SYSTEM AND METHOD FOR SELECTING AN OPERATING LEVEL OF A HEATING, VENTILATION, AND AIR CONDITIONING SYSTEM

• US 20080083834A1
• Filed: 10/04/2006
• Published: 04/10/2008
• Est. Priority Date: 10/04/2006
• Status: Abandoned Application

• Current Assignee: Telkonet Incorporated
• Original Assignee: Telkonet Incorporated
• Inventors: Zirpoli, Robert, Pitt, Ronald L., Krebs, Steve
• Application Number:
  US11/538,461
• Publication Number:
  US 20080083834A1
• Time in Patent Office: Days
• US Class Current: 237/2A
• CPC Class Codes: B60H 1/00892 Devices specially adapted for avoiding uncomfortable feeling, e.g. sudden temperature changes B60H1/00885 takes precedence
• 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 11/38 Failure diagnosis
• CPC Class Codes: F24F 11/46 Improving electric energy efficiency or saving
• CPC Class Codes: F24F 11/526 giving audible indications
• CPC Class Codes: F24F 11/56 Remote control
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 11/64 using pre-stored data
• CPC Class Codes: F24F 11/65 for selecting an operating mode
• CPC Class Codes: F24F 11/77 by controlling the speed of ventilators
• CPC Class Codes: F24F 11/86 by controlling compressors within refrigeration or heat pump circuits
• CPC Class Codes: F24F 2110/10 Temperature
• CPC Class Codes: F24F 2110/20 Humidity
• CPC Class Codes: F24F 2120/00 Control inputs relating to users or occupants
• CPC Class Codes: F24F 2120/10 Occupancy
• CPC Class Codes: G05D 23/1919 characterised by the type of controller

Abstract

A method and apparatus for selecting an operating level of an HVAC system uses historic and predicted drive durations to ensure that drive periods fall within the recommended minimum and maximum drive times, thereby increasing efficiency and reducing strain on the system. The method comprises the steps of: receiving a minimum and a maximum drive time of the HVAC system; determining a current temperature of a room; estimating, based on a prior drive operation of the HVAC system, a time to drive the current temperature to a predefined desired temperature; and selecting an operating level of the HVAC system based on a relationship of the calculated drive time to the minimum drive time and the maximum drive time. Selecting the operating level comprises at least one of: selecting a fan speed; activating a compressor; activating an auxiliary or emergency heating element; or activating an auxiliary or emergency cooling element.

Claims

1. A method for selecting an operating level of a heating, ventilation, and air conditioning (HVAC) system, the method comprising:

estimating a time to drive a current temperature of a room to a predefined desired temperature; and

selecting an operating level of the HVAC system based on a relationship of the estimated drive time to a predefined minimum drive time and a predefined maximum drive time.

2. The method of claim 1, wherein selecting the operating level comprises at least one of:

selecting a fan speed;

activating a compressor;

activating an auxiliary heating element;

activating an auxiliary cooling element;

activating an emergency heating element;

or

activating an emergency cooling element.

3. The method of claim 1, wherein the drive time is estimated based on a prior drive operation of the HVAC system.

4. The method of claim 3, wherein selecting the operating level comprises:

obtaining an operating level of the prior drive operation;

if the estimated drive time is less than the minimum drive time, selecting an operating level lower than the operating level of the prior drive operation;

else if the estimated drive time is greater than the maximum drive time, selecting an operating level higher than the operating level of the prior drive operation; and

else if the maximum drive time is greater than the estimated drive time and if the minimum drive time is less than the estimated drive time, selecting an operating level equal to the operating level of the prior drive operation.

5. The method of claim 3, wherein estimating the drive time comprises:

obtaining a temperature at a beginning of the prior drive operation;

obtaining a temperature at a midpoint of the prior drive operation;

obtaining a temperature at an end of the prior drive operation;

calculating a drive curve using the beginning, midpoint, and end temperatures; and

using the drive curve to estimate a time at which the desired temperature will be reached.

