Heat recovery and demand ventiliation system

Abstract

A ventilation system for an air conditioning system includes dampers, a heat exchange unit, and a control unit. One damper controls the flow of ambient air into the system. The other damper controls the flow of relief/exhaust air that is cannibalized from return air from a room or space being cooled (or heated) by the air conditioning system. The ventilation system utilizes a control algorithm in the control unit to calculate, at stepped spaced apart increasing room ventilation rates, increasing CO2 concentrations in the air in the room that are below a maximum desired CO2 concentration in a room. The control algorithm permits a control unit in the ventilation system to open and close the dampers to maintain a CO2 concentration in the room that is below the desired CO2 concentration level.

1 . In combination with a building structure including
 a room with a maximum occupancy rating of at least twenty people per 1,000 sq. ft of occupied space,   an air conditioning system including
 a heat transfer coil, 
 a first section of duct (D 4 ) leading to the heat transfer coil to direct supply air from the building structure over the coil, and 
 a second section of duct (D 2 ) leading away from the heat transfer coil to carry air from the coil back into the building, 
   the improvements in the building structure comprising   (a) a ventilation control unit attached to the first section of duct and including
 (i) a housing ( 23 ), 
 (ii) a heat exchange unit ( 12 ), 
 (iii) a third section of duct (D 1 ) connected to said first section of duct (D 4 ) to direct a first portion of return air from the room into said first section of duct, 
 (iv) a fourth section of duct (D 3 ) to direct a second portion of return air from the room over said heat exchange unit, 
 (v) a fifth section of duct (D 5 ) to direct ambient air over said heat exchange unit into said third section of duct (D 1 ), said heat exchange unit maintaining said second portion of return air separate from said ambient air and transferring heat between said second portion of return air and said ambient air, 
 (vi) a sixth section of duct (D 6 ) to direct said second portion of return air from said heat exchange unit into the outside atmosphere, 
 (vii) an outlet damper ( 16 ) controlling the flow of said second portion of return air over said heat exchange unit ( 12 ) and into the outside atmosphere, 
 (viii) an inlet damper ( 15 ) controlling the flow of said ambient air over said heat exchange unit ( 12 ), 
 (ix) a control unit operatively associated with said inlet and outlet dampers to control the rate of flow of said ambient air and said second portion of said return air, respectively, through said dampers, 
 (x) a first flow sensor operatively associated with said inlet damper to generate signals to said control unit representing the rate of flow of ambient air through said inlet damper, 
 (ix) a second flow sensor operatively associated with said outlet damper to generate signals to said control unit representing the rate of flow of ambient air through said outlet damper, 
 (x) a CO2 sensor in the room to generate signals to said control unit representing the concentration of CO2 in the air in the room; 
   (b) a first fan to direct said ambient air into said fifth section of duct, over said heat exchanger, and into said first section of duct;   (c) a second fan to direct said second portion of return air from said fourth section of duct, and through said fourth section of duct over said heat exchanger, and into the atmosphere;   (d) a control algorithm in said control unit to calculate, at stepped spaced apart increasing room ventilation rates, increasing CO2 concentrations in the air in the room that are below a maximum desired CO2 concentration in the room.