Burner firing rate determination for modulating furnace
AssigneeHoneywell International Inc.
InventorsTimothy J. Nordberg, Brent Chiain, Michael W. Schultz, Douglas D. Bird
Life of this patent
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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.
Claims13
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 first stage ON parameter based upon a length of time a W1 (first stage heat) ON signal is asserted by the two-stage thermostat during a current heating cycle;
- defining a second stage ON parameter based upon a length of time a W2 (second stage heat) ON signal is asserted by the two-stage thermostat during the current heating cycle;
- calculating a burner firing rate for the current heating cycle based, at least in part, on the first stage ON parameter and second stage ON parameter;
- and
- operating the variable rate burner at the calculated burner firing rate.
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 according to the formula:
- StartingRate
- =
- MinimumRate
- +
- (
- LastFiringRate
- -
- MinimumRate
- )
- *
- N
- OffTime
- ,
-
- 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;
- 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.
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 a current heating cycle based, at least in part, on the second stage ON parameter;
- operating the variable rate burner at the calculated burner firing rate;
- wherein calculating the burner firing rate comprises calculating a burner firing rate according to the formula:
- FiringRate
- =
- W
-
-
- 1
-
-
- Rate
- +
- FiringRange
- *
- (
- W
-
-
- 2
-
-
- OnTime
- FurnaceOnTime
- )
- ,
- where FiringRate is the calculated burner firing rate,
- W1Rate 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 or available burner firing range,
- W2OnTime is the amount of time that the W2 (second stage heat) ON signal is received during the current heating cycle, and
- FurnaceOnTime is a length of time the furnace is operating during the current heating cycle.
Dependencies are inferred from the claim text.