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• $45 for an air-conditioning or furnace tune-up ($85 value)
• $45 for an appliance diagnosis ($85 value)

Forced-Air Furnaces: Let There Be Heat

The winter months would be nigh unbearable without central heating. Read on to learn how forced-air furnaces keep things toasty.

There’s nothing quite as awful as being able to see your breath on a cold winter’s night from your own living-room couch. Unfortunately, heating systems have been known to break down, often when the thermometer reaches its lowest depths. Although mechanics train for years to be able to fix faulty furnaces, the forced-air system itself is relatively straightforward, consisting of only four main parts: the thermostat, the burner, the heat exchanger, and the blower.

Once the thermostat senses that the air temperature has dropped below a set number (say, 72 degrees Fahrenheit), it sends an electrical signal to the burner. Attached to the burner is the gas valve, which controls the flow of fuel, and the igniter, which sets the fuel ablaze safely within the metal confines of the burner. Next to the burner is the heat exchanger, a piece of metal that warms quickly over the flames of the burner. The blower sends cold air whooshing over the exchanger, quickly raising the air’s temperature as it enters the duct system to warm the house and swiftly melt any snowballs trapped in the vents.

Bonus Points

• Each room typically has two vents—one for the hot air and one to carry the colder air back to the furnace, where the cycle repeats.
• As soon as the desired temperature is reached, the thermostat shuts off the burner to conserve energy.