Abstract:
A defrost control scans, in a predetermined sequence, the several evaporators of a refrigeration system of the type that is installed in a supermarket and that typically comprises a series of refrigerated food display cases in which the evaporators are mounted. Individual to each evaporator is a defrosting means and a sensing device that operates to put the defrosting means in a standby, ready-to-operate condition whenever it senses that the evaporator is in need of defrost. When the control means reaches, in the scanning sense, an evaporator whose defrosting means has been placed in a ready-to-operate condition, it acts to initiate actual operation of the defrosting means associated with that evaporator. In these circumstances, the scanning of evaporators that follow in the predetermined sequence is temporarily arrested. This assures against overloading of the defrosting means, which may typically be of the "hot gas" type, and hence particularly sensitive to overloading.