View Full Version : Letters in gase codes

04-07-2004, 11:06 AM
Hi Guys,

R402(A) R402(B)

R409(A) R409(B)

Most refrigerents have a letter after them, some as above have them same number but different letters. Does anybody out there know what the difference is with the refrigerents to give them that code. I cannot see anything obvious unless it is to do with oil compatability, if so why does R22 have no leter code as was/is he case with R11/R12/FX90 (Can't find a "R" number for this one.

No specific reason for wanting to know this just curious?



04-07-2004, 11:57 AM
Hi,Ray :)

The Refrigerants are seperated according to there toxicity A,B,C .Flammability is expressed with 1,2,3.The ASHRAE handbook shows most refrigerants structure,hope this helps.

Best regards


04-07-2004, 12:30 PM

The numbering code for refrigerants is fairly straightforward. I?ll try to distil it here. The numbering system that indicates the type and composition is not to be confused with the safety categories in EN 378.

By convention the prefix ?R? denotes a refrigerant in accordance with ISO 817. Similarly some users or suppliers use the acronym of the composition, for example CFC 12 or CFC11, HCFC 22, HFC 407C and so on.

R22 does not have a letter suffic because it is a single fluid.

From then on the numbering system gets a little more complex, but it?s understandable.

The International Standards Organisation (ISO) has a standard (ISO 817) that describe how single compounds (unblended fluids) are numbered, R12, R11 etc. This numbering system denotes the chemical composition of the compound, and gives the number of Fluorine atoms, Chlorine Hydrogen and Carbon attachments etc. A low case letter after the number denotes a particular isomer of the compound.

Blends are not covered in this standard, but they get their number from ASHRAE and the code again is fairly simple.
Zeotropic blends are numbered starting at 400,
Azeotropic blends start at 500.
Where there are two or more blends using the same components in differing proportions, they have a suffix as a CAPITAL letter and appear in the order that AHRAE approve them, not necessarily the order they appear on the market. So R407 C is similar to but not interchangeable with R407 D. and so on.
Organic gases used as refrigerants, e.g. Ammonia, Water, CO2, are numbered from 700 and show the atomic weight of the molecule. So Ammonia is R717, Water is R718 etc.

To complicate matters, some manufacturers use their own numbers as trade names?? FX 90 is, I think a trade number.
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05-07-2004, 02:36 AM
To add to Argus's excellent description, a letter is added when the integer atomic weights are the same. Thus CO2 is R744 and N2O is R744a.

05-07-2004, 03:27 AM
ATOFINA's Forane FX90 was given ASHRAE code identification R419A in October 2003