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Hydrofluoroolefin-The Fourth Generation Refrigerant

Tongue-twisting terms used to identify the chemical make-up of the refrigerants we use are a long standing tradition in the HVACR industry. Throughout our history we’ve dealt with Dichlorodifluoromethane (R-12), Chlorodifluoromethane (R-22)… which, as if one chemical term to describe it wasn’t enough to describe this one, Difluoromonochloromethane and
Monochlorodifluoromethane are also used… and of course there’s Tetrafluoroethane (R-134A) and Difluoromethane and Pentafluoroethane (R410a). And now, we can add Tetrafluoropropene, R-1234yf.


From a technician’s perspective, rather than use the specific chemical identifiers for refrigerants, we, of course, lean on the categories…CFC – Chlorofluorocarbon…(R-12) HCFC – Hydro-chlorofluorocarbon….(R-22), and HFC – Hydrofluorocarbon (R-134a and R-410a) to label what we’re working with when it comes to servicing refrigeration systems. And to this alphabet soup of identifiers we can add now HFO – Hydrofluoroolefin, refrigerants that are listed as having a zero Ozone Depletion Potential and a very low Global Warming Potential.

Figure One breaks things down into a timeline from the 1930s when the refrigeration industry was in its infancy, to where we are today.

Figure One

One way to consider the impact of an HFO refrigerant on the environment is to compare it to carbon dioxide. Compared to R-134a, which has a GWP that is 1,430 greater than carbon dioxide, and R-410a, which is listed as having a GWP that is 2,090 times greater, R-1234yf is identified as having a GWP that is just 4 times that of carbon dioxide.

Other factors that have been reported relative to pure HFOs are that they have no temperature glide and they have an excellent coefficient of performance. They are also described as having other characteristics similar to R-134a, including its toxicity rating, and the previously mentioned system performance. When it comes to the issue of flammability of HFOs,

Figure Two (courtesy of ESCO Group) shows a table that is used to categorize refrigerants in regard to their flammability and toxicity.

Figure Two

HFO refrigerants are in the category A2L, which means they are considered to be low toxicity and a rated as being slightly flammable. HFO 1234yf is also categorized as a medium pressure refrigerant.

When it comes to rating HFO 1234yf in regard its capacity to transfer heat, the partial temperature/pressure chart shown in Figure Three (courtesy of ESCO Group) provides some insight on this.

Figure Three

The concept to consider here is the idea that the lower the boiling point of a refrigerant, the more work it can do. And comparing the three refrigerants in the highlighted areas shown illustrates the capacity of HFO 1234yf.

Note that the boiling point for R-12 is shown as being between -20°f and -25°F. In the case of R-134a, the chart shows that the boiling point is between -10°F and -15°F. And, when considering HFO 1234yf, the area of temperature is, like R-12, between -20°F and -25°F.

In addition to the importance of staying up to date regarding new developments in refrigerants in regard technicians taking a green approach to servicing HVACR equipment, there’s also the aspect of testing for EPA Section 608 certification to consider. Recent changes to rulings and information about new refrigerants are now part of the updated exam. And, while technicians who already hold an EPA cert are grandfathered and don’t have to re-test, those preparing for their initial certification will be testing under the new regulations. For more information, you can contact ESCO Group at 800-726-9696.

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