Abstract: A heat transfer unit includes an inlet manifold; an outlet manifold spaced from the inlet manifold; and a plurality of conduits coupling the inlet manifold to the outlet manifold, wherein at least on the conduits is coupled to the outlet manifold at an oblique angle. In one form, the conduit includes a L-Coil. In another form, the conduit includes a D-Coil. In another form, the conduit includes a coil having two or more C-shaped sections. Each conduit includes a section arranged in an interior space of a heater box, and at least one heater is arranged in the interior space of the heater box.