website-boilerMost U.S homes are heated with either furnaces or boilers. While furnaces heat air and distribute the heated air throughout the home’s ducts. Boilers heat water and provide either hot water or steam for heating. The steam or water is distributed via pipes to radiators, baseboards or coils.


Typically, as the thermostat temperature drops below the set point a circuit closes (a temperature sensor) allows current to flow to the hot water circulator, signaling the heating process to begin.

Gas fired boilers have a gas control valve to allow gas to flow into the burner tubes. Oil fired boilers have an oil pump which delivers oil at high pressure to an atomizing nozzle which sprays into the fire chamber. The fuel is ignited with a pilot light or electric igniter, in the case of a gas fired unit, or a high voltage spark created by a transformer on oil fired units.

The water circulates within a closed system beginning at the boiler, passing through a device that captures and purges air from the system.  The expansion tank within the system deals with the change in volume of water as the temperature rises.

The water or steam then passes into the distribution system to carry the heat throughout the home to the radiators, baseboards and other radiant and convective equipment. As the water circulates it releases its heat energy and cools down, in older systems gravity is used to convey the water back to the boiler. Newer systems use a circulator pump to move water and pump it back through the boiler.

The boiler stops firing when the internal temperature sensor indicates the “HI” limit temperature for the water has been reached. The circulator stops the flow of water when the living area thermostat indicates the desired temperature has been reached.


There are safety devices within a boiler that must be checked to ensure your family and home’s safety. The flame must be signaled to shut down, and the combustion gases resulting from burning fuel are contained in the heat exchanger, which cannot have cracks. Please always contact a licensed professional to handle any service needs.