Thermostat shows a relay error and cannot control the boiler; heating does not turn on or off as requested.

Safety first: If you will touch any wiring or the boiler, switch off power at the breaker and close the boiler’s service switch. If unsure, contact a qualified heating technician.

• Check Relay power: Verify the Netatmo Relay (the white plug‑in or wired box near the boiler or router) is firmly plugged into a powered outlet or correctly wired to the boiler. Confirm the LED on the Relay is lit.
• Reduce distance and obstacles: Move the Relay closer to the Wi‑Fi router and, if possible, closer to the boiler. Avoid placing it behind metal panels or inside metal cabinets.
• Reboot devices: Unplug the Relay for 30 seconds, then plug it back in. Remove one battery from the thermostat for 30 seconds and reinsert. Wait 2–3 minutes for reconnection.
• Re‑pair thermostat and Relay: In the Netatmo Energy app, go to Settings > Manage my home > Thermostat > Install/Pair Relay and follow the on‑screen steps to re‑associate the thermostat with the Relay.
• Check boiler control wiring: If the Relay is wired to the boiler, verify the two low‑voltage control wires are firmly connected to the boiler’s thermostat terminals and to the Relay’s control terminals. Tighten loose screws with power OFF.

If the error persists and the Relay LED never turns on or keeps blinking red, the Relay module may be defective and should be replaced.