Boiler runs continuously even when the thermostat setpoint is reached and the app shows no call for heat.

Danger: Boiler and Relay wiring may carry mains voltage. Switch off power at the breaker and boiler switch before touching any wires.

• Check app status: Confirm in the Netatmo app that the thermostat is not calling for heat (no flame icon).
• Isolate thermostat circuit: With power OFF, disconnect one thermostat control wire at the boiler. Restore power briefly: if the boiler still runs, the issue is inside the boiler, not the Netatmo Relay.
• Test Relay contact: If the boiler stops when the thermostat wires are removed but runs when they are connected, the Relay contact may be stuck closed. Replace the Netatmo Relay.
• Inspect for bypass wiring: Ensure no installer has bridged the thermostat terminals permanently inside the boiler.

Continuous boiler operation can waste energy and damage the system; if you cannot safely diagnose the wiring, contact a heating technician immediately.