Abstract: A gas-fired heater includes a plurality of burners and one or more valves corresponding to one of the burners and operating between a closed position and an open position. A fuel supply is in fluidic communication with at least one of the burners when the one or more valves are in the open position. A modulator receives a temperature signal and computes, as a function of the temperature signal, and emits at least one control signal. The modulator then operates the one or more valves between the open position and the closed position as a function of the at least one control signal and controls the one or more valves to either activate or deactivate the burners for incrementally modulating a heat input to the gas-fired heater.