HVAC_AntiFreezeControlStartup (FB)¶

Application example¶

Certain actuators / aggregates - for example (water filled) HVAC heater coils, HVAC plate type heat exchangers etc. - might be exposed to outdoor air flow at intake which involves the potentially risk of frost damage.

Functionality¶

HVAC_AntiFreezeControlStartup does a controlled startup (ramping up) of the actuator preloading for a given maximum time (tPreloadMax) or until a preload threshold (rPreloadThreshold) is reached. For example HVAC heater coil: flushing the heater coil until return temperature (rPreload) exceeds a temperatur limit (rPreloadThreshold). In case the preload threshold is not reached within the preload maximum time an startup error is signaled (xStartupError). This procedure is started if xEnable is set to TRUE and the outdoor air temperatur is below startup threshold (rStartupThreshold), otherwise there is no startup at all.

After successfull preload there is pause (tFollowUp) to get the system settled. End of the pause is signaled by xStartupDone = TRUE to allow subsequent control actions - for example SequenceControl - to take over control of the actuator.

InOut:

Scope	Name	Type	Initial	Comment
Input	xEnable	BOOL	TRUE	Enable
	rOutdoorAirTemp	REAL		Outdoor air temperatur
	rStartupThreshold	REAL	8.0	Startup threshold
	rPreload	REAL		Preload
	rPreloadThreshold	REAL	20.0	Preload threshold
	tPreloadMax	TIME	TIME#10m0s0ms	Preload maximum time
	tFollowUp	TIME	TIME#10m0s0ms	Preload follow-up time.
	xReset	BOOL	FALSE	Reset
	itfDateTimeProvider	Util.IDateTimeProvider	Globals.g_dtpDateTimeProvider	Source for the current date and time information in milliseconds since 1.1.1970 00:00:00.000
Output	xStartup	BOOL		Startup indication
	xPreload	BOOL		Preload indication
	rOutPreload	REAL		Actuator preload signal (0..100%).
	xStartupDone	BOOL		Startup sucessful done
	tRemaining	TIME		Time remaining until startup is done
	xStartupError	BOOL		Startup error indication
	xError	BOOL		Error indication
	eErrorID	Error		Error ID