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Mercedes-Benz to begin equipping top models with CO2 air conditioning systems starting in 2017; adapting other models for R1234yf

From 2017, Mercedes-Benz will offer in Europe the S- and E-Class as the first production passenger cars equipped with CO2 air conditioning systems. These completely newly developed systems are based on the DIN specifications defined by the automotive standards committee of the German Association of the Automotive Industry (VDA).

Due to especially quickly available and high cooling performance, CO2 air conditioning systems swiftly provide for a pleasant feel-good climate inside vehicles even in very hot weather, the company said, while at the same time complying with legal requirements for low global warming potential refrigerants and avoiding the use of R1234yf, which Mercedes has found problematic. (Earlier post.)

The EU is mandating a limit of 150 for the global warming potential (GWP) index of refrigerants used in mobile air conditioning systems. Apart from CO2, R1234yf is the only refrigerant produced on an industrial scale to date with which the future requirements of the EU directive for air conditioning systems in new vehicles can be met.

The current dominant refrigerant R134a has a GWP of 1,300; the sanctioned low GWP replacement refrigerant R1234yf has a GWP of 4; and R744 (CO2) of 1. The Mercedes solution thus offers an even lower impact on the climate than R1234yf, while avoiding the in-use issues Daimler identified back in 2012.

The use of CO2 as a refrigerant necessitates the redesign of crucial components. CO2 air conditioning systems operate at a pressure of more than 100 bar—some ten times higher than that of today’s systems. This means that all components including the hoses and seals need to be redesigned.

Mercedes-Benz has drafted corresponding standards together with all German automobile manufacturers and numerous suppliers in the automotive standards committee of the German Association of the Automotive Industry (VDA). The publicly accessible DIN specification documents also offer other companies an opportunity to quickly launch development activities of their own. This would create the prerequisites for swift market penetration by this high-tech air conditioning system, the company suggests.

Mercedes-Benz has assumed a pioneering role in this respect. It is the first automobile manufacturer to award not only development contracts but also to place production orders for CO2 air conditioning systems and their components.

Adapting other models for R1234yf. Despite the exceptionally short time frame, the high level of quality targeted by Mercedes-Benz for CO2 air conditioning systems has already been realized in the new development for the company’s top models.

However, deployment throughout the entire vehicle fleet will not be feasible by the effective date of the new EU directive on 1 January 2017. To also meet the EU requirements on schedule for all other model series, the company has developed safe and reliable solutions for the use of R1234yf

The R1234yf refrigerant has different flammability properties than the R134a refrigerant used in the industry to date. In order to ensure a continued high standard of safety for its customers in the future, Mercedes-Benz has carried out extensive testing on all its vehicle models.

The result is a comprehensive package of vehicle-specific measures in order to guarantee Mercedes-Benz’ high safety standards for the models using the R1234yf refrigerant.

In particular, these include a specially developed protective system tailored to the given vehicle configuration. In the event of a severe frontal collision, the patent-pending 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.

This is made possible by a gas generator, which releases inert argon gas specifically at the relevant hot spots. This effectively keeps the mixture from bursting into flames.

As a result, this solution ensures that customers’ justifiable safety needs and Mercedes-Benz’s high safety standards will continue to be met in the future. At the same time, it also provides the company with another means of helping to protect the climate.


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Super, I hope Tesla will copy that soon for Model S and Model X and then also find a replacement for that lead-acid battery. How hard can it be for a 100k USD car?


The obvious solution to problems with hoses and seals is to eliminate the hoses and seals as consumer refrigeration gear does.  However, with CO2 being as cheap as it is, it may be simpler to stick with things that leak for the other advantages involved with e.g. engine-driven compressors.

Dr. Strange Love

Recharge weekly.

What is the lubricant?

Dr. Strange Love

Recharge weekly.

Special interests keeping the refigeration industry relevent.


CO2 is used as a solvent both in enhanced oil production and in dry cleaning, so I suspect that a wide variety of hydrocarbon oils would work with it.


The lube is not the problem, sealing high pressure with a rotating shaft is.


Propane! Wait... Did I say that?

I think its cheap, easy, heavier than air, and can basically be a better refrigerant than most solutions... Though it has a flammability range of 10 feet... Its really not that bad for the environment either, mixes well with lubricant and uses relatively low pressures.

I mean how dangerous is a pound of propane? If cars can use CNG and LPG I mean why would this be inherently more dangerous?


If D-B is avoiding R1234yf because of flammability, there's no way they'd go with propane (or isobutane, or anything similar).  CO2 is the way to go.  If there are issues with seals there is always the option of hermetically sealed elecric compressors.


I thought the R1234yf had an issue where it etched the glass on the windshield. Propane is fairly hard to ignite... Sure it could rupture in a crash...but odds are I would do it in the engine bay. Its been used in cars by others before, seemed to have great properties.

I know 1234yf is still new and machines cost an arm and a leg, but it just seems like soon as a patent expires we get a new refrigerant. What's really crazy is molecules similar to what is in R134a is a propellant in over the counter canned airs and such... So all this ghg attention to autos is achieving results how again?

I'd be for CO2 as long as the change the refrigerant handling laws for servicing it...I dont want to risk jail/large fines if I have to make a repair to the system.

What's the high and low side pressure difference on CO2 systems? I wouldn't assume piston seals, but rather seals in general on the system being a problem.

I just want an AC that is efficient, cools very effectively in high temperature and humidity regions 100F and 90%, and is relatively cheap to service and has a good track record for reliability.

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