How Do Refrigerants Get Their Name?

This is a topic that I see a lot and to be honest I don’t fully understand. In an effort to educate myself and to show others I am going to take the time today to fully understand exactly how new and old refrigerants get their name. Let’s take a look.


Let’s start out simple. For each refrigerant an identifying number will be assigned to it. This number consists of a prefix made up of letters and a suffix made up of digits. An example of this can be seen in R-22. R is our letter prefix and 22 is our numbered suffix. This standard numbering system was first developed by the DuPont company and was released for use in 1956. Since then ANSI/ASHRAE has adopted this numbering system under Standard 34. (Standard 34 is the number designation and safety classification of refrigerants.)

Standard 34 is always changing and being updated by ASHRAE. I wish there was a specific link that I could point you to but since it is always updating I will point to AHSRAE’s library and the most recent Standard 34 document that I could find.

The goal of this numbering system is to allow an engineer, technician, or anyone else to easily identify the chemical composition of the refrigerant that they are working with. Each number in the refrigerant name has it’s own specific purpose and provides a clue as to how the refrigerant is made.

The Prefix

As I mentioned above the prefix contains a letter. Usually this letter is composed of the letter ‘R’ for refrigerant. Further examples being R-12, R-22, R-134a, R-410A, etc.

However, there are some cases where the letter C can be used in the prefix to show the sign of Carbon. These can also be preceded by the letters B, C, F, or a combination of these letters. These letters indicate any presences of Fluorine, Bromine, or Chlorine. Any compounds containing Hydrogen must be preceded by the letter H. Examples of these are HFC-134a, HFC-404A, HCFC-22. These types of prefixes are informal and should not be used for technical purposes as most companies and users prefer the ‘R’ prefix method.

The Suffix

There are four numbers in the suffix of a refrigerant. Now, you may be saying to yourself right now but I can think of a refrigerant that only has two numbers. You would be right, R-12 and R-22 only have two. The other two numbers in front are treated as a zero and do not show unless there is a need for them. Lastly, unlike everything else in the world refrigerant numbers read from right to left instead of left to right.

Ok, so now that we have that established let’s break down a refrigerant’s name:

  • Again, starting from the right. The right most number equals the number of Fluorine atoms per molecule.
  • The second number from the right equals one plus the number of hydrogen atoms per molecule.
  • The third number from the right equals the number of carbon atoms minus one. If it is zero it is not normally written but assumed as I had mentioned earlier.
  • The fourth number is relatively new to refrigerants. This number equals the number of double bonds in the molecule. Like before this is omitted when zero. The only time I see this number used is when working with the new Hydrofluroolefin refrigerants such as HFO-1234YF.

Another thing that you may have noticed when looking at refrigerant names are suffixes that end with an A, a, B, or C. While these are not as common we should go into these as well:

  • A suffix with a lower case letter such as a, b, or c indicate an isomer. Isomers are two or more compounds with the same formula but have a different arrangement of atoms in the molecule thus giving them different properties. That is how we can have R-134 and R-134a. Exact same refrigerant but arranged differently creating a different effect.
  • A suffix with a upper case B and a number indicates the number of Bromine atoms when used.
  • A suffix with an uppercase letter such as A, B, or C indicate the different percentages of refrigerants that are blended together. This is why you could see refrigerants that have a very similar name such as R-401A and R-401B. These refrigerants are made of the same blended refrigerants but at different percentages.

Series of Refrigerants

Using the numbering system above we can now visualize the different groups or series of refrigerants by their numbers. If you review the below list you begin to see a formulation of the numbers and how they are categorized.

  • 000 Series: These are your methane based compounds. Please note that some refrigerants may not have 3 digits like R-12 or R-22. In this instance, just like when working with a number, the leading zero was dropped. These are methane based refrigerants but we just need to remember to put the zero in front. R-12, R-11, and R-22 are all examples.
  • 100 Series: These are your ethane based refrigerant compounds. A very popular example here would be your HFC R-134a that is used in automotive applications.
  • 200 Series: These are your propane based compounds. R-290, as an example.
  • 300 Series: These are your cyclic organic compounds.
  • 400 Series: These are your Zeotropes refrigerants such as R-410A or R-404A. At the time of writing this article this series covers some of your most popular refrigerants used.
  • 500 Series: These are your Azeotropes refrigerants.
  • 600 Series: These are your organic compound refrigerants.
  • 700 Series: These are your inorganic compound refrigerants. An example here would be Ammonia or R-717.
  • 1000 Series: These are your unsaturated organic compound refrigerants. An example here would be the new HFO-1234YF refrigerant used for automobiles.


Well folks that about wraps it up on refrigerant naming and numbering. I know I learned a lot writing this article and I hope that I was able to help you as well.

Thanks for reading,

Alec Johnson



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