A furnace that frequently shuts off due to overheating may indicate what issue?

A furnace that frequently shuts off due to overheating primarily points to issues with airflow or debris obstructing effective heat exchange, which is most commonly caused by dirty filters or ducts. When filters become clogged or ducts are obstructed, airflow is significantly reduced. This inadequate airflow prevents the furnace from effectively dispersing heat, leading to overheating. The furnace's safety mechanisms then engage to shut the system down to prevent damage or safety hazards, indicating that maintenance is needed.

Proper ventilation is essential for the efficient operation of a furnace, but it does not typically cause shutting off due to overheating. A functioning thermostat, while crucial for temperature regulation, would not result in a furnace shutting off unless it is misreading temperatures or settings. High energy efficiency relates to how well the furnace converts energy to heat, and has no direct connection to shutdowns from overheating. Therefore, the presence of dirty filters or ducts aligns most accurately with the symptoms exhibited by the furnace.