Owner's Manual
Page 21
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 remove from wallplate M28103 Batteries are depleted. Insert 2 fresh AA alkaline batteries M28101 19 69-2222EF-03 The warning flashes about 30 days before leaving home for more than a month. Battery replacement RTH7400/RTH7500 Series Grasp thermostat and pull to run on AC power when installed. 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 remove from wallplate M28103 Batteries are depleted. Insert 2 fresh AA alkaline batteries M28101 19 69-2222EF-03 The warning flashes about 30 days before leaving home for more than a month. Battery replacement RTH7400/RTH7500 Series Grasp thermostat and pull to run on AC power when installed. Install fresh batteries immediately when the LO BATT warning begins flashing.