Batteries are not required if the Honeywell T6 Pro Z-Wave Programmable Thermostat was wired to run on 24 VAC power when installed. To provide optional backup power, install three fresh AA alkaline batteries immediately when the low battery alert appears.

Additional considerations

• The alert appears about two months before the batteries are depleted. Even if the low battery alert does not appear, you should replace batteries once a year, or before leaving home for more than a month.
• If batteries are inserted within two minutes, the time and day will not have to be reset. All other settings are permanently stored in memory, and do not require battery power.
• When the battery power is low, the thermostat’s backlight is disabled to save battery power.
• When battery power is critically low, only the alert icon and the battery icon are displayed, and the thermostat cannot control the HVAC system. Batteries must be replaced immediately.

To replace the batteries in a Honeywell T6 Pro Z-Wave Programmable Thermostat 

1. When the low battery alert appears, press gently to loosen the thermostat and then carefully pull it from the wall mount.

   
    

2. Insert fresh alkaline AA batteries. Match the polarity of the batteries with the + / – marks inside the battery compartment.

   
    

3. Reinstall the thermostat to the wall mounting plate.