The Secrets of High-Efficiency Furnaces

burners-in-furnacesLast week we discussed fuel efficiency in gas furnaces and how to understand AFUE ratings, which is how the efficiency of furnaces is measured.

But this topic brings up another set of questions: why is the efficiency in furnaces improving? Older furnaces would have an AFUE rating between 56% and 70%, which meant quite a bit of energy waste. But today, for a furnace to earn the ENERGY STAR certificate from the Department of Energy, it must have an AFUE of at least 90%. And some can score as high as 98.5%. What is making furnaces today so much better at using natural gas efficiently than older models?

You could just chalk it up to “they got better at making them!” Which is partially true. But there are some interesting “secrets” to why modern furnaces waste less energy than old ones.

Lighter Heat Exchanger Construction

The heat exchanger is one of the essential parts of how a furnace runs. This metal container is where the combustion gas from the burners gathers, and its heat raises the temperature of the metal walls. Air from the blower moves around the heat exchanger and picks up the heat. Newer furnaces have lighter heat exchangers that are more effective at getting larger amounts of heat transferred to the air.

Electronic Ignition

The old standing pilot light is no longer the way that a furnace ignites the gas burners. Instead, an electronic ignition system uses a hot surface—like the filament in a lightbulb—to start up the burners. Without a pilot light that constantly uses natural gas through the winter, the furnace will waste less power.

Sealed Combustion

The combustion chamber of a furnace is where the burners ignite. The burners need to draw on air in order to work, and in older furnaces this was done by making the combustion chamber open to the air. However, this also allowed some of the heat to escape as well. To stop this heat loss, sealed combustion chambers were created. Where does the combustion chamber draw on the air it needs? It comes through a PVC pipe that goes to the outdoors. Along with assisting with energy efficiency, sealed combustion is safer for a home and prevents the furnace from drying out the indoor air.

Multi-Stage Furnaces

The standard furnace has burners that are either on or off. But multi-stage furnaces can run the burners at lower capacities when necessary, so the furnace doesn’t need to run at maximum power all the time. This not only means less energy used over the season, but it helps the furnace to provide more even heating that won’t make a home stuffy.

Condensing Furnaces

These are the super-efficient furnaces that can reach 98.5% AFUE. The way these furnaces achieve this is by using a second heat exchanger. The vapor from the first heat exchanger moves to this second one instead of going out the flue. The second heat exchanger condenses the vapor and draws even more heat out of it.

If you want to have furnace installation in Hendersonville, NC that will save you energy, contact our team. We’ll have the right energy-efficiency furnace set up in your home.

Comfort Central, Inc.: Serving Western North Carolina’s Heating, Cooling, and Indoor Environmental Needs.

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