What can occur if a vent that is too large is installed on an induced draft furnace?

Installing a vent that is too large on an induced draft furnace can lead to condensation of vent gases. This occurs because the larger diameter of the vent allows exhaust gases to exit the furnace at a lower velocity and cooler temperatures. When the temperature of these exhaust gases drops below their dew point, condensation can form within the vent. This moisture can lead to various issues, including corrosion of the vent and the furnace itself, as well as the potential for mold growth or water damage in nearby areas.

The design of vent systems for induced draft furnaces is critical, as these systems are designed to efficiently carry away combustion byproducts. If the vent is oversized, it disrupts the intended flow dynamics, resulting in inefficient performance and potential condensation problems instead of maintaining proper exhaust gas temperatures.