BURNER FIRING RATE DETERMINATION FOR MODULATING FURNACE

• US 20100009302A1
• Filed: 07/10/2008
• Published: 01/14/2010
• Est. Priority Date: 07/10/2008
• Status: Active Grant

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Chian, Brent, Schultz, Michael W., Nordberg, Timothy J., Bird, Douglas D.
• Granted Patent: US 8,123,518 B2
• Time in Patent Office: Days
• US Class Current: 431/12
• CPC Class Codes: F23N 1/02 conjointly with air supply
• CPC Class Codes: F23N 2223/54 Recording
• CPC Class Codes: F23N 2227/02 Starting or ignition cycles
• CPC Class Codes: F23N 2227/10 Sequential burner running
• CPC Class Codes: F23N 2237/10 High or low fire
• CPC Class Codes: F23N 2241/02 Space-heating
• CPC Class Codes: F23N 5/203 using electronic means

Abstract

A modulating furnace having a variable rate burner and a controller is operated at a first burner firing rate for a first period of time, and a higher burner firing rate once the first period of time has expired. In some instances, the burner may be operated only while the controller is receiving a call for heat from a thermostat or the like.

Claims

1. A method of operating a modulating furnace having a burner configured to operate at multiple burner firing rates and a controller configured to accept a call for heat, the method comprising the steps of:

operating the burner at a first rate for a first period of time; and

increasing the burner firing rate of the burner after the first period of time expires;

wherein the burner is operated while the controller is receiving a call for heat and is not operated when the call for heat ceases.

2. The method of claim 1, wherein operating the burner at a first rate for a first period of time includes operating the burner at a minimum burner firing rate for a selectable period of time.

3. The method of claim 2, wherein increasing the burner firing rate of the burner includes operating the burner at a second rate for a second period of time.

4. The method of claim 3, further comprising increasing the burner to a third fire rate that is greater than the second rate after the second period of time ends.

5. The method of claim 4, wherein the third fire rate is a maximum fire rate.

6. The method of claim 1, wherein the call for heat includes a W1 (first stage heat) ON signal from a two-stage thermostat.

7. The method of claim 6, wherein the call for heat further comprises a W2 (second stage heat) ON signal from the two-stage thermostat.

8. A method of operating a forced air furnace having a variable rate burner and a controller, the method comprising the steps of:

receiving a call for heat;

determining an initial burner firing rate that is based at least in part on a weighted average of one or more previous operating parameters of the forced air furnace;

operating the variable rate burner at the initial burner firing rate for a predetermined period of time; and

adjusting the burner firing rate after the predetermined period of time expires if the controller is still receiving a call for heat.

9. The method of claim 8, further comprising stopping the burner if the call for heat ceases.

10. The method of claim 8, wherein determining an initial burner firing rate comprises determining an initial burner firing rate based at least in part on a weighted average between a predetermined minimum burner firing rate and a previous burner firing rate.

11. The method of claim 10, wherein the weighted average includes a weighting parameter, and wherein the weighting parameter is a function of an Off time of the forced air furnace during a previous heating cycle.

12. The method of claim 8, wherein determining the initial burner firing rate comprises determining an initial burner firing rate according to the formula:

$\mathrm{StartingRate}=\mathrm{MinimumRate}+\left(\begin{array}{c}\mathrm{LastFiringRate}-\\ \mathrm{MinimumRate}\end{array}\right)*\frac{N}{\mathrm{OffTime}},<br><br>$

where StartingRate is the initial burner firing rate,

MinimumRate is a predetermined minimum burner firing rate,

LastFiringRate is the burner firing rate at the end of a previous heating cycle,

OffTime represents how long the burner was off just prior to receiving the call for heat, and

N is a parameter that can be adjusted to further weight the StartingRate.

13. The method of claim 8, wherein adjusting the burner firing rate after the predetermined period of time comprises ramping up the burner firing rate by a determined amount at each of one or more predetermined intervals.

14. A method of operating a forced air furnace comprising a variable burner firing rate burner and a controller, the controller configured to accept signals from a two-stage thermostat, the method comprising the steps of:

defining a second stage ON parameter based upon a length of time a W2 (second stage heat) ON signal is received;

calculating a burner firing rate for the current heating cycle based, at least in part, on the second stage ON parameter; and

operating the variable rate burner at the calculated burner firing rate.

15. The method of claim 14, further comprising the step of defining a first stage ON parameter based upon a length of time a W1 (first stage heat) ON signal is received, and wherein the calculating step calculates the burner firing rate for the current heating cycle based, at least in part, on the first stage ON parameter and the second stage ON parameter, and wherein the first stage ON parameter is based upon a length of time the W1 (first stage heat) ON signal is on during the current heating cycle and the second stage ON parameter is based upon a length of time the W2 (second stage heat) ON signal is on during a current heating cycle.

16. The method of claim 15, further comprising resetting the first stage ON parameter to zero at the end of the current heating cycle.

17. The method of claim 15, further comprising resetting the second stage ON parameter to zero at the end of the current heating cycle.

18. The method of claim 14, further comprising storing a final calculated burner firing rate when a previous heating cycle ends.

19. The method of claim 18, wherein calculating the burner firing rate based on the first stage ON time and the second stage ON is also based at least in part on the stored calculated burner firing rate.

20. The method of claim 14, wherein calculating the burner firing rate comprises calculating a burner firing rate according to the formula:

$\mathrm{FiringRate}=W<br><br><br><br>1<br><br><br><br>\mathrm{Rate}+\mathrm{FiringRange}*\left(\frac{W<br><br><br><br>2<br><br><br><br>\mathrm{OnTime}}{\mathrm{FurnaceOnTime}}\right),$

where FiringRate is the calculated burner firing rate,

W1 Rate is a minimum burner firing rate or a burner firing rate calculated using a previous burner firing rate,

FiringRange is a parameter based upon a desired burner firing rate,

W2OnTime is the amount of time that a W2 (second stage heat) ON signal is received during a current heating cycle, and

FurnaceOnTime is a length of time the furnace is operating during the current heating cycle.