On To HFO1234yf
If you’ve attended any trade shows in the last few years, you might have noticed that all the heavy hitters in the A/C business have been unveiling new tools and Recovery/Recycling/Recharging (RRR) equipment designed to meet the SAE standards for servicing the newest automotive refrigerant, HFO1234yf. Many models globally are using the new gas and domestically, at least one manufacturer has chosen to include it in a platform offered for sale right here in the U.S.
News was breaking over Daimler’s decision not to use HFO1234yf even as the SAE committee was meeting in Orlando.
The decision to identify a replacement for R134a was made in response to regulations passed by the European Commission, banning the sale of “new model platforms” using R134a starting in 2011 and banning the use of the gas all together by the 2014 model year. The concern was the global warming potential of R134a, an environmental condition where certain chemical compounds act as a blanket of insulation in the upper atmosphere. One of the first alternatives to be considered was CO2, also referred to as R744.
At first glance, this appeared an ideal solution. Refrigerants (and other chemicals) were being analyzed and rated in terms of their global warming potential and assigned a numeric grade called a “GWP” number. R134a has a GWP of 1,300 (according to the online resource, EngineeringToolbox.com) and the maximum allowed by the new rules was a GWP of 150. CO2 is actually the baseline for establishing a GWP rating, making its rating 1. Can’t get much better than that. But there were other concerns that surfaced as the idea of using R744 in an automobile was being considered.
First, in order for it to work, the system would have high side operating pressures in the 2,000-plus psi range. This could pose safety issues to both the technician and the passengers if used in a conventional design. Second, CO2 systems weren’t that good at cooling cabins in climates that were on the high end of the normal temperature range. It might do the job in Trenton, but wouldn’t cut the mustard in Phoenix.
Third, in terms of total emissions, CO2 systems polluted more than their R134a counterparts. And fourth, the cost of a system using secondary loop design features to keep the high pressure circuit out of the cabin (and also control the threat of high CO2 cabin levels in the event of a system leak) were costly and complex.
|Ward Atkinson, former SAE committee co-chair, briefs MACS attendees on the State of the Industry.|
Other alternatives were assessed and considered, including the substitute eventually agreed on — HFO1234yf. Unlike others, though, HFO1234yf had pressure and temperature characteristics very similar to R134a. It was nearly a drop-in replacement that would require very little on the manufacturing side to adopt. One flaw to HFO1234yf is its classification as “mildly flammable.”
But tests conducted proved to everyone involved that the risk was manageable. (As a side note, it was found that several other fluids residing under the hood were more susceptible to combustion in an accident scenario than the new gas was). The conclusions appeared to be so favorable that Atkinson even told Motor Age in an interview a few years back that the topic of “R744 was a dead horse” and that “1234yf would be the replacement of choice.” Aftermarket tool and equipment companies spent resources and capital to bring the needed service equipment to market and as noted, some manufacturers started producing production vehicles fitted with HFO1234yf systems.
Some auto manufacturers, however, were holding back. Late last year, Daimler dropped a bombshell announcement, stating that tests they had conducted independently assessing the flammability risk of the new gas indicated issues that were outside of what they considered an acceptable level. They announced publicly that, because of these test results, they would not consider the use of HFO1234yf in any of their products and even recalled a few models that had been delivered state-side fitted with HFO1234yf systems. What makes the announcement even more staggering is that Daimler, along with other German manufacturers that have since added their support to Daimler’s position, where part of the original process that selected HFO1234yf in the first place.