A rethermalization system for heating refrigerated food on trays, maintaining the food in a refrigerated condition until heated, and heating some of the food to a desired temperature at a serving time while maintaining the rest of the food in a refrigerated condition. The system has a cart which docks inside a refrigerator. The cart has shelves on which trays of food reside. In the shelves there are heaters. The operator programs the system using an intricate series of commands at an operator interface. A first controller interprets the commands and sends the program to a second controller. The second controller controls the heating cycle of the heaters. A current sensor is provided to sense whether there is current to the heaters. The second controller polls the current sensor and compares the findings to what is called for in the program. The second controller sends a status signal, based on the comparison, to the first controller, which provides a response, based on the comparison, to the operator interface.