The maximum distance depends on the structure and obstacles between the devices. It is advisable to place the Gateway in a central area of the flat (in an area with a good Wi-Fi signal if you will be using this type of connection). The sensors must be wall-mounted, in an area not exposed to heat sources such as direct sunlight, not above the radiators but at least 1 metre away from them, and should not be placed on any shelves covering the radiator.