Abstract: A multi-oil fired furnace having a heat exchanger that extends rearwardly of the combustion chamber and utilizes laminar air flow around the combustion chamber to minimize the width and height dimensions of the cabinet shell for the furnace. The heat exchanger includes an exhaust header having a central opening and a cluster of concentrically arranged exhaust tubes connected to the combustion chamber. A vertical baffle forces the flow of air through a central opening that is concentric with the combustion chamber into a group of horizontal baffles directing the air into a generally laminar flow pattern against the outer surface of the combustion chamber before being discharged from the cabinet shell in a selected one or more of three possible directions. The fan control switch is mounted on a mounting plate that is welded to the combustion chamber to provide a planar contact surface for the switch mechanism.