Freezing of a mini-split heat pump can result from several factors:

• Airflow Obstruction: When the air filter or fan blades inside the indoor unit accumulate dust and dirt, airflow becomes restricted. This impedes the evaporation of moisture on the heat exchanger, increasing the likelihood of frost formation.

• Refrigerant Insufficiency: Insufficient levels of refrigerant often stem from leaks in the refrigeration system. These leaks cause a pressure drop, lowering the evaporator temperature of the heat pump below freezing and leading to frost buildup.

• Extended Operation: Prolonged periods of continuous operation, especially during cooler nighttime temperatures, can cause the heat pump's evaporator to cool excessively. This excessive cooling contributes to the formation of frost.

• Poor Drainage: A clogged drainage system in the heat pump can result in the accumulation of moisture, which may freeze on the evaporator, particularly in cooler conditions.

Addressing these issues promptly can help prevent freezing and maintain the efficient operation of your mini-split heat pump.