@mark.cockcroft check this out
I got one of these zigbee eTRVs to work but I think it's not great: because essentially you have to always ensure that the setpoint is above the internal temperature sensor of the TRV until you reach your desired temperature.
you can achieve partial open and close but by using the zen thermostat driver it's a dance/fight with the internal sensor.
When the radiator starts warming up the internal sensor will register a higher temperature much sooner than the room sensor, that's the issue.
We need better drivers
