With the EU MAC directive banning R134a taking effect in January 2017, German automaker Daimler began using R1234yf, an HFO, in its Mercedes-Benz cars in Europe, with the exception of several models that employ CO2 as a refrigerant.
However, for vehicles with 1234yf systems, “we have implemented a comprehensive safety concept to reduce the risk of fire formation,” said René Olma, globalcommunications, Mercedes-Benz Cars, Stuttgart, Germany.
All current passenger car models with gasoline engines of the Mercedes-Benz, Mercedes-AMG & Mercedes-Maybach brands have been equipped with a so-called “inertization” system. “This reduces the risk of fire in the event ofan accident with these vehicles with R1234yf,” said Olma.
In case of a severe frontal collision, the system ensures that the resultant refrigerant/air mixture is separated from the hot engine components in the engine compartment and that these components “are furthermore cooled in a highly effective manner.”
While R1234yf has been deemed safe to use in mobile air conditioning (MAC) by government authorities in the U.S. Daimler has a long history of questioning R1234yf. In 2012, it announced results of a study showing the potential combustibility of R1234yf in the event of a severe collision.
R1234yf is described by the German Environment Agency (Umweltbundesamt or UBA) as flammable and, in the event of fire, formingtoxic, highly corrosive hydrofluoric acid (HF). A current ASHRAE study –ASHRAE-1806, “Flammable Refrigerants Post-Ignition Risk Assessment” – isdoing a risk assessment of the creation of hydrofluoric acid in the combustion of A2L refrigerants like R1234yf.
As an alternative to R1234yf, since 2017, Daimler’s Mercedes-Benz S 400 Coupé has used CO2 in MAC. In addition, in all variants of the S-Class (Sedan, Coupé & Cabriolet) a CO2 air conditioning system is employed in the main volume carriers S 560 and S 400 d. Also in the E-Class, the CO2 air conditioning system is available in some variants as part of the Thermotronic equipment. “In order to reach the necessary quality level, we start with a slow production ramp-up of the new air conditioning systems and will decide on a further case-by-case use,” said Olma.
To read the complete cover story on HFOs in Accelerate Magazine from which this article was excerpted, click here.
“We have implemented a comprehensive safety concept to reduce the risk of fire formation.”René Olma, Mercedes-Benz Cars