What is the relationship between the outdoor fan's current draw during defrost and ice buildup?

The relationship between the outdoor fan's current draw during defrost and ice buildup is that a higher amount of ice buildup typically results in a higher current draw. When ice accumulates on the outdoor coil, it creates additional resistance against the airflow. As the fan works harder to overcome this resistance in order to maintain proper airflow and facilitate defrosting, it draws more electrical current.

During a defrost cycle, the system activates to remove ice from the coils, and the additional load on the fan motor due to the physical presence of ice requires more energy. Therefore, as ice buildup increases, the demand for current also increases, leading to higher current draw as the system attempts to operate efficiently and manage the defrost process. Understanding this relationship is crucial for diagnosing potential operational issues in HVAC systems, as excessive ice buildup could impact efficiency and performance.