Method and system for supply-air re-circulation

Patent metadata

Field	Value
Publication number	US-10955165-B2
Application number	US-201816208880-A
Country	US
Kind code	B2
Filing date	Dec 4, 2018
Priority date	Dec 4, 2018
Publication date	Mar 23, 2021
Grant date	Mar 23, 2021

Abstract

An HVAC system includes an evaporator coil disposed between a supply air duct and a return air duct. A re-circulation duct fluidly couples the supply air duct and the return air duct. A damper is disposed in the re-circulation duct and is moveable between an open position and a closed position. A controller is operatively coupled to a variable-speed compressor, a variable-speed circulation fan, and the damper. Responsive to a determination that the variable-speed circulation fan is operating at the minimum speed and the suction pressure is above the pre-determined threshold, the controller signals the damper to move to the open position. Responsive to a determination that the variable-speed circulation fan is not operating at the minimum speed or the suction pressure is below the pre-determined threshold, the controller signals the damper to move to the closed position.

First claim

What is claimed is:

1. A heating, ventilation, and air conditioning (HVAC) system comprising:
an evaporator coil disposed between a supply air duct and a return air duct;
a re-circulation duct, wherein the re-circulation duct fluidly couples the supply air duct and the return air duct;
a damper disposed in the re-circulation duct, the damper being moveable between an open position and a closed position;
a variable-speed circulation fan for circulating air around the evaporator coil;
a variable-speed compressor fluidly coupled to the evaporator coil;
a controller operatively coupled to the variable-speed compressor, the variable-speed circulation fan, and the damper;
a pressure sensor disposed in a suction line between the evaporator coil and the variable-speed compressor, the pressure sensor being configured to measure a refrigerant pressure in the suction line;
wherein the controller is configured to:
determine if the variable-speed circulation fan is operating at a minimum speed and if a suction pressure measured by the pressure sensor is above a pre-determined threshold;
responsive to a determination that the variable-speed circulation fan is operating at the minimum speed and the suction pressure is above the pre-determined threshold, signaling the damper to move to the open position; and
responsive to a determination that the variable-speed circulation fan is not operating at the minimum speed or the suction pressure is below the pre-determined threshold, signaling the damper to move to the closed position.

2. The HVAC system of claim 1 , wherein the speed of the variable-speed circulation fan is modulated responsive to a speed of the variable-speed compressor.

3. The HVAC system of claim 1 , wherein moving the damper to the open position reduces a volume of air supplied via the supply air duct.

4. The HVAC system of claim 1 , wherein the HVAC system operates in at least one of a cooling mode and a dehumidification mode.

5. The HVAC system of claim 4 , wherein the pre-determined threshold is in the range of approximately 130 psi to approximately 150 psi when the HVAC system is operating in the cooling mode.

6. The HVAC system of claim 4 , wherein the pre-determined threshold is in the range of approximately 110 psi to approximately 130 psi when the HVAC system is operating in the dehumidification mode.

7. The HVAC system of claim 1 , wherein moving the damper to the open position increases latent capacity of the HVAC system.

8. A heating, ventilation, and air conditioning (HVAC) system comprising:
an evaporator coil disposed between a supply air duct and a return air duct;
a re-circulation duct that fluidly couples the supply air duct and the return air duct;
a damper disposed in the re-circulation duct, the damper being moveable between an open position and a closed position;
a variable-speed circulation fan for circulating air around the evaporator coil;
a variable-speed compressor fluidly coupled to the evaporator coil;
a controller operatively coupled to the variable-speed compressor, the variable-speed circulation fan, and the damper;
wherein the controller is configured to:
determine if the variable-speed circulation fan is operating at a minimum speed;
monitor an operating parameter of the HVAC system;
determine if the operating parameter of the HVAC system exceeds a pre-determined threshold;
responsive to a determination that the variable-speed circulation fan is operating at the minimum speed and the operating parameter exceeds the pre-determined threshold, signaling the damper to move to the open position; and
wherein the operating parameter is a refrigerant pressure in a suction line.

9. The HVAC system of claim 8 , wherein the speed of the variable-speed circulation fan is modulated responsive to a speed of the variable-speed compressor.

10. The HVAC system of claim 8 , wherein moving the damper to the open position reduces a volume of air supplied via the supply air duct.

11. The HVAC system of claim 8 , wherein the HVAC system operates in at least one of a cooling mode and a dehumidification mode.

12. The HVAC system of claim 8 , wherein a pressure sensor is configured to monitor the operating parameter in the suction line.

13. A method of utilizing a re-circulation duct, the method comprising:
determining with an HVAC controller if a variable-speed circulation fan is operating at a minimum speed;
monitoring an operating parameter of an HVAC system;
determining if the operating parameter of the HVAC system exceeds a pre-determined threshold;
responsive to a determination by the HVAC controller that the variable-speed circulation fan is operating at the minimum speed and the operating parameter exceeds the pre-determined threshold, signaling with the HVAC controller a damper disposed in a re-circulation duct that fluidly couples a supply air duct and a return air duct to move to an open position; and
wherein the operating parameter is a refrigerant pressure in a suction line.

14. The method of claim 13 , wherein the monitoring the operating parameter includes monitoring the refrigerant pressure in the suction line with a pressure sensor.

15. The method of claim 13 , wherein the operating parameter is an air temperature in the supply air duct.

16. The method of claim 15 , wherein the monitoring the operating parameter includes monitoring the air temperature in the supply air duct with a temperature sensor.

17. The method of claim 13 , comprising diverting air from the supply air duct to the return air duct via the re-circulation duct responsive to opening the damper.

Assignees

• Lennox Ind Inc

Inventors

• Goel Rakesh
• Perez Eric

Classifications

• F24F2003/0446

  with a single air duct for transporting treated air from the central station to the rooms · CPC title

• F24F11/30

  for purposes related to the operation of the system, e.g. for safety or monitoring · CPC title

• F24F2110/40

  Pressure, e.g. wind pressure · CPC title

• F24F2110/30

  Velocity · CPC title

• F24F2110/20

  Humidity · CPC title