How a Furnace Works
Furnaces heat your home by circulating heated air through your ductwork. That air is heated by the burning of fuel within the furnace. Furnaces can be fueled by natural gas, propane or oil. As the fuel burns, the hot gases that are generated move through the heat exchanger, and are vented outdoors through the flue pipe. Simultaneously, the air circulating through your ducts pass over the heat exchanger, and that hot air is then circulated throughout your house.
Furnaces can vary widely in efficiency.
That efficiency is measured by the furnace’s annual fuel efficiency, or AFUE rating.
Standard furnaces have an average AFUE rating of around 80%. This means that for every dollar you spend 80 cents is used to heat your home and 20 cents is lossed in the burning process and exhausted outdoors through the flue pipe
.High Efficiency Furnaces
High Efficiency Furnaces go one step further, and use a secondary heat exchanger to extract even more heat. High-efficiency furnaces can have ratings as high as 96% AFUE, which translates to an energy loss of only 4% or 4 cents. So it’s very easy to see how much more energy is used to heat your home and translates to a far more efficient heating system.
Two Stage Furnaces
Most older gas furnaces are single stage furnaces, which means it operates on one specific btu output. It’s either on or off. A two stage gas furnace is kind of like having two furnaces in one, one stage for cool days and another stage for colder days. On a call for heat the furnace operates on it’s first stage heat, lowest btu output, if the house isn’t satisfied after a determined period of time, it then turns on it’s 2nd stage, highest btu output, to satisfy the heating demand for your home. A far more efficient furnace than a single stage unit.
Variable Speed Furnace
Variable speed refers to the furnaces blower motor, which operates at different speeds to control the amount of air circulating through your furnace. As the temperature of your house gets closer to it’s desired set point, the blower motor slows down to precisely deliver the correct amount of air to your home. Variable speed motors use less electricity, quieter operation, better indoor air quality, and deliver more even temperatures throughout your home, eliminating hot and cold spots and are by far the most efficient furnaces on the market.