What is the purpose of a sight glass in a refrigeration system?

The sight glass in a refrigeration system serves a crucial diagnostic function by indicating the presence of refrigerant within the system. When functioning properly, the sight glass allows technicians to visually inspect the refrigerant flow and determine whether the system is appropriately charged with refrigerant. The presence of bubbles in the sight glass can indicate that the system is low on refrigerant, while clear liquid without bubbles generally signifies proper operation. This ability to diagnose issues helps in maintaining the efficiency and reliability of the refrigeration system, assisting technicians in troubleshooting and preventing potential problems related to refrigerant levels. The other options, while related to refrigeration, do not accurately describe the main purpose of a sight glass.