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Condensing Boiler Venting is the key to safety and efficiency

January 28, 2015

Condensing boilers are the modern and efficient way to heat your home.  The combustion process in condensing boilers relies of a fan to push air through the combustion chamber and heat exchanger while traditional boilers rely on a open flame and natural draft.  The natural draft is a simple but inefficient process while the forced air is slightly more complicated but much more efficient.

The bottom line is that the ventilation is much different than a traditional atmospheric boiler.  The good news is that there are now more options than ever.  High efficiency boilers use a sealed combustion process.  Air is pushed into the burner by a fan.  This air is usually piped from the outside directly to the boiler to minimize drafts.  Room air can often be used, but in most cases, especially residential, this is not optimum as the room air has been heated so the energy that was used to heat the air was wasted.

Vertical TerminationOnce the propane or natural gas fuel has been burned and the gas has passed through the heat exchanger, it is critical that this flue gas is properly sent outside.  Traditional boilers would use a chimney in most cases to carry the flue gas outside.  The natural convection of the hot flue gases would rise naturally up the chimney.  Because high efficiency boilers use a fan to drive the gases, and because their flue gases are not as hot as a traditional boiler (resulting in low NOx emissions), a chimney cannot be used directly as the flue-way.  It can be used as the chase that holds a flue pipe. The Prestige is approved to be vented through a chimney using a flexible polypropylene flue-way. This allows the flue-way to be installed around bends in a chimney making it much easier to use the chimney as a chase.

If an existing chimney cannot be used the Prestige and Challenger can both be vented Sidewall Terminationvertically through a roof or horizontally through a wall.  There are many options for the terminations of the venting that will allow it to both function properly and look attractive.  Engineered terminations are highly recommended because they can help prevent flue gas recirculation, which can destroy a boiler.  It is important that the location of the venting be considered.  It must be located far enough from doorways and windows so that the flue gas cannot enter the house.

Jim Lavallee Plumbing
Serving Eastern Massachusetts and the Boston area
Phone: Toll-free (888) 884-412

(original article)

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