Can a UL Listed product be modified in the field if the manufacturer indicates that the revision is ok and sends out new parts?

Large signs do. Electric signs so large that shipment in one carton or fully assembled is impractical may be divided into sections.

Flooding and other natural disasters prompt many questions about water-damaged electrical equipment. Can the equipment be dried out? Are the circuit breakers and fuses safe to use? Can switchboards be re-energized?