all work related to depressurization of the system (soldering, replacing the filter, removing tubes) should be carried out only after thoroughly purging the system with nitrogen and in a well-ventilated area.

The second aspect is the toxicity of combustion products. Although the refrigerants themselves may be (non-toxic) in small doses, when exposed to an open flame (soldering torch) they break down into phosgene and other toxic compounds. Inhaling freon vapors in high concentrations causes suffocation, since the gas displaces oxygen, and can also lead to frostbite of the skin upon contact with the liquid phase (boiling point is extremely low).

Another hidden threat is high pressure. Even with the refrigerator turned off, if it has warmed up to room temperature, the gas pressure can reach 6-10 atmospheres (and higher for R134a). Abruptly opening the system without relieving pressure through the Schrader valve may result in personal injury and flying metal fragments. Always check for residual pressure before starting soldering.

⚠️ Attention: It is strictly forbidden to check the tightness of the system with an open flame! To find leaks, use only a soap solution or electronic leak detectors configured for a specific type of gas. Using fire in the presence of a possible R600a leak is guaranteed to result in an explosion.

It is also worth remembering about chemical reactivity. Synthetic oils used with R134a are aggressive to some types of rubber and plastics, so only compatible materials are used in such systems. Contact of such oil on the skin can cause irritation, and permanent stains on clothing.

Frequently asked questions and myths about refilling refrigerators

There are many myths surrounding the topic of “liquids in the refrigerator,” which often lead to damage to equipment. One of the most common is “the refrigerator needs to be refueled periodically, like a car.” This is an absolute lie. The refrigeration circuit is a sealed welded system. If there is no leak, the refrigerant circulates there for decades without loss. If the gas has disappeared somewhere, it means that a hole (microleak) has formed, which needs to be found and sealed. A simple refueling without eliminating the cause of the leak will give a temporary effect for a couple of weeks or months.

Another myth says that “the more gas, the better the cooling.” This is a dangerous misconception. Excess refrigerant causes liquid freon to enter the compressor, causing water hammer and instant valve failure. Lack of gas leads to compressor overheating and insufficient cooling. Refueling must be done strictly according to the weight indicated on the nameplate, accurate to the nearest gram.

Many also ask whether it is possible to replace R1