Danfoss AK-PC 781A User Manual page 58

Configuration - continued
8. Set monitoring of compressor
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next page
9. Set operation time for compres-
sor
Press the +-button to go on to the
next page .
10. Set Misc. functions
58
In our example we use:
- Common high-pressure pressure
control for all compressors
- One general safety monitoring
unit for each compressor
(The remaining options could have
been selected if specific safety
controls for each compressor had
been required).
Set min. OFF-time for the compres-
sor relay
Set min. ON-time for the compres-
sor relay
Set how often the compressor is
allowed to start
The settings only apply to the
relay that cuts the compressor
motor in and out.
They do not apply to unloaders.
If the restrictions overlap, the
controller will use the longest
restriction time.
In our example we do not use
these functions.
Capacity controller RS8HE202 © Danfoss 2017-07
AO max. limit
Limit the voltage on the analog output.
5 - Compressors
In this screen the capacity distribution between the compressors
is defined.
Capacities that need to be set depend upon the "compressor ap-
plication" and "Step control mode" that has been selected.
Nominal capacity (0.0 – 1000.0 m
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 compressors
and coupling pattern.
Main step
Set the nominal capacity of the main step (Set the percentage 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 emergency
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 pres-
sure 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.
If the limit is exceeded, the entire compressor capacity will be
cutout.
Tc max. limit
Limit value read in °C
Pc Max delay
Time delay for the alarm Pc max
T0 Min limit
Minimum value for the suction pressure in °C
If the limit is reduced, the entire compressor capacity will be
cutout.
T0 Max alarm
Alarm limit for high suction pressure P0
T0 Max delay
Time delay before alarm for high suction pressure P0.
Safety restart time
Common time delay before restarting the compressor.
(Applicable to the functions: "Sd max. limit", Pc max. limit" and
"P0 min. limit).
SH Min alarm
Alarm limit for min. superheat in suction line.
SH Max alarm
Alarm limit for max. superheat in suction line.
SH alarm delay
Time delay before alarm for min./max. superheat in suction line.
Sd cut out temperature
Set the desired cut-out temperature.
8 - Compressor safety
Common safety
Choose whether an overall, common safety input for all compres-
sors is desired. If the alarm is activated, all compressors will be
cutout.
Oil pressure etc
Define here whether this type of protection should be con-
nected.
For "General", there is a signal from each compressor.
Individuel Sd pr. compressor
Select whether an Sd measurement should be made for each
compressor.
Max discharge temp.
Cutout temperature.
3 /h)
AK-PC 781A