What refrigerant was used in Soviet refrigerators: ammonia or freon?

The question of what exactly substance provided cold in kitchen appliances during the Soviet Union worries not only collectors of rare household appliances, but also those who still use the legendary Zila and Biryusa. Many people mistakenly believe that all models used exclusively the same gas, but the real engineering picture was much more complex and depended on the year of manufacture and the manufacturing plant. Understanding what what refrigerant is charged into a particular unit is critical for proper disposal or repair.

The history of the development of refrigeration equipment in the USSR has gone from toxic and explosive substances to relatively safe compounds that are still used in various variations today. If you are planning to revive an old unit, you need to know exactly what was in its lines, since mixing different types of oils and gases can lead to instant failure of the compressor. In this article we will analyze in detail the evolution of refrigerants and their impact on the design of equipment.

The evolution of refrigerants: from ammonia to freon

At the dawn of the Soviet refrigeration industry, engineers were faced with a dilemma: the availability of raw materials versus operational safety. In the very first models that appeared in the 30s and 40s, the main working fluid was ammonia (R717). This substance had excellent refrigeration properties, but had one critical drawback - high toxicity and flammability. A leak of such gas in a confined space of an apartment could lead to tragic consequences, which required special precautions during production.

The situation changed dramatically with the beginning of mass synthesis organofluorine compounds, known to us as freons. These substances were inert, odorless and, most importantly, did not burn or explode. The transition to new refrigerants made it possible to simplify the design of refrigerators, removing complex secondary safety systems, and making them truly mass-produced. It was freon that became the standard for the vast majority of equipment produced in the second half of the 20th century.

⚠️ Attention: Ammonia (R717) has a sharp, suffocating odor even at low concentrations. If you smell ammonia when you turn on your old refrigerator, immediately ventilate the room and do not try to start the unit again without checking the system for leaks.

Despite the transition to new technologies, some industrial and specialized installations continued to use ammonia systems much longer than household models. In the household segment, by the 60s dichlorodifluoromethane almost completely supplanted competitors. However, knowing that ammonia could have been used in the earliest models helps to understand the design features of some rare examples preserved in museums or private collections.

Freon R12: “King” of Soviet refrigerators

When we talk about a standard Soviet refrigerator, in 95% of cases we are talking about the refrigerant R12 (dichlorodifluoromethane). This substance became the gold standard for household appliances for many decades. Its physical properties were ideal for low and medium pressure compressors, which were mass-produced at factories in Saratov, Moscow and Krasnoyarsk. R12 had a high latent heat of vaporization, which made it possible to effectively cool the chambers even with not the most powerful engines.

An important characteristic of R12 was its compatibility with mineral oils, which were used to lubricate the rubbing parts of the compressor. Unlike modern synthetic oils, mineral oils dissolved perfectly in this freon, ensuring reliable return of lubricant to the compressor crankcase. This made the system very reliable: compressors those years could work for decades without human intervention, if no mechanical breakdowns occurred.

However, R12 also had a serious environmental drawback, which was discovered in the USSR later than in the West. When released into the atmosphere, this gas destroyed the ozone layer of the planet. That is why, at the end of the 80s, an international process began to abandon R12 (Montreal Protocol), which led to a gradual change in the composition of gases in later models of Soviet and post-Soviet technology.

Why was R12 stopped being used?

Although R12 was ideal for technology, it turned out that one chlorine atom in its molecule can destroy up to 100 000 ozone molecules in the upper atmosphere. This led to a global ban on its production and use in new devices.

Technical characteristics and comparison table

To understand the difference between substances used in different periods, it is necessary to refer to their physical and chemical properties. Engineers chose the refrigerant for a reason, but based on condensation and boiling pressure. Boiling point R12 at atmospheric pressure was about -29.8 ° C, which was optimal for achieving the required temperatures in the freezer compartment of a household refrigerator.

The table below shows a comparison the main parameters of refrigerants that could be found in equipment produced in the USSR and in the countries of the social bloc. Pay attention to the difference in operating pressure, as this directly affected the thickness of the tube walls and the design of the compressor.

As can be seen from the table, the transition from R12 to more modern analogues (for example, R134a, which began to be used in the later Atlant or Biryusa models in the late 80s - early 90s) was dictated by the environment, and not by improving cooling capacity. Moreover, R134a requires the use polyester oilsthat are hygroscopic (absorb moisture), which imposed new requirements on the quality of assembly and evacuation of the system.

Design features of systems with R12

The use of R12 freon dictated its design conditions for the refrigeration circuit. Because this refrigerant operated at relatively low pressures, the condenser and evaporator tubes could be made of thin-walled steel, making production cheaper. However, there was a downside: R12 had high penetrating power. The molecules of this gas were so small that they could leak through microscopic pores in the metal or poor-quality soldering, which would be impenetrable to other gases.

That is why in Soviet refrigerators so much attention was paid to the quality of soldering of the joints of copper and steel tubes. Tightness systems was the main condition for the long life of the unit. The design often used a so-called “crying” evaporator (the rear wall of the refrigeration chamber), which was made of aluminum or steel with brazed channels. A leak in such an evaporator often meant the end of the life of the refrigerator, since overcooking aluminum at home is impossible.

