What is the purpose of a liquid line sight glass?

The purpose of a liquid line sight glass is to indicate the flow of refrigerant and to check for the presence of bubbles. This is important because bubbles in the sight glass suggest that there may be a refrigerant shortage or moisture in the system. When the sight glass is clear and shows a steady flow of liquid without bubbles, it indicates that the refrigerant system is adequately charged with refrigerant and functioning properly.

In the context of refrigeration systems, maintaining the correct charge levels is crucial for efficiency and reliability. If the sight glass shows the presence of bubbles, it serves as a warning sign for the technician to investigate further, potentially leading to the identification of leaks or moisture problems that could compromise system performance.

Other options would not serve this specific function. Measuring the pressure, monitoring the temperature, or ensuring oil circulation are managed by different components and indicators in a refrigeration system, which do not provide the same visual diagnostic capability as a sight glass.