AK-PC
572
User
Guide RS8KH202 © Danfoss 2019-03
7
Safety functions
Control optimisation
The controller continually registers the different pressures in the
system.
The pressures are automatically adjusted for the most energy-
optimal pressure.
If the pressure approaches a threshold value, the controller will
adjust the different references to maintain control.
Min./max. suction pressure Po
The suction pressure is recorded continuously.
If the measured value falls below the set minimum limit,
the compressors will immediately cut out.
If it exceeds the max. value, an alarm will be generated once
the time delay has elapsed.
LP switch
On/off signal on a DI input
If a signal is received, all compressors will immediately be stopped.
HP switch
On/off signal on a DI input
If a signal is received, all compressors will immediately be stopped.
Fan capacity will increase depending on how much the
Pgc measurement exceeds the reference.
Min./max superheating via Ss and Po measurement
Temperature sensor on an AI input.
If superheating is higher or lower than the set limits, an alarm
will be generated once the time delay has elapsed.
Max. discharge gas temperature Sd
Temperature sensor on an AI input.
There is an Sd for the MT group and an Sd for the LT group.
If the temperature nears the set max. temperature, the capacity of
the compressor will be reduced
The compressors will be stopped if the temperature nears
the set max. temperature value.
Liquid injection in the MT suction line
This function is configured in the AUX_DO output.
There are no configuration values. The controller determines when
liquid injection is required.
Sensor failure
If lack of signal from one of the connected temperature sensors or
pressure transmitters is registered an alarm will be given.
• In the event of a Po error, regulation will continue with a set
capacity in daytime operation (e.g. 50%), and a set capacity in
night operation (e.g. 25%), but with a minimum of one step.
• In the event of a Pgc error, the fan capacity that corresponds
to how much compressor capacity is connected will cut in.
Compressor regulation will remain normal.
• When there is an error on the Sd sensor the safety monitoring of
the discharge gas temperature will be discontinued.
• When there is an error on the Ss sensor the monitoring of the
superheat on the suction line will be discontinued.
• In the event of an error on the outdoor temperature sensor,
Sc3, 35°C will be used as a reference.
NB: A faulty sensor must be OK within 10 minutes before a sensor
alarm is cancelled.
A sensor alarm can be reset manually by pushing the
"X-button" for 2 seconds when the alarm is shown in the
display "Active alarms".
Fan error alarm
On/off signal on a DI input. Possible only if the input is not used
for its intended purpose.
If the signal is received, an alarm is given.
General DI alarm
On/off signal on a DI input. Possible only if the input is not used
for its intended purpose.
The controller contains one general alarm input, to which alarm
text and delay times can be connected.
Alarm and text will appear when the delay time has elapsed.
Info
In normal operating conditions, the temperature at Sd will be
between 60 and 70°C - depending on whether it is winter or
summer.
If the "Heat reclaim" function is to raise the condensing pressure,
the temperature may increase to 90° or higher.
The Sc3 sensor should be positioned so that it measures the air
intake temperature for the gas cooler. If it measures a temperature
that is too high, the system's COP will become impaired.
The Sgc signal must be stable. If this cannot be done using a sur-
face sensor, it may be necessary to use an immersion tube sensor.
If the power supply to AK-PC 572 or the high pressure valve Vhp
fails, the system cannot be controlled. We recommend installing
an emergency supply (UPS) for both the controller and the valve
to avoid faults. A relay in the UPS should be incorporated into the
controllers safety circuit so that it can restart safely.
