What does the presence of bubbles in the sight glass indicate?

• A. The refrigerant is too hot
• B. The refrigerant is not sufficiently subcooled
• C. The system has excessive pressure
• D. The filter is clogged

Answer: (B)

The presence of bubbles in the sight glass is indicative of the refrigerant not being sufficiently subcooled. In a refrigeration system, a sight glass is used to visually check the state of the refrigerant. When refrigerant enters the sight glass as a mix of liquid and vapor, it suggests that the liquid refrigerant has not adequately removed its heat and has not been fully condensed into a liquid state.

Sufficient subcooling is essential to ensure the refrigerant is in a liquid state before it enters the expansion valve or evaporator coil. If there are bubbles present, it implies that some of the refrigerant is still in a vapor state, which may affect the efficiency and performance of the system and lead to inadequate cooling performance.

The other options may pertain to different conditions in the refrigeration cycle but do not directly explain the presence of bubbles in the sight glass as effectively as the lack of sufficient subcooling does.