Last month Punxsutawney Phil retreated into his hole after seeing his shadow, indicating that unfortunately an early Spring is not on the horizon. Whether or not you believe that a groundhog can predict when the change of seasons will happen, most people can agree that this severe winter does not show any signs of stopping. Unprecedented amounts of snowfall and record-breaking low temperatures across North America have left many wondering when this weather will end.
As we curse Old Man Winter under our breath and see if there is any way we can afford a last minute trip to the Bahamas, it might be time to accept our fate: winter is here to stay, for at least a little while longer. So let’s show appreciation where appreciation is due and high-five our heating systems – metaphorically, of course -by taking great care of them. Please consider the following furnace “fun facts” as you enjoy the comfort of your warm home.
How do furnaces work?
Furnaces distribute their heat by warming the house air as it passes through the furnace. The furnace fan draws cool air in from the rooms through the return registers and ducts. The air is warmed as it passes over a hot metal box inside the furnace cabinet called a heat exchanger. The warm air is pushed out to the rooms through the supply ducts. The house air can be thought of as moving in a loop, passing by the furnace periodically to be reheated.
Gas and oil furnaces have three major components: a heat exchanger, a burner, and a blower. Electric furnaces have a heating element rather than a burner to generate heat. Furnace life expectancies depend on many things, but there are some averages:
- Conventional and mid-efficiency furnaces typically last about 18 to 25 years.
- High efficiency furnaces typically last about 15 to 20 years.
Furnaces are usually stored in a cabinet. There are also operating and safety control, and an air filter in the furnace. Gas and oil furnaces have a vent to get rid of the exhaust products. Some furnaces have accessories such as humidifiers or central air conditioning systems. Electronic air cleaners may replace conventional filters.
Why do they sometimes not work?
For most furnaces and boilers, terminal failure is usually a crack or hole in the heat exchanger. Since most of the heat exchanger is not visible, the heat exchanger cannot be fully inspected during a Home Inspection. Because a Home Inspection is not technically exhaustive, the likelihood of failure is based on probability rather than testing or equipment tear-down.
A conventional gas-fired furnace, for example, contains a heat exchanger having an average life expectancy of 18 to 25 years. There are, however, manufacturers of gas-fired, forced-air furnaces whose heat exchangers have a reputation for failing sooner.
Most high efficiency furnaces require more air flow across the heat exchangers than conventional furnaces. Replacing a conventional furnace with a high efficiency furnace can be tricky. Older, smaller ductwork and/or an air conditioning coil can restrict air flow, increasing the temperature rise within the furnace. This can result in premature failure of the heat exchangers and void the warranty. This condition may not be identified in the Home Inspection.
Electric furnaces and boilers contain electric heating elements and controls for the elements. Every single component can be replaced. With age, however, electric systems get to a stage where replacement of the entire unit makes sense due to lost reliability and a lack of available replacement parts.
With individual electric heaters, failure probability is not meaningful, since replacing individual heaters is not a significant expense. Electric heating elements are like light bulbs. Their life expectancy is not well defined, and their failure can’t be accurately predicted.
If you want to learn more about your home and enjoyed these tips, order a copy of the Home Reference Book. Was there another home maintenance item you haven’t seen us cover yet? Comment below or let us know on Twitter or Facebook and we’ll do our best to help out.