How is defrost normally accomplished in a low temperature case?

Defrost in a low-temperature case is typically accomplished by shutting off the compressor and energizing electric defrost heaters. This method is effective because it allows for the removal of ice and frost that can accumulate on the evaporator coils during normal operation. The frost buildup can hinder the efficiency of the refrigeration system, reducing its ability to maintain low temperatures.

By turning off the compressor, the refrigeration cycle is paused, and the electric heaters provide heat directly to the coils. This heat melts the frost, which then drains away as water, clearing the coil surfaces for optimal airflow and heat exchange once the compressor is turned back on. This process ensures a return to normal operation without damaging components or significantly impacting stored products.

The other options do not effectively address the defrosting issue. Running the compressor at a lower setting or increasing the refrigeration cycle may not adequately remove the frost and would likely exacerbate the problem. Using warm air from the environment is not a controlled method and could lead to inconsistent temperatures within the case, potentially jeopardizing the integrity of the stored items.