What makes a high efficiency gas furnace so efficient?
The furnaces that are available today are many times more efficient than the systems that were installed just a decade or two ago. This is partially due to the fact that furnaces are simply built better nowadays, but also because of the new technology and features that have emerged in the heating industry in recent years (as you’ll see below).
These advancements have allowed high efficiency furnaces to do two things: extract more heat out of the gas they consume and only use the amount of energy that’s necessary to get the job done at any given time.
Common components of a high efficiency gas furnace
• Electronic ignition. Today’s furnaces use an electronic ignition in lieu of the gas-powered pilot lights that are used in older furnace. This ignition is only used when the furnace needs to turn on, which is more energy-efficient than keeping a small flame burning at all times.
• Two-stage heating. Temperatures here in the St. Louis area can change significantly from day to day and week to week. That’s why many high efficiency gas furnaces come with two-stage heating. The lower stage consumes less energy and is used a majority of the time, while the higher stage only kicks on when it’s very cold out and more heat is required.
• Variable speed blower. Similar to two-stage heating, a variable speed blower operates at different capacities depending on how much it’s needed at any given time. When more airflow is needed (like when your air filter begins to clog), a faster speed is used. When the blower detects that less airflow is needed, it switches to a lower speed to conserve energy.
• Second heat exchanger. Any high efficiency gas furnace with an AFUE rating above 90 percent is a “condensing furnace.” This means that it uses a second heat exchanger to extract heat from the exhaust gasses that would otherwise be vented out of your home with less efficient systems. This allows condensing furnaces to do more with less fuel.
• Sealed combustion. In order for the combustion process to work properly, your furnace needs to draw in a certain amount of air. Unlike furnaces with unsealed combustion, which utilize (heated) air from around your home, sealed combustion furnaces draw in air from outside in order to conserve energy and improve safety levels.