User Manual

Control concept
Closed-loop control strategy
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The connection is made between the pins of block PID_CTL and a location on
the SEQLINK block. The order in which the PID_CTR blocks are connected
must be the same as that of the sequence. The connections to the SEQLINK
block need not be continuous: connected pins and unused pins may be
interspersed.
For example, 1 = Re-heater, 2 = Pre-heater, 3 = Dampers, 6 = Cooling coil.
This method of connection is used to interconnect PID_CTR blocks on different
charts, or in cases where individual project-specific sequence-controller
elements or aggregates are to be deleted from an off-the-shelf solution (CAS
library).
Communication between one sequence controller element and another flows
via the pins [ToLower] → [FmHigher] and [ToHigher] → [FmLower].
The block recognizes configuration errors and shows these at the Token State
output [TknSta]. If, e.g., the control action [Actg] of an individual sequence-
controller element is incorrectly set, the associated sequence controller
element is disabled and an error message is displayed.
Example: Output from elements 4 and 6 [TknSta] = HEL_CSEQ Output from
elements 3 and 5 [TknSta] = CEL_HSEQ:
Examples of automatically deactivated sequence elements:
In all the examples illustrated, several aggregates are deactivated. This is a
precaution, as the sequence elements cannot determine which of the
aggregates has incorrectly set parameters. For this reason, the aggregates are
disabled one after the other until there is a clear transition to the next
sequence.