Abstract: Some embodiments of the present invention enable a user to select from different appearances and sound types by providing different door chime assembly housing covers. The housing covers can be different in shape, size, appearance, and/or acoustic property, and preferably can be releasably mounted a housing base. A door chime assembler, manufacturer, or user can therefore select from different door chime assembly appearances and acoustic properties by selecting one of two or more different housing covers. The door chime assembly can employ a number of different features that change the sound quality of the door chime assembly, including a domed or tented housing cover shape, a housing cover having curved edges and corners, an open acoustic chamber unbroken by internal walls, and side wall housing apertures. Other significant advantages are provided by the use of a door chime assembly transformer that is mounted to the door chime assembly housing.

Abstract: Some embodiments of the present invention enable a user to select from different appearances and sound types by providing different door chime assembly housing covers. The housing covers can be different in shape, size, appearance, and/or acoustic property, and preferably can be releasably mounted a housing base. A door chime assembler, manufacturer, or user can therefore select from different door chime assembly appearances and acoustic properties by selecting one of two or more different housing covers. The door chime assembly can employ a number of different features that change the sound quality of the door chime assembly, including a domed or tented housing cover shape, a housing cover having curved edges and corners, an open acoustic chamber unbroken by internal walls, and side wall housing apertures. Other significant advantages are provided by the use of a door chime assembly transformer that is mounted to the door chime assembly housing.

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.

Abstract: A direct air heater using the air to be heated as combustion air includes means for maintaining a constant flow of air across the burner. The heater also includes means for recirculating inside air and means for controlling the flow of inside air, preferably, to maintain a constant pressure in the space being heated.