Automatic displacement ventilation system with heating mode

1. A ventilation system for an occupied space, comprising:

at least one supply register with a displacement-type diffuser providing a plurality of uniform openings that maintain a uniform flow of ventilation air at a non-mixing flow rate that promotes stratification of air in said occupied space;

at least one first exclusive return register positioned closer to a ceiling than a floor of said occupied space and configured to withdraw air from said occupied space;

at least one second exclusive return register positioned closer to the floor than the ceiling and configured to withdraw air from said occupied space; and

a central control system including a controller with at least a heating mode and a cooling mode, configured to control flow of heated or cooled air to said at least one supply register and selectively to control flow of air into said at least one first exclusive return register and said at least one second exclusive return register in response to a mode of the controller, wherein

during the cooling mode, the central control system causes cooled air to flow through said at least one supply register at the non-mixing flow rate, and causes air to be withdrawn from the occupied space only through said at least one first exclusive return register at a level proximate the ceiling, and

during the heating mode, the central control system causes warm air to flow through said at least one supply register at the non-mixing flow rate, and causes air to be withdrawn from the occupied space only through said at least one second exclusive return register.

2. The system according to claim 1 , wherein

during the heating mode, said central control system is further configured to regulate a volume rate of flow through said at least one second exclusive return register such that a rate of air exchanged in said occupied space is responsive to outdoor air temperature.

3. A system according to claim 2 , wherein

said central control system includes a feedforward control mechanism with at least one outdoor air temperature input.

4. A system according to claim 1 , wherein

said central control system includes a contamination detector located in a central return duct and the central control system is configured to deactivate a fan responsively to a detection of a contaminant by said contamination detector.

5. A system according to claim 1 , further comprising an air circulating fan controlled to mix warm, stratified air in said occupied space during the heating mode.

6. A system according to claim 5 , wherein said air circulating fan hangs from the ceiling of said occupied space and extends into said occupied space.

7. A system according to claim 5 , wherein

said air circulating fan is controlled responsively to a local temperature gradient in said occupied space.

8. A system according to claim 1 , wherein each said at least one supply register is configured such that a face area thereof, through which air is supplied to said occupied space, is adjusted by the central control system based on the mode of the controller.

9. A system according to claim 1 , wherein the central control system and the at least one supply register are configured such that:

during the cooling mode, cooled air is supplied to said occupied space through a first face area of said at least one supply register at a first velocity; and

during the heating mode, warm air is supplied to said occupied space through a second face area of said at least one supply register at a second velocity,

wherein the first face area is greater than the second face area, and

the first velocity is less than the second velocity.

10. A system according to claim 1 , wherein during the cooling mode the cooled air is supplied from said at least one supply register from a first output portion thereof, and during the heating mode, the warm air is supplied from said at least one supply register from a second output portion thereof, the first and second output portions being different.

11. A system according to claim 10 , wherein the first output portion and the second output portion have no portion in common.

12. A system according to claim 10 , wherein the first output portion is arranged relatively higher in said occupied space than said second output portion.

13. A system according to claim 1 , wherein air flow output from said at least one supply register is such that the air flow has a horizontal component as a primary component.

14. A ventilation system for an occupied space, comprising:

a supply register configured as a displacement-type diffuser having a plurality of uniform openings for providing a uniform flow of air at a non-mixing flow rate that promotes stratification of air in said occupied space;

a first exclusive return register configured to withdraw air at a level proximate a ceiling of said occupied space;

a second exclusive return register configured to withdraw air from said occupied space at a level near a floor thereof;

a central control system including a controller with at least a heating mode and a cooling mode, configured to control flow through said supply register, the first exclusive return register, and the second exclusive return register based on a mode of the controller,

wherein during the cooling mode, the central control system disables flow through the second exclusive return register and enables flow through the first exclusive return register such that cool air is supplied to said occupied space through the supply register at the non-mixing flow rate, and air is withdrawn from said occupied space through the first exclusive return register, and

during the heating mode, the central control system disables flow through the first exclusive return register and enables flow through the second exclusive return register such that warm air is supplied to said occupied space through the supply register and air is withdrawn from said occupied space through the second exclusive return register.

15. A system according to claim 14 , wherein the supply register is configured such that a face area thereof, through which air is supplied to said occupied space, is adjusted by the central control system based on the mode of the ventilation system.

16. A system according to claim 14 , wherein the central control system and the supply register are configured such that:

during the cooling mode, cooled air is supplied to said occupied space through a first face area of the supply register at a first velocity; and

during the heating mode, warm air is supplied to said occupied space through a second face area of the supply register at a second velocity,

wherein the first face area is greater than the second face area, and

the first velocity is less than the second velocity.

17. A system according to claim 14 , wherein air flow from said supply register exits said supply register at least one of horizontally or substantially horizontally.

18. A system according to claim 14 , wherein during the cooling mode the cooled air is supplied from said supply register from a first output portion thereof, and during the heating mode, the warm air is supplied from said supply register from a second output portion thereof, the first and second output portions being different, with said first output portion having a greater surface output area to output the cooled air than said second output portion to output the warm air.