Patent ID: 7726142

Claim:
A roof enclosed HVAC system for a vehicle cab, comprising: a roof upper panel; a roof lower panel; a fresh air duct communicated with a fresh air inlet exposed to an exterior of the cab; a recirculation air duct communicated with a recirculation air inlet exposed to an interior of the cab; a conditioned air duct communicated with an air outlet exposed to the interior of the cab; an HVAC unit mounted between the roof upper and lower panels, the HVAC unit comprising a fan unit, a heater unit and an evaporator unit, the heater and evaporator units being concentrically arranged around and surrounding the fan unit; the fan unit comprising an annular impeller driven by a motor mounted in the center of the impeller, the impeller having an annular upper wall, an annular lower wall surrounding an inlet chamber, and a plurality of impeller blades extending between the upper and lower walls, the blades forcing air radially outwardly upon rotation of the fan unit, the fresh air duct and the recirculation air duct being communicated with the inlet chamber, and the conditioned air duct receiving air forced outwardly by the fan unit through the heater unit and the evaporator unit; the roof lower panel having a central opening therein, and the fan unit is positioned adjacent said central opening; a cover panel is mounted adjacent to the central opening, and an outer portion of the cover panel and an inner portion of the roof lower panel forming a portion of the recirculation duct; and a recirculation filter is mounted in the recirculation duct between the cover panel and the roof lower panel.