This new easy to install and to operate CO2 enrichment controller is factory calibrated and inspected for optimum performance. The SPC-1 is designed with a photo sensor to defeat CO2 enrichment during dark periods and a large easy to read real-time LED display. The SPC-1 also is programmed with a preset differential (hysteresis) of 20 PPM and offers an elevation adjustment feature to fine tune performance. Quick Start Installation Instructions are available in English and Español. Like all of Green Air Products high quality controllers, the SPC-1 is constructed with durable components and a rust and scratch resistant, black anodized aluminum chassis to ensure that this controller will perform as expected for years to come. Operates on 120 Volt AC with 12 Amp switching capacity.