Refrigerants are classified by ASHRAE, and their familiar ‘ R’ numbers are assigned according to certain rules. For example, the classification of halogen
Refrigerants derived from saturated hydrocarbons and consisting of only one substance is illustrated by the example below:
R = Refrigerant
■ Lowercase letter denotes specific isomer (molecular formulation)
The number of fluorine (F) atoms
The number of hydrogen (H) atoms +1
The number of carbon (C) atoms -1 (omitted when digit is zero).
Mixtures are designated by their respective refrigerant numbers and mass proportions. For example
R = Refrigerant
Uppercase letter denotes specific compositon, i. e. % components
Chronological numbering designating the components of the mixturre, but not the percentage of the constituents
400 series denotes zeotropic mixture
Zeotropic mixtures are assigned an identifying number in the 400 series. This number designates which components are in the mixture, and the following upper case letter denotes the proportions. The numbers are in chronological order of the refrigerant’s approval by ASHRAE.
Example: R407A (R32/R125/R134a (20/40/40)), R407B (R32/R125/R134a (10/70/20)), R407C (R32/R125/R134a (23/25/52)), etc.
Azeotropic mixtures are in the 500 series. Example: R507 (R125/R143a (50/50)).
Miscellaneous organic compounds are in the 600 series; numbers are given in numerical order, for example, R600a, isobutane; and inorganic compounds are in the 700 series. Identification numbers are formed by adding the relative molecular mass of components to 700.
Example: R717 corresponds to ammonia which has a molecular mass of 17.
Posted in Refrigeration and Air Conditioning