Rated for 15 amps @ 120 volts. The CO2-4 has four timers that are used to control your CO2. In addition to all the features of the CO2-2, the CO2-4 adds two additional internal timers. The “Overall Cycle timer“ allows the user to decide how long the supplemental CO2 is kept in the growing area prior to being exhausted. When the “Overall Cycle“ time expires, the CO2-4 turns ON the exhaust outlets and enables the “Exhaust Cycle Timer“, which controls the amount of time the exhaust fans will run. When complete, the cycle is reset and the CO2 cycle starts again. The CO2-4 can also be used with the PPM-1c sensor for unequalled Parts-Per-Million performance.