The Solaira SMaRT 34 Digital Variable Controller is water-resistant enclosure for indoor and outdoor use, with a 1-5 setting control for optimum comfort setting and energy savings. It was built-in temperature sensor inhibits the heaters when the temperature exceeds the pre-determined set point of between 41 deg. F to 77 deg F. Zero-voltage switching and soft-start function add as much as 30% to the emitter life. Once installed it's relatively maintenance-free, with optional occupancy monitoring and remote control (sold separately). The maximum load (208-240V): 6.4 kW, 34 Amps. NOTE: MUST BE INSTALLED BY A CERTIFIED ELECTRICIAN