When you compare the AFUE ratings of high-efficiency furnaces manufactured today against standard furnaces manufactured 16 to 30 years ago, the difference in fuel efficiency is startling. Old-school furnaces scored low with 60 to 80 AFUE, while today’s best furnaces, such as the Lennox SLP99V, reach 99 AFUE. That’s a bundle of energy savings with modern furnaces, and the modern furnace burner plays an important role in saving you energy dollars.

Basics of HVAC Furnaces, the Burners, and Home Heating

From the moment the thermostat sends a call for heat, the parts of your HVAC furnace go to work in sequence, like a round of “Row Row Row Your Boat,” i.e., not simultaneously. Once the call for heat is received, gas (or oil or propane) flows into the burner and mixes with air. The mixture is ignited into a very hot flame as it exits the burner.

The burner’s hot flame heats up the heat exchanger, which is where return airflow is pulled through. The return airflow is heated and sent back to the living spaces via supply air ducts.

Types of Burners

The furnace burner is one of the three parts that account for high AFUE. They are the heat exchanger, the variable-speed blower motor, and the burner. There are two basic types of burners used in residential HVAC furnaces.

  • Upshot burners are used in older furnaces with natural draft venting and with furnaces that use ambient air for burner-flame ignition. Upshot burners are not especially energy efficient, and dangerous backdrafts are possible.
  • Inshot burners are used in high-efficiency furnaces. Inshot burners are often two-stage burners, which means they can adjust to a high or a low home-heating demand.

Further, air used for inshot burner ignition is piped in from outside the home. This all but eliminates the possibility of poisonous backdrafts. Also, a second heat exchanger may be used in furnaces with very high AFUE ratings.

Now that you’re up to date on the furnace burner and its importance to HVAC efficiency, contact the pros at Mowery Heating, Cooling and Plumbing for a furnace burner tuneup!