AK-PC 572 User Guide RS8KH202 © Danfoss 2019-03 11
Pump down
Pump down function
To avoid too many compressor starts/stops with low load, it is possible to define a pump down
function in which the compressors are stopped when the suction pressure falls to "Pump down
limit Po".
This limit has been set at 6 K below the reference point for Po.
Yes /No
Fac: No
Injection OFF delay Delay of the forced closing of expansion valves, if the controller calls for cut in of compres-
sors, but the compressors are in a locked situation and therefore cannot start.
Min: 0 s
Max: 300 s
Fac: 120 s
Configuration
Configuration
Compressor mode Set the type of compressor to be used for regulation:
• Multi + Single:***
)
First compressor has unloaders. The remaining ones are one-step units
• CRII4+Single **
)
First compressor is CRII4 compressor. The remaining ones are
one-step units
(In the event that CRII is selected it will not be possible to select oil management)
• Single-step only: All are one-step compressors
• None:
DO-demand
Fac:
Speed+single
No. of compressors Set the number of compressors on the suction circuit MT
This is a total amount.
If regulating with two compressors only, DI3 and DO3 can be used for the AUX1 function.
DI + DO-demand
Min: 1
Max: 3
Fac: 3
Lead comp. 1 size Set the nominal compressor capacity for the first compressor (it is defined under
“Compressor mode”)
Min: 1 m3h
Max: 20 m3h
Fac: 1 m3h
Comp. 2 size Set the nominal compressor capacity for compressor 2
Min: 1 m3h
Max: 20 m3h
Fac: 1 m3h
Comp. 3 size Set the nominal compressor capacity for compressor 3
Min: 1 m3h
Max: 20 m3h
Fac: 1 m3h
VSD Min. speed ***: For speed
Min. speed at which the compressor will cut out
Min: 10 Hz
Max: 60 Hz
Fac: 30 Hz
VSD Start speed
***: For speed
Minimum speed at which the compressor will start (must be set to a higher value than
“VSD Min. speed”)
Min: 20 Hz
Max: 60 Hz
Fac: 45 Hz
VSD Max speed
***: For speed
Highest permitted speed for compressor
Min: 40 Hz
Max: 120 Hz
Fac: 60 Hz
CRII Period time **: For CRII
Set the period time for the unloader valve (on time + off time)
Min: 10 s
Max: 60 s
Fac: 20 s
Comp1 min Cap **: For CRII
Configure the minimum capacity at which the compressor will stop
Min: 10 %
Max: 50 %
Fac: 10 %
Comp1 start Cap **: For CRII
Configure the capacity at which the compressor will stop
Min: 10 %
Max: 100 %
Fac: 30 %
Compressor timers Compressor timers
Lead comp.1 Restart Min. period of time for re-starting the first compressor.
Set the forced on+Off-time before it can be switched on again. The setting is to prevent incor-
rect operation.
To prevent a compressor breakdown, the setting must be made in accordance with the
requirements of the compressor supplier.
Min: 1 min.
Max: 60 min
Fac: 5 min
Comp. Restart Min. period of time for restarting remaining compressors
Set the forced On+Off-time before it can be switched on again. The setting is to prevent
incorrect operation.
Min: 1 min.
Max: 60 min
Fac: 5 min
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