User Manual

Control concept
Closed-loop control strategy
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● Programmable offset (for P and PD controllers)
● Programmable initial integrator value (for PI or PID controllers)
● Programmable runtime for control variable (0 – 100%, 100 – 0%) and
positioning speed
● Type of operation (direct acting or reverse acting) can be selected
A sequence controller can be implemented by interconnecting several PID_CTR
blocks. The sequence linker SEQLINK can also be used, where appropriate. The
only function of this block is to enable individual sequence elements to be
deleted without the need to create new connections.
The PID_CTR block is used:
● As the master controller in a sequence cascade control configuration (e.g.,
room/supply air cascade).
● In temperature and humidity control loops
The following functions are integrated in the CAS_CTR block:
● Can be programmed for P, PI, PID or PD control action
● Proportional controller output with minimum and maximum limit control
● Setpoints for heating and cooling sequences, and for energy recovery
● Setpoint depending on type of operation, for energy recovery
● Initialization of integrator (initial value)
Universal PID controller
The PID_CTR block can be used as a universal stand-alone controller in a plant
for the control of any control variables, e.g.:
● Temperature, temperature differential
● Pressure, pressure differential
● Velocity
● Absolute humidity, relative humidity
The PID_CTR block can be configured as a P, PI or PID controller. The following
parameter settings are used to define the control action:
● Gain [Gain]
● Integral action time [Tn]
● Derivative action time [Tv]
As an option, the gain [Gain] can be influenced with the [GainFac] input. It can
be useful to correct the gain factor in this way when controlling outside air
dampers, e.g., as the effect of the damper positions can depend on the outside
air temperature. The correction factor is defined with the gain scheduling block
ADAGAIN.
The actuator runtime can be set. Specifying the actual actuator run-times
makes it possible to tune the controller more accurately to the actuator
concerned, so improving the control quality of the control system.
The correcting range is limited by specifying the minimum and maximum output
variable. In this process, the minimum of the two values is always set as the
maximum value. In other words, the maximum value may be below the
minimum value; there is no need to update the minimum value.
[Nz] is a zone on either side of the setpoint, within which the controller does
not respond. As soon as the difference between the setpoint [Sp] and the
CAS_CTR cascade
controller
Control action
Correcting range