Introduction

man testing efficiency of furnace
Photo: Keller & Keller
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Before chilly autumn nights set in, you need to make an appointment for your furnace's annual checkup. Without this yearly cleaning and inspection, a system can wear itself out quickly, pump deadly carbon monoxide into your home, or simply stop working.

We asked This Old House plumbing and heating expert Richard Trethewey to show us the proper steps that a service professional would follow for an oil-burning forced-air furnace; the basics on a gas system are similar. In both, fuel is mixed with air and ignited, heating a sealed chamber. Fresh, filtered air then blows across the outside of the hot chamber and into the heating ducts. (Homes with radiators have boilers instead of furnaces. These heat water instead of air, but the annual checkup is similar.) In all, the dangerous exhaust from the combustion chamber is vented out a flue or chimney.

Whatever type of system you have, don't wait until it breaks down to call for service. A clean, well-adjusted heating system will save you money on fuel and prolong furnace life. Annual servicing is cheap—typically less than $100—especially when compared with the price of a new furnace. "You wouldn't wait more than a year to service your car," Richard says. "The heat in your house is just as important."
Ask TOH users about Fall Upkeep

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    Tools List

    • Phillips screwdriver
      Screwdriver
    • Wire brush
    • shop vacuum
      Shop vacuum
    • strap wrench
      Strap wrench
    • combustion analyzer
      Combustion analyzer

    Shopping List

    1. Foil tape

    2. Oil filter
    (for oil-powered systems)

    3. Air filter

    4. Oil nozzle
    (for oil-powered systems)