What observation indicates a potential refrigerant leak in a refrigeration system?

A high evaporator superheat accompanied by bubbles in the liquid line sight glass serves as a significant indicator of a potential refrigerant leak in a refrigeration system. Superheat refers to the temperature of refrigerant vapor above its saturation temperature at a given pressure. When superheat levels are high, it suggests that the refrigerant is transitioning from liquid to vapor before it can effectively absorb heat, indicating that not enough refrigerant is circulating in the system.

The presence of bubbles in the sight glass further confirms this suspicion. A normal functioning system should have a sight glass that is either clear (indicating a proper liquid refrigerant level) or a slight mixture of liquid and vapor. Bubbles suggest that there is insufficient liquid refrigerant entering the evaporator, which can happen due to a leak in the system causing the refrigerant levels to drop or due to other refrigerant flow issues.

In summary, the combination of high superheat and the sight glass showing bubbles is a clear signal that the system may be experiencing a refrigerant leak or some sort of malfunction affecting its efficiency and operation.