How Do Oil Furnaces Work?

Ever wonder how your home heating system works? The first step is to identify how you heat your home. If it’s an oil furnace, you have the type of system that has been a reliable source of comfort to U.S. homeowners since the 1920s.

While the size and capabilities of today’s models are different, the general idea of how an oil furnace works has remained remarkably the same. It burns fuel oil to heat the air in your home’s living spaces.

Whether you are just curious about heating systems in general, want to learn about the furnace in a home you’ve recently moved into, are planning to replace your current oil furnace, or are considering switching to an oil furnace, knowing how oil heat works can be helpful. In this article we’ll answer the question, “how do oil furnaces work?”, take a closer look at the parts of an oil furnace, and answer some frequently asked questions about heating oil systems.

A Carrier dealer standing in a kitchen-answering the question how do oil furnaces work.

How Does an Oil Furnace Work?

So, how does an oil furnace work? An oil furnace burns fuel oil to create heat that is absorbed by air circulating into the furnace. It’s called a forced air system because a fan is used to pull air from your home into the furnace and then back out to your living areas.

Here’s a more detailed, step-by-step look at how a typical oil heating system works:

When the thermostat in your home senses the temperature cooling down, it signals the furnace to start creating warm air for your home.
A fuel pump draws heating oil from an on-site storage tank to the furnace burner assembly.
An ignition system lights the fuel oil to create heat in a combustion chamber.
Heat from oil combustion enters a metal heat exchanger.
Cool indoor air passing over the heat exchanger absorbs heat from the heat exchanger.
A blower (fan) pushes the heated air to your home’s living areas through ductwork that runs between your walls, floors and/or ceilings.
Cold air circulates back to the furnace through another series of “return air” ducts, and the process continues.

Your local Carrier dealer understands the ins and outs of oil heating system operation. If you have questions about your system operation, our dealer locator can help connect you with a Carrier oil furnace expert near you. Understanding oil furnace cleaning best practices can help improve the lifespan of your unit.

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Parts of an Oil Furnace

The main parts of an oil furnace include:

Oil tank – Home heating oil is stored on-site in a tank typically located in a basement or garage, or outside, either above ground or buried.
Thermostat – Your thermostat is typically wall-mounted in a central location in your home. It is used to set indoor air temperature and give you control of your heating system.
Fuel pump – The fuel pump is a part of the burner assembly. It pulls fuel oil from the tank and delivers it to the burner nozzle for ignition.
Burner assembly – The burner assembly includes several oil burner parts needed for combustion, including the fuel pump, a small blower wheel for combustion air, electronic controls, and the burner nozzle.
Combustion chamber – This is an enclosed metal chamber where fuel oil is burned to create heat that is transferred to the heat exchanger.
Heat exchanger – The heat exchanger is often a tubular-shaped metal housing attached to the combustion chamber. Indoor air passes over the heat exchanger to absorb heat from furnace combustion.
Blower – Most furnace blowers are an encased fan with electronic controls and a large blower wheel that moves air into the furnace and back out into your home.
Controls – Oil furnaces have electronic controls that manage furnace operation. There is usually a main control board as well as smaller controls for the blower and burner assemblies.

FAQs About How Oil Furnaces Work

What is the difference between an oil furnace and a gas furnace?

The big difference between these types of furnaces is the fuel source and how it is delivered to the furnace. Natural gas furnaces rely on a stream of natural gas piped into your home from your local natural gas utility company. Oil furnaces rely on fuel oil that is delivered to your home and stored in an oil tank on your property.

What are the key parts of an oil furnace?

The furnace itself will include a burner assembly, combustion chamber, heat exchanger, blower (fan), and electronic controls that manage furnace operation.

If my oil furnace stops working, how can I tell what part needs to be repaired?

While troubleshooting or repairing an oil furnace is best left to furnace service professionals, there are a few things you can try before you make the call. Check your air filter to be sure it isn’t due for cleaning or replacing. Double check your thermostat settings to be sure you are set for heating and that the temperature is set correctly. If these things check out, common furnace repairs include the ignitor, various sensors and limit switches, and the blower motor. Older units might start having issues with cracked or corroding heat exchangers. Depending on the type (and price) of a needed repair, you might start investigating the cost to replace an oil furnace if yours is 15 years old or older. Scheduling a regular oil furnace cleaning can extend the life of your oil furnace.