Controller with dynamic temperature compensation

• US 7,784,705 B2
• Filed: 02/27/2006
• Issued: 08/31/2010
• Est. Priority Date: 02/27/2006
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Smith, Gary A., Kasper, Gary P., Wacker, Paul C.
• Primary Examiner(s): Norman; Marc E
• Application Number:
  US11/276,391
• Publication Number:
  US 20070200004A1
• Time in Patent Office: 1,646 Days
• Field of Search: 236/1.C, 236/44.C, 236/46.C, 374/1, 621/766, 621/57, 622/31
• US Class Current: 236/44.00C
• 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 11/62 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 2110/10 Temperature
• CPC Class Codes: F24F 2110/20 Humidity

Abstract

An electronic device such as an HVAC controller that accounts for internal heating in determining an environmental condition such as temperature or humidity in the space surrounding the HVAC controller. The HVAC controller may calculate a transient heat rise value that is based upon a powered time period and a first order time lag, especially during a time period before which the HVAC controller reaches a steady state temperature condition.

Claims

1. A method of dynamic temperature compensation in an HVAC controller, the method comprising the steps of:

measuring a temperature within the HVAC controller;

determining a temperature offset, wherein the temperature offset is a function of time since the HVAC controller was most recently powered up;

determining a corrected temperature as a function of time based on the measured temperature and the temperature offset; and

operating the HVAC controller in accordance with the corrected temperature.

2. The method of claim 1, wherein determining the temperature offset is a function of how long the HVAC controller was powerless subsequent to a previous time period where the HVAC controller was powered up.

3. The method of claim 1, wherein determining the temperature offset is a function of how long the HVAC controller was powerless subsequent to having been powered up during a previous time period for a sufficient time to reach a steady state temperature condition.

4. The method of claim 1, wherein the HVAC controller comprises a housing, and the measuring step occurs within the housing.

5. The method of claim 1, wherein the temperature offset does not decrease with respect to time while the HVAC controller remains continuously powered up.

6. A method of dynamic temperature compensation in an HVAC controller having a housing, the HVAC controller being capable of selectively providing a control signal to an HVAC unit, the method comprising the steps of:

measuring a temperature within the housing of the HVAC controller;

calculating a transient heat rise independent of the control signal that is selectively provided to the HVAC unit;

calculating a corrected temperature based on the measured temperature and the transient heat rise; and

operating the HVAC controller in accordance with the corrected temperature.

7. The method of claim 6, wherein the step of calculating a transient heat rise is carried out repeatedly at least until the HVAC controller reaches a steady state temperature condition.

8. The method of claim 6, wherein calculating a transient heat rise comprises calculating a transient heat rise based upon a mathematical model.

9. The method of claim 6, wherein the transient heat rise is calculated using the following formula:

${\mathrm{HeatRise}}_{i+1}={\mathrm{HeatRise}}_i+\left(1-{\mathrm{e<br><br>}}^{-\frac{\mathrm{\Delta <br><br>}<br><br><br><br>t}{\mathrm{tau}}}\right)*\left({\mathrm{HeatRise}}_{\mathrm{SS}}-{\mathrm{HeatRise}}_i\right),$

where;

HeatRise_i+1 is the transient heat rise;

HeatRise_i is a previously calculated transient heat rise;

Δ

t represents a time increment since calculating HeatRise_i;

tau represents a time constant; and

HeatRise_SS represents a steady state heat rise value.

10. The method of claim 9, wherein Δ

t is set equal to one second.

11. The method of claim 10, wherein tau is set equal to 45 minutes.

12. The method of claim 6, further comprising a step of displaying the corrected temperature.

13. A method of dynamic temperature compensation in an HVAC controller having a housing, the method comprising the steps of:

measuring a temperature within the housing of the HVAC controller;

calculating a transient heat rise while the HVAC controller is powered prior to a loss of power to the HVAC controller;

storing in a non-volatile memory the transient heat rise;

storing in the non-volatile memory a time parameter indicating when power is lost;

after a resumption of power to the HVAC controller, calculating a decayed heat rise based upon the transient heat rise and time parameter stored in the non-volatile memory;

calculating a corrected temperature based upon the decayed heat rise; and

operating the HVAC controller in accordance with the corrected temperature.

14. The method of claim 13, wherein calculating a transient heat rise comprises calculating a transient heat rise based upon a mathematical model.

15. The method of claim 13, wherein the time parameter comprises a date and/or time stamp stored when the transient heat rise value is stored.

16. The method of claim 13, wherein calculating the decayed heat rise comprises adjusting the transient heat rise to account for cooling while power is lost.

17. The method of claim 13, wherein the decayed heat rise is calculated using the following formula:

${\mathrm{HeatRise}}_{\mathrm{new}}={\mathrm{HeatRise}}_{\mathrm{old}}+\left(1-{\mathrm{e<br><br>}}^{-\frac{T}{\mathrm{tau}}}\right)*\left({\mathrm{HeatRise}}_{\mathrm{SS}}-{\mathrm{HeatRise}}_{\mathrm{old}}\right),$

where;

HeatRise_new is the decayed heat rise;

HeatRise_old is the transient heat rise stored before the loss of power;

T represents a time duration during which the HVAC controller was not powered;

tau represents a time constant; and

HeatRise_SS represents a steady state heat rise value.

18. A method of dynamic thermal compensation in an HVAC controller, the method comprising the steps of:

measuring a parameter within the HVAC controller;

calculating a parameter correction factor, wherein the parameter correction factor is a function of time since the HVAC controller was most recently powered up;

calculating a corrected parameter value based on the measured parameter and the parameter correction factor; and

operating the HVAC controller in accordance with the corrected parameter.

19. The method of claim 18, wherein the measuring step comprises measuring a relative humidity within the HVAC controller.

20. The method of claim 19, wherein the calculating a parameter correction factor is based at least in part upon a temperature within the HVAC controller.

21. The method of claim 19, wherein the step of calculating a corrected parameter value comprises calculating a corrected relative humidity value in accordance with the formula:

RH_actual=RH_measured+(A+B*RH_measured)*HeatRise,

where;

RH_actual is the corrected relative humidity value;

RH_measured is the measured relative humidity value;

HeatRise represents a temperature rise inside the HVAC controller; and

A &

B are correction factors relating to a particular HVAC controller.

22. The method of claim 21, wherein A is set equal to 0.294 and B is set equal to 0.0294.

23. An HVAC controller having a housing, the HVAC controller configured to:

measure a temperature within the housing;

determine a transient heat change, wherein the transient heat change is a function of how long the HVAC controller has been powered up; and

determine a corrected temperature based on the measured temperature and the transient heat change.

24. The HVAC controller of claim 23, wherein the HVAC controller is configured to determine the transient heat change as a function of how long the HVAC controller was powerless subsequent to a previous time period where the HVAC controller was powered up.