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Configuration - continued
5. Set values for capacity of the
compressors
Press the +-button to go on to the
next page
6. Set values for main step and any
unloaders
Press the +-button to go on to the
next page
7. Set values for safe operation
Press the +-button to go on to the
next page
AK-PC 781
In our example there are no
unloaders and hence no changes.
In our example we select:
- Safety limit for discharge
temperature = 120°C
- Safety limit for high condensing
pressure = 103.5 bar
- Safety limit for low suction
pressure = -40°C
- Alarm limit for high suction
pressure = -5°C
- Alarm limit for min. and max.
superheat, respectively = 5 and
35 K.
Capacity controller RS8GG602 © Danfoss 2015-03
LT Comp. release delay
LT-control. Delay on input signal from MT
MT-Comp.request delay
MT-control. Delay on input signal from LT
MT Comp. release delay
MT-control. Delay on output signal to LT
Injection heat exchanger
Selects whether an output signal is to be sent for start/stop
of liquid injection in a cascade heat exchanger
Pump down
Select whether a pump down function is required on the last
running compressor
Pump down limit Po (-80 to +30 °C)
Set the actual pump down limit
VSD min speed (0.5 – 60.0 Hz)
Min. speed where the compressor must cutout
VSD start speed (20.0 – 60.0 Hz)
Minimum speed for start of Variable speed drive (Must be set
higher than "VSD Min. Speed Hz")
VSD max speed (40.0 – 120.0 Hz)
Highest permissible speed for the compressor motor
VSD safety monitoring
Select this if input for monitoring of the frequency converter
is required
PWM period time
Period time for bypass valve (on time + off time)
PWM Min. capacity
Minimum capacity in the period time (without a minimum
capacity the compressor will not be cooled)
PWM Max. capacity
Limitation of capacity during period time (100 = no limit)
Load shed limits
Select which signal is to be used for load limitation
(only via network, a DI + network or two DI + network)
Load limitation period
Set the maximum time permitted for load limitation
Load shed limit 1
Set max capacity limit for load shed input 1
Load shed limit 2
Set max capacity limit for load shed input 2
Override limit Po
Any load below the limit value is freely permitted. If the P0
exceeds the value, a time delay is started. If the time delay
runs out, the load limit is cancelled
Override delay 1
Max. time for capacity limit, if P0 is too high
Override delay 2
Max. time for capacity limit, if P0 is too high
Kp Po (0.1 – 10.0)
Amplifications factor for PI regulation
Advanced control settings
Select whether the advanced capacity control settings
should be visible
Po filter
Reduce changes in the Po reference
Pc filter
Reduce changes in the Pc reference
Minimize cycling
The control zone may vary for connections and disconnec-
tions
when regulating with step coupling.
Initial start time (15 – 900 s)
The time after start-up where the cut-in capacity is limited to
the first compressor step.
Unloading mode
Select whether one or two capacity controlled compressors
are allowed to be unloaded at the same time at decreasing
capacity
5 - Compressors
In this screen the capacity distribution between the com-
pressors is defined.
Capacities that need to be set depend upon the "compressor
application" and "Step control mode" that has been selected.
Nominal capacity (0.0 – 100000.0 kW)
Set the nominal capacity for the compressor in question.
For compressors with variable speed drive the nominal
capacity must be set for the mains frequency (50/60 Hz)
Unloader
Number of unload valves for each compressor (0-3)
6 - Capacity distribution
The installation is dependent on the combination of com-
pressors and coupling pattern.
Main step
Set the nominal capacity of the main step (Set the percent-
age of the relevant compressor's nominal capacity) 0 -
100%.
See Section 5.
59
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