Method and apparatus for reheat dehumidification with variable speed outdoor fan

• US 10,161,662 B2
• Filed: 11/30/2015
• Issued: 12/25/2018
• Est. Priority Date: 11/30/2015
• Status: Active Grant

• Current Assignee: Lennox Industries Incorporated (Lennox International Incorporated)
• Original Assignee: Lennox Industries Incorporated (Lennox International Incorporated)
• Inventors: Goel, Rakesh, Berg, Eric
• Primary Examiner(s): Trpisovsky, Joseph
• Application Number:
  US14/954,558
• Publication Number:
  US 20170153052A1
• Time in Patent Office: 1,121 Days
• Field of Search: 62115, 62215, 62226, 622281, 62229
• CPC Class Codes: F25B 2400/0403 for the condenser
• CPC Class Codes: F25B 2400/0417 for the subcooler
• CPC Class Codes: F25B 2400/05 Compression system with heat exchange between particular parts of the system
• CPC Class Codes: F25B 2400/077 Compressor control units, e.g. terminal boxes, mounted on the compressor casing wall containing for example starter, protection switches or connector contacts
• CPC Class Codes: F25B 2600/111 of condenser fans
• CPC Class Codes: F25B 2600/2501 Bypass valves
• CPC Class Codes: F25B 2700/02 Humidity
• CPC Class Codes: F25B 2700/21171 of the fluid cooled by the evaporator
• CPC Class Codes: F25B 40/02 Subcoolers
• CPC Class Codes: F25B 49/02 for compression type machines, plants or systems
• CPC Class Codes: F25B 49/027 Condenser control arrangements
• CPC Class Codes: F25B 6/04 arranged in series
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

An HVAC system includes an indoor unit having a return air duct and a supply air duct in an enclosed space. The HVAC system includes an outdoor unit having a variable-speed condenser fan. A first temperature sensor is disposed in at least one of the return air duct, the supply air duct, or an enclosed space. A controller is operatively coupled to the first temperature sensor, and the variable-speed condenser fan. The controller is configured to determine whether at least one of over-cooling or over-heating of air in the enclosed space is occurring. Responsive to a determination that at least one of over-cooling or over-heating of air in the enclosed space is occurring, the controller adjusts a speed of the variable-speed condenser fan.

Claims

1. A heating, ventilation, and air conditioning (HVAC) system comprising:

an indoor unit comprising a return air duct and a supply air duct in an enclosed space;

an outdoor unit comprising a variable-speed condenser fan;

a first temperature sensor disposed in the return air duct;

a second temperature sensor disposed in the supply air duct;

a controller operatively coupled to the first temperature sensor and the variable-speed condenser fan;

wherein the controller is configured to;

measure, using the first temperature sensor, an air temperature in the return air duct;

measure, using the second temperature sensor, an air temperature in the supply air duct;

determine a temperature difference between the air temperature in the return air duct and the air temperature in the supply air duct; and

determine whether the temperature difference is increasing, decreasing, or remaining stable;

wherein, responsive to a determination that the temperature difference is increasing, the controller reduces a speed of the variable-speed condenser fan; and

wherein responsive to a determination that the temperature difference is decreasing, the controller increases the speed of the variable-speed condenser fan.

2. The system of claim 1, wherein the controller is configured to detect humidity of air in the enclosed space.

3. The system of claim 1, wherein the controller is configured to decrease a speed of the variable-speed condenser fan responsive to a determination that over-cooling occurs.

4. The system of claim 3, wherein decreasing the speed of the variable-speed condenser fan reduces over-cooling by the HVAC system.

5. The system of claim 1, wherein the controller is configured to increase a speed of the variable-speed condenser fan responsive to a determination that over-heating occurs.

6. The system of claim 5, wherein increasing the speed of the variable-speed condenser fan reduces over-heating by the HVAC system.

7. The system of claim 1, wherein:

adjustment of the speed of the variable-speed condenser fan maintains an S/T ratio of the HVAC system in a range of approximately −

0.1 to approximately 0.1; and

the S/T ratio is a ratio of sensible heat removed from the enclosed space to total heat removed from the enclosed space.

8. A method comprising:

receiving, by a controller associated with a heating, ventilation, and air conditioning (HVAC) system, an air temperature in a return air duct and an air temperature in a supply air duct;

determining, via the controller, a temperature difference between the air temperature in the return air duct and the air temperature in the supply air duct;

determining, via the controller, if the temperature difference is increasing, decreasing, or remaining stable;

responsive to a determination that the temperature difference is increasing, reducing, via the controller, a speed of a variable-speed condenser fan of the HVAC system; and

responsive to a determination that the temperature difference is decreasing, increasing, via the controller, the speed of the variable-speed condenser fan.

9. The method of claim 8, wherein the determination that the temperature difference is increasing is indicative of over-cooling.

10. The method of claim 9, wherein the reducing the speed of the variable-speed condenser fan corrects over-cooling by the HVAC system.

11. The method of claim 8, wherein the determination that the temperature difference is decreasing is indicative of over-heating.

12. The method of claim 11, wherein the increasing the speed of the variable-speed condenser fan corrects over-heating by the HVAC system.

13. The method of claim 8, comprising maintaining an S/T ratio of the HVAC system in a range of approximately −

0.1 to approximately 0.1, wherein the S/T ratio is a ratio of sensible heat removed from an enclosed space to total heat removed from the enclosed space.

14. The method of claim 13, wherein the maintaining maximizes a latent capacity of the HVAC system.

15. The method of claim 13, wherein the maintaining facilitates air dehumidification without an associated change of temperature of conditioned air.

16. A heating, ventilation, and air conditioning (HVAC) system comprising:

an indoor unit comprising a return air duct and a supply air duct in an enclosed space;

an outdoor unit comprising a variable-speed condenser fan;

a first temperature sensor disposed in the return air duct;

a second temperature sensor disposed in the supply air duct;

a controller operatively coupled to the first temperature sensor, the second temperature sensor, and the variable-speed condenser fan;

wherein the controller is configured to;

measure, using the first temperature sensor, an air temperature in the return air duct;

measure, using the second temperature sensor, an air temperature in the supply air duct;

determine a temperature difference between the air temperature in the return air duct and the air temperature in the supply air duct; and

determine whether the temperature difference is increasing, decreasing, or remaining stable;

wherein, responsive to a determination that the temperature difference is increasing, the controller reduces a speed of the variable-speed condenser fan; and

wherein responsive to a determination that the temperature difference is decreasing, the controller increases the speed of the variable-speed condenser fan;

wherein adjustment of the speed of the variable-speed condenser fan maintains an S/T ratio of the HVAC system in a range of approximately −

0.1 to approximately 0.1; and

wherein the S/T ratio is a ratio of sensible heat removed from the enclosed space to total heat removed from the enclosed space.