Preparation of a DIN specification series for CO2 air-conditioning systems
Under EU Regulation (EC) No. 842/2006 it has only been possible since 2011 to use substances that have a global warming potential (GWP) of less than 150 in air-conditioning systems in new series of cars. The GWP is an index that denotes the ratio of its effect as a greenhouse gas over a period of one hundred years. This limit value also applies to all new vehicles as from 2017. Refrigerant type R1234yf, which satisfies the requirements of this regulation, is an alternative to refrigerant R134a, which has previously been used in air-conditioning systems. As a result of the almost total compatibility of R1234yf with the existing equipment in established air-conditioning systems, carmakers and suppliers can continue to use the components that have been used for many years in their systems. This is one very good point in favor of R1234yf. A wide range of tests has confirmed that R1234yf can be used safely in motor vehicles. However, tests whose scope went beyond the requirements of product safety legislation showed indications that the possibility of a fire could not be ruled out completely in every vehicle model in the event of an accident.
R744 (CO2) is a safe alternative refrigerant to R1234yf. However, the use of R744 requires considerably higher operating pressures. That means that it cannot be used with the components of established air-conditioning systems without modification. In view of the partly critical test results with R1234yf, German motor manufacturers have decided to concentrate on and complete the development of air-conditioning systems that are suitable for the use of R744.
At the same time, as the development and testing work, a series of specifications entitled “Road vehicles – R744 air-conditioning systems” has been prepared. The aim of this is to standardize the components for R744 systems for cars. In addition to the requirements on components of R744 air-conditioning systems, these specifications also describe the process requirements for their development and qualification. The series of specifications was prepared in 2014 and will be published in the second half of 2015 in German and English. It currently consists of 18 individual specifications with the label “DIN SPEC 74102 and following numbers” for individual components such as heat exchangers, compressors, valves and connectors. Other specifications for other components are still being developed. The specifications provide valuable information for the qualification of components for component developers and manufacturers. This will make it possible to use components with the same or similar design in all R744 vehicle air-conditioning systems, regardless of vehicle type. In this way, the series of specifications will make an important contribution to safety, quality and cost optimization for the manufacture and operation of air-conditioning systems containing R744 refrigerant.