RETA Certified Assistant Refrigeration Operator (CARO) Practice Exam

During hot gas defrost, high-pressure gas is introduced into the evaporator to melt frost and ice buildup. This process is essential in refrigeration systems that use evaporators exposed to freezing temperatures, which can lead to a reduction in efficiency or even operational failure due to frost accumulation.

When high-pressure gas enters the evaporator, it provides the necessary heat to raise the temperature of the surfaces covered in frost and ice, causing it to melt. The defrosting process efficiently clears the evaporator coils, allowing the refrigeration system to return to normal operation.

In contrast, cold gas flowing through the evaporator, releasing refrigerant into the atmosphere, or pumping liquid refrigerant directly to the compressor do not facilitate the defrosting process effectively. The key aspect of hot gas defrost is the utilization of high-pressure gas for heating, making it a crucial component for maintaining optimal performance in refrigeration systems.