Start-Up and Shutdown
RTAF-SVX001K-EN
67
Unloading Unstaging
The figure below shows the normal transition from full
load to minimum load while the chiller is running.
Figure 45.
Sequence of events: unloading unstaging
Running
(All
Compressors
& Max
Capacity)
All Compressors Running At
Less Than Max Capacity
De-Energize the
Maximum Capacity
Relay after
Adjustable Filter
Time (0 to 600 Sec)
Remove Maximum
Capacity Submode
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Running
6/
6
6 13/
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3
3 201
1
2
2
2
2
StageOff Setpoint Met
***
7/
//
7 3
// 0/
//
0 2
// 012 - 9/
//
9 2
// 7/
//
7 2
// 012
Running
Lag Circuit Mode: Shutting Down
SubMode: Operational Pumpdown
*
Operational Pumpdown
(0 Seconds to
Max Pumpdown Timer(Default: 2 min.))
Fully Close EXV
Close Condenser
Rfgt Tank Solenoid
Valve
****
IF
*
No Pumpdown Required
Pumpdown
Required
Close EXV
(0 to 25 Seconds)
7/
7
7 30/
/
0
0 2
2
0
0
0
1
1
2
2
Normal Pumpdown Termination
**
Criteria is Met for Last Circuit
Send Stop
Command To Lag
Compressor
2
2
0
0
12
Continue to Control Capacity
by Modulating Compressor
Capacity (Speed, Port Loader,
Economizer)
***
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.
*
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.
Stop Lag Circuits
Condenser Fans
Energize Lag
Circuit Heaters
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0
0
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2
2
2
2
2
Running
Lag Circuit Mode: Auto
Continue to Control
Capacity by Modulating
Lead Compressor
Running Last
Compressor at
Min Capacity
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9 2
2
2
2
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0
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Running
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1 5/
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5 2012
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Enforce All Running
Mode Diagnostics
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2
Enforce All Non Operational Pumpdown
Diagnostics
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E
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ow
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2
Enforce Running Mode Diagnostics for Chiller,
Last Compressor and its Circuit
6/
6
6 12/
2
2 2012 -12/
2
2 11/
1 2012
Check for Normal
Pumpdown Termination
Criteria Met
**
6/
6 1
1
1
1
1
//
4
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2
2
**
Operational Pumpdown - See Satisfied Setpoint Operational
Pumpdown sequence diagram for specific criteria.
Perform Operational
Pumpdown for Last
Circuit if Required
*