Thermostat shows E20 and indicates calibration error; temperature readings are clearly wrong.

Safety: No high-voltage work is needed.

Steps:

• Compare the thermostat temperature reading with a reliable reference thermometer placed nearby.
• Enter the thermostat settings and check the temperature offset or calibration menu. Reset the offset to 0 or factory default.
• If the reading is still off by more than a few degrees, perform any built-in calibration procedure described in the Schneider Electric manual.
• Update the thermostat firmware to the latest version via app or gateway, as some calibration issues are firmware-related.
• If the error persists and readings are far off, the internal sensor or ADC circuitry is defective; replace the thermostat.