USCG Exam PracticeRefrigeration and air conditioning
A sight glass in the liquid line downstream of the receiver shows a steady stream of bubbles during normal operation. What does this indication most likely represent?
- A. Normal operation; bubbles confirm the refrigerant is fully evaporated before the metering device
- B. The system is overcharged, causing flash gas to form in the high-pressure liquid line
- ✓ The system is undercharged or has a restriction, resulting in incomplete liquid fillCorrect
- D. Non-condensable air has been successfully purged and is passing through the sight glass
Why C is correct
NAVEDTRA 14075 §6-3 states that a sight glass lets the operator see whether the liquid is solid (fully charged) or full of bubbles (undercharged or restricted). Bubbles in the liquid line indicate the system is not delivering a full column of liquid refrigerant to the metering device.
Cited:NAVEDTRA 14075 §6-3