"HONEYWELL" PROGRAMMABLE THERMOSTAT *5-2 day programming *Large backlit display *Accuracy of 1 degree permanent and temporary override set point retained in power loss *Battery change reminder *Works with gas, oil and electric *Single stage heating and and cooling, and heat pumps without auxiliary heat, no electric baseboards *Multi stage heating and cooling and heat pumps with auxiliary heat *works with furnace (warm air) central air, hot water, steam or gravity *750 millivolt 24V gas fireplaces *Replaces Ace no. 4387205 *Discovery ACC, CON, NBR, SUP, EXP