How Long Do Furnaces Last?

By: Brian Schutt  |  March 15, 2017

It’s time for a quick history lesson on furnaces in Indianapolis homes.

When I was young, my grandpa would tell me stories about installing a gravity furnace—called that because it did not include a fan. Rather, they just relied on the fact that hot air rises to work. The number of parts making up gravity furnaces could be counted on one hand. The heat exchangers were often made of cast iron, and there were no electronics.

Their simplicity and rugged design meant they would essentially last forever. In fact, there are still homes across Indianapolis with these type of furnaces—converted from coal to oil and natural gas—now over 50 years old!

Higher Efficiency Furnaces Over the Years

The problem with gravity furnaces was always their efficiency (or lack thereof). No matter the fuel you put into them, 50 percent or more would be wasted.

And so, beginning in the 1970s, in response to government regulations and market demand, furnace manufacturers began improving the efficiency of these heating machines—whether fueled by natural gas or electricity.

First, we saw the addition of a fan to push air through the house and the thinning of the heat exchanger walls—boosting furnace efficiencies above 70 percent. Then, manufacturers replaced the standing pilot with an electronic ignition, added a second fan to control exhaust flow, and included a secondary heat exchanger to extract more heat—boosting efficiencies to 90 percent. And now, computers regulate all these devices to push efficiencies up to 98 percent.

Trading Durability for Higher Efficiency in Furnaces

Granted, getting 98 percent of what you pay for is clearly better than getting 40 percent. However, all the technology increases did result in durability decreases. Thinner walls in the heat exchanger meant they would crack more easily. Extra fan motors would wear down and need to be replaced. The electronic ignition required cleaning and eventually replacement.

Simply put, today’s higher-efficient gas furnaces will not last as long as the old gravity furnace. Not because they were designed to fail, but because they were designed for efficiency. And as a result, more technology means more can go wrong.

How to Get the Most Life From Your Furnace

Many of today’s manufacturers proclaim their new gas furnaces can last 15-20 years. My experience agrees with this; however, many factors affect how long a furnace lasts.

You can do a few things to get the most life from your furnace. First, change air filters regularly. Also, get the system fully cleaned twice a year by a professional. And finally, make sure your furnace properly fits the size of your home.

Give us a call at 317-203-8149 if we can be of any help in keeping your current furnace alive, or replacing your old heating system.

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