Display shows E2 and thermostat stops heating or switches to backup control mode

Safety first: Turn OFF power to the thermostat at the breaker before opening the wall box.

Steps to troubleshoot:

• 1. Inspect sensor terminals:
  • Remove the Heatit thermostat from the wall.
  • Locate the NTC floor sensor terminals.
  • Check that no stray wire strands are bridging between the two sensor terminals or to adjacent terminals.
• 2. Measure sensor resistance:
  • Disconnect the sensor wires from the thermostat.
  • Use a multimeter to measure resistance across the sensor leads.
  • If the reading is very low (e.g. <1 kΩ) or near 0 Ω, the sensor is shorted.
• 3. Check for moisture or damage:
  • If the sensor is in a conduit, check for water ingress at the wall box.
  • Dry the box and conduit if wet; moisture can cause a temporary short.
• 4. Replace the sensor if shorted:
  • Install a new Heatit NTC floor sensor following the installation guide.
  • Route the sensor in a protective conduit to avoid future damage.
• 5. Reconnect and test:
  • Reconnect the new sensor to the NTC terminals.
  • Restore power and verify that the E2 code clears and temperature readings are stable.