Furnace with improved efficiency controls
Example implementations of the present disclosure relate to systems and methods for improving the efficiency of a furnace. This process may include initiating combustion of the fuel in the burner assembly at an intermediate firing rate; operating the furnace in warm-up stage following initiating the combustion of the fuel, the warm-up stage including operating the burner assembly at the intermediate firing rate and not operating the circulation blower; operating the furnace in a boost stage following the warm-up stage, the boost stage including operating the burner assembly at the intermediate firing rate and initiating operation of the circulation blower; and operating the furnace in a low-capacity setting following the boost stage, the low-capacity setting including operating the burner assembly at a low-capacity firing rate, the low-capacity firing rate being a lower firing rate than the intermediate firing rate.
1 . A furnace comprising:
a heat exchanger;
an inducer fan configured to move air from an air inlet through a combustion flow path;
a burner assembly configured to combust a fuel and provide heat to the heat exchanger within the furnace;
a circulation blower configured to circulate a conditioned air flow through the furnace and absorb heat from the heat exchanger; and
control circuitry operably coupled to the inducer fan, the burner assembly, and the circulation blower, the control circuitry configured to:
initiate combustion of the fuel in the burner assembly at an intermediate firing rate, the intermediate firing rate being greater than a minimum firing rate and less than a maximum firing rate;
operate the furnace in a warm-up stage for a first period of time following initiating the combustion of the fuel, the warm-up stage including operating the burner assembly at the intermediate firing rate, operating the inducer fan, and maintaining the circulation blower in an off state;
operate the furnace in a boost stage for a second period of time following the first period of time, the boost stage including operating the burner assembly at the intermediate firing rate, operating the inducer fan, and operating the circulation blower to flow circulation air through the furnace; and
operate the furnace in a low-capacity setting following the second period of time, the low-capacity setting including operating the burner assembly at a low-capacity firing rate, operating the inducer fan, and continuing operation of the circulation blower, the low-capacity firing rate being a lower firing rate than the intermediate firing rate.
2 . The furnace of claim 1 , wherein the low-capacity firing rate is based on a requested heating demand from a conditioned space, and
wherein the continuing operation of the circulation blower in the low-capacity setting includes adjusting the operation of the circulation blower based on the requested heating demand.
3 . The furnace of claim 1 , wherein the low-capacity firing rate is less than a required firing rate for ignition.
4 . The furnace of claim 1 , wherein the intermediate firing rate is between 55% and 75%.
5 . The furnace of claim 1 , wherein the intermediate firing rate is 65%.
6 . The furnace of claim 1 , wherein the second period of time is a set period of time, the set period of time being greater than 5 seconds.
7 . The furnace of claim 6 , wherein the set period of time is based on a furnace type associated with the furnace, the furnace type being one of either a furnace make or model.
8 . The furnace of claim 6 , wherein the set period of time is adjusted by an operator prior to initiating the combustion of the fuel.
9 . The furnace of claim 1 , wherein the second period of time is a variable period of time, the variable period of time ending based on a furnace condition.
10 . The furnace of claim 9 , wherein the furnace condition is an indication condensate has formed in a secondary heat exchanger.
11 . The furnace of claim 10 , wherein the furnace is a condensing furnace, and
wherein the secondary heat exchanger is a condensing heat exchanger.
12 . A method of controlling a furnace to improve efficiency, the furnace including a heat exchanger, an inducer fan, a burner assembly, and a circulation blower, the method comprising:
initiating combustion of a fuel in the burner assembly at an intermediate firing rate, the intermediate firing rate being greater than a minimum firing rate and less than a maximum firing rate;
operating the furnace in a warm-up stage for a first period of time following initiating the combustion of the fuel, the warm-up stage including operating the burner assembly at the intermediate firing rate, operating the inducer fan, and maintaining the circulation blower in an off state;
operating the furnace in a boost stage for a second period of time following the first period of time, the boost stage including operating the burner assembly at the intermediate firing rate, operating the inducer fan, and initiating operation of the circulation blower; and
operating the furnace in a low-capacity setting following the second period of time, the low-capacity setting including operating the burner assembly at a low-capacity firing rate, operating the inducer fan, and operating the circulation blower to flow circulation air through the furnace, the low-capacity firing rate being a lower firing rate than the intermediate firing rate.
13 . The method of claim 12 , further comprising:
receiving a call for a requested heating demand,
wherein the low-capacity firing rate is based on the requested heating demand from a conditioned space, and
wherein the continuing operation of the circulation blower in the low-capacity setting includes adjusting the operation of the circulation blower based on the requested heating demand.
14 . The method of claim 12 , wherein the low-capacity firing rate is less than a required firing rate for ignition.
15 . The method of claim 12 , wherein the intermediate firing rate is a pre-selected firing rate for the furnace.
16 . The method of claim 12 , wherein the second period of time is a set period of time, the set period of time being greater than 5 seconds.
17 . The method of claim 16 , wherein the set period of time is based on a furnace type associated with the furnace, the furnace type being one of either a furnace make or model.
18 . The method of claim 17 , further comprising:
setting the set period of time at a first time prior to initiating combustion of the fuel; and
adjusting the set period of time based on an operator input at a second time prior to initiating combustion of the fuel, the second time being after the first time.
19 . The method of claim 12 , wherein the second period of time is a variable period of time, the variable period of time ending based on a furnace condition.
20 . The method of claim 19 , wherein the furnace condition is an indication condensate has formed in a heat exchanger.