VARIABLE CAPACITY FURNACE

1 . A furnace for a heating, ventilation, and air conditioning (HVAC) system, comprising:

a fuel valve configured to regulate an amount of fuel supplied to a burner of the furnace;

a draft inducer blower configured to draw an air flow into the burner; and

a controller configured to:

determine a target operating parameter value of the furnace;

determine an air to fuel ratio corresponding to the target operating parameter value; and

control operation of the fuel valve, the draft inducer blower, or both based on the air to fuel ratio.

2 . The furnace of claim 1 , wherein the controller comprises a memory device, and the air to fuel ratio and the target operating parameter value are stored on the memory device.

3 . The furnace of claim 2 , wherein the memory device comprises:

a plurality of air to fuel ratios including the air to fuel ratio stored on the memory device; and

a plurality of target operating parameter values including the target operating parameter value stored on the memory device,

wherein each target operating parameter value of the plurality of target operating parameter values corresponds to a respective air to fuel ratio of the plurality of air to fuel ratios.

4 . The furnace of claim 3 , wherein the memory device comprises a lookup table stored thereon, and the lookup table associates each target operating parameter value of the plurality of target operating parameter values with the respective air to fuel ratio of the plurality of air to fuel ratios.

5 . The furnace of claim 1 , wherein the target operating parameter value corresponds to a firing rate of the furnace.

6 . The furnace of claim 5 , wherein the target operating parameter value comprises a value indicative of a position of the fuel valve.

7 . The furnace of claim 1 , wherein the controller comprises a memory device, the memory device comprises a lookup table stored thereon, the lookup table comprises a plurality of target operating parameter values including the target operating parameter value and a plurality of air to fuel ratios including the air to fuel ratio, and each target operating parameter value of the plurality of target operating parameter values corresponds to at least one air to fuel ratio of the plurality of air to fuel ratios.

8 . The furnace of claim 7 , wherein the lookup table is a first lookup table, the memory device comprises an additional lookup table stored thereon, the additional lookup table comprises a plurality of additional target operating parameter values and a plurality of additional air to fuel ratios, each additional target operating parameter value of the plurality of additional target operating parameter values corresponds to at least one additional air to fuel ratio of the plurality of additional air to fuel ratios, and the additional lookup table is associated with an additional furnace different from the furnace.

9 . The furnace of claim 8 , wherein the furnace and the additional furnace comprise different configurations, different models, different components, different operating capacities, or any combination thereof.

10 . The furnace of claim 9 , wherein the controller is configured to:

receive an identification of the furnace; and

reference the lookup table to determine the air to fuel ratio corresponding to the target operating parameter value based on the identification of the furnace.

11 . A furnace controller for a furnace of a heating, ventilation, and air conditioning (HVAC) system, comprising:

processing circuitry; and

a memory, wherein the memory comprises instructions that, when executed by the processing circuitry, cause the processing circuitry to:

determine a target firing rate of the furnace;

determine an air to fuel ratio of a plurality of air to fuel ratios corresponding to the target firing rate; and

control operation of a fuel valve of the furnace, a draft inducer blower of the furnace, or both based on the air to fuel ratio.

12 . The furnace controller of claim 11 , wherein the memory comprises a database, the database comprises the plurality of air to fuel ratios and a plurality of target firing rates including the target firing rate, and each target firing rate of the plurality of target firing rates is associated with at least one air to fuel ratio of the plurality of air to fuel ratios in the database.

13 . The furnace controller of claim 11 , wherein the target firing rate corresponds to a position of the fuel valve.

14 . The furnace controller of claim 11 , wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to:

receive data indicative of a temperature within a conditioned space from a sensor;

receive data indicative of a set point temperature of the conditioned space; and

determine the target firing rate based on the temperature within the conditioned space, the set point temperature of the conditioned space, or both.

15 . The furnace controller of claim 14 , wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to:

determine a temperature differential between the temperature within the conditioned space and the set point temperature of the conditioned space; and

determine the target firing rate based on the temperature differential.

16 . The furnace controller of claim 11 , wherein the instructions, when executed by the processing circuitry, cause the processing circuitry to:

adjust a position of the fuel valve based on the target firing rate; and

control operation of the draft inducer blower of the furnace based on the air to fuel ratio.

17 . A furnace for a heating, ventilation, and air conditioning (HVAC) system, comprising:

a burner configured to receive a flow of fuel and an air flow, to mix the flow of fuel and the air flow produce an air-fuel mixture, and to ignite the air-fuel mixture to generate combustion products;

a heat exchanger system configured to receive the combustion products and direct the combustion products therethrough; and

a controller comprising a memory, wherein the controller configured to:

determine a target operating parameter value of the furnace based on data received by the controller;

select an air to fuel ratio of a plurality of air to fuel ratios stored on the memory, wherein the air to fuel ratio corresponds to the target operating parameter value; and

control operation of the furnace to produce the air-fuel mixture with the air to fuel ratio.

18 . The furnace of claim 17 , comprising:

a fuel valve configured to regulate the flow of fuel directed to the burner; and

a draft inducer blower configured to draw the air flow into the burner and to draw the combustion products through the heat exchanger system,

wherein the controller is configured to control operation of the fuel valve, the draft inducer blower, or both to produce the air-fuel mixture with the air to fuel ratio.

19 . The furnace of claim 18 , wherein the target operating parameter value corresponds to a position of the fuel valve, the data comprises a measured temperature indicative of a current temperature of a conditioned space associated with the furnace and comprises a set point temperature of the conditioned space, and the controller is configured to determine the target operating parameter value based on a temperature differential between the measured temperature and the set point temperature.

20 . The furnace of claim 17 , wherein:

the memory comprises a lookup table,

the lookup table comprises the plurality of air to fuel ratios and a plurality of target operating parameter values including the target operating parameter value,

each target operating parameter value of the plurality of target operating parameter values is associated with at least one air to fuel ratio of the plurality of air to fuel ratios in the lookup table, and

the controller is configured to reference the lookup table to select the air to fuel ratio corresponding to the target operating parameter value.