Safety Functions - Danfoss AK-PC 351 User Manual

Safety functions

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.
Max. condensing pressure Pc
If the condensing pressure reaches the upper permissible value,
the controller will connect all condenser fans to keep the pressure
down. At the same time, a portion of the compressor capacity will
be disconnected. If the pressure remains near the threshold value,
even more compressors will be disconnected.
All compressors will be disconnected immediately if the threshold
value is exceeded.
LP switch
On/off signal on a DI7 input
If a signal is received, all compressors will immediately be stopped.
HP switch
On/off signal on a DI8 input
If a signal is received, all compressors will immediately be stopped.
Fan capacity will increase depending on how much the
Pc measurement exceeds the reference.
AK-PC 351 User Guide RS8GZ302 © Danfoss 2015-06
Max. discharge gas temperature Sd for digital scroll / stream
Temperature sensor on an AI input.
A signal can be received from a Pt 1000 Ohm sensor on the pres-
sure pipe.
If the temperature nears the set max. temperature, the capacity of
the compressor will be increased so that the compressor can cool
down itself.
The compressors will be stopped if the temperature reaches up to
the set max. temperature value.
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 (S4 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 Pc error, the condenser 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.
• In the event of an error on the outdoor temperature sensor,
Sc3, the permanent setting value will be used as a reference.
NB: A faulty sensor must be OK within 10 minutes before a sensor
alarm is cancelled.
General DI alarm
On/off signal on a DI8 input
If the input is used as general alarm input alarm text and delay
times can be connected.
Alarm and text will appear when the delay time has elapsed.
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