Refrigeration Operating Engineer License Practice Exam 2026 – The All-in-One Guide to Success!

The formation of bubbles in the sight glass is a common effect of undercharging in a refrigeration system. When the system is undercharged, there isn't enough refrigerant to absorb the heat efficiently, resulting in a mix of liquid and vapor refrigerant in the sight glass. This often manifests as bubbling, indicating that the refrigerant is not entirely in the liquid state.

Undercharging leads to inadequate cooling and can create conditions where the refrigerant begins to vaporize prematurely. The presence of these bubbles signifies that the system is not operating at optimal efficiency and may not be effectively transferring heat. This is crucial for maintaining the proper functioning of the refrigeration cycle.

In contrast, if there were a sufficient amount of refrigerant, the sight glass would typically show a clear liquid without bubbles, reflecting that the refrigerant is in an appropriate state for effective heat exchange. Identifying bubbles in the sight glass is an important diagnostic indicator, prompting the need to check and potentially refill the refrigerant in the system.