USCG Exam PracticeRefrigeration cycle and components
During routine rounds, an engineer observes high head pressure, high discharge temperature, and the compressor working harder than normal, but the sight glass shows a solid liquid column. Which condition BEST explains these symptoms?
- A. The system is undercharged with refrigerant
- B. The expansion valve bulb has lost its charge
- ✓ Non-condensable gas (air) is trapped in the condenserCorrect
- D. The compressor suction valves are broken
Why C is correct
Non-condensable gas such as air collects in the top of the condenser and receiver, raising head pressure without contributing to cooling. This produces high head pressure and high discharge temperature with the compressor overworked. An undercharge would show low head pressure and bubbles in the sight glass, not a solid column.