A Portland Homeowner’s Guide to Condensing Gas Furnaces

Any Portland homeowner planning a furnace upgrade should consider a condensing gas furnace. Because they’re able to extract heat from the combustion gases that other furnaces simply vent to the outdoors, condensing gas furnaces use less fuel, saving homeowners money on fuel costs. An important consideration for the environment—and your wallet!

All gas furnaces use a primary heat exchanger to extract the majority of the heat energy produced by the burn process. Once this heat is extracted, conventional furnaces then dispose of the combustion by-products—including water vapor and carbon dioxide—by venting them to the outdoors. Unfortunately any heat retained in the by-products is sent outside as well.

Before disposing of the by-products, a condensing gas furnace sends them through a secondary heat exchanger, which removes additional heat from the exhaust gases to the point that the water vapor condenses into a liquid state, giving the condensing furnace its name. With a secondary heat exchanger, condensing furnaces can extract substantially more heat from each unit of gas, which is why they have AFUE ratings of 90 percent and higher.

Once the secondary heat exchanger has done its job, the condensed moisture is drained from the system, often into a floor drain, and any remaining gases are vented outdoors. To prevent corrosion from the moisture, the secondary heat exchanger is usually stainless steel and the drain system is well sealed, with plastic drain and vent pipes.

Condensing gas furnaces can also increase their efficiency by incorporating new technology such as modulating gas valves—which regulate how much gas is burned, thus using less gas when less heat is needed—and variable-speed furnace blowers—which adjust fan speeds according to temperature and air flow requirements, thus preventing hot and cold cycles of airflow in the home while using less energy than conventional motors.

If you need more information about condensing gas furnaces, or any other topic related to heating your home, contact Roth Heating & Cooling. We’ve helped customers in the Portland area better understand their heating and cooling options for over 36 years.