ℹ
info Honeywell
Status REPLACE BATTERY
Battery warning indicator; low battery state detected by thermostat.
? What Causes This
Batteries are nearing depletion or malfunctioning (if AC-powered, may be an issue with the charger).
ⓘ What This Means
(1) Install fresh AA alkaline batteries immediately. Follow up within 2 minutes if replacing AC power. (2) Verify connection if hardwired system.
Source: page 17 of the official manual
From the manual
This error code appears in:
Honeywell Focuspro Th6220d