The KTRRB air conditioning controller was specially developed for air conditioning systems in 2- or 4-pipe systems with de-energized closed valves. The KTRRB is used as an individual room temperature controller with an internal sensor or as an external controller with an optional remote sensor. The optional external flow sensor is used to automatically switch the controller to heating or cooling mode in 2-pipe operation depending on the flow temperature; alternatively, this input can be used as an H/C changeover contact. In the event of a sensor break or sensor short circuit, the heating is activated with a switch-on time of 30 % to prevent cooling or frost damage in the room. An internal switch can be used to configure the existing contact input as an ECO contact or standby contact. ECO function: If this function is selected, the temperature is set to 3 K lower in heating mode and 3 K higher in cooling mode. Standby function: If this function is selected, the controller is switched off (frost protection remains active). Surface/wall mounting or by means of adapter plate on flush-mounted box.