.BuildingControlLib.BuildingControl.VDI3813.ApplicationFunctions.Examples.TesterFunctionSelection .BuildingControlLib.BuildingControl.VDI3813.ApplicationFunctions.Examples.TesterFunctionSelectionBlock that implements functionality of "Function selection" from VDI 3813 [1, section 6.5.22, p. 70 - 72].
"The room climate can be influenced by various control functions (see Figure 44) (RA-FL section 6, column 21; informative function block Figure 45), which can either be specified by the operator or determined automatically depending on specific states. Based on the currently selected control function, the application functions Room supply air temperature cascade control, Room temperature control, Fan control and Night-time cooling can decide whether to be active or not. The following control functions are selectable:
OFF: control inactive
AUTO: control active with automatic changeover between heating and cooling modes
HEATING: control active in heating mode
COOLING: control active in cooling mode
PRECOOL: control active in cooling mode, but using comfort setpoint for heating
NIGHTCOOL: only night-time cooling active
Apart from the selection of a control function by the operator (e. g. via a time program), a change of function can also be triggered by the dewpoint being reached in cooling mode. In this case, the controller remains inactive (OFF). If automatic room-by-room changeover between heating and cooling is permissible (e. g. with four-pipe systems), and is selected by the operator (F_BMS = AUTO), the function decides on changing the active function (HEATING or COOLING) depending on the current setpoints (T_SETPT) and the room temperature (T_ROOM). In doing so, the function must make sure that, for systems having just one joint register or one joint area for heating and cooling purposes, changeover takes place via the OFF function, after an appropriate holding time to allow any open valves to close."[1, section 6.5.22, p. 70 - 72]
Implementation of the functionality of function selection. Assumption is made that T_ZE (Temperature in the middle between comfort setpoints) is the arithmetic mean of the cooling and heating set points.