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Anatomy of a High Efficiency Condensing Furnace

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Anatomy of a High Efficiency Condensing Furnace
Anatomy of a High Efficiency Condensing Furnace

Components of a condensing furnace are similar to a conventional furnace. The primary difference is in the dual heat exchangers.

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In the tutorial Gas Furnace Types and Efficiency Ratings I describe the two main types of gas furnaces in the home, the conventional furnace and the newer high efficiency condensing furnace. The technologies used in these furnaces directly impact their AFUE efficiency rating. Only condensing furnace technology achieves the highest efficiency ratings of over 90% AFUE, with some furnaces reaching over 98% AFUE.

AFUE is an acronym for Annual Fuel Utilization Efficiency and is the metric used to measure furnace efficiency. It is simply a ratio between the amount of fuel converted to heat and the amount of fuel which enters the furnace. The higher the AFUE the more efficient the furnace.

The condensing furnace is so efficient and extracts so much heat from the combustion process that its exhaust vent / flue is just warm to the touch, not “burn your fingers hot” like a conventional furnace.

So what makes the conventional furnace and condensing furnace so different, and how does the condensing furnace work? Well, that’s what I’ll explain in this tutorial called Anatomy of a High Efficiency Condensing Furnace. In this tutorial you’ll learn the following about a condensing furnace and its components:

    Fuel Combustion
  • Gas burner
  • Electronic ignition
  • Combustion chamber
  • Combustion air intake
    Heat Extraction
  • Primary heat exchanger
  • Secondary condensing heat exchanger
  • Condensate drain line

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