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Siemens Standard application AHU CE1P3977en_02
Building Technologies Functions 01.02.2010
5.10.4 DX cooling control
Direct expansion evaporator is enabled:
Main Index > Configuration > Configuration 1 > Cooling = DX [x]Step
Main Index > Configuration > Configuration 1 > Cooling 2 = DX [x]Step
Main Index > Unit > Temp control > Cooling > Direct expansion
Main Index > Unit > Temp control > Cooling 2 > Direct expansion
Parameter Range Function
Command – Off
– Stage1
– Stage2
– Stage3
Present state of direct expansion evaporator.
Go to page with the staged output settings.
Fdbk – Ok
– Alarm
Present value of the feedback for the direct expansion
evaporator.
Go to page with digital input settings. For example, you
can set the time for jitter protection (Default: 1 s).
Alarm – OK.
– Alarm
Present alarm state of direct expansion evaporator.
Go to page with digital input settings. For example, you
can set the time for jitter protection (Default: 0 s).
Start up delay fdbk 0...36000 [s] Defines the period after a start without feedback before a
feedback alarm is triggered. Jitter time is enabled exclu-
sively if the feedback is pending after this period.
Min run time 0...36000 [s] Define the minimum runtime after a start.
Min off time 0...600 [s] Minimum idle time for the direct expansion evaporator af-
ter a stop.
Min stage time 5...600 [s] Minimum runtime for a stage prior to stepping up to the
next step.
Note: This period remains active when intervening using
the operator unit: Even for a direct jump from off to stage
3, the output remains on each individual step for the mini-
mum runtime.
Start stage 1 0...100 [%] Controller refrigerator demand to start the first stage.
Start stage 2 Start stage 1...100 [%] Controller refrigeration demand to start the second stage.
Start stage 3 Start stage 2...100 [%] Controller refrigeration demand to start the third stage.
Stage hys off 0...Start stage 1 [%] Shutdown hysteresis of the stages. See example.
Start stage 1 = 20 %
Start stage 2 = 40 %
Start stage 3 = 60 %
Stage hys off = 10 %
Off stage 3: 50 %
Off stage 2: 30 %
Off stage 1: 10 %
Feedback can only be used as alarm, when Contact function = NO (Normally
Open) and the element is set to ON.
Prerequisite
Parameter
Example of shutdown
hysteresis
Note
Basis Document Siemens Climatix Control System
BDCX.100820.01GB
Page 82
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