When the Thermostat loses the radio connection with its Relay, a 'Thermostat not reachable' message is displayed in the application. If the Thermostat is still powered, a '!' logo is displayed on its screen (see here); otherwise, the last display that preceded the power failure remains frozen.

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Whenever you install Netatmo Smart Radiator Valves or following a reboot (firmware update, power outage, etc.), the products can take up to 15 minutes to reconnect to the Relay and synchronize with the Netatmo app.

Improving the wireless connection between the Relay and the Thermostat

1. Check the Thermostat power supply:
   1. Remove the batteries and check that none have leaked. If you see traces of oxidation on the Thermostat, clean them with a cotton swab and white vinegar.
   2. Insert brand new and unexpired 1.5V AAA alkaline batteries, and check that the screen flashes and displays the “Searching for Relay” logo, then the temperatures after a few minutes. Press the + and - buttons to test their operability: the Thermostat screen must not display the “Searching for Relay” logo again.
2. If possible, reduce the distance between the Relay and Thermostat.
   Note: You can extend the wires from the boiler adapter (Help).
3. If moving the modules is not possible, try changing their orientation. A slight difference in position can sometimes significantly improve the transmission of the radio signal.
4. Walls and ceilings (very thick and/or with metal reinforcement) and some surfaces can absorb the radio signal. If possible, place the Relay and the Thermostat in the same room (at least to temporarily test their operation) or favor thin partitions between the modules.
5. For optimal transmission of radio waves, the Relay and the Thermostat shouldn't be located:
   • Within 50 cm of other electrical equipment, whether or not it's using radio communications.
   • Behind or inside the frame of the boiler or stove.
   • Very close to each other (less than 10cm).
   • Behind a television.
   • Near an aquarium.
   • In or on a metal object.
   • In a closed cabinet.
   • Near several electric wires or cables.

Radio signal range

The radio protocol is designed for a range of 100 meters in open space. However, heating products are intended exclusively for indoor use. Consequently, the expected effective range is generally between 10 and 20 meters. This distance strongly depends on the physical environment, varying with the thickness and materials of the walls (reinforced concrete, stone, or metal surfaces drastically reduce the signal, unlike drywall or wood).

Updated August 27, 2026 08:04