What is a Burner in a Gas Furnace?

A burner in a gas furnace is the section of the furnace where the gas (fuel) mixes with air and is burned, which subsequently heats up the house. Sometimes the fuel and air mix directly at the area where it is burned, or it is mixed beforehand, in something called a pre-mixer.

Furnace burners run on different types of fuel, including propane, gas, and oil. Some gas furnaces run on a single burner while other furnaces have a multiple burner setup.


How do furnace burners work?

We have worked on a lot of furnace burners at weather-tech.net. When your thermostat signals to the furnace that it needs to produce heat, it completes the task in the following steps:

First, the air and fuel mix together. The fuel comes in through a valve and rushes through an orifice which siphons in fresh air around venturi openings at the head of the burner.  This is called an ‘inshot’ burner. The gas and the fresh air mix inside the burner and, as they exit the end, are ignited by a Glow plug or H.S.I. (Hot Surface Igniter).  The air can be brought in from the outside of the house through a PVC air intake pipe or simply taken from the ambient air around the furnace.

As the flame shoots from the burner it is then pulled through an ‘S’ shaped channel, which is made of metal and is commonly referred to as the heat exchanger.  The ‘S’ shape is to increase the contact time the flame has with the heat exchanger, which in turn increases the efficiency.  A smaller motor referred to as a ‘ventor’ motor, ‘inducer’ motor, or simply exhaust fan, is used to overcome the resistance of the ‘S’ shaped heat exchanger and pulls this flame through.  With high efficient furnaces, there are two heat exchangers.  The one we just described, and the secondary heat exchanger.  The secondary is where the combustion air is pulled through a number of small tubes wherein it get so much heat removed from it that it condenses.  This is why they also call high efficient furnaces, condensing furnaces.  All high efficient furnaces need a drain for this reason.  This condensation is also quite caustic which is why it should be handled with more precaution than a normal drain.

Once completely pulled through the heat exchangers, it then gets pushed out of the home through the PVC venting by the same ventor motor.

The main blower in your furnace, much larger than the ventor motor, is the blower that delivers air to all the rooms in your home.  It pulls air from your home using the return air ductwork, blows it across the heat exchangers in your furnace, collecting the heat off of the ‘sealed’ heat exchanger, and delivers that, now heated air, to all the rooms using the ‘supply’ ductwork.


What types of furnace burners are there?

There are three primary types of furnace burners installed in homes: Conversion, Inshot, and Upshot.

  • Conversion burner – A conversion burner actually converts one type of fuel to another before mixing it with air.
  • Inshot burner – An inshot burner is one of the most common burners with high-efficiency furnaces, which often use indraft furnaces.
  • Upshot burner – Upshot burners are common in older furnaces, which are often natural draft furnaces.

Some of these furnace burners have single burners, while others have multiple burners.


What are the benefits of furnace burners?

Furnace burners are an essential component to your HVAC configuration. Furnace burners are the primary component that provides heat to your house. Regular maintenance is crucial to improving the lifespan of your furnace burner.


How do I care for my furnace burner?

One of the most important things you can do to increase the longevity of your furnace burner is to contact a local HVAC professional to have the furnace burner cleaned and inspected regularly. You can include the cleaning and inspection alongside your regular heating and cooling system maintenance schedule. In addition, do not hesitate to contact a certified furnace repair professional to troubleshoot any issues you might be having.

Some common issues with furnace burners include cracks, rust, clogs, and the unit not providing enough heat. Your HVAC technician can help you decide what the best, most cost-effective course of action is.


What if my furnace burner needs replaced?

Fixing or replacing a furnace burner is typically not a do-it-yourself project. Contact your local heating repair contractor to schedule a visit. They are experts in the field and can assess your furnace burner. Keep in mind that it might be more cost effective to replace the unit, but they can make their recommendation on-site.


Steve De Vries is a “Red Seal” refrigeration technician with over 20 years of experience in the HVAC industry. He has been a certified Lennox Premier technician since 2006. Steve is also a Master gas-fitter licensed by the province of Manitoba. Along with his Red Seal Provincial accreditation he also holds an electrical license. Born and raised in Winnipeg Manitoba, Steve has a very good understanding of a diverse climate and the affects it has on our construction. Well versed in duct design, fabrication, ventilation, and air quality, Steve understands all the variables to take into consideration for our region as well as the science to achieve desired comfort, which is so much more than just temperature.