USCG Exam PracticeRefrigeration cycle and components
On a marine refrigeration plant, the sight glass in the liquid line between the receiver and the metering device shows a steady stream of bubbles. This indication most likely means the system is:
- A. Properly charged and operating normally
- B. Overcharged, causing high head pressure
- ✓ Undercharged or has a restriction in the liquid lineCorrect
- D. Experiencing liquid floodback to the compressor
Why C is correct
A sight glass full of bubbles indicates the liquid line is not carrying a solid column of liquid refrigerant, which points to an undercharge (low refrigerant level) or a restriction upstream of the sight glass. A fully charged, properly operating system shows a clear, solid liquid flow in the sight glass.