What can cause the evaporator coils to freeze?

The freezing of evaporator coils is primarily linked to insufficient airflow or low refrigerant charge. When there is inadequate airflow across the evaporator coils, the heat transfer process is hindered, leading to a drop in coil temperature. If the airflow is insufficient, the refrigerant inside the coils does not absorb enough heat, causing it to cool below the freezing point of moisture in the air surrounding the coils. This results in frost or ice accumulation on the coils.

Additionally, a low refrigerant charge has a similar effect. It can prevent the evaporator from receiving adequate refrigerant to absorb heat properly. When there is not enough refrigerant circulating through the evaporator, the pressure within the evaporator coils drops, which can also lead to freezing conditions as the refrigerant does not vaporize effectively, causing the coil temperature to drop significantly.

In contrast, excessive refrigerant charge could lead to other malfunctions, such as increased pressure and potential compressor damage, but it does not directly cause freezing of the coils. High ambient temperatures would typically lead to higher system pressures and may increase the evaporator temperature, reducing the likelihood of icing. Continuous operation without rest generally does not contribute to freezing, as regular cycling can help manage temperature and pressure effectively.