User Manual

Control concept
Closed-loop control strategy
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● Each sequence may include any number of elements
● The setpoint for each element of a sequence can be defined separately, but set points must not be
allowed to decrease in the direction from the heating sequence to the cooling sequence.
● The setpoint for energy recovery can be selected and is either at the midpoint between the setpoint of
the first heating element and that of the first cooling element, or (depending on the method of energy
recovery currently possible), it may be equivalent to the setpoint of the first heating element (if the
extract air temperature is higher than the outside air temperature) or equivalent to the setpoint of the
first cooling element (if the extract air temperature is lower than the outside air temperature).
● The gain of each sequence element can be influenced individually. In this way, e.g., the amplification
factor (gain) of the energy-recovery element varies as a function of the difference between the extract
air temperature and the outside air temperature, in order to achieve an almost constant loop gain.
● For each element, P, PI, PID, PD or on/off control can be selected. The control parameters for each
element (controller gain, integral action time and derivative action time) can be adjusted individually.
● If all the sequence elements have the same parameter values, the sequence responds in exactly the
same way as a single PI(D) controller whose output variable is distributed to individual aggregates
within the plant.
● The controller output and the integrator of the sequence element is limited in the range [YctrMin] to
[YctrMax]. For this purpose, the high limit of the last enabled sequence element of the heating and
cooling sequence is limited with an anti-windup strategy (limitation of I/portion on manipulated variable
limits). All other limit values are controlled by straightforward selection of the minimum or maximum
value.
● The rate of change of the output of each sequence element is limited to the speed of the connected
actuator. This helps improve control quality.
● The type of operation of each element (heating/cooling or humidification/dehumidification) can be
selected individually for each element.
● Only one element of the sequence can have a controlling function. When the output of a controlling
sequence element reaches [YctrMin] or [YctrMax], control is transferred to the nearest adjacent active
element ("ON").
Naming convention
The term higher is applied to sequence elements that correspond to higher set points in the sequence
diagram (normally cooling or dehumidification).
The term lower is applied to sequence elements that correspond to lower set points in the sequence
diagram (normally heating, energy recovery or humidification).
Configuration of a sequence controller
Essentially, the sequence controller consists of individual PID_CTR blocks. with each PID_CTR block acting
as a sequence-controller element for an aggregate.
The PID_CTR blocks are connected (from "Low" to "High") in the same order as the control sequences
(1…n) of the sequence controller. Accordingly, the connection of the PID_CTR blocks must take account of
the intended operating range (e.g., for heating) and the order of switching.
For example, aggregates:
1 = Re-heater, 2 = Pre-heater, 3 = Dampers, 4 = Cooling coil
Control series for heating: 3 ---> 2 ---> 1
Cooling control sequence: 4 ---> …