Central Heating

Hive Mini Thermostat..no cold water?

Anonymous user 14/09/2026 - 10.36 AM

I self-installed a Hive Mini Thermostat, connecting the reviver in OpenTherm to my Viessmann Vitodens 025-w boiler, and have commissioned it via the “U” menu, to tell the boiler there is an OpenTherm controller connected. For some reason the boiler seems to show an error on first-turn-on, a FA9 (burner failed error), which the manual states is related to an OT controller. As well as a “No Connection” symbol, which the manual says is lack of connection to the OT controller. The Hive receiver (OT controller) it self, has all green lights, meaning that it itself is saying it is getting information from the boiler. Strangely, turning in the heating via the Hive app does fire the boiler and the heating comes on, however, due to the burner failed fault, I do not get any hot water. Does anyone have any idea as to why this may happen or how to resolve it?