When the Smart Thermostat and Extension Kit lose their radio link, the Smart Thermostat can’t send temperature measurements to the Extension Kit anymore. Also, any changes made to the Smart Thermostat’s settings won't take effect until the radio link is reconnected.
How to manually control the Extension Kit without a radio link.
When the Extension Kit hasn’t gotten a room temperature update from the Smart Thermostat, it will continue to operate with the last settings received from the Smart Thermostat.
When the radio connection is lost, you can manually switch heating and hot water on or off directly on the Extension Kit. To do so press the button on top of the Extension Kit until you reach the setting you prefer, as shown below.
Note: You will only be able to use these control options in the following cases:
If the Extension Kit has not received a temperature reading for more than 30 minutes.
If you restart the device and a connection with the Smart Thermostat has not yet been made.