A condensing furnace is a high-efficiency heating system that extracts heat from combustion gases as they cool and condense, achieving efficiency ratings of 90 to 98.5 percent AFUE. By recovering latent heat that traditional furnaces vent to the atmosphere, these units reduce fuel consumption and operating costs by 15 to 25 percent. They represent the current standard for residential and commercial heating applications.
Technical Operation
Condensing furnaces use a secondary heat exchanger positioned after the primary unit to capture heat from cooling flue gases. As gases cool below the dew point (approximately 130 degrees Fahrenheit for natural gas), water vapor condenses and releases significant energy. This condensate collects in a trap and drains through a floor drain or condensate pump, requiring a neutralizer to meet discharge codes.
Benefits and Considerations
These furnaces reduce heating costs to 1,200 to 1,500 BTU input per dollar spent compared to 1,000 to 1,200 BTU for standard units. Installation requires careful attention to venting, as vent pipes must handle corrosive condensate. Higher upfront costs of 15 to 25 percent are offset by energy savings within 5 to 8 years, making them a sound long-term investment.