Abstract: A boiler control utilizing a pressure sensor is provided that operates the system in the low fire mode if the load is light and can be satisfied in that mode. If the low fire operation is inadequate to hold the load, and the pressure drops, the boiler is then operated in a modulating mode which includes a high fire limit.

Abstract: A boiler control utilizing a pressure sensor is provided that operates the system in the low fire mode if the load is light, and can be satisfied in that mode. If the low fire operation is inadequate to hold the load and the pressure drops, the boiler is then operated in a modulating mode which includes a high fire limit. This is accomplished by sensing the variation of a pressure responsive means and by providing a burner control system that monitors that pressure responsive means.

Abstract: A timer means having a time delay on reapplication of control allows a single probe low water cutoff and feedwater makeup device to function. The time delay preventing reapplication of power to a burner while simultaneously causing a feedwater mechanism to add water to a boiler provides safe operation of the boiler without oscillations caused by momentary losses of water.

Abstract: A conductive fluid probe, one particularly used in sensing a boiler water, is operated with pulsed energy from the charging and discharging of a capacitor. The charging is allowed to occur in a normal resistance-capacitor manner, while the discharge is rapidly accomplished. The energy of both halves of the charge and discharge cycle are substantially the same even though the magnitudes of peak voltages are substantially different thereby operating the probe with a minimum of electrolysis and a maximum cleaning action.

Abstract: A resistive fluid or boiler water type of detecting system has been disclosed. A single conductor type of probe having a plurality of conducting regions that are capable of conducting a bidirectional electric current in either a full bidirectional mode or in a unidirectional mode has been disclosed. The single probe element is capable of three separate and distinct states of operation. The first state is when there is an absence of current, the second is when there is a unidirectional portion of the bidirectional current flowing, and the third state is when the full bidirectional electric current is allowed to flow. An output device is responsive to these three states to provide different types or levels of control.