Motor Vehicle Air Conditioning Motor vehicle air conditioners (MVACs) provide comfort cooling for passengers in cars, trucks, buses, planes, trains, and other forms of transportation. The MVAC end-use is unique due to use in widely varying ambient conditions, likelihood of accidents, and the location of a part of the system―the evaporator―inside the passenger compartment. All refrigerants approved for use in MVAC have associated use conditions. MVAC: Passenger Air Conditioning in Light-Duty, Medium-Duty, Heavy-Duty and Off-Road Vehicles Air-conditioning systems used to cool passenger compartments in light-duty, medium-duty, heavy-duty and off-road vehicles are typically charged during vehicle manufacture and the main components are connected by flexible refrigerant lines. MVAC: Passenger Air Conditioning in Buses and Trains Air-conditioning systems used to cool passenger compartments in buses and trains are typically manufactured as a separate unit that is pre-charged with refrigerant and installed onto the vehicle in a separate enclosure (e.g., roof mounted).

The refrigerant charge for these systems is much larger than those for other MVAC systems.San Diego, Calif., United States Carrier Corp., a subsidiary of United Technologies Corp. (NYSE:UTX), today launched the AvantAC™ All-Electric Air-Conditioning System for the North American market. It’s the first modular rooftop all-electric system in North America, providing passenger comfort in intercity and transit buses independently of vehicle engine speed. The innovative AvantAC air conditioner uses aircraft power generation and management technology from another United Technologies subsidiary, Hamilton Sundstrand, a global supplier of technologically advanced aerospace and industrial products whose systems are on more than 90 percent of the world's commercial, corporate, regional and military aircraft. The generator provides the required capacity consistently, even with the bus engine idling. “While higher fuel costs increase demand for public transportation, bus fleets are challenged to provide cleaner operating, more fuel efficient equipment,” says Michael Dormer, managing director, Carrier North America Bus.

“The AvantAC system meets both of these requirements. It generates and controls its own power, or it can use power supplied by a hybrid drive.” The AvantAC All-Electric system features multiple, electrically driven, self-contained “plug-and-play” modules installed on the vehicle roof. The system employs a belt-driven generator to produce electric power independent of engine speed, rather than using the conventional system of a vehicle engine driving a large refrigeration compressor. window units ac and heatSeveral small compressors for the cooling circuits are located inside the rooftop unit.ice forming on outside ac unit The independent power supply and all system functions are controlled using intelligent power controller architecture, enabling balanced interaction. hvac units for home

Advanced electronics ensure cooling performance is continuously and automatically adjusted to the required demand. Optimum temperature, air distribution and humidity control are provided by the system at all times – even when the bus engine is idling at only 700 RPM instead of running at 2000-plus RPM. The AvantAC unit’s refrigeration system comes self-contained, fully sealed, factory charged with the industry standard, non-ozone depleting R134a refrigerant and fully tested. Without refrigerant piping running through the bus, the AvantAC system virtually eliminates refrigerant leaks, traditionally one of the key reliability risks and costs associated with conventional systems. Carrier’s extensive experience in packaged systems design suggests that leak rates for such systems are close to zero. As a result, the AvantAC system requires an estimated  refrigerant charge up to 80 percent less than a typical conventional system based on an average of 300 buses over a 12-year product lifespan.

“No time-consuming field brazing or threading is needed,” Dormer says.  “Downtime can be significantly reduced, while environmental performance is enhanced.” “Reliability is imperative in the intercity and transit bus segments,” Dormer adds.  “A poorly functioning air-conditioning system can mean uncomfortable passengers, or worse, that the bus has to be taken out of service. That’s why Carrier designed reliability into the AvantAC manufacturing platform.” It has long been recognized that any industrial system operating on AC power offers more reliability and lower maintenance costs than systems dependent on DC power, especially in the public transport segment. The AvantAC All-Electric system’s brushless wound field AC generator comes in four sizes to match different applications. Sufficient constant voltage ensures that the system runs using extended lifetime AC components, increasing preventive maintenance intervals significantly. For example, the expected life of an AC-powered blower motor generally exceeds its DC-powered equivalents by a factor of six.

Flexible To Meet All Requirements The AvantAC system’s intelligent control enables zoning to be applied to meet specific load requirements in defined areas of the bus. Overall weight distribution can be improved and the driver section can receive special treatment. Return air grilles can be located in virtually any position to suit all types of vehicle design. Flexible air transition ducts allow the system to be accommodated easily to different roof radii and supply air interface connections. The AvantAC All-Electric system covers the industry standard capacity range from 16 kW to 40 kW. Due to the constant cooling output at any speed, the system can provide the necessary capacity to maintain the set temperature – even in “Stop and Go” applications typical of intercity and transit bus routes. Carrier Transicold provides industry-leading transport temperature control and anti-idling solutions with a complete line of equipment for refrigerated trucks, trailers and containers, auxiliary power units for heavy-duty trucks and transport air-conditioning systems for buses and recreational vehicles.