Thermostat display shows E1 and heating does not turn on

Safety first: Turn off power to the thermostat at the circuit breaker before removing it from the wall. Verify power is off with a non-contact voltage tester.

Steps to troubleshoot E1 (floor sensor open):

• 1. Check sensor wiring at the thermostat:
  • Remove the Fibaro thermostat from the wall plate carefully.
  • Locate the floor sensor terminals (usually marked as NTC or SENSOR).
  • Ensure both sensor wires are firmly clamped in the terminals and not loose or corroded.
• 2. Inspect the sensor cable:
  • Look for visible damage, cuts, or pinched sections where the cable enters the wall box.
  • If the cable sheath is damaged, the internal conductors may be broken, causing an open circuit.
• 3. Measure sensor resistance:
  • Disconnect the two sensor wires from the thermostat.
  • Use a multimeter set to resistance (Ω) and measure across the two sensor leads.
  • A typical 10k NTC sensor should read between ~5–25 kΩ depending on floor temperature. If the meter shows OL or infinite resistance, the sensor is open and must be replaced.
• 4. Verify sensor type in the Fibaro app / thermostat menu:
  • Restore power and enter the thermostat configuration menu or use the Fibaro Home Center app.
  • Confirm the selected sensor type (e.g., 10k NTC) matches the installed floor sensor specification.
  • Incorrect sensor type can trigger error detection or incorrect readings.
• 5. Replace the floor sensor if faulty:
  • If resistance is out of range or open, install a new compatible Fibaro/10k NTC floor sensor.
  • Route the new sensor in a conduit if possible to ease future replacement.
  • Reconnect to the SENSOR/NTC terminals and tighten screws firmly.

When to call a professional: If the sensor is embedded in the floor without conduit and cannot be replaced without breaking tiles or screed, consult a heating professional for alternative control strategies (e.g., switching to air sensor only) or floor repair.