An evaporator controller for a plural-coil evaporator of a refrigeration system, the evaporator controller comprising a mode determiner for selecting a mode of operation of the evaporator from a plurality of modes of operation, wherein one mode uses a first coil of the plurality of coils of the evaporator, another mode uses a second coil of the plurality of coils of the evaporator and at least one mode uses more than one of the plurality of coils, based on selection data and a refrigeration requirement, and a selection data updater for updating the selection data based on the selected mode of operation and a process variable of the refrigeration system.