Danfoss AK-CH 650 User Manual

AK-CH 650 Capacity controller RS8ER302 © Danfoss 2016-02 81
Reference for compressor control
Regulating sensor
The regulating sensor can be set at P0 or S4.
By setting the regulating sensor to S4, the P0 sensor's signal will
be used for frost protection monitoring (LP safety).
The S3 signal is used only for monitoring.
The Reference
The reference for the regulation can be dened in 2 ways:
Either
Ref = P0 setting + P0 optimisation + Night displacement
or
Ref = setting + night displacement + Ext. Ref + S3 oset
Setting
A basic value for the brine temperature is set.
P0 optimization
This function displaces the reference so that regulation will not
take place with a lower brine temperature than required.
The function cooperates with controllers on the individual
refrigeration appliances and network system manager. The system
manager obtains data from the individual appliance sections and
adapts the brine temperature to the optimum energy level. The
function is described in the manual for the system manager.
With this function you can read which appliance is most heavily
loaded at the moment as well as the displacement allowed for the
brine temperature reference.
Night displacement
The function is used to change the suction pressure reference for
night time operation as an energy saving function.
With this function the reference can be displaced by up to 25 K
in positive or negative direction. (When you displace to a higher
temperature, a positive value is set).
Displacement can be activated in three ways:
• Signal on an input
• From a system managers override function
• Internal time schedule
The “night displacement” function can not be used when
regulation with the override function “P0-optimisation” is
performed. (Here the override function will itself adapt the brine
temperature to the max. permissible).
The function can be used if a short change in the brine tempera-
ture (e.g. up to 15 min.) is needed. Here the P0 optimisation will
not be able to compensate for the modication.
Ext. Ref. - Override with a 0 - 10 V signal
When a voltage signal is connected to the controller the reference
can be displaced. In the setup it is dened how big a displacement
is to take place at max. signal (10 V).
S3 oset
With this function it is possible to delay the reference, based on a
measured S3 temperature.
The sensor can be located, for example, in the return temperature
of the brine or in the store premises. This allows a reference to be
achieved that is adjusted to the current load. In the case of an er-
ror on the S3 sensor, the contribution to the reference is omitted.
The oset is calculated on the basis of the following expression:
S3 oset = K1 (S3 temp. – TrefS3Oset.),
where K1 is a multiplication factor and "TrefS3Oset" is the S3
temperature that does not give reference oset.
For example:
- The reference temperature of the brine is to be oset based on
the shop temperature
- At 18°C no reference oset is required, i.e. S3 ref = 18
- For each increase of 1°C in shop temperature, a reduction in
reference of 0.5K is required, i.e. K1 = -0.5
- The contribution to the reference therefore becomes: -0.5 x ("S3
temp" - 18)
Limitation of reference
To safeguard yourself against a too high or too low regulation
reference, a limitation of the reference must be set.
Forced operation of the compressor capacity in the suction
group
A forced operation of the capacity can be carried out which
disregards the normal regulation.
Depending on the selected form of forced operation, the safety
functions will be cancelled.
Forced operation via overload of requested capacity
The control is set to manual and the desired capacity is set in % of
the possible compressor capacity.
Forced operation via overload of digital outlets
The individual outputs can be set to MAN ON or MAN OFF in the
software. The control function disregards this but an alarm is sent
out that the outlet is being overridden.
Forced operation via change-over switches
If the forced operation is done with the switch-over on the front of
an expansion model, this is not registered by the control function
and no alarm is sounded. The controller continues to run and
couples with the other relays.
Extra cooling
If the brine temperature increases more than desired, a function
can be selected that will activate a relay. The function is activated
if the set value is exceeded and the associated delay time has
elapsed.
The temperature value is set as a maximum value that is higher
than the reference (e.g. 4K above the reference).
There are two delay times. One is activated under normal regu-
lation, and the other is longer and is only activated during the
cooling down phases — during start-up — after defrosting.
P0 ref
Max.
Min.

Danfoss AK-CH 650 Specifications

General

Brand	Danfoss
Model	AK-CH 650
Category	Controller
Language	English