Anybody who has a hot water or steam heating system in their home needs to know how a boiler works. The boiler is the most important part of a steam or hot water heating system because it is what actually provides the heater. A boiler is defined as "a closed vessel in which water or other liquid is heated, steam or vapor is generated, steam is superheated, or any combination thereof, under pressure or vacuum, for use external to itself, by the direct application of energy from the combustion of fuels, from electricity or nuclear energy."
According the "ASME - (American Society of Mechanical Engineers) Boiler and Pressure Vessel Code" boilers may be classified as
Section I Power Boilers - process boilers, power boilers and high pressure boilers
boilers in which steam or other vapor is generated at a pressures exceeding 15 psig
high temperature water boilers intended for operation at pressures exceeding 160 psig and or temperatures exceeding 250 degrees F
Section IV Heating Boilers - commercial boilers, industrial boilers, heating boilers, low pressure boilers
boilers in which steam or other vapor is generated at a pressures not exceeding 15 psig
high temperature water boilers intended for operation at pressures not exceeding 160 psig and or temperatures exceeding250 degrees F
A boiler then is an enclosed vessel, a container that water or liquid is placed within and heated by an external energy. The steam or hot water or fluids that is produced flows thru an enclosed system of pipes that can produce heat in your home via a radiator, baseboards or pipes embedded in the floor your home.
In larger applications the product of the boiler superheated steam or water is used to drive large turbines and generator to produce electrical power for a building or a city.
In a hot water heating system, the water is heated to the proper temperature and pumped through pipes to radiators to produce warmth. In a steam boiler the water is turned into steam which flows through pipes and radiators to produce warmth. Most home heating systems with boilers will be hot water heating systems. Some older homes and larger homes may have steam heating systems. Both steam and hot water heating systems are excellent means of keeping your home warm.
How a Boiler Works
The boiler usually sits on top of a burner in which fuel is burned to produce heat. The fuel produces the heat, the water or steam in the boiler is used to distribute the heat through the house usually via pipes and radiators.
The most common fuel for boilers in the United States today is natural gas which is usually piped directly into the house from a pipeline that runs under the street or road. In rural areas not served by natural gas lines the most common fuel for boilers is propane gas which is kept in a large tank in the yard and piped into the house. Propane is usually more expensive than natural gas.
In some areas of the US mainly New England there are some boilers that are heated by fuel or heating oil. Outside of the Northeast oil fired boilers are actually very rare. Many oil fired boilers have been converted to burn natural gas or propane. The reason natural gas and propane are more popular is that they are much cheaper fuels.
There are also a small number of boilers around that burn other fuels. Before Word War II many boilers burnt coal. Today, some people particularly in rural areas burn wood because it is often cheaper than natural gas or propane. There are also boilers that burn other more exotic fuels such as waste oil, wood pellets and even corn cobs.
Boilers and Forced Air Heating
Something to keep in mind is that most homes in the United States do not use a boiler for heat. Most American and Canadian homes are heated via forced air in which a device called a furnace heats air that is blown through the house to provide heat.
The cost of operating a forced air heating system and operating a boiler is pretty much the same but forced air heating systems are usually cheaper to install. Forced air heating is cheaper because it doesn’t require the installation of a network of pipes and radiators to distribute heat to the house.Many people will confuse boilers with forced air furnaces because both devices usually sit in the basement and use the same kinds of fuel. Boilers are more common in colder areas because they can provide more heat.