A combustion furnace includes a blower housing with a centrifugal blower impeller disposed therein and plural heat exchanger tubes disposed substantially around a major portion of the periphery of the impeller. The heat exchanger tubes receive combustion gasses from plural burner nozzles and discharge combustion gasses to a plenum in communication with a motor driven inducer gas pump. The integrated blower housing and heat exchanger may be disposed in a cabinet including support structure for a fuel delivery manifold, associated burner nozzles and forming air inlet and outlet openings for air being circulated by the blower.