As HVAC technology continues to advance, the conventional forced-air furnace is gradually being replaced by improved high-efficiency models. Among the more efficient types of heating systems are condensing furnaces. While condensing furnaces are in many ways similar to standard fuel-burning heating systems, they have important differences that make them highly energy efficient and cost effective.
At the basic level, a condensing furnace operates the same as a conventional forced-air furnace. As indoor temperatures decrease, a thermostat senses the changes and switches on the furnace. Burners ignite inside the unit and create heat that’s absorbed by the heat exchanger. A fan blows air across the heat exchanger. The air absorbs the heat and the fan sends the 
warmed air through your home. Exhaust gases from the fuel combustion process are safely vented to the outdoors. Cooled indoor air comes back to the furnace through the return ductwork. The air is filtered, and the heating process begins again.
The most important difference between conventional and condensing furnaces is in how condensing units handle the exhaust gases produced by burning the fuel that generates heat.
- Exhaust process is slower: In traditional furnaces, the process of getting rid of exhaust gases is relatively quick. The condensing model, in contrast, uses a slower exhaust process so that better use can be made of the exhaust gases.
- A second heat exchanger recovers more heat: Before venting exhaust gases to the outdoors, a condensing furnace uses a second heat exchanger to extract more heat from these still-warm gases. This heat is recycled to further warm your home. This reduces the amount of fuel that the condensing furnace uses, which increases system efficiency. Condensing furnaces can achieve Annual Fuel Utilization Efficiency (AFUE) ratings of up to 98 percent, which means 98 percent of the energy in the fuel is converted to usable heat.
Marsh Heating & Air Conditioning has more than 38 years of professional experience serving HVAC customers in the Twin Cities area. Contact us today for more information on condensing furnaces and how they can improve your home comfort while increasing the efficiency of your heating system.
Our goal is to help educate our customers in Minneapolis-St. Paul, Minnesota about energy and home comfort issues (specific to HVAC systems). For more information about condensing furnaces and other HVAC topics, download our free Home Comfort Resource guide.
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