How Does an Oil Furnace Work?

Date: December 20, 2023

Your Furnace Heats the Air in Your Home

furnaces Also known as a warm-air or forced-air system, a furnace produces heated air inside its combustion chamber. Here is how that warm air then gets distributed throughout your home.

  • Inside an oil-fired furnace, heating oil is mixed with air and burned.
  • The heat exchanger transfers the heat to the air, which is pushed through the heat exchanger by the furnace’s blower fan.
  • The fan blows the heated air through a network of air ducts before the warm air exits through registers or vents throughout your home.
  • Combustion gases are safely vented out of your home through a flue pipe.

Furnace Benefits

Besides heat, the ductwork that connects with your furnace can provide other kinds of conditioned air, including through:

  • a central air conditioning system
  • a whole-house humidifier
  • an air cleaning system or air purifier

Old Furnaces Vs. New Furnaces

The oil furnaces of today can operate at a range of speeds and include other efficiency-enhancing features, such as microprocessor-based controls, high-pressure flame-retention burners and durable heat exchangers. Here is a look at different furnaces operate, according to the U.S. Energy Department. The newer the furnace, the higher its efficiency rating, which is defined by its Annual Fuel Utilization Efficiency (AFUE).

Older, low-efficiency furnaces:

  • Natural draft that creates a flow of combustion gases
  • 56% to 70% AFUE.

Mid-efficiency furnaces:

  • Exhaust fan controls the flow of combustion air and combustion gases more precisely.
  • Compact size and lighter weight to reduce cycling losses.
  • Small-diameter flue pipe
  • 80% to 83% AFUE.

High-efficiency furnaces:

  • Condensing flue gases in a second heat exchanger for extra efficiency
  • Sealed combustion
  • 90% to 98.5% AFUE.

Learn more about efficiency ratings, furnace maintenance and more.

Replacing Your Old Furnace

If your oil furnace is more than 25 years old, or if you’ve had more than a few repairs in the last couple of years, it’s time to start thinking about replacing your heating equipment. As noted above, today’s high-efficiency furnaces provide extra heat more efficiently than units made a generation ago.
Higher efficiency means more energy savings, which of course translates into lower energy costs. This is why it pays to learn as much as you can about today’s high-tech heating solutions—and your heating oil equipment service contractor can help you, with all of the latest information on new, high-efficiency heating oil furnaces.

When discussing your heating oil furnace replacement options with your heating expert, you’ll most likely learn about the importance of proper sizing.

  • Sizing refers to the heating system’s Btu rating. If your equipment contractor installs something too powerful (oversized), it will give you more heat than you need, wasting energy and money.
  • But if the system doesn’t have enough power (undersized), your home will not feel comfortable, and you will spend more on fuel because the heating oil furnace will switch on and off throughout the day.
  • To determine how much power your home’s heating system needs, an experienced heating-oil-system installer will do tests that show how much heat your home loses in the winter.

Find out how much you could save with a furnace installation.