I'm not sure if an ice maker can handle the dynamic load of a grow room. Much like a condensing unit for a walk in refrigerator, it is made to keep an specific space within a target temperature. That space never changes, and any outside input (heat) is absorbed over a period of time. An 1k HID lamp requires 4000btu of cooling power to offset its heat. Can your ice maker provide 6k-24kbtu of cooling?