Display shows E7 and thermostat refuses to switch heating on

Safety first: Turn OFF power at the breaker. This error can indicate a dangerous wiring or load fault. Do not repeatedly reset without inspection.

Steps to troubleshoot:

• 1. Inspect load wiring:
  • Remove the thermostat and inspect the load (OUT) terminals and connected cables.
  • Look for burnt insulation, melted plastic, or signs of arcing.
• 2. Isolate the load:
  • Disconnect the floor heating or panel heater wires from the thermostat load terminals.
  • Cap the load wires safely with wire nuts or terminal blocks.
• 3. Test thermostat without load:
  • Restore power with the load disconnected.
  • If E7 disappears and the thermostat behaves normally, the problem is likely in the load or wiring.
• 4. Test floor heating resistance:
  • With power OFF, measure resistance between the two heating cable conductors and between each conductor and earth.
  • Compare with the manufacturer's specified resistance. Very low resistance or continuity to earth indicates a short.
• 5. Correct load issues:
  • If the heating cable is shorted, it must be replaced or repaired by a floor heating specialist.
  • If the total load current exceeds the thermostat rating, use an external Heatit relay or contactor.
• 6. Replace thermostat if internal triac is damaged:
  • If E7 persists even with no load connected, the internal power component is likely defective.
  • Replace the thermostat with a new Heatit unit.