Thermostat shows E12 and refuses to control outputs due to configuration error.

Safety: No high-voltage work is required for configuration changes.

Steps:

• Enter the installer or commissioning menu using the procedure in the Schneider Electric manual (often holding specific keys for several seconds).
• Review key parameters: system type (heat only, cool only, heat/cool, heat pump), sensor type (room, floor, combined), control mode (on/off, PWM, proportional), and output assignments.
• Correct any obviously conflicting settings (e.g., selecting floor sensor when none is connected, or enabling both 2‑pipe and 4‑pipe modes simultaneously).
• If unsure, use the Restore Factory Defaults option and then re-run the guided setup wizard.
• After saving settings, reboot the thermostat. If E12 persists, the internal configuration memory (EEPROM/flash) may be damaged; replacement is required.