What is a Furnace?
A traditional home comfort system has two parts: an outdoor unit, such as an air conditioner or heat pump, and an indoor unit. The furnace is the indoor unit that heats and circulates warm air through your home in the winter, and in the summer, it takes the cool air from the outdoor unit and works as a fan to circulate it throughout your home. The indoor and outdoor units are designed to work together. And when the furnace is properly matched with a heat pump or air conditioner, the result is maximum efficiency and extended system life. Furnace heating ability is measured with an Annual Fuel Utilization Efficiency (AFUE). The AFUE calculates the amount of fuel converted to heat in proportion to the amount of fuel entering the furnace. This is commonly expressed as a percentage. A higher AFUE percentage indicates a more efficient furnace. Think of it in the terms of dollars, if you have an 80% AFUE furnace, 80 cents of every dollar is used to heat your home, 20 cents goes up the chimney; if you had a 95% AFUE furnace, 95 cents of every dollar heats your home, only 5 cents goes up the chimney. A gas furnace uses natural gas, although some models can be converted to utilize propane. An electricity source is required to run the control systems, blower and some accessories. There are a wide variety of gas furnaces in different sizes and efficiencies.
The basic components of a furnace system are:
- A Burner: Through which gas (natural or propane) is delivered and burned.
- A Heat Exchanger: Where the heat produced from the burning gas is transferred to the air distribution system (blower).
- Ductwork: To transfer the heated air throughout the home.
- A Flue or Vent Pipe: To exhaust by-products of combustion (such as water vapor and carbon dioxide) to the outside.
Single Stage Furnace:
Single-stage furnaces offer many new features not found on older furnaces. One feature is an inducer that draws the correct quantity of combustion air into the furnace for the most efficient operation possible. Another is an electronic ignition system that replaces the old wasteful pilot light. A third is a powerful, direct-drive blower that sends warmth to all the rooms in your home. These features will help make your home more comfortable, while reducing your heating fuel bills. Most of us have probably lived in a house with a single stage furnace. The furnace is either on or off, nothing in between. As a result, the furnace waits for the temperature in the house to get cold, most times colder than comfortable, before turning on. Then, the furnace pumps the house full of heat until the thermostat shuts the system down, and the cycle starts again. Single stage furnaces are the most inefficient in terms of energy, but they are the lowest cost to purchase.
Two-stage furnaces are a little smarter than the single stage furnace. Rather than a simple on/off operation, its flame can be on/high, on/low, or off. Adding this second flame setting makes a dramatic difference in energy costs. Two-stage furnaces operate at low capacity during most of the operating cycle to maintain your level of comfort. On bitter cold days, the second stage is there to maintain comfortable temperatures. Two stage furnaces are much quieter than single stage furnaces and have a slightly higher cost.
There are many reasons for choosing a variable speed furnace, but the main reason is comfort. The term “variable-speed” refers to the furnace’s fan motor, which moves at different speeds to accurately control the flow of heated and cooled air throughout your home. In terms of comfort, it’s one of the most comfortable gas furnaces you can buy because you avoid those long, cold periods. Variable-speed furnaces circulate more air throughout the home for longer periods of time, reducing air stratification room-to-room and floor-to-floor. These longer run cycles can improve air quality by increasing air filtration. Advanced technology allows a variable-speed furnace to continually monitor incoming data and automatically make the adjustments necessary to meet the comfort needs of your heating and cooling system. Variable-speed furnaces offer significant operating cost savings and whisper quiet operation. Variable-speed furnaces also feature an ECM blower motor that uses less electricity than a 100 watt light bulb. Standard furnace motors use nearly 500 watts.