- 1). Check that the gas you are looking at has a number with an R prefix. The "R" stands for refrigerant, and if the "R" is not present, the gas you are trying to identify is probably not a refrigerant.
- 2). Check the numbers following the R. These will depend on the chemical group the refrigerant belongs to. The following rules apply only to hydrocarbons and hydrocarbon derivatives. The first digit on the code represents the number of fluorine atoms in the refrigerant. The next number in the sequence refers to the number of hydrogen atoms in the chemical plus one. The third number refers to the number of carbon atoms in the refrigerant minus one, and the fourth number refers to the amount of unsaturated carbon-carbon bonds present. If the refrigerant has only one carbon bond, or does not hold any unsaturated carbon-carbon bonds, the zero is omitted from the code. Sometimes the code will have a lowercase letter, "a" for example, after the number. This refers to the particular isomer (configuration) of the chemical.
- 3). Check if the first number of the R code is a 4, 5, 6 or 7. This means that the refrigerant is either a zeotropic mixture (4), an azeotropic mixture (5), a miscellaneous organic compound (6), or an inorganic compound (7). These first numbers do not refer to the detailed composition of the refrigerant, but have been assigned to the group to differentiate them from the hydrocarbon group and each other.
- 4). Refer to the internationally approved list of refrigerants to identify the refrigerant. This list can be found on websites hosted by such organizations as the American Society of Heating, Refrigerating and Air-Conditioning Engineers or the International Institute of Refrigeration.
- 5). Ensure that the code is exactly the same as that present on the label of the refrigerant gas you are attempting to identify. For example, a mixture with an "A" following the three digit number is a different refrigerant to the same R number with a "B." This is because while both mixtures contain the same refrigerant ingredients, the amount of each ingredient used in the mixture is different.
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