RETROFITTING A CONSTANT VOLUME AIR HANDLING UNIT WITH A VARIABLE FREQUENCY DRIVE

• US 20090236432A1
• Filed: 09/22/2008
• Published: 09/24/2009
• Est. Priority Date: 03/19/2008
• Status: Active Grant

• Current Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Original Assignee: Rockwell Automation Technologies Incorporated (Allen-Bradley Co., Inc.)
• Inventors: Malloy, Ronald M.
• Granted Patent: US 8,955,761 B2
• Time in Patent Office: Days
• US Class Current: 236/49.300
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/58 using Internet communication
• CPC Class Codes: F24F 11/63 Electronic processing
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 11/81 by controlling the air supply to heat-exchangers or bypass channels
• CPC Class Codes: F24F 2110/00 Control inputs relating to air properties
• CPC Class Codes: F24F 2110/50 Air quality properties
• CPC Class Codes: F24F 2110/70 Carbon dioxide
• CPC Class Codes: F24F 2120/10 Occupancy
• CPC Class Codes: F24F 3/044 Systems in which all treatment is given in the central station, i.e. all-air systems
• CPC Class Codes: G05B 15/02 electric
• CPC Class Codes: Y02B 30/00 Energy efficient heating, ventilation or air conditioning [HVAC]
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating
• CPC Class Codes: Y02B 30/90 Passive houses; Double facade technology

Abstract

A system and methods providing real-time monitoring, management and control of a variable frequency drive retrofit to a constant volume air handling unit without making significant mechanical or control system changes. Customers and vendors are provided with a more informative and economically attractive air handling unit. The system also provides a finer granularity of control over conditioned air properties such as temperature, humidity and air quality.

Claims

1. A system that provides real-time monitoring, management and control of a variable frequency drive retrofit to a constant volume air handling unit, the system comprising:

a variable frequency drive (VFD) connected to a blower for controlling the angular velocity of the blower;

an intake temperature sensor (ITS) for determining the intake air temperature;

a discharge temperature sensor (DTS) for determining the discharge air temperature;

a damper end switch (DES) for determining the percentage a damper is open; and

a controller communicatively coupled to the VFD, ITS, DTS, and DES for analyzing air conditions and instructing the VFD to operate a blower to generate the required air volumetric flow rate.

2. The system of claim 1, the controller is further communicatively coupled to an air quality sensor located in the conditioned space for assuring a minimum level of air quality.

3. The system of claim 1, the controller is further communicatively coupled to a motion sensor located in a conditioned space for providing greater efficiency of operation by reducing heating and cooling requirements when the conditioned space is not occupied.

4. The system of claim 1, the controller can operate in economizer mode by using outside air to provide cooling.

5. The system of claim 1, the controller determines if economizer mode is possible based on the outside air damper open approximately fifteen percent or greater.

6. The system of claim 1, the controller anticipates cooling coil icing and increases the fan angular velocity to avoid coil freezing or frosting.

7. The system of claim 1, the variable frequency drive controller can be located remotely from the variable frequency drive.

8. The system of claim 2, the air quality sensor is a carbon dioxide measurement sensor.

9. The system of claim 1, the controller can be installed prior to the installation of the remaining system components and function as a system analyzer providing a report of expected cost savings after installing the rest of the system components.

10. The system of claim 9, the controller includes an embedded weather service database of local weather tables for calculating the expected cost savings.

11. The system of claim 1, the controller maintains historical annual reports of actual cost savings for up to fifteen years.

12. A method that provides real-time monitoring, management and control of a variable frequency drive retrofit to a constant volume air handling unit, the method comprising:

adjusting a volumetric flow rate of a constant volume blower with a variable frequency drive (VFD);

determining an upstream intake air temperature from an upstream temperature sensor (UTS);

determining a downstream intake air temperature from a downstream temperature sensor (DTS);

determining the percentage an outside air damper is open from a damper end switch (DES); and

controlling the variable frequency drive by collecting data from the UTS, DTS, and DES for analyzing air conditions and instructing the VFD to operate a blower to generate the required air volumetric flow rate to meet the configured conditions.

13. The method of claim 12, data from an air quality sensor in the conditioned space is included in controlling the variable frequency drive.

14. The method of claim 12, further comprising installing a controller at least two weeks prior to the installation of the remaining system components for generating a report of the expected cost savings of the installed system.

15. The method of claim 12, data from a temperature sensor in the conditioned space is included in controlling the variable frequency drive.

16. The method of claim 12, data from a motion sensor in the conditioned space is included in controlling the variable frequency drive.

17. A system for providing real-time monitoring, management and control of a variable frequency drive retrofit to a constant volume air handling unit, the system comprising:

means for controlling the angular velocity of a constant volume blower;

means for determining the upstream intake air temperature;

means for determining the downstream intake air temperature;

means for determining the percentage an outside air damper is open; and

means for analyzing air conditions in a constant volume air handling system and operating a blower to generate the required air volumetric flow rate.

18. The system of claim 17, further comprising means for determining if people are present in the conditioned space.

19. The system of claim 17, further comprising means for determining if the air handling unit can be operated in economizer mode.

20. The system of claim 17, further comprising means for generating a report of the cost savings of installing the system prior to installing the system.

21. The system of claim 17, further comprising means for generating monthly reports verifying the cost savings of the installed system.

22. The system of claim 17, further comprising means for generating annual reports verifying the cost savings of the installed system and archiving the annual reports for at least fifteen years.