Owner's Manual
Page 21
Insert 2 fresh AA alkaline batteries M28101 19 69-2222EF-03 Battery replacement RTH7400/RTH7500 Series Grasp thermostat and pull to remove from wallplate M28103 Batteries are depleted. The warning flashes about 30 days before leaving home for more than a month. Install fresh batteries immediately when the LO BATT warning begins flashing. Even if the warning does not appear, you should replace batteries once a year, or before batteries are optional (to provide backup power) if your thermostat was wired to run on AC power when installed.
Insert 2 fresh AA alkaline batteries M28101 19 69-2222EF-03 Battery replacement RTH7400/RTH7500 Series Grasp thermostat and pull to remove from wallplate M28103 Batteries are depleted. The warning flashes about 30 days before leaving home for more than a month. Install fresh batteries immediately when the LO BATT warning begins flashing. Even if the warning does not appear, you should replace batteries once a year, or before batteries are optional (to provide backup power) if your thermostat was wired to run on AC power when installed.