Another feature was the heating system. In early R12 models, manual defrosting was often used, but the refrigerant itself contributed to the formation of an ice coat on the evaporator due to the low moisture content in the circuit (if charged correctly). Natural convection air flows were used to remove heat, since R12 effectively cooled the walls of the evaporator, removing heat from the products.

⚠️ Attention: If you hear a hissing sound when the tube of an old refrigerator is punctured, this may not only be residual freon pressure. In rare cases, when freon decomposes under the influence of an open flame (for example, when trying to solder without nitrogen), phosgene is formed - a chemical warfare agent. Soldering can only be done after thoroughly purging the circuit with air or nitrogen.

Problems of compatibility and replacement of refrigerants

Today, when the original R12 is prohibited from production and is found only in warehouse stocks or during regeneration, owners of rare equipment are faced with the question of replacement. Often, technicians suggest filling the refrigerator with an analogue, for example R600a (isobutane) or R134a. This is a complex process that requires deep knowledge of thermodynamics. Simply replacing the cylinder will not work and can be dangerous.

The main problem lies in the oil. As mentioned earlier, R12 works in tandem with mineral oil. R134a requires polyester (POE) and R600a requires either mineral or alkylbenzene (AB). If old mineral oil is left in a system with R134a, it will curdle and clog the capillary tube, and the compressor will burn out due to overheating. Completely changing the oil in a sealed circuit is a labor-intensive task and does not always guarantee 100% results.

In addition, the amount of refrigerant also varies. R12 required about 140-170 grams of substance (depending on the model), while isobutane R600a required only 60-70 grams. Refilling “by eye” will lead to incorrect operation: either the refrigerator will not freeze, or the compressor will work with overload, trying to compensate for the lack of cooling capacity.

Environmental aspect and recycling

The environmental issue became dominant at the end of the USSR and in the first years of independence. Refrigerants, which have served faithfully for decades, turned out to be the main enemies of the ozone layer. Ozone-depleting potential (ODP) freon R12 was taken as a unit, and it was from it that they started when developing new standards. This has led to the fact that old refrigerators began to be viewed not just as scrap metal, but as a source of potential danger.

Modern recycling rules require mandatory collection of the refrigerant before sending the case for melting. In Soviet times, they didn’t think about this: a refrigerator that had served its life was simply taken to a landfill, where it rusted, and the freon slowly evaporated into the atmosphere. Today, there are fines for unauthorized release of freon into the atmosphere, although control is difficult for private individuals.

It is important to understand that even an old, non-working refrigerator may contain remnants of freon under pressure. Therefore, when handing over equipment for scrap or recycling, you should make sure that the organization has a license to work with ozone-depleting substances. This will help minimize the harm that our everyday comfort caused to the planet in the 20th century.

How to determine the type of refrigerant in your refrigerator

If you are the proud owner of a Soviet refrigerator or got it from your dacha, and you need to find out what it is filled with, you don’t have to be an analytical chemist. In most cases, the information is contained directly on the unit body. Manufacturers of the USSR were required to label equipment in accordance with GOSTs, indicating the type and amount of refrigerant.

Look for a metal plate (nameplate) or sticker. In early models, it may have been glued to the inside wall of the refrigerator compartment, often above a shelf or on a side wall. In later models (late 70s - 80s), the sign was most often moved to the back wall of the refrigerator, at the bottom, next to the compressor. The type of refrigerant (for example, “Freon-12” or “R12”) and its mass in grams will be indicated there.

If the plate is lost or unreadable, you can focus on the year of manufacture and model:

• Models before the 1950s (for example, KhTZ-120, "Moscow") - with high probability ammonia.
• Models from the 1950s to the end of the 1980s (“Zil”, “Biryusa”, “Krion”, “Saratov”, “Dnepr”) - almost guaranteed R12.
• Models of the late 1980s - early 1990s (late Atlant, Orsk) - may contain R134a or transitional mixtures.

The type of compressor can also serve as an indirect sign. If the motor-compressor has a marking beginning with “DH” (Donbass Refrigeration) or “FG” (Freon Sealed), this almost always indicates work with freons. Ammonia compressors had a different design and marking, often of the open type with seals, which was extremely rare in household refrigerators after the 50s.

Is it possible to fill an old refrigerator with freon yourself?

Theoretically it is possible, but this requires special equipment: a pressure gauge station, a vacuum pump, scales and a cylinder with freon. Without evacuation of the system (removing air and moisture), the refrigerator will not work for a long time, and the presence of moisture will lead to freezing of the capillary tube and corrosion.

Why do not modern refrigerators use R12?

R12 is prohibited by international agreements due to its destructive effect on the ozone layer. Its production has been stopped and stocks are being destroyed. Modern refrigerants (R600a, R134a, R513A) have zero ozone depletion potential.

Is freon from an old refrigerator dangerous for humans?

R12 itself is not toxic under normal conditions, but at a concentration of more than 30% in the air it displaces oxygen, causing suffocation. The main danger arises from contact with an open fire: when burned, freon releases phosgene, a deadly gas.

What to do if a Soviet refrigerator runs out of freon?

It is necessary to find and eliminate the cause of the leak (often it is corrosion of the evaporator or condenser). You can't just add gas - the system is sealed. After repairs, vacuuming and refilling are required strictly by weight, which can only be done by a master with equipment.