Heating System Guides

Consumer Buying Guides to Home Heating and Air Conditioning Systems

Central Heat Forced Air Systems – Gas, Oil and Electric Furnaces

Forced air central heating systems remain the most common type of heating system for homes.  Central heating systems are efficient, affordable and very effective.  They are often called forced air heating systems because a blower fan is used to distribute heated air throughout the home.  Central heating systems also work well with a central air conditioner, with the furnace blower used to circulate cooled air.

There are several types of forced air heating systems in use today, and they are easily identified by the type of fuel they use, or energy, to heat the home.  Those that use natural gas or propane for fuel are the most common. Gas furnaces are easily converted from natural gas to propane by switching the gas valve. Along with Gas fueled systems, home heating oil is used as a fuel source in Oil Furnaces, which convert the light heating oil into heat.

Furnaces that burn home heating oil differ slightly from gas furnaces. Electric furnaces heat with the use of electric coils and are primarily used where the construction of the home makes it difficult to vent a gas or oil furnace. Popular today, many homeowners are converting from oil furnace to gas or propane, and since the systems use quite a bit of similar components for distribution of the treated air, the payback is quick.

The Components of a Central Furnace Heating System

Here is an overview of the primary components of a central heating system.

  • Burner Assembly or Heating Element
    In gas and oil furnaces, the heating assembly includes a fuel valve or port that dispenses the fuel, a burner, and an igniter that fires it to produce heat.  An oil furnace also has an oil pump.  In an electric furnace, heavy-gauge electric resistance coils produce the heat.
  • Furnace Blower Fan
    The blower fan uses an electric motor to circulate air through the home’s heating system.
  • Heat Exchanger
    Gas and oil furnaces use a heat exchanger to transfer heat from the combustion gases, which contain carbon monoxide, into the system without mixing the air.
  • Duct Work
    Usually made from sheet metal, duct work is used to carry heated air to the rooms of the home as well as circulate cold air back to the furnace to be heated.

How Central Heating Systems Work

Putting all the pieces together, here is how these forced air heating systems work.  The burner fires or the coils heat up.  In an electric furnace, the blower fan moves cold air over the coils and pushes it through the duct work into the home while pulling cold air into the furnace.  In a gas or oil furnace, the hot combustion gases pass through the heat exchanger on their way out the flue.  Cold air is circulated over the heat exchanger to heat it and is then pushed into the duct work.  High-efficiency furnaces use 2 heat exchangers to transfer up to 98% of the heat before it is lost out the flue.

Finally – Central heat and air systems are fairly simple and are easy to maintain.  Most last about 20 years but with good maintenance can work effectively for longer.  They remain a very cost-effective way to heat any home.