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Understanding the Refrigerant "R" Nomenclature

The chemical names for the fluorinated refrigerants are long and cumbersome. A numbering system was developed by DuPont to identify the different products. The number was originally part of the registered trade name but was later donated to the industry by the DuPont Company to avoid confusion and the proliferation of different numbers for the same product.

The number assigned to each refrigerant is related to its chemical composition and the system has been formalized as ASHRAE Standard 34. The numbering system rules are as follows:

1. The first digit on the right is the number of fluorine (F) atoms.

2. The second digit from the right is one more than the number of hydrogen (H) atoms.

3. The third digit from the right is one less than the number of carbon (C) atoms. When this digit is zero it is omitted from the number.

4. The fourth digit from the right is equal to the number of unsaturated carbon-carbon bonds in the compound. When this digit is zero, it is omitted from the number.

5. The number of chlorine (Cl) atoms is found by subtracting the sum of the flourine (F), bromine (Br - if present) and hydrogen (H) atoms from the total number that can be attached to carbon. With one carbon, the total number of attached atoms is four. With two carbons, the total number is six and with three carbons, the total number is eight.

6. In some cases, part or all of the chlorine atoms are replaced with bromine and the letter B is used in the number. The number following the letter B shows the number of bromine atoms present.

7. Blends are designated by their respective refrigerant numbers and weight proportions. rest of text okay, add this. To differentiate among blends having same components with different proportions, an uppercase letter shall be added to designation. For example, R-402A and R-402B.

8. Zeotropic blends that have been commercialized shall be assigned an identifying number in the 400 series. This number designates which components are in the mixture but not the amount of each. The amount of each component is designated as described in 7 above. For example the 60/40 weight % mixture of R-12 and R-114 would be R-400 (60/40).

9. Azeotropic compounds that have been commercialized shall be assigned an identifying number in the 500 series. It is not necessary to cite the percentages parenthetically once a 500 series is assigned.

10. The 600 series has been assigned to miscellaneous organic compounds. Within the organic 600 series, the assignments are serial.

11. The 700 series has been assigned to inorganic compounds with relative molecular masses less than 100. Within the 700 series, the relative molecular mass of the compounds is added to 700 to arrive at the identifying refrigerant numbers. When two or more inorganic refrigerants have the same relative molecular masses, uppercase letters (i.e., A, B, C, etc.) are added to distinguish among them.

12. The 1000 series has been assigned to unsaturated organic compounds.