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RS8HP102 © Danfoss 2018-09
AK-CC 750A
or when the set delay time has expired.
• Drip tray heating element
The drip tray heating element is switched off when the set delay
time has expired. This delay time is applicable from the end of
defrost (state 3).
Adaptive defrost
This function can cancel planned defrosts which are not neces-
sary, and on its own initiative it can start a defrost if the evapora-
tor is about to be blocked by rime and ice.
This function is based on a registration of the air flow through the
evaporator. By using the AKV (stepper) valve as mass flowmeter
for the refrigerant flow it is possible to compare the energy admis-
sion on the refrigerant side with the energy emission on the air
side. Via this comparison the air flow through the evaporator can
be determined and hence also the amount of ice/frost build-up on
the evaporator surface.
Automatic adaptation to the evaporator
When adaptive defrost is activated it will carry out an automatic
tuning in order to adapt itself to the relevant evaporator. The first
tuning takes place after the first defrost so that tuning can be car-
ried out on an evaporator without ice/rime formation. New tuning
subsequently takes place after each defrost (but not at night with
night blinds). In a few cases it may happen that the function is not
correctly adapted to the relevant evaporator. This is usually be-
cause the automatic adjustment has been made under abnormal
operating conditions at start-up/on testing the system. This will
result in the function reporting an error state. If this happens, a
manual reset of the function should take place while briefly set-
ting the function switch to "OFF".
Status display
For each evaporator it is possible to display the current operating
status for adaptive defrost:
0: OFF Function not activated
1: Error
Reset to be carried out
2: Tuning Function carries out automatic tuning
3: OK - no ice build-up
4: Slight ice build-up
5: Medium ice build-up
6: Heavy ice build-up
Restrictions and sensor signals:
The following connections/signals must be used:
- Expansion valve type AKV/ETS/CCMT
- Temperature signal from both S3 and S4
It is essential that the S3 and S4 sensors are located in the air
flows of the evaporator inlet and evaporator outlet. The sensors
must be mounted in such a way that the effects of external heat
sources, such as fan motors, are minimised as far as possible.
- Pressure signal from condensation pressure Pc
The Pc signal can be received from a pressure transmitter which
is connected to the controller, or it may be received via data
communications from the system unit.
(Several controllers may share the same Pc signal.)
If the controller does not receive a Pc signal, it will use a constant
value for the condensation pressure.
- Adaptive defrosting cannot be used if one of the following
refrigerants are used for regulation: R23, R513B, R13B1 or user-
defined.
This function can only cancel planned defrosts which start from
a defrost schedule – either an internal schedule or an external
schedule in the system unit. Other defrost start signals will always
result in defrost.
This function will only cancel defrost if all evaporator sections so
permit.
Function selection
This function can be set to operate in one of the following ways:
0. OFF:
The function is stopped. Any alarms are removed and the func-
tion is reset.
1. Monitoring only::
The function is used exclusively to monitor the formation of
ice on the evaporator – the function will not cancel planned
defrosts.
If the function detects severe ice/rime formation on an evapora-
tor, an alarm "Appliance A – air flow reduced" is transmitted.
The alarm is removed at the start of the next defrost.
2. Skipping of defrosts by day (appliances with night blinds)
This setting is used if function is only to cancel unnecessary
defrosts by day, and if night blind is used for the appliance.
This function undertakes new tuning only when defrost takes
place during day operation.
The controller MUST be set to night state when night time cover
is set for the appliance – this may take place via a schedule in
the controller or alternatively via a signal from the system unit.
This is because there is a risk of the function detecting the
formation of rime/ice on the evaporator when night blind is set
for the appliance. (A greater reduction in air flow may occur as
a consequence of a small distance between night blinds and
products.
It is important for night time cover to be removed from the
appliance when the controller switches to day operation. If not,
there is a risk of incorrect tuning, and hence missing data for
cancelling defrosts. Correct tuning will take place only after the
next defrost.
3. Skip defrost day and night (refrigeration rooms and appliances
without night blind)
This setting is used if the function is to cancel defrosts for rooms
and appliances without night blind.
New tuning of the function takes place after each defrost.
4. Full adaptive defrost
This setting is used if the function is to start defrosts on its
own initiative. The setting can ideally be used in refrigeration/
frost rooms where the time of defrost