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ManualsBrandsSiemens ManualsBuilding automationDesigo Building Automation System 6.2 - Technical Principles
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Control concept
Superposed plant controls
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CM110664en_07 79 | 351
Step 5: Step-up sequence
The step-up sequence is then started for the new plant operating mode. The remaining aggregates are
switched on per the data in the function table. The switch on takes place in the table sequence from left to
right, in other words, the first aggregate in the switch sequence is the switched on first.
The parameterized times for the time on delay is active during step-up.
The step-up delay can be activated using a fixed delay time or a maximum timeout or deactivated using the
immediate option. The length of the delay for timeout depends on the switch on state of the monitored
sequence elements. Transition to the next sequence occurs as soon as it reports switched on, that is, the
process value of the block [PrVal] <> Off. It switches after the timeout time expires when the switch on
message is not sent.
When a sequence element with a life-safety or plant-safety priority is switched on, the preset delay times
will take effect first.
Step 6: Monitoring switch on state
A process alarm (off normal) is generated when the monitored aggregate is not switched on after the
sequence delay time expires.
The current switch sequence is immediately aborted when the current plant operating mode is not
AllLifeSafety and the exception value [EcptVal] is selected as the operating mode.
If, however, the exception value [EcptVal] is already the plant operating mode, the switch sequence is not
aborted and the plant operating mode does not change.
Switch on aggregates
The following figure shows the switch response and monitoring mechanism for block CMD_CTL.
The system initially checks if the new plant operating mode is an AllLifeSafety mode. The Look Ahead
check takes place in the second step, followed by the check and abort of on-going sequences. The next
step is to run the shut-down series, where objects 8 and 4 are switched off to the extent they have not yet
be shut down. The sequences are then switched on one after the other in the follow-on switch on series.