Furnaces burn fuel in order to create heat. Any time that fuel is used as a heat source, combustion gases are produced as a byproduct and those gases need to be safely vented away. The exhaust vent that’s connected to gas-powered clothes dryers, for example, captures combustion gases as they are produced and vents them out of your home. Furnaces have similar mechanisms for venting combustion gases, but the process differs depending on the type of heating system you have in your home. Today we’re going to talk about how different furnaces vent combustion gases and what you can do to ensure your heating system continues to vent gases properly!
How are combustion gases produced in a furnace?
As we mentioned above, combustion gases like carbon monoxide (CO) are produced as a byproduct when fuel is burned. When your furnace is in a heating cycle, it ignites a set of burners that produce multiple flames. Those flames are directed into the heat exchanger, where the hot combustion gases that are produced heat up the walls of the heat exchanger.
Your furnace blows air over the hot exterior walls of the heat exchanger, while the combustion gases are safely contained inside the heat exchanger’s chamber. So after the hot combustion gases do their job inside the heat exchanger, where do they go? The answer depends on the efficiency of your furnace.
How does a standard-efficiency furnace vent combustion gases?
In a standard-efficiency furnace, a flue pipe is attached to the heat exchanger and combustion gases exit the heat exchanger through that pipe. The flue pipe typically extends upwards and out of the home’s roof, where the gases are expelled outside.
In older systems, combustion gases rise naturally out of the heat exchanger during and after every heating cycle. Newer mid-efficiency systems have a draft inducer fan that forcefully pushes combustion gases out of the heat exchanger and into the flue pipe to be exhausted out of your home.
How does a high-efficiency furnace vent combustion gases?
If your furnace has an AFUE rating of 90% or above, it has not one but two different heat exchangers. The first heat exchanger works just like the heat exchanger in a standard-efficiency system. However, when combustion gases leave the first heat exchanger, they are directed into a second heat exchanger, where more heat is extracted and used to heat your home.
By the time combustion gases leave the second heat exchanger, they are a liquid form because so much heat has been removed from them. As a result, the liquid byproducts are drained out of the system using PVC pipes that either point to a floor drain or extend out the side of your home.
How can you ensure your furnace vents combustion gases properly?
No matter what kind of furnace you have, it’s important to ensure that combustion gases are vented properly out of your home. If combustion gases like carbon monoxide were to get into your home’s airflow, they could make your family sick and could even be deadly.
The best way to ensure your furnace vents combustion gases properly is to schedule a furnace tune-up every year. During a tune-up, we’ll check for heat exchanger cracks, clogs in the flue pipes and other common problems that can hinder your furnace’s venting process. We’ll fix any venting problems that we find in order to ensure your heating system vents combustion gases safely all winter long.
If you have any questions about how a furnace vents gas, or if you’d like a heating system serviced or installed in your home, contact Hydes, your Coachella Valley furnace installation and repair contractor.