Whether traveling on an endless high traffic intercity bus route or a 600 mile motor coach tour showcasing the interior of Alaska and Yukon Territory, personal comfort is key to the quality of the experience. An HVAC system properly designed for each transportation vehicle can eliminate adverse health effects such as congestion, drowsiness, headaches and irritated eyes, and contribute to the enjoyment of the trip. Maintaining a high comfort level for numerous passengers confined in a small space for long periods of time is quite an engineering challenge. Fortunately, Prevost Car Company of Ste. Claire, Quebec has spent the past 69 years producing bused and motor homes with optimal comfort as a primary objective.

        Prevost is renowned in the transportation industry for technical expertise, superior quality control and uncompromising standards. In the continual search for excellence, Prevost engineers reviewed the components of their vehicle HVAC systems. They determined that the existing wire mesh air filters were not doing the best job of maintaining good indoor air quality with continuous exposure to roadway dirt and dust. With this problem identified, the Prevost R & D team designed a state-of-the-art climatic control system that provides heating and cooling with adequate amounts of conditioned, filtered air into each vehicle, in all weather conditions. The team’s main filtration objectives were to achieve a higher airborne pollutant arrestance efficiency without restricting the air flow required to maintain the sophisticated climatic control system.

        Fresh air is drawn into the system from the outside as needed. Uniform interior temperature is controlled by a six-stage electronic energy management control system. The heater and evaporator cores are mounted in the second left-hand baggage bay for easy accessibility. The second right-hand bay holds the condenser core, which is hinge-mounted to provide access to he two motors and two axial fans. A Carrier 05G compressor is mounted in the rear engine compartment and is directly driven by the engine through V-belts. Twin axial condenser exhaust fans and infinite velocity circulation blowers are key. The airflow in the main system may vary from 2200 C.F.M. to 2700 C.F.M., maintaining 2200 C.F.M. in heat mode. This flow gives a 400 to 500 pi/m face velocity at the filter. Fifteen percent of fresh air is mixed with returned air. It passes through a Permatron electrostatic air filter, then through the cooling and heating coils before being thrown back into the coach, through grills below the windows on both sides of the vehicle.

        Permatron’s exclusive Accumulator ChamberŅ design allows the air filter to maintain a high dirt holding capacity of 130 grams without face loading of restricting air flow requirements. Independent tests using standards of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, Inc. show the filter in this application has an average arrestance efficiency of 78% and an initial resistance of 0.11 IN. WG. Permatron air filters are permanent, washable and constructed to outlast the system in which they are installed. Prevost’s filter maintenance schedule involves monthly rinsing with water. Fine quality materials – galvanized steel frames and polypropylene media which never loses its electrostatic charge – stand up to regular cleaning and require no replacement.