The "Optimum start control" function is available when switching from "Unoccupied" mode to "Economy" or "Comfort" mode.

With “Optimum start control”, the thermostat determines when to preheat the room as per room temperature and scheduled temperature setpoint.

Optimum start control” can be influenced by entering “Warm-up gradient” to define warm-up speed. For example, the factory setting of “Warm-up gradient” is 30 min/K. When the room temperature is 1 °C lower than the setpoint, thermostat will start pre-heating the room 30 minutes earlier.

See Managing application settings for more information about “Optimum start control” and “Warm-up gradient”.