Is a two-way pipe system the best choice for your high-efficiency furnace? Every gas-fired furnace requires a pipe that will exhaust dangerous fumes such as carbon monoxide, which are produced by the combustion of natural gas. However, a gas-fired furnace also needs to take in air in order to feed the combustion process. In some cases, intake air may simply be taken directly from the interior of the house and therefore, a separate pipe for intake air isn’t required.
However, in most installations of high efficiency furnaces today, especially those with AFUE ratings of 95%, a two way pipe system is the most common setup. The second pipe, known as the combustion air pipe, extends to the outside of the house through a hole in an exterior wall. It inducts outdoor air and conveys it to the furnace-combustion chamber.
Here are some reasons why the two way pipe system is considered preferable in high-efficiency furnaces:
- It preserves the indoor pressure differential. When indoor air is consumed by furnace combustion, the pressure differential inside the house may tip toward negative. This means more outdoor air drawn into the house through cracks and gaps in the structure. During the winter, the infiltration of cold outdoor air increases heating costs as your furnace works harder to compensate. Inducting furnace combustion air through a pipe helps keep the pressure differential inside the house neutral and reduces outdoor air infiltration.
- Cleaner combustion. Combustion air drawn directly from the outdoors is cleaner and less likely to contain indoor pollutants such as detergents, cleaners, volatile organic compounds (VOCs) like formaldehyde, and other aerosol products. These substances may contaminate or degrade sensitive furnace-combustion components such as flame sensors, igniters, and others.
- Less competition for indoor air. Other existing components inside the house already affect indoor-air balance. These include water heaters and bathroom and kitchen exhaust fans. Inducting furnace-combustion air from outdoors reduces the number of components that are using indoor air and affecting indoor air balance.
Ask the Ace Hardware Home Services pros for more information about the benefits of a two way pipe system for high-efficiency furnaces. We’ve been helping Dayton-area homeowners for 43 years and counting.
