Danfoss AK-CH 650 User Manual

88 Capacity controller RS8ER302 © Danfoss 2016-02 AK-CH 650
A overriding limit is set for the suction pressure as well as a delay
time for each digital inlet.
If the suction pressure during load shedding exceeds the set
overriding limit and the attached delay times for the two digital
inlets expire then load shedding overrides the signals so that the
compressor capacity can be increased until the suction pressure
is again under the normal reference value. The load shedding can
then be activated again.
Alarm:
When a load shedding digital inlet is activated, an alarm will be
activated to inform that the normal control has been bypassed.
This alarm can however be suppressed if so desired.
Heat exchanger injection
The controller can emit a start/stop signal for liquid injection in
the heat exchanger.
The function can be connected with compressor operation in the
following manner:
• Fluid injection is synchronised with compressor start/stop
Here the injection signal comes ON when the rst compressor is
started and goes OFF when the last compressor cuts out.
• Pump down on the last compressor
Here the injection signal will come ON when the rst compressor
is started.
When the required capacity has dropped to 0%, the injection
signal goes OFF, but the last compressor remains running until
suction pressure P0 has reached a set pump down limit, after
which it stops.
Liquid injection in suction line
The high-pressure gas temperature can be kept down by means of
liquid injection into the suction line.
The injection is accomplished with a thermostatic expansion valve
in series with a solenoid valve. The solenoid valve is connected to
the controller.
Control can be carried out in two ways:
1. The liquid injection is exclusively controlled on the basis of the
superheat in the suction line. Two values are set – a starting
value and a dierential where the injection is stopped again.
2. The liquid injection is both controlled by the superheat (as
described above) and by discharge temperature Sd. Four values
are set – two as mentioned above and two for the Sd function,
a starting value and a dierential. The liquid injection is started
when both starting values have been passed, and is stopped
again when just one of the two functions cuts out.
Time delay
A time delay can be set which ensures that the injection is delayed
during start up.

Danfoss AK-CH 650 Specifications

General

Brand	Danfoss
Model	AK-CH 650
Category	Controller
Language	English