What might be a likely consequence of improperly sizing a mid-efficiency furnace?

Improperly sizing a mid-efficiency furnace can indeed lead to a variety of operational issues, but one of the most critical consequences is the potential for heat exchanger corrosion. This occurs because an oversized furnace can lead to short cycling, where the furnace turns on and off frequently without properly heating the space. This rapid cycling does not allow the heat exchanger to reach sufficient temperatures, which can cause moisture to build up within the unit. When this moisture condenses on the heat exchanger, it creates an environment conducive to corrosion, ultimately compromising the furnace's efficiency and lifespan.

While other components of the furnace might experience stress or malfunction due to improper sizing, the specific consequence of heat exchanger corrosion is particularly significant as it directly affects the furnace’s integrity and safety. Recognizing the importance of correct sizing not only enhances efficiency but also helps in preventing costly repairs and prolonging the lifespan of the heating system.