AK-HP 780
Heat pump controller RS8GF202 © Danfoss 2015-08
51
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
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
Advanced control settings
Select whether the advanced capacity control settings
should be visible
Kp Po (0.1 – 10.0)
Ampliflication factor for P0 regulation
Min. capacity change (0 – 100 %)
Set the minimum capacity change needed before the capac-
ity distributor connects or disconnects compressors
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 pump capacity will be cutin.
If the limit is exceeded, the entire compressor capacity will
be cutout
Pd Max limit
Maximum value for the discharge pressure in °C.
3 K below the limit, the entire pump capacity will be cutin
and the compressor capacity reduced.
If the limit is exceeded, the entire compressor capacity will
be cutout.
Pc Max delay
Time delay for the alarm Pd max limit
P0 Limit
Regulation parameter which protects against low suction
pressure.
P-band (above P0 limit)
Regulation parameter which protects against low suction
pressure.
In our example we select:
- Safety limit for discharge
temperature = 120°C
- Safety limit for too high discharge
pressure = 50°C
- Safety limit for low suction
pressure = -2°C
- Alarm limit for high suction
pressure = 10°C
- Alarm limit for min. and max.
superheat, respectively = 5 and
35 K.
In our example there are no
unloaders and hence no changes.
