Which type of burner control is characterized as continuous adjustment of the fuel flow?

Modulating control is characterized by the continuous adjustment of the fuel flow to match the thermal demand of the system. This type of control allows for fine-tuning of the burner operation, ensuring that the fuel input is proportionate to the heat output required at any given moment. This means that as the demand for heat fluctuates, the burner can seamlessly adjust the fuel flow to maintain optimal combustion efficiency and provide stable operation.

In contrast, on-off control involves the burner operating at full capacity or not at all, which can lead to inefficient fuel use and temperature swings. Automatic control might suggest some level of adjustment but doesn't specify the continuous nature of modulation. Fixed control typically implies a constant fuel flow without adjustment capabilities. Thus, modulating control is the most effective and responsive method for managing fuel flow in relation to the system's needs.