Key Parts of Your Furnace & Definitions

What are the most essential parts of your furnace? In this article we will give you some key terms and definitions that give you a better depiction and understanding of the components within your furnace and how it works. There are four different types of furnaces – oil, gas, electric and dual fuel. While there are a variety of types of furnaces, most heating systems operate in the same way using the same basic functions and mechanisms to deliver heat to your home.

  • Return Ducts – These ducts retrieve air that has been cooled within the home and returns it back to the furnace so it can run through the process again to be reheated and redelivered to your home.
  • Air Filter  As the furnace pulls the air in through the return duct the air filter is in place before the blower motor to catch particles, dust and any other debris from your air. This is in place for two reasons, first and foremost to protect the motor of the furnace, and secondly to improve the air quality of your home by removing pollutants and allergens.
  • Blower Motor* – This is an electric motor with a fan that is in place to evenly supply a current of air through the furnace. This forced movement pushes the air past the heat exchanger (warming the air) and into the supply plenum which then supplies the heated air to the rest of your home.
    *These are the things that look similar to a hamster wheel located at the base of your furnace.
  • Thermostats – A gauge that measures the temperature inside your house. This will tell your ignitor when it should turn on to get the heating process started.
  • Hot Surface Ignitor – When the furnace receives a signal from the thermostat that it is time to turn on, it sends an electrical current to the ignitor which will then burn red hot to light the burner upon start up.
  • Burners – When the furnace receives a signal from the thermostat that it is time to turn on, fuel is sent to the burners which is then ignited by the hot surface ignitor. This produces an even, controllable flame that provides heat to the heat exchanger.
  • Heat Exchanger* – This is the part of the furnace that is made to deal with the heat! This is the first place that combustion gasses enter after they have been produced by the burners. Once the combustion gasses are in the heat exchanger chamber, the heat from the gases are now absorbed into the metal walls. Within the chamber, the combustion gases are cooled and vented into a pipe by the draft inducer blower and safely removed from the home. At the same time this is happening, the blower motor is pushing the air from your home past the heat exchanger, picking up the heat from the exchanger walls and then pushed to the plenum supply ducts to heat your home.
    *It is important to note that this is the part of the furnace that deals with carbon monoxide. It is critical to have the heat exchanger inspected with your yearly furnace maintenance. Over time, cracks can develop within the exchanger and carbon monoxide can leak into your home, confiscating the safety of you and your family.
  • Flue – Also called an exhaust stack, is where all the unwanted exhaust is disposed. This exhaust is composed of the fuel combustion from the oil and gas furnaces as well as carbon monoxide. In some homes, this exhaust may be filtered to go out of the chimney, in others it is just sent out of the home through a pipe or vent. *Electric furnaces do not have a flue.
  • Supply Plenum – This is a duct attached to your furnace that will distribute the heated air through out the home.