Patent ID: 7832464

Claim:
An HVAC unit comprising; a housing defining a primary inlet, a mixing chamber, a first zone outlet, and a second zone outlet, wherein said housing conveys airflow from said primary inlet to said first and second zone outlets, an evaporator supported by said housing downstream of said primary inlet for cooling air being from said primary inlet, a heater core supported by said housing in said heater air path downstream of said evaporator for heating cool air delivered from said evaporator, a zone valve for apportioning airflow from said mixing chamber between said first zone outlet and said second zone outlet, said housing defining a cold bias outlet downstream of said evaporator for bleeding cool air from said evaporator, said housing defining a hot bias outlet downstream of said heater core for bleeding hot air from said heater core, and a mixing valve sub-assembly comprising a casing defining: (i) a cold bias inlet and a hot bias inlet and a second zone inlet, and means for attaching said casing with said cold bias inlet in sealing engagement with said cold bias outlet and with said hot bias inlet in sealing engagement with said hot bias outlet and with said second zone inlet in sealing engagement with said second zone outlet, (ii) a proportioning chamber having a cylindrical wall and circular end walls downstream of said cold bias inlet and said hot bias inlet and said second zone inlet for receiving and mixing air from said cold bias inlet and said hot bias inlet and said second zone inlet and producing a stream of mixed air having a predetermined temperature independent of the temperature of the air exiting said first zone outlet, (iii) a third zone aperture in said cylindrical wall for directing mixed air out of said casing, and (iv) a cold bias conduit for conveying air from said cold bias inlet to said proportioning chamber and a hot bias conduit for conveying air from said hot bias inlet to said proportioning chamber and a second zone conduit for conveying air from said second zone inlet to said proportioning chamber, wherein said hot bias conduit terminates in a hot bias aperture in said cylindrical wall, said cold bias conduit is forked to extend around said hot bias conduit and terminates in a cold bias aperture in each of said circular end walls, and said second zone conduit terminates in a second zone aperture in said cylindrical wall, and wherein said hot bias aperture is substantially diametrically opposite to said third zone aperture and said second zone aperture is disposed substantially at a right angle to said diametrically opposite hot bias and third zone aperture; and a mixing valve disposed in said proportioning chamber for producing said stream of mixed air.