Danfoss ADAP-KOOL AK-PC 783 Design Manual page 59

Capacity controller with cascade control, refrigeration control systems
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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 783
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 RS8GN202 © Danfoss 11-2013
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)
Load shed limits
Select how many load shedding inputs are required
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. See Section 5.
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%.
Unload
Readout of the capacity on every unloading 0-100%.
7 - Safety
Emergency cap. day
The desired cut-in capacity for daily use in the case of emer-
gency operations resulting from error in the suction pressure
sensor/ media temperature sensor.
Emergency cap. night
The desired cut-in capacity for night operations in the case
of emergency operations resulting from error in the suction
pressure sensor/ media temperature sensor.
Sd max limit
Max. value for discharge gas temperature
10 K below the limit, the compressor capacity should be
reduced and the entire condenser capacity will be cutin.
If the limit is exceeded, the entire compressor capacity will
be cutout
Pc Max limit
Maximum value for the condenser pressure in °C
3 K below the limit, the entire condenser capacity will be
cutin and the compressor capacity reduced.
59

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