When the burner is in high fire, what is at its maximum rate?

In a steam boiler system, when the burner is in high fire, it operates at its maximum output, which involves the maximum fuel input being combusted. This process necessitates an optimal air-fuel ratio to ensure complete combustion of the fuel. The air-fuel ratio is crucial because it determines how effectively the burner can mix air with the fuel to achieve the best combustion efficiency and energy output.

At high fire, fuel input increases significantly, and to facilitate that, the amount of air supplied must also correspondingly increase to maintain the proper air-fuel ratio. An imbalance would lead to inefficient combustion, resulting in incomplete fuel burning, increased emissions, and reduced efficiency.

While the fuel input is indeed at its highest during high fire, the key aspect of this question relates to the concept of maintaining the correct proportions for effective combustion. Hence, the air-fuel ratio aligns with the notion of maximum performance in this scenario, as it plays a pivotal role in achieving optimum combustion conditions necessary for the efficient functioning of the burner.

Other aspects like water flow may also increase during high fire, but they are typically regulated by different parameters, and exhaust pressure is more a result of combustion efficiency rather than a direct factor in the firing rate of the burner. Thus