Digital 2 heat/1 cool. 1 week programming with 4 periods per day. For use with central gas, oil, or electric furnaces and A/C. For millivolt systems. Does not work with heat pump systems or electric baseboard heat. Precise temperature control (+/-1 degree). Easy-to-install. No. RTH221B1021/E1: Programmable: 7-Day Programmable, Width: 4-3/4″, Height: 3″, Depth: 1″, Color: Off White, Pkg Qty: 1, Package Type: Clamshell
