56
Capacity
controller RS8HE202 © Danfoss 2017-07
AK-PC 781A
1. Go to Configuration menu
2. Select Suction group
3. Set values for the reference
Press the +-button to go on to the
next page
4. Set values for capacity control
Configuration - continued
3 - Reference mode
Displacement of suction pressure as a function of external signals
0: Reference = set ref night offset from external 0-10
V signal
1: Reference = set ref offset from P0 optimization
Setpoint ( -80 to +30°C)
Setting of required suction pressure in °C
Offset via Ext. Ref
Select whether a 0-10V external reference override signal is required
Offset at max input (-100 to +100 °C)
Displacement value at max. signal (10)
Offset at min input (-100 to +100 °C)
Displacement value at min. signal (0 V)
Offset filter (10 - 1800 Sec)
Here you can set how quickly the reference must become effective.
Night Offset via DI
Select whether a digital input is required for activation of night
operation. Night operation can alternatively be controlled via internal
weekly schedule or via a network signal
Night Offset (-25 to +25 K)
Displacement value for suction pressure in connection with an active
night setback signal (set in Kelvin)
Max reference (-50 to +80 °C)
Max. permissible suction pressure reference
Min reference (-80 to +25 °C)
Min. permissible suction pressure reference
4 - Compressor application
Select one of the available compressor configuration here
Lead compressor type
• Variable
The following options are available for variable:
Screw compressorer
The following options are available for screw compressors
No. of compressors
Set number of compressors (total)
No. of unloaders
Set number of unloader valves
Ext. compressor stop
An external switch can be connected which will start and stop the
compressor control.
Control sensor
Po: Suction pressure Po is used for control
S4: Media temperature S4 is used for control
Pctrl: Control pressure from the low-pressure circuit for cascade
Po refrigerant type
Select refrigerant type
P0 Refrigerant factors K1, K2, K3
Only used if “Po refrigerant type” is set to custom (contact Danfoss for
information)
Pctrl refrigerant type
Select refrigerant type
Pctrl refrigerant factors K1, K2, K3
Only used if “Pctrl refrigerant type” is set to custom (contact Danfoss
for information)
Step control mode
Select coupling pattern for compressors
Cyclic: Runtime equalisation between compressors (FIFO)
Best fit: Compressors are cut in/out in order to make the best possible
fit to actual load
MT/LT coordination
Control methods between cold and frost for cascade.
MT Release: MT-control. The controller must connect to a relay so that
a signal can be sent to the controller in the LT circuit.
LT Release:LT-control. The controller must receive a signal from the
controller in the MT-circuit.
MT Coord: MT-control. A signal must both be received and sent.
LT Coord: LT-control. A signal must both be received and sent.
Set control of compressors
The configuration menu in the
Service Tool has changed now.
It shows the possible settings for
the selected plant type.
In our example we select:
- External compressor stop
-VSD + single step
- 4 compressors
- P0 as signal to the regulation
- Best fit
In our example we select the
settings:
- Suction set point = -15°C
- Night offset value = 5 K.
The settings are shown here in the
display.
There are several pages, one after
the other.
The black bar in this field tells you
which of the pages is currently
displayed.
Move between the pages using
the + and - buttons.
If a "Variable" or "screw compres-
sor" is chosen in the first line, its
type must be determined in the
next line.
Summary of Contents for AK-PC 781A
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