USCG Exam PracticeRefrigeration cycle and components
Freezer evaporator coils must be defrosted periodically because frost accumulation has which direct effect on system performance?
- A. It raises the suction pressure, causing the low-pressure cutout to trip
- ✓ It insulates the coil and blocks airflow, reducing the evaporator's capacity to absorb heatCorrect
- C. It causes liquid refrigerant to flood back to the compressor
- D. It increases the condensing pressure by restricting refrigerant flow through the coil
Why B is correct
A layer of frost on a freezer coil acts as insulation and blocks airflow across the coil, steadily cutting the evaporator's heat-transfer capacity regardless of how well the rest of the plant operates. Frost accumulation does not directly raise suction pressure, cause liquid floodback, or affect condensing pressure.
Cited:NAVEDTRA 14075 §6-5