Today's boiler plant is equipped with electronic (digital or analog) controls for each boiler to control flame monitoring, fuel and air valves, and startup and shutdown sequences. Further, the plant is equipped with a separate microprocessor, the plant master, which coordinates all boilers and equipment while recording data and providing a communications link. The modern plant master controller may be a proprietary combination of hardware and software specially designed for boilers or it may be a general-purpose industrial controller programmed for the needs of the plant.
In addition to flame loss or instability, the following can also cause a boiler shutdown (Figure 2):