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Why Are Newer Furnaces More Efficient Than Older Ones?

furnace-burners-ignitedCurrent home heating systems work better and at higher energy efficiency than ones from 20, 30, even 10 years ago. We can chalk this up to an investment in research to improve the products, as well as the nebulous idea of “progress.” But there are specifics behind why heaters waste less energy today than the models of the not-too-distant past.

For example, look at the natural gas furnace. Gas furnaces once had AFUE ratings between 56% and 70%. That means that even at the most efficient level, a furnace was converting only 70% of its natural gas into heating power and letting 30% go to waste.

Fast-forward to today. The best furnaces available for homes have AFUE ratings of 98.5%, which means only 1.5% of the natural gas goes to waste. Lower-end furnaces can have AFUE ratings between 85% and 90%. The standard for a furnace to earn the ENERGY STAR label from the Department of Energy is 90% AFUE.

So the question is: “What’s changed?” Well, quite a bit!

Electronic Ignition Systems

One of the major changes in furnace technology is the elimination of the standing pilot light and its replacement with electronic ignition systems. A standing pilot light must use gas continually in order to keep burning so that it can ignite the burners whenever they turn on. An electronic ignition system gets rid of this drain on natural gas and instead uses a small amount of electrical power to start up the burners as they come on.

Better Heat Exchanger Construction

Heat exchangers are the metal chambers that hold the hot combustion gas from the burners and then transfer the heat through their metal walls to the air stream. Old furnaces had heavy exchangers with thick walls, but newer construction allows for light heat exchangers that transfer heat faster and more effectively.

Condensing Furnaces

The most efficient furnaces—the ones with 98.5% AFUE—are condensing furnaces. This means they have a second heat exchanger that collects the exhaust vapor from the first heat exchanger and condenses it to squeeze out even more heat.

Sealed Combustion

The standard furnace for decades used atmospheric combustion, which means the furnace drew on the air around its cabinet to aid with combustion. The combustion chamber in this type of furnace is open to the house: you could look inside and see the blue flames from the burners. Newer furnaces use sealed combustion, with a combustion chamber that is closed off from the house. These furnaces draw air from the outside of the home through a PVC pipe. Sealed combustion furnaces are more efficient because the the combustion chambers don’t lose heat due to exposure.

Variable Speed Fans

Blower fans in older furnaces are only capable of running at a single speed. The blowers are either on or they’re off. Newer variable speed furnace fans allow the blower to ramp down to lower power levels when necessary. In fact, most variable speed fans will work at their lower setting 60% of the time, and this helps lower the furnace’s energy consumption. As a bonus, it helps spread heat more evenly through a house.

If you are looking for a furnace installation in Lincoln Park, Chicago, contact Brilliant Electric Heating & Cooling. We’ll help you find the right high-efficiency furnace for you!

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