According to an international agreement, refrigerants are represented by the letter R (as in Refrigerants) followed by a two- or three-digit number and, in some cases, one or two letters. The designation Rxyz is determined by the chemical composition of the molecule, as described below.
The methane, ethane and propane series:
Here, (x) gives the number of carbon atoms in the chemical formula, minus one.
- (x) = 0 is the methane series, but the 0 is ignored for these compounds. Examples are R12 and R22.
- (x) = 1 is the members of the ethane series, such as R114, R124 and R134a.
- (x) = 2 is the propane series, e.g. R290 (propane).
For these groups, (y) describes the number of hydrogen atoms plus one and (z) describes the number of fluorine atoms.
Zeotropic and azeotropic mixtures
- (x) = 4 refers to zeotropic mixtures. The components in the mixture have different boiling points, and thus the refrigerant mixture has a temperature glide. R407A and R407C are examples of such refrigerants (see section 5.7).
- (x) = 5 refers to azeotropic mixtures. These act like homogeneous substances with one specific boiling point, and therefore they have no glide. R502 and R507 are examples of azeotropic mixtures (see section 5.7).
Here, (y) and (z) are ordinal numbers.
High organic compounds
- (x) = 6 means that the composition is organic, e.g. butane, R600, and isobutene, R600a. This group has several subgroups, for example hydrocarbons, oxygen compounds, sulfuric compounds and nitrogen compounds.
The subgroups have been assigned different number series within the main group, so (y) and (z) describe the subgroup and order within the subgroup.
- (x) = 7 refers to inorganic compounds, such as ammonia, R717, water, R718, and carbon dioxide, R744.
In this group, (y) and (z) are the molar mass.
Unsaturated organic compounds
- (x) = 11 stands for unsaturated ethane compounds, such as R1150 (ethylene).
- (x) = 12 stands for unsaturated propane compounds, such as R1270(propylene). The (y) and (z) are the same as for the ethane and propane series.
Letters at the end
The last letter, if any, in the designation number means different things:
- Lower-case letters describe the structure of the molecule. For example, R600 is butane and R600a is isobutane. These two compounds have the same chemical formula, but different spatial arrangements, and they therefore have slightly different properties.
- Capital letters describe specific mixing proportions of different components. For example, R407 A-E are mixtures of the refrigerants R32, R125 and R134a. R407A has the following mixing proportions: 20% R32, 40% R125 and 40% R134a, while R407C consists of 23% R32, 25% R125 and 52% R134a.