Diagnosis
Inaccurate temperature sensing. This is caused by heat generated internally by the device or by an external source influencing the sensor.
How to Fix It
Apply a temperature offset to calibrate the reading. Press Menu > Preferences > Temperature Offset. The default is 0°. If the thermostat reads higher than actual, set a negative offset (e.g., -3°). If it reads lower, set a positive offset. Adjust in 1-degree increments, wait 2 hours for stabilization, and verify with a known-accurate thermometer placed next to the thermostat.
If That Didn't Work
The thermostat's location is causing the error. Ensure it is mounted on an interior wall, away from direct sunlight, drafts, doorways, heat-producing electronics (like TVs or lamps), and air vents. Relocating the thermostat to a neutral location is the permanent solution, which may require running new low-voltage wire.
Heads Up
The thermostat generates a small amount of its own heat. This is why the offset feature exists. Do not install it on a wall with in-wall electrical conduits that generate heat, as this will skew readings permanently.