System and process for controlling the flow of air and fuel to a burner

A process for optimally operating and air and fuel regulating system for a burner having first and second pressure regulating valves for controlling the air and fuel flow to the burner, first and second pressure sensors for sensing the differential pressure of the air flow and the fuel flow, respectively, across the burner, wherein said sensors are fluidly connected downstream of said first and second valves, and a combustion interface controller including a microprocessor having an input which is electrically connected to the first and second differential pressure sensors and an output which is connected to first and second pressure regulating valves, comprising the steps of:

• (a) deriving an optimal set of air and fuel flow rates by measuring the optimal differential pressures of the air flow and the fuel flow across the burner, respectively, for each point across the firing range of the burner;
• (b) entering the optimal air and fuel differential pressures derived at step (a) into the microprocessor, and
• (c) electrically adjusting the position of air flow and fuel flow valves by means of the microprocessor for any selected point on the firing range until the pressures sensed by the differential air and fuel flow sensors are equal to the optimal differential air and fuel flow pressures entered into the memory of the microprocessor for that particular point on the firing range.

A process for optimally operating an air and fuel regulating system for a burner having first and second pressure regulating valves for controlling the air and fuel flow to the burner, first and second pressure differential sensors for sensing the differential pressure of the air flow and the fuel flow, respectively, across the burner, wherein said sensors are fluidly connected downstream of said first and second valves, and a combustion interface controller including a microprocessor having an input which is electrically connected to the first and second differential pressure sensors and an output which is connected to first and second pressure regulating valves, comprising the steps of:

• (a) igniting the burner;
• (b) recording the differential pressure of the air flow across the burner at a plurality of related points along the firing range of the burner;
• (c) correlating the differential pressures obtained in step (b) with air flow rates;
• (d) detachably connecting a flowmeter across the fuel flow of the system;
• (e) recording the differential pressure of the fuel flow across the burner at a plurality of selected points along the firing range of the burner;
• (f) recording the flow rate indicated by the flowmeter at each of the plurality of selected points in order to correlate a fuel flow rate with fuel flow differential pressure;
• (g) interpolating both the recorded values of the air flow differential pressures and their corresponding air flow rates across the firing range of the burner;
• (h) interpolating both the recorded values of the fuel flow differential pressures and their corresponding fuel flow rates across the firing range of the burner;
• (i) computing the air and fuel differential pressures at each point along the firing range of the burner which corresponds to the stoichiometrically optimal air-to-fuel ratio;
• (j) operating the burner across its entire firing range at the air and fuel differential pressure derived at step (i) while monitoring the resulting flue gases with an oxygen probe;
• (k) adjusting the air and fuel differential pressures at all points in the firing range where the oxygen probe indicates a state of inefficient combustion;
• (l) operating the burner across the lower half of its firing range in a plurality of excess air modes while recording the heat output of the burner;
• (m) deriving an optimal set of air and fuel differential pressures across the firing range of the burner by splicing the air and fuel differential pressures corresponding to the most efficient excess air mode onto the adjusted air and fuel differential pressures derived at step (k);
• (n) entering the air and fuel differential pressures derived at step (m) into the memory of the microprocessor, and
• (o) electrically adjusting the position of air flow and fuel flow valves by means of the microprocessor for any selected point on the firing range until the pressures sensed by the differential air and fuel flow sensors are equal to the optimal differential air and fuel flow pressures entered into the memory of the microprocessor for that particular point on the firing range.