Furnace with improved efficiency controls

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.