Input might be utilized by external heat pump to enable heating or cooling only.

Configuration > I/O allocation settings > Digital inputs > Cooling/(Heating) changeover 1 (2)

If this digital input is allocated then it is used to enable changeover heating or cooling signal.

DI "on" - disable heating / enable cooling

DI "off" - enable heating / disable cooling

If the input has not been configured, change-over is handled by the internal controller signal.

Related topics:

Changeover function