Danfoss AK-PC 781A User Manual page 57

Configuration - continued
Press the +-button to go on to the
next page
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 781A
The compressor capacity is set in
displaced volume per hour. m
See compressor data.
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 RS8HE202 © Danfoss 2017-07
MT Coord release before start: LT starts and MT following. A
signal must be both received and sent.
LT-Comp.request delay
LT-control. Delay on output signal to MT
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
/h. MT-control. Delay on output signal to LT
3
Injection heat exchanger
Selects whether an output signal is to be sent for start/stop
of liquid injection in a cascade heat exchanger
Comp. run signal DO
If "yes" is selected, an output is reserved that shows if the
compressors are operating.
Pump down
Select whether a pump down function is required on the last
running compressor
Synchronous speed
No: There will be two analog outputs available.
Yes: There will be one analog output.
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 Start capacity
Minimum capacity at which the compressor will start (must be
set to a higher value than "PWM Min. capacity")
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 P0
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
Easy PI Selection
Group setting for the 4 control parameters: Kp, Tn, + acceleration
and - acceleration. If the setting is set to "user defined" the 4
control parameters can be fine-tuned.
Kp Po (0.1 – 10.0)
Amplifications factor for PI regulation
Tn Po
Integration time for PI-regulation
+ Zone acceleration (A
Higher values result in a faster regulation
- Zone acceleration (A
Higher values result in a faster adjustment
Advanced settings
Po filter
Reduce changes in the Po reference
Pc filter
Reduce changes in the Pc reference
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 compres-
sors are allowed to be unloaded at the same time at
decreasing capacity
AO filter
Absorber changes at the analog output
+ )
)
-
57