ABSTRACT
The basic gas-fired boiler is a packaged piece of equipment that utilizes natural gas to produce hot water or steam. Hot water and steam boilers are pretty similar in terms of operating characteristics. Larger boilers will most certainly have more than a single stage of control, and can even be equipped with proportional firing rate control. When a boiler is equipped with proportional firing rate controls, a proportional controller will exist, that operates a modulating burner. All boilers will be equipped with a high limit controller, normally of the manual reset variety. A simple method of interlocking boiler operation to overall system operation is to install a water flow switch in the supply main. A typical boiler sequencing controller will minimally have an input for a hot water temperature sensor, and outputs for boiler control.
