USCG Exam PracticeRefrigeration cycle and components
A freezer coil operating below 32°F must be defrosted periodically because frost accumulation will have which effect on system performance?
- A. It raises suction pressure by restricting vapor flow to the compressor
- ✓ It insulates the coil and blocks airflow, steadily reducing cooling capacityCorrect
- C. It causes liquid refrigerant to return to the compressor, resulting in slugging
- D. It increases head pressure by reducing condenser cooling water flow
Why B is correct
Frost and ice buildup on a freezer coil acts as insulation and blocks airflow across the coil, steadily cutting cooling capacity. Defrosting restores heat transfer. Slugging is caused by liquid floodback from the evaporator, and head pressure is governed by condenser performance, not frost on the evaporator coil.
Cited:NAVEDTRA 14075 §6-5