USCG Exam PracticeRefrigeration principles and systems
A sight glass in the liquid line between the receiver and the metering device shows a steady stream of bubbles. What does this most likely indicate?
- A. The system is overcharged and head pressure is elevated
- B. The condenser tubes are fouled, reducing heat rejection
- ✓ The system is undercharged or there is a restriction in the liquid lineCorrect
- D. The evaporator coil is frosted over, blocking airflow
Why C is correct
NAVEDTRA 14075 §6-3 states that a sight glass showing bubbles indicates the system is undercharged or restricted, while a solid liquid column indicates a fully charged system. An overcharge raises head pressure but does not produce bubbles at the sight glass; fouled condenser tubes and a frosted evaporator affect pressures and capacity but do not directly cause bubbling at the liquid-line sight glass.
Cited:NAVEDTRA 14075 §6-3