The debate about which refrigerant to use in automotive HVAC systems is a long and drawn out one. Climate change concerns have been influencing legislation in this regard for many years. In this extract from QUBE's HVAC intelligence service, Vanessa Scholfield considers the issues and the background behind the latest dispute involving Daimler and Honeywell.

In the early 1990s HVAC systems in passenger cars used a chlorofluorocarbon known as R12 (Freon) as the refrigerant. However, as concerns grew over the potential damage caused by such CFC’s, HVAC system suppliers moved to hydrofluorocarbons, and more specifically the HFC known as R134a.

Since 2003, the EU has been discussing the second Climate Change review and has taken the decision to ban R134a for use in automotive HVAC systems on environmental grounds. The new EU rules stipulate that vehicle manufacturers will have to have phased out the use of R134a in new models from 2011 and in all new vehicles from 2017. Faced with this ruling, there has been little overall consensus from the vehicle manufacturers on which way to go in selecting a substitute refrigerant. Two options emerged as the main contenders; CO2 –based systems (R744) as favoured by the German manufacturers and a “drop in” system known as HFO-1234yf.

The German manufacturers took the decision to use R744 in 2007, and became the first automotive companies anywhere in the world to do so. Audi, BMW and Mercedes-Benz were early adopters. Unfortunately this move did not receive a warm welcome outside Germany and a number of other vehicle manufacturers and suppliers worldwide pursued the HFO-1234yf solution.

In 2009, the German automotive industry trade association, VDA, called for a common agreement among all vehicle manufacturers on a standard refrigerant to be used worldwide. Following a period of extensive tests on HFO-1234yf by more than a dozen vehicle manufacturers from China, France, Germany, India, Italy, Japan, Korea, Sweden and the USA and 20 suppliers from Asia, Europe and the USA it was agreed that the industry recommendation was for HFO-1234yf to be adopted worldwide. Given these results the German automotive industry decided to use HFO-1234yf as the refrigerant for automotive HVAC systems. The results of the testing programme showed that the new refrigerant has a GWP of 4 as opposed to the 1,430 of the old R-134a that has been in use until now. If the German manufacturers had decided to “go it alone” with R-744 it would have resulted in risks related to product liability on important export markets.

The future of the new internationally recognised R1234yf refrigerant was put in doubt late September 2012 when Daimler engineers reported that under certain conditions the new refrigerant can be flammable. According to Daimler it has alerted the relevant authorities to the findings of its tests. It would appear that Daimler's collision tests, that go above and beyond the legally prescribed requirements, have shown that the chemical can be ignited in certain extreme circumstances. As a result of the findings from Daimler's study, the chemical will not be used in Mercedes-Benz vehicles and it will continue to use what it describes as the "proven and safe" R134a refrigerant in its vehicles. Daimler has made its results known to other German vehicle manufacturers and as a result Volkswagen has also announced that it will not be using the new refrigerant. Where this leaves the position with the authorities in Europe remains to be seen.

In early February 2013, the situation became even more unclear when BMW announced it was withdrawing from the industry group established to test the safety of the new refrigerant. It is thought that Audi has also quit the group. BMW claims that it is not the test results that are necessarily wrong but it is not convinced the methods applied are sufficient to achieve a definitive conclusion that guarantees BMW's high safety standards. The working group, comprising Daimler and 12 other car makers, was set up to review the position and was established in November 2012. It is due to report its findings by the end of February 2013. The European Commission has made no comment so far.

See also: US: Honeywell claims SAE has 'high level of confidence' in new low-CO2 refrigerant

This article is extracted from the QUBE automotive HVAC intelligence service

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