What is a common sign that indicates low refrigerant charge in a system?

A common sign indicating a low refrigerant charge in a refrigeration system is reduced cooling capacity and longer run times. When the refrigerant charge is low, there isn’t enough refrigerant circulating through the system to absorb heat effectively, which leads to a decrease in the system's ability to cool the air or space it is intended to refrigerate. As a result, the system will struggle to maintain the desired temperature, causing it to run for extended periods in an attempt to reach the setpoint. This extended operation can lead to greater wear on the components, reducing efficiency and potentially causing further issues in the system.

The other options, while they may also indicate problems within the refrigeration system, are not specific indicators of low refrigerant charge. Increased energy usage could result from various inefficiencies within the system, not solely low refrigerant levels. Frequent compressor cycling can be due to overheating or other issues rather than just a reduced refrigerant charge. Unusual sounds could indicate mechanical problems or improper operation but are not exclusively linked to low refrigerant levels. Therefore, the combination of reduced cooling performance and extended run times serves as a clear and specific indicator of a low refrigerant charge.