Abstract: A plurality of planar walls for a HVAC enclosure enclose an interior volume subjected to negative pressure which pressure tends to draw undesirable contaminants into the volume through fastener apertures used to attach the walls together. A corner joint construction for the enclosure includes inner and outer L-shaped members formed with tortuous engaged end extensions. The members cooperate to form an L-shaped volume for the length of each corner joint of the enclosure and an end chamber also extending for the length of the joint is formed by the extensions at each L-shaped volume leg edge. The L-shaped volume and the end chambers isolate the outermost member from interior volume. Fasteners used to fasten the walls to the corner joint are fastened in communication with the end chambers or the L-shaped volume to isolate the interior volume from the fastener apertures.

Abstract: A louver assembly, which acts as a water-removing inertial separator, is located in the air intake of an enclosure maintained at negative pressure. The louver includes a number of spaced vanes, each formed without discontinuities by simple bending into a stair-step-like configuration when viewed end-on. Air enters the enclosure by passing between adjacent vanes, experiencing changes of direction of between 70 degrees and 90 degrees at the vane's surfaces to separate water therefrom.