Display shows Er4 and thermostat output is locked off

Safety first: Turn OFF power at the breaker if you need to access wiring or sensors.

Steps to troubleshoot:

• 1. Check temperature limits:
  • Enter the installer menu and review max floor temperature and any limit sensor settings.
  • Set max floor temp to a safe but realistic value (e.g. 27–35°C depending on floor type).
• 2. Allow system to cool:
  • Turn off heating for several hours to let the floor cool.
  • Once cooled, Er4 should clear automatically.
• 3. Verify sensor placement:
  • If possible, check that the floor sensor is not directly touching the heating cable.
  • Reposition sensor centrally between heating runs.
• 4. Check floor covering compatibility:
  • Ensure the floor covering (e.g. wood, vinyl) is approved for the set temperature.
  • Reduce max floor temp if the covering is sensitive.
• 5. Replace faulty sensor:
  • If the sensor reports high temperature even when floor is cool, replace the Heatit NTC floor sensor or external limit sensor.