HVAC_RotaryHeatExchanger (FB)¶

FUNCTION_BLOCK HVAC_RotaryHeatExchanger

HVAC rotary heat exchanger.

Functionality¶

HVAC_RotaryHeatExchanger provides a control strategy for a HVAC rotary heat exchanger taking into account:

control of bypass damper
differential pressure monitoring
optional cleaning operation
malfunction detection
malfunction locking
operational time

The heat exchanger is requested if:

it is enabled (xEnable = TRUE)
setpoint reaches/exceeds request threshold (rSetpt >= rReqTreshold)

optional cleaning operation¶

If the rotary heat exchanger had not been enabled for a given time (tCleanMaxOff) it is enabled and set to rCleanPos for tCleanTime.

malfunction detection¶

If a hardware malfunction is detected via hardware error indication (input) or differential pressure monitor xError is set to TRUE, eErrorID is set to Error.HardwareError.

malfunction locking¶

Malfunction locking makes the difference how to handle / recover from a detected hardware malfunction.

Malfunction locking enabled (xMalFuncLock := TRUE): If a malfunction is detected, the rotary heat exchanger (xOn) is shut off. If the hardware malfunction is gone, xError / eErrorID and rotary heat exchanger shutoff are kept until a reset (xReset := TRUE).

Malfunction locking disabled (xMalFuncLock := FALSE): If a malfunction is detected, the rotary heat exchanger (xOn) is NOT shut off. The rotary heat exchanger recovers from a hardware malfunction automatically.

InOut:

Scope	Name	Type	Initial	Comment
Input	`xEnable`	`BOOL`	TRUE	Enable
	`rSetpt`	`REAL`	0.0	Setpoint, 0..100(%)
	`rReqTreshold`	`REAL`	0.0	Request threshold, 0..100(%)
	`xDifferentialPressureMonitor`	`BOOL`	TRUE	Differential pressure monitor - TRUE => signaling proper differential pressure
	`tCleanMaxOff`	`TIME`	TIME#2880m0s0ms	Maximum off time to enable cleaning operation
	`tClean`	`TIME`	TIME#0ms	Cleaning operation duration, set to T#0S to disable cleaning operation
	`rCleanPos`	`REAL`	100.0	Cleaning operation setpoint, 0..100(%) - 0% => closed, 100% => open
	`xErri`	`BOOL`	FALSE	Error indication - rotary heat exchanger is signaling an error
	`xMalFuncLock`	`BOOL`	FALSE	Enable the malfunction locking
	`xOpTimeInit`	`BOOL`	FALSE	Initialize the operational time with a given value (tInit).
	`tOpTimeInit`	`LTIME`	LTIME#0ns	Initialization value
	`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	`xOn`	`BOOL`		Rotary heat exchanger is switched on, bypass dampers closed
	`rSetptOut`	`REAL`		Actual setpoint
	`tToNextClean`	`TIME`		Remaing time to next clean operation
	`tOpTime`	`LTIME`		Operational time
	`xError`	`BOOL`		Error indication
	`eErrorID`	Error		Error ID

Methods:

SetError

Structure:

SetError (Method)