Patent ID: 8230825

Claim:
A boiler control system for controlling the operation of a boiler ( 100 ), comprising: A) a combustion air control system ( 200 ) including a combustion air fan ( 210 ) for supplying combustion air to the boiler ( 100 ) and a combustion air damper ( 220 ) for controlling the amount of combustion air supplied to the boiler ( 100 ) by the combustion air fan ( 210 ); B) a fuel control system ( 300 ) including a burner ( 310 ) for supplying fuel to the boiler ( 100 ) and a fuel valve ( 320 ) for controlling the amount of fuel supplied to the boiler ( 100 ) by the burner ( 310 ); C) a flue gas sensing system ( 400 ) including an oxygen sensor ( 410 ) and a flue gas differential sensor ( 420 ), wherein the oxygen sensor ( 410 ) senses the amount of oxygen in the flue gas leaving the boiler ( 100 ) and the flue gas differential sensor ( 420 ) senses a change in a predetermined characteristic of the flue gas associated with a change in the combustion air control system ( 200 ); and D) a boiler controller ( 500 ) having a system demand setpoint ( 510 ), a flue gas oxygen setpoint ( 520 ), and a flue gas differential setpoint ( 530 ), (i) wherein the boiler controller ( 500 ) is in operative communication with the combustion air control system ( 200 ), the fuel control system ( 300 ), and the flue gas sensing system ( 400 ), and (ii) wherein the boiler controller ( 500 ) controls coarse-level operation of the combustion air fan ( 210 ) and the fuel valve ( 320 ) based upon the system demand setpoint ( 510 ), and (iii) wherein when the flue gas differential sensor ( 420 ) has sensed a change in the flue gas predetermined characteristic that meets the flue gas differential setpoint ( 530 ) the boiler controller ( 500 ) controls the fine-level operation of the combustion air fan ( 210 ) to maintain the flue gas oxygen setpoint ( 520 ) based upon the amount of oxygen in the flue gas sensed by the oxygen sensor ( 410 ).