Refrigerants are classified by ASHRAE, and their friends 'R' numbers are assigned in accordance with certain rules. For example, classification of refrigerants derivatives of hydrocarbons, saturated and consisting of one substance only shown in the example below:
Zeotropic mixtures are given an identification number in the 400 series. This number determines which components in the mixture, and the next letter upper case indicate the percentage. Rooms are arranged chronologically refrigerant approval of ASHRAE.
Example: R407A (R32/R125/R134a (20/40/40)), R407B (R32/R125/R134a (10/70/20)), R407C (R32/R125/R134a (23/25/52)), and other
AZEOTROPIC mixture 500 series. Example: R507 (R125/R143a (50/50)).
Other organic compounds in the 600 series; figures in ascending order, for example, R600a, isobutane; and inorganic compounds in the 700 series. Identification numbers are formed by adding a relative molecular mass of components up to 700.
Example: R717 corresponds to ammonia, which has a molecular mass of 17.