Abstract: An ice machine includes a plurality of cooling tubes with each cooling tube having an inner tube and an outer tube extending around the inner tube to define an annular cavity between the inner tube and the outer tube. When refrigerant flows through the annular cavity between the inner tube and the outer tube, water in the inner tube freezes. The ice machine may also include a shell defining an internal cavity through which the plurality of cooling tubes extend; a water source operably connected to a water pump to flow water through the inner tube; a refrigerant source operably connected to a refrigerant pump to flow refrigerant through the annular cavity; and a heater operably connected to the internal cavity of the shell to flow a heated fluid through the internal cavity and across the plurality of cooling tubes.