Frost formation on the evaporator is usually an indication of what issue?

Frost formation on the evaporator is typically a sign of low refrigerant levels or airflow issues. The evaporator coil is designed to absorb heat from the surrounding area, and when it is operating correctly, the refrigerant inside should effectively facilitate this heat exchange. If the refrigerant level is low, there isn't enough refrigerant to absorb heat efficiently, which can lead to a drop in temperature on the evaporator coils. This drop can cause moisture in the air to freeze on the coils, resulting in frost formation.

Similarly, airflow issues can also contribute to frost. If there is insufficient airflow over the evaporator coils—due to a dirty air filter, blocked ducts, or a malfunctioning blower fan—the heat is not transferred effectively. This can cause the temperature of the coil to drop below freezing, leading to frost buildup. This frost can further inhibit airflow, exacerbating the problem.

In contrast, normal operation would not lead to frost, as the system is designed to maintain a balance of temperature and humidity. Too much refrigerant can cause other issues such as flooding the evaporator, but it does not typically result in frost formation. Blocked drainage may create water accumulation issues but does not directly lead to frost on the evaporator.