What common sign indicates insufficient refrigerant in a refrigeration system?

The presence of frost or ice on the evaporator coil is a common sign of insufficient refrigerant in a refrigeration system. When refrigerant levels are low, the system cannot effectively absorb heat from the indoor air, leading to a decrease in the pressure within the evaporator coil. This drop in pressure can cause the temperature of the coil to fall below freezing, resulting in moisture from the air freezing on the coil's surface. Over time, this buildup of frost or ice can impede airflow and reduce the overall efficiency of the system, ultimately affecting its cooling performance.

In contrast, increased energy consumption would more likely be associated with other issues, such as a malfunctioning compressor or dirty coils, rather than directly indicating low refrigerant levels. Unusual noises from the compressor can indicate mechanical issues or stress within the system but do not specifically point to a refrigerant shortage. Foul odors may be a sign of biological growth, dirty components, or electrical problems, which are not directly related to refrigerant levels. Therefore, the frost or ice accumulation serves as the most clear and specific indicator of insufficient refrigerant in the system.