Boiler vs Furnace — What’s the Difference?

Boiler vs Furnace — What’s the Difference?
  • Opening Intro -

    Two of the most common systems for heating a building are a boiler and a furnace. Both systems use a fuel source such as natural gas, oil, propane or electricity to function.


Both the manner in which each delivers heat differs substantially.

The Basic Operation of a Boiler

Boilers work on the principle of radiation. A boiler heats water to either steam or hot water in a central tank. This is the “boiler” portion of the system. The heated water is then channeled through a system of tubes or pipes throughout the building. Heat is radiated to the area to be heated through the pipe or tube system.

  • How a Boiler Circulates Heat

    To make radiation more efficient, numerous metal fins are attached to the piping.

    Heat is transferred to the fins from the pipes, creating more surface area for heat dissipation. Water circulates back to the boiler through a return system.

    In some modern systems, a network of tubing is run through a floor and concrete is poured over the tubing. The concrete is heated and acts as the heat transfer medium, replacing metal finned tubing.

    As hot air rises and cold airs falls, the system creates a natural circulation of air. Once the water is heated in the boiler, the system provides a steady, even flow of heat.

    For this reason, large, industrial boilers are a popular choice of factories and commercial buildings.

    In some systems, solar panels can be used to heat the water for the system. Valves are used to shut off water or steam to a particular area if zone heating is desired. Modern boilers are normally 90 percent efficient or better.


The Basic Operation of a Furnace

A furnace normally uses the principle of forced air to provide heat. A furnace consists of a combustion chamber, a heat exchanger and a blower to heat a building. Fuel is ignited in the combustion chamber. A series of burners are used in the combustion chamber. Harmful gases, such as carbon monoxide are expelled through the chimney.

  • How Heat Circulates with a Furnace

    The heat radiates from the combustion chamber to heat the air in the heat exchanger. A large electric fan, or blower, moves the hot air from the heat exchanger through the building through a series of ducts.

    Each room normally contains a cold air return, where colder air is forced back to the furnace. A filter is used to clean the air as it returns to the furnace. Ducts can contain dampers to block the flow of warm air to provide zone heating.

    A furnace can normally heat a building or room more quickly, but it does not maintain the heat as well as a boiler. As the air cools, the furnace will turn on and off, or cycle, on a needed basis. During cold periods, a furnace can cycle several times per hour.

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Choosing the right system depends on a variety of factors. These include the initial cost of installation, maintenance costs, heating needs, useful life of a system, monthly fuel consumption and climate conditions. A discussion with a heating engineer regarding your heating needs may be the best way to choose the right system.

Addy Reeds is a freelance writer from Eugene, Oregon. She discovered her passion for journalism while attending the University of Oregon. Follow her on Twitter and Facebook: @addyreeds1;

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