PreRinseOperationValveAnalog

PreRinseOperationValveAnalog (FB)

FUNCTION_BLOCK PreRinseOperationValveAnalog

Short description

Control of the start-up operation of a ventilation system Typical application: preparation of a ventilation system at low outside temperatures

Representation

Function description

General

This function block is used to control the start-up operation of a ventilation system depending on the current outside temperature rOAT and the current return temperature rRnT of the heater circuit. It guarantees the defined and effective preheating of the heater circuit before enabling the fans of the ventilation system (goal: prevention of frost damage to the heater circuit).

Control

The start-up operation (preheating and control signal ramp) starts with a rising edge (FALSE > TRUE) at the input xRequest, if the current outside temperature rOAT falls below the threshold rMaxOAT is below the threshold. The output xEn is activated (= TRUE) and is used to indicate active start-up operation or to enable the heater pump. The control signal rHeaterY is fixed to the setpoint / parameter rYStart and is used to control the heater valve.

Value range for the setpoint / parameter rYStart

The setpoint / parameter may only take values > 0 % The start-up operation ends after the minimum duration tMinTime (Condition: no return temperature sensor is present ( rRnT <= -20.0 °C )).

The start-up operation ends if the current return temperature rRnT falls below the threshold rMinRnT exceeds the threshold (Condition: a return temperature sensor is present ( rRnT > -20.0 °C )). The start-up operation can be terminated at any time via the input xRequest (= FALSE). After the end of the start-up operation, a linearly falling (start value = rHeaterY ) signal ramp with the duration rYStart tRamp is generated on the control signal - heater valve from start-up operation. During the generation of this signal ramp and during the start-up operation the output xRamp is active (= TRUE). If the duration of the start-up operation exceeds the threshold tMaxTime, the fault message for timeout is activated (= TRUE). At the output tET the elapsed time is displayed during the start-up operation. In the inactive state ( xRequest = FALSE) the outputs assume the following states:\

xEn	xRamp	rHeaterY	tET	xAlarm	Notes
FALSE	FALSE	0.0 %	Last value	FALSE	xRequest = FALSE

Legend: X = don't care

CODESYS

InOut:

Scope	Name	Type	Initial
Input	xRequest	BOOL
Input	rOAT	REAL
Input	rRnT	REAL	-22.2
Output	xEn	BOOL
Output	xRamp	BOOL
Output	rHeaterY	REAL
Output	tET	TIME
Output	xAlarm	BOOL
Input Const	udiMaxTime	UDINT	30
Input Const	rYStart	WORD	80
Input Const	udiRamp	UDINT	8
Input Const	eMinTimeBase	eTime	eTime.Minute
Input Const	udiMinTime	UDINT	2
Input Const	rMinRnT	REAL	30
Input Const	rMaxOAT	REAL	10