What occurs in a furnace when the cooling coil becomes excessively dirty?

When a cooling coil becomes excessively dirty, it restricts the airflow due to obstructions caused by dust, dirt, and debris accumulation. This restriction results in reduced efficiency in the overall air circulation system within the furnace. As the air encounters resistance while trying to pass through the dirty coil, the supply airflow decreases.

A decrease in supply airflow can lead to various operational issues, including potential overheating of the system, reduced cooling effectiveness, and increased energy consumption. The dirty condition of the coil has a significant impact on the ability of the furnace to effectively process air, ultimately lowering the volume of airflow that can exit the supply ducts. Proper maintenance, including regular cleaning of the cooling coil, is crucial to ensure optimal system performance.