In the conventional showcase, the timer-control has been widely used for the defrost operation. However, the timer-control requires the unnecessary energy consumption, because the defrost operation is executed at fixed intervals irrespective of the quantity of the frost in the showcase. Therefore, the quantity of the frost in the showcase should be detected to avoid the unnecessary defrost operation. In this research, the parameters to detect the quantity of the frost are selected based on the temperatures of the specified positions in the showcase, and a new control method is developed, by which the defrost operation is executed only when a large quantity of the frost is produced in the showcase.
