Why does a heat pump icing up occur and how can it be prevented or resolved?

A heat pump icing up occurs when moisture in the air freezes on the outdoor unit during cold weather. This can happen when the heat pump is running in heating mode and the outdoor temperature is below freezing. To prevent or resolve this issue, it is important to ensure proper airflow around the unit, regularly check and replace air filters, and schedule regular maintenance to keep the system running efficiently. Additionally, installing a defrost control system can help melt any ice buildup on the unit.