This variable control lets you manually adjust the fan speed for fans in your greenhouse from 30% to 100% of output capacity (Minimum output depends on fan). It also has the ability to turn a fan on and off. Controller comes in a weather proof electrical enclosure suited for greenhouse environments. Great option for equipment requiring a controller that can handle higher amperages like the ACF 24" variable speed exhaust fan. Operates on 110/120 voltage up to 10 amps. Wiring required.