By Elvis L. Hoffpauir, MACS president and COO
In 1884, William Whiteley placed ice blocks in trays under horse-drawn carriages and blew the air inside by attaching a fan to the axle. From there, advances in mobile air conditioning were driven purely by ingenuity and engineering prowess. But now it’s regulatory forces that drive new engineering solutions, and the mobile A/C service industry can expect new challenges in the future.
For more than 50 years, CFC-12 was considered a benign refrigerant. Replacing leaking refrigerant was accepted as a normal service procedure because of its low cost, but the Montreal Protocol which addressed the earth’s ozone depletion problem, changed all that. New regulations made it illegal to vent refrigerant, so the industry responded with new equipment and service procedures, and the world’s auto manufacturers switched to HFC-134a, which did not affect the ozone layer.
The new refrigerant is a potent global warming gas, with a global warming potential (GWP) of 1430. Under new European Union regulations, refrigerant must not exceed a GWP of 150. This launched an on-going quest to commercialize refrigerants meeting that threshold.
In recent years, vehicle manufacturers have reduced refrigerant emissions by reducing leakage rates and system charges. These changes have also resulted in substantially longer service intervals, as evidenced in previous MACS Field Service Surveys. The new 2013 Field Service Survey (currently underway) is expected to reflect even greater service intervals.
Regulations target two types of emissions identified with mobile A/C systems: direct emissions that result from leaks or improper servicing, and indirect emissions generated by the energy required to operate the system (tailpipe emissions). Of the two, the latter is greater over the lifetime of the vehicle. Federal fuel mileage regulations offer the OEMs fuel mileage credits for reductions in mobile A/C emissions. This means A/C systems will become even more complex and offer new service challenges.
These changes include: reduced reheat temperature control, using externally controlled, variable displacement or fixed compressor controls; the addition of an internal heat exchanger (or suction line heat exchanger) for improved cooling performance; automatic default to 100% recirculated air whenever the outside temperature is above 75 degrees; and using pulse width modulated power to limit blower motor energy consumption.
Given current trends in Europe, for the next few years there will probably not be a common global refrigerant. Potential replacements for R-134a include high-pressure carbon dioxide and blend refrigerants that use operating pressures that are common today.
In hybrid and electric vehicles, we may see a secondary loop system for cooling occupants, batteries and other onboard electronic equipment. Circulating a low-pressure liquid chilled by a small refrigeration loop reduces the complexity of providing pressurized refrigerant to multiple points in the vehicle. Higher efficiency powertrains will result in less engine heat, complicating occupant comfort and window defogging. This will be a bigger problem in electric vehicles (EVs). Heat pumps (reverse-cycle refrigeration systems) have limitations at colder temperatures, so supplemental electric heat may be required to meet the demands. Assuming supplemental heat will be required in cold weather, and given the complexity of cooling occupants and components in hot weather, the HVAC system becomes a total vehicle environment management system with complex controls.
Finally, as smaller vehicles with less interior volume enter the fleet, passengers will be closer to the windows. This results in more direct sun load on occupants and increased solar load per cubic foot of interior space. In inclement weather, there is greater potential for window fogging due to passengers being closer to the windows and occupant respiration creating more moisture input per cubic foot of interior space.
With each new challenge comes new technology. Technicians must be adequately trained to service these complex HVAC systems, and MACS will tell you how to find it.
The Mobile Air Conditioning Society’s blog has been honored as the best business to business blog in the Automotive Aftermarket by the Automotive Communications Awards and the Car Care Council Women’s Board!
When having your mobile A/C system professionally serviced, insist on proper repair procedures and quality replacement parts. Insist on recovery and recycling so that refrigerant can be reused and not released into the atmosphere.
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You can E-mail us at firstname.lastname@example.org . To locate a Mobile Air Conditioning Society member repair shop in your area. Click here to find out more about your car’s mobile A/C and engine cooling system.
The 34th annual Mobile Air Conditioning Society (MACS) Worldwide Training Conference and Trade Show, Power Up will take place January 16-18 2014 at the Sheraton New Orleans.