Ice Breaker: Refrigerant Numbering System Explained

November 3, 2008
Chemical composition of HCFC-22.

There are many different types of refrigerant used in our industry today. They are produced by several different manufacturers and have numerous ways of identification. One proper method of identification is referring to a refrigerant by its ANSI/ASHRAE designation.

This standardized numbering system was first developed by E.I. DuPont and released for general use in 1956. Since then it has been adopted by ANSI/ASHRAE as part of Standard 34 (Number Designation and Safety Classification of Refrigerants).

This numbering system allows a technician or engineer to easily identify the chemical composition of a refrigerant. Each digit of the numbering system has its own significance in identifying the compounds that make up a refrigerant.

The basic structure of the numbering system is the “chemical group” of refrigerant, followed by a dash (-) and a series of numbers and letters. For example, HFC-134a is represented by “HFC” as its chemical group and “134a,” which identifies the chemical composition of the refrigerant. In years past “R” was used instead of the refrigerant’s chemical group. HFC-134a would have been referred to as R-134a.


Here is a brief explanation of the number system used after the dash (-):

• The rightmost digit equals the number of fluorine atoms per molecule.

• The second digit from the right (tens digit) equals one plus the number of hydrogen atoms per molecule.

• The third digit from the right (hundreds digit) equals the number of carbon atoms minus one. If zero, it is not normally written but assumed. For example HCFC-22 has one carbon atom.

• The fourth digit (thousands digit) equals the number of double bonds in the molecule. This is omitted when zero and in practice is rarely used.

• A suffix with a capital B and a number indicates the number of bromine atoms, when used.

A suffix of an uppercase letter (A, B, C, etc.) indicates different percentages of refrigerants blended together. For example R-402A and R-402B are made up of the same refrigerants, but with different percentages of each refrigerant.

A suffix of a lower-case letter (a, b, c, etc.) indicates an isomer. Isomers are chemical compounds that have the same atomic compounds and molecular weights, but different molecular structures and properties. For example, the figure shows that HCFC-22 is made up of one carbon atom, one hydrogen atom, and two fluorine atoms. (It also contains one chlorine atom, but it is not identified in the numbering system.)


This numbering system also allows refrigerants to be grouped into series. Below is an explanation of the various refrigerant groups.

-000 series: methane-based compounds.

-100 series: ethane-based compounds.

-200 series: propane-based compounds.

-300 series: cyclic organic compounds.

-400 series: zeotropes.

-500 series: azeotropes.

-600 series: organic compounds.

-700 series: inorganic compounds.

-1000 series: unsaturated organic compounds.

For example, HCFC-22 is in the “000 series” of refrigerants, meaning it is a methane-based compound. R-134a is in the “100 series” of refrigerants, meaning it is an ethane-based compound.

Publication date: 11/03/2008