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How Your Heating System Works – Part 1: Boilers

Knowing how your heating system works will help you evaluate its efficiency and determine which system is best for your home. The two most common home heating systems used in the Massachusetts area are boilers and furnaces. In this post, the first of two on “How Your Home Heating System Works,” we will cover two different types of boilers.

A boiler is at the heart of a water-based or “hydronic” heating system that uses heated water or steam to deliver heat throughout your home. It circulates water around the powerful burner flame to absorb the heat.
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  • Water Boiler: Water boilers heat water without boiling it, and the water is circulated through the baseboards, radiant floor panels or other heat-emitting devices that transfer the heat from the water to the room air. Between the time you turn up your thermostat and begin feeling the warmth a number of things occur:
    • The thermostat sends a signal to the controls on the oil burner.Water B
    • Fuel is sent to the burner through a fuel pump. A nozzle then atomizes the fuel into a mist, which is sent into the combustion chamber.
    • The mist is mixed with air and ignited. This will cause the combustion chamber to get very hot.
    • Water is heated in the combustion chamber and pumped through a system of ducts to be released by your radiators throughout your rooms.
    • As the water begins to cool, it is sent back to the boiler to be heated until your home reaches the desired temperature.
    • Emissions from the system’s combustion are sent through the flue pipe and out the chimney. Higher-efficiency boilers will release fewer emissions and more effectively use the heated air, causing less energy to be wasted.
  • Steam Boiler: Steam boilers heat water to the boiling point to create steam that is circulated through the radiators, which transfer the heat to the ambient air. For steam boilers to heat your home, the following occurs:
    • The thermostat sends a signal to the controls on the oil burner.
    • Fuel is sent to the burner through a fuel pump. A nozzle then atomizes the fuel into a mist, which is sent into the combustion chamber.
    • The mist is mixed with air and ignited. This will cause the combustion chamber to get very hot.
    • A heat exchanger will allow air to absorb the generated heat and propel it via a blower throughout the home’s ducts.
    • Emissions from the system’s combustion are sent through the flue pipe and out the chimney. Higher-efficiency boilers will release fewer emissions and more effectively use the heated air causing less energy to be wasted.

There are many variants on the traditional boiler, such as hydro-air systems, which use a boiler to heat water that is then circulated through an air handler, which heats the air that circulates through your house.

Check back soon as our next article will discuss how furnaces work, and in the meantime, visit energy.gov to find out more about boiler efficiency and maintenance.