What is a common sign of low refrigerant levels in a system?

Frost buildup on the evaporator coil is a clear indication of low refrigerant levels in a refrigeration system. When there is insufficient refrigerant, the coil does not receive enough fluid to absorb heat efficiently. This leads to a drop in temperature in and around the evaporator coil, causing moisture in the air to freeze and form frost. The evaporator coil is designed to operate at temperatures that allow for effective heat transfer and cooling, so when the refrigerant is low, the temperature drops significantly below the normal operating range, resulting in frost formation.

Other signs of low refrigerant can include the continuous cycling of the compressor or higher than normal temperatures at the evaporator outlet. Still, the presence of frost is a particularly telling visual sign of the underlying issue, indicating both inadequate refrigerant levels and potential problems with the system's efficiency.