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Unloading Unstaging
The figure below shows the normal transition from full
load to minimum load while the chiller is running.
Figure 9.
Sequence of events: Unloading unstaging
All Compressors Running At
Less Than Max Capacity
6
6
6
6
6
6
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1
1
1
2
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2
2
2
0
0
0
1
1
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2
2
2
-
Running
Running
(All
Compressors
& Max
Capacity)
Remove Maximum
Capacity Submode
6/ 6 6 13/
3 3 201
/
1
2
2
2 2
De-Energize the
Maximum Capacity
Relay after
Adjustable Filter
Time (0 to 600 Sec)
Continue to Control Capacity
by Modulating Compressor
Capacity (Speed, Port Loader,
Economizer)
6
6
6
6
6
6
6
6
6
6 6
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/
1
1
1
1
1
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2
2
2
2
2 2
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2
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2
2
0
0
0
0
0
1
1
1
1
1
2
2
2
2
2
-
-
-
7
7 7
7
7
7
7
7
7
7
7
Enforce All Running
Mode Diagnostics
*
Operational Pumpdown is required if the Outdoor Air Temperature is less
than 50F, or the Entering Evaporator Water Temperature is greater than
(outdoor air temperature – 10F). With AFD, compressors will be at max
speed for operational pumpdown.
* *
Operational Pumpdown - See Satisfied Setpoint Operational
Pumpdown sequence diagram for specific criteria.
RTAF-SVX002D-EN
StageOff Setpoint Met
7/
7 3 / / 0/
/ /
0 2 / / 012 - 9/
/ /
Running
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7
7
7
7
7
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3
3
3
0
0
0
0
0
0
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/
2
2
2
0
0
0
1
1
1
2
2
2
Lag Circuit Mode: Shutting Down
SubMode: Operational Pumpdown
Operational Pumpdown
(0 Seconds to
Max Pumpdown Timer(Default: 2 min.))
Close EXV
(0 to 25 Seconds)
7/ 7 7 30/
0 0 2
/
2
0
0 0
1
1
2
2
Fully Close EXV
No Pumpdown Required
IF*
Close Condenser
Rfgt Tank Solenoid
Valve* * * *
Pumpdown
Required
Perform Operational
Pumpdown for Last
Circuit if Required
6/ 6 6 12/ 2 2 2012-12/ 2 2 11/ 1 2012
Check for Normal
6/ 6 1
/ /
1
1
1
1
4
4
4
4
4
4
4
4
4
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/
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/
/
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/
2
2
2
2
2
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
2
2
2
2
2
2
2
Pumpdown Termination
Criteria Met
/
/
/
/
/
/
3
3
3
3
3
0
0
0
0
0 0
0
0
0
0
0
/
/
/
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/
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2
2
2
2
2
0
0
0
0
0
1
1
1
1
1
2
2
2
2
2
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7
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7
7
7
7
7
7
7
7
7
7
7
/
/
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3
3
3
3
3
3
0
0
0
0
0
0
0
0 0
0
0
0
0
/
/
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/
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/
2
2
2
2
2
2
7
7
7
7
7
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7
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7
7
/
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/
3
3
3
3
3
3
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
/
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2
2
2
2
2
2
2
2
2
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
2
2
2
2
2
2
2
E
Enforce All Non Operational Pumpdown
Diagnostics
Normal Pumpdown Termination
* * *
Criteria is Met for Last Circuit
9 2 / / 7/
/ /
7 2 / / 012
/ /
9
9
9
9
9
9
9
9
9
9
9
9
/
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/ /
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2
2
2
2
2
2
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7
7
7
7
7
/
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/ /
/
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/
2
2
2
2
2
2
0
0
0
0
0
0
1
1
1
1
1
1
Running
Lag Circuit Mode: Auto
*
9 9 2
/
/
2 2 2
2
2 2 2
8 8
8
8 8
8
/ /
/
201
1
1
2
2
2
Send Stop
Command To Lag
Compressor
Stop Lag Circuits
Condenser Fans
Energize Lag
Circuit Heaters
*
2
2
0
0
12
* *
0
0
0
0
0
0
1
1
1
1
1
1
2
2
2
2
2
2
-
-
9
9
9
9
9
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9 9
9
9
9
9
9
/
/
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/
2
2
2
2
2
2
2
2
2
2
2
2
2
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8
8
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8
8
/
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2
2
2
2
2
2
0
0
0
0
0
0
1
1
1
1
1
1
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2
2
2
2
2
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9
/
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2
2
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2
2
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2
2
2
2
2
2
2
2
2
0
0
Enforce Running Mode Diagnostics for Chiller,
d
o
ow
o
w
n
n
n
* *
*Note: The decision to stage off another compressor is determined by the
Average Running Compressor Load Command, Water Temperature Error,
and Time since Last Stage. Compressors will stage off in the reverse order
they staged on. All fixed speed compressors will stage off before variable
speed compressors stage off.
* * *
*If Condenser Refrigerant Tank is installed.
Start-Up and Shutdown
* *
2
2
2
2
2
2
-
1
1
1
1
1
1
1
1
1
1
1
1
/ /
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4
4
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4
4
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/ /
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2
2
2
2
2
2
0
0
0
0
0
0
1
1
1
1
1
1
2
2
2
2
2
2
1
1
1
1
1
1
/
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4
4
4
4
4
4
/
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/
2
2
2
0
0
0
1
1
1
2
2
2
-
1
1
1
2
2
2
2
2
2
/
/
/
/
/
/
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/
1
1
1
1
1
1
/
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2
2
2
0
0
0
Running
Continue to Control
11
/ 1 5/
1
1
5 5 2012
/
Capacity by Modulating
Lead Compressor
9
9
9
9
9
9
9
9
9
9
9
9
9
9
/
/
/
/
/
/
2
2
2
2
2
2
2
2
2
2
2
2
2
8
8
8
8
8
8
8
8
8
8
8
8
8
8
/
/
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/
2
2
2
2
2
2
0
0
0
0
0
0
1
1
1
1
1
1
2
2
2
2
2
2
-
-
1
1
1
1
1
1
2
2
2
2
2
2
2
2
2
2
2
2
2
2
/
/
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/
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/
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
/
/
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/
/
/
2
2
2
2
2
2
0
0
0
0
0
0
1
1
1
1
1
1
2
2
2
2
2
2
Last Compressor and its Circuit
1
1
1
2
2
2
Running Last
Compressor at
Min Capacity
19
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