USCG Exam PracticeAir conditioning, ventilation, and compressed air
On a freezer evaporator coil, frost and ice buildup reduces system capacity. Which of the following correctly explains the mechanism by which frost reduces capacity?
- A. Frost lowers the refrigerant boiling point, reducing the temperature differential with the space
- ✓ Frost insulates the coil and blocks airflow, reducing heat transferCorrect
- C. Frost causes the metering device to overfeed refrigerant, flooding the compressor
- D. Frost raises suction pressure, causing the low-pressure cutout to trip
Why B is correct
NAVEDTRA 14075 §6-5 states that a layer of frost insulates the coil and blocks airflow, steadily cutting capacity. The frost acts as a thermal barrier and restricts the air circulation needed to transfer heat from the space to the refrigerant.
Cited:NAVEDTRA 14075 §6-5