Roof assembly for an air handler

An air handler (or air handler section) includes an enclosure containing various internal HVAC components and a bi-directional alignment system that during factor assembly of the enclosure helps align the enclosure's entire roof to the internal components. To help align the roof in a widthwise direction, a tapered lead-in edge in the upper corners of a block-off panel for an evaporator, filter rack, damper, fan and/or other HVAC component engages a roof rail that runs along the length of the roof. The upper corners of the block-offs also include a landing edge that engages the underside of the roof rail to help support the weight of the roof. Cross rails attached to the underside of the roof and extending along the width of the enclosure include an inclined lead-in flange that engages the upper edge of the various internal HVAC components, thereby helping align the roof in a lengthwise direction.