6. The method of claim 5, wherein the drive curve is described by equation T=C+Ae^t/B, in which T is temperature, t is time, and A, B, and C are constants;

wherein constants A, B, and C are calculated using equations;

B=−

(t₁−

t₀)/ln{(T₂−

T₁)/(T₁−

T₀)};

A=(T₁−

T₂)/(e<sup>−

t1/B</sup>−

e<sup>−

t2/B</sup>); and

C=T₁−

A*e<sup>−

t/B</sup>;

in which T₀ is the temperature at the beginning of the prior drive operation and to is the beginning time of the prior drive operation;

T₁ is the temperature at the midpoint of the prior drive operation and t₁ is the midpoint time of the prior drive operation; and

T₂ is the temperature at the end of the prior drive operation and t₂ is the end time of the prior drive operation;

and wherein the drive time is estimated using equation

7. The method of claim 3, wherein estimating the drive time comprises:

obtaining a plurality of temperature data samples over a period of time, the period of time corresponding to the prior drive operation;

calculating a plurality of drive curves, each curve calculated using a different data sample subset;

determining which curve best fits the data samples; and

using the best fit curve to estimate the time at which the desired temperature will be reached.

8. The method of claim 7, wherein the curves are described by equation T=C+Ae⁻

t/B, in which T is temperature, t is time, and A, B, and C are constants;

wherein constants A, B, and C are calculated using equations;

9. The method of claim 8, wherein determining which curve best fits the data samples comprises:

calculating, for each curve, theoretical temperature values for each sample time in the data set using equation T=C+Ae<sup>−

t/B</sup>;

calculating a fit value for each curve using equation

10. The method of claim 9, wherein using the best fit curve to estimate the drive time comprises using the curve having the highest calculated fit value.

11. The method of claim 1, wherein the predefined minimum drive time comprises a current level minimum drive time, wherein the predefined maximum drive time comprises a current level maximum drive time, and wherein the method further comprises:

operating the HVAC system at the selected operating level;

after operating the HVAC system for a predefined period of time, determining an elapsed operating time of a current drive operation at a current operating level;

if the current level elapsed time is less than the current level minimum drive time, continuing to operate the HVAC system at the current operating level; and

if the current level elapsed time is greater than the current level maximum drive time, selecting a new operating level higher than the current operating level and operating the HVAC system at the new higher operating level.

12. The method of claim 1, wherein the predefined minimum drive time comprises a total system minimum drive time or a current level minimum drive time, wherein the predefined maximum drive time comprises a total system maximum drive time or a current level maximum drive time, and wherein the method further comprises:

operating the HVAC system at the selected operating level;

after operating the HVAC system for a predefined period of time, determining a new current temperature;

re-estimating the drive time based on the operation of the HVAC system during the predefined period of time;

determining an elapsed operating time of a current drive operation occurring prior to the predefined period of time;

summing the re-estimated drive time, the predefined period of time, and the elapsed time;

if the sum is less than the minimum drive time, selecting a new operating level lower than the originally selected operating level; and

else if the sum is greater than the maximum drive time, selecting a new operating level higher than the originally selected operating level.

13. An apparatus for governing a temperature of a room by selecting an operating level of a heating, ventilation, and air conditioning (HVAC) system, the apparatus including an interface coupled to the HVAC system to control the operation thereof by control signals, the apparatus comprising:

a controller including a processor coupled to a memory, the memory storing an environmental control program including program instructions for controlling the operation of the HVAC system by generating the control signals and further storing data; and

a temperature sensor coupled to the controller for providing, at any given time, a signal representing the temperature within the room;

wherein the controller is configured to estimate a time to drive a current temperature of the room to a predefined desired temperature; and

wherein the controller is configured to select an operating level of the HVAC system based on a relationship of the estimated drive time to a predefined minimum drive time of the HVAC system and a predefined maximum drive time of the HVAC system.

14. The apparatus of claim 13, wherein selecting the operating level comprises at least one of:

selecting a fan speed;

activating a compressor;

activating an auxiliary heating element;

activating an auxiliary cooling element;

activating an emergency heating element;

or

activating an emergency cooling element.

15. The apparatus of claim 13, wherein the controller is configured to estimate the drive time based on a prior drive operation of the HVAC system.

16. The apparatus of claim 15, wherein selecting the operating level comprises:

obtaining an operating level of the prior drive operation;

if the estimated drive time is less than the minimum drive time, selecting an operating level lower than the operating level of the prior drive operation;

else if the estimated drive time is greater than the maximum drive time, selecting an operating level higher than the operating level of the prior drive operation; and

else if the maximum drive time is greater than the estimated drive time and if the minimum drive time is less than the estimated drive time, selecting an operating level equal to the operating level of the prior drive operation.

17. The apparatus of claim 15, wherein estimating the drive time comprises:

obtaining a temperature at a beginning of the prior drive operation;

obtaining a temperature at a midpoint of the prior drive operation;

obtaining a temperature at an end of the prior drive operation;

calculating a drive curve using the beginning, midpoint, and end temperatures; and

using the drive curve to estimate a time at which the desired temperature will be reached.

18. The apparatus of claim 17, wherein the drive curve is described by equation T=C+Ae⁻

t/B, in which T is temperature, t is time, and A, B, and C are constants;

wherein the controller calculates constants A, B, and C using equations;

B=−

(t₁−

t₀)/ln{(T₂−

T₁)/(T₁−

T₀)};

A=(T₁−

T₂)/(e<sup>−

t1/B</sup>−

e<sup>−

t2/B</sup>); and

C=T₁−

A*e<sup>−

t1/B</sup>;

in which T₀ is the temperature at the beginning of the prior drive operation and to is the beginning time of the prior drive operation;

T₁ is the temperature at the midpoint of the prior drive operation and t₁ is the midpoint time of the prior drive operation; and

T₂ is the temperature at the end of the prior drive operation and t₂ is the end time of the prior drive operation;

and wherein controller estimates the drive time using equation

19. The apparatus of claim 15, wherein estimating the drive time comprises:

obtaining a plurality of temperature data samples over a period of time, the period of time corresponding to the prior drive operation;

calculating a plurality of drive curves, each curve calculated using a different data sample subset;

determining which curve best fits the data samples; and

using the best fit curve to estimate the time at which the desired temperature will be reached.

20. The apparatus of claim 19, wherein the curves are described by equation T=C+Ae e⁻

t/B, in which T is temperature, t is time, and A, B, and C are constants;

wherein the controller calculates constants A, B, and C using equations;

21. The apparatus of claim 20, wherein determining which curve best fits the data samples comprises:

calculating, for each curve, theoretical temperature values for each sample time in the data set using equation T=C+Ae<sup>−

t/B</sup>;

calculating a fit value for each curve using equation

22. The apparatus of claim 21, wherein using the best fit curve to estimate the drive time comprises using the curve having the highest calculated fit value.

23. The apparatus of claim 13, wherein the predefined minimum drive time comprises a current level minimum drive time;

wherein the predefined maximum drive time comprises a current level maximum drive time;

wherein the controller is further configured to operate the HVAC system at the selected operating level;

wherein the controller is further configured to, after operating the HVAC system for a predefined period of time, determine an elapsed operating time of a current drive operation at a current operating level;

wherein the controller is further configured to, if the current level elapsed time is less than the current level minimum drive time, continue to operate the HVAC system at the current operating level; and

wherein the controller is further configured to, if the current level elapsed time is greater than the current level maximum drive time, select a new operating level higher than the current operating level and operate the HVAC system at the new higher operating level.

24. The apparatus of claim 13, wherein the predefined minimum drive time comprises a total system minimum drive time or a current level minimum drive time;

wherein the predefined maximum drive time comprises a total system maximum drive time or a current level maximum drive time;

wherein the controller is further configured to operate the HVAC system at the selected operating level;

wherein the controller is further configured to determine a new current temperature after operating the HVAC system for a predefined period of time;

wherein the controller is further configured to re-estimate the drive time based on the operation of the HVAC system during the predefined period of time;

wherein the controller is further configured to determine an elapsed operating time of a current drive operation occurring prior to the predefined period of time;

wherein the controller is further configured to sum the re-estimated drive time, the predefined period of time, and the elapsed time;

wherein the controller is further configured to, if the sum is less than the minimum drive time, select a new operating level lower than the originally selected operating level;

and wherein the controller is further configured to, if the sum is greater than the maximum drive time, select a new operating level higher than the originally selected operating level.