Abstract: This invention features a condensate drain that drains condensate from an impeller housing as well as an impeller housing having such a drain. This condensate drain is configured so as to allow the condensate from the exhaust to be continuously drained from the housing while the impeller is or is not operating. Preferably, the impeller housing includes a housing shell having an aperture in fluid communication with the housing interior. A top portion of the aperture extends above an interior surface of the housing shell to minimize the venturi effect of air flowing by the aperture responsive to rotation of the impeller. The interior surface of the housing further includes a dished region proximate the aperture, where the bottom of the dished region is arranged to correspond with a bottom edge of the aperture.

Abstract: A noise cancellation device for a centrifugal blower comprises, in a first embodiment, a rod mounted in the output of a blower and generally axially parallel to the impeller so that as the impeller rotates, the blades of the impeller sweep past the rod much as in the manner that the blades sweep past the cutoff section of the blower output. The rod is positioned a specified distance away from the cutoff such that it generates a tone which interferes with the pure tone otherwise generated by the impeller blades sweeping past the cutoff in an out of phase condition to thereby eliminate the pure tone or "spike" normally experienced at a fundamental frequency and harmonics thereof. In a second embodiment, a nose-like projection extends inwardly from a sidewall of said blower housing and is positioned substantially in the same position as the rod of the first embodiment. The nose-like projection may be integrally formed as part of the blower housing.

Abstract: A noise cancellation device for a centrifugal blower comprises a rod mounted in the output of a blower and generally axially parallel to the impeller so that as the impeller rotates, the blades of the impeller sweep past the rod much as in the manner that the blades sweep past the cutoff section of the blower outlet. The rod is positioned a specified distance away the cutoff such that it generates a tone which interferes with the pure tone otherwise generated by the impeller blades sweeping past the cutoff in an out of phase condition to thereby eliminate the pure tone or "spike" normally experienced at a fundamental frequency and harmonics thereof.