Display shows E8 and thermostat intermittently reboots or freezes

Safety first: Turn OFF power at the breaker before tightening any terminals.

Steps to troubleshoot:

• 1. Check supply wiring:
  • Remove the thermostat and inspect the L (live) and N (neutral) terminals.
  • Tighten terminal screws and ensure copper conductors are fully inserted.
• 2. Verify circuit:
  • Confirm the thermostat is on a stable circuit not heavily loaded with motors or large appliances.
  • If possible, move the thermostat to a dedicated heating circuit.
• 3. Measure voltage:
  • With power ON (and using proper safety precautions or a qualified electrician), measure voltage between L and N at the thermostat.
  • It should be close to the nominal (e.g. 230 V). Large drops when heating turns on indicate wiring or supply issues.
• 4. Inspect for corrosion:
  • Look for corrosion on terminals or in the wall box that could increase resistance.
• 5. Replace thermostat if internal PSU is faulty:
  • If supply is stable but E8 persists, the internal power supply circuit is likely defective.
  • Replace the thermostat with a new Heatit model.