What feature does a condensing gas furnace include to enhance efficiency?

A condensing gas furnace utilizes a secondary heat exchanger as a crucial feature to improve its overall efficiency. This component works by capturing and utilizing the heat from the exhaust gases produced during combustion, which would otherwise escape into the atmosphere. In a traditional furnace, a significant amount of heat is lost with those gases, but a condensing furnace is designed to recover this heat, enhancing the unit's efficiency dramatically.

The secondary heat exchanger cools the exhaust gases, causing water vapor to condense. This process not only extracts additional heat energy from the flue gas but also leads to the formation of condensate, which is drained away. The increased efficiency allows condensing furnaces to achieve higher Annual Fuel Utilization Efficiency (AFUE) ratings, often exceeding 90%. This means they convert a greater percentage of fuel used into heat for the home, reducing energy costs and environmental impact.

Features like two-stage heating capability and variable speed blowers improve comfort and may contribute to efficiency but do not specifically aid in the recovery of lost heat in the way that a secondary heat exchanger does. The thermostatic expansion valve is typically used in refrigeration systems, not in gas furnaces, making it irrelevant to this context. Overall, the mechanics of a secondary heat exchanger are what