User Manual

Control concept
Closed-loop control strategy
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The lowest sequence-controller element (Low) corresponds to control
sequence 1, and the highest (High) to control sequence n.
The lowest sequence-controller element controls a reverse-acting aggregate (if
used).
The type of operation may also be reversed during normal operation, (e.g., for
energy recovery) but the order of the sequences must not be affected.
In the sequence controller, the set points [Sp] of sequence-controller elements
(1…n) must increase incrementally:
[Sp]
1
≤ [Sp]
2
≤ [Sp]
3
≤ ... ≤ [Sp]
n
In the transition from one control sequence to the next, continuous control is
maintained if all the control sequences with the same type of operation (direct
or reverse acting) also have the same setpoint.
When the type of operation changes, the neutral zone is defined by the set
points (e.g., heating setpoint / cooling setpoint).
The PID_CTR blocks can be connected to form a sequence controller via:
● Direct connection
● SEQLINK connection
Direct connection
The individual PID_CTR blocks are connected directly with each other. The
[ToLower] pins are connected to the [FmHigher] pins, and the [FmLower] pins
are connected to the [ToHigher] pins.
SEQLINK connection
With this method, the individual PID_CTL blocks are connected via the
SEQLINK block. The sequence linker block SEQLINK is a wiring block with no
function other than that of connecting other blocks.
Options for connecting
sequence controller
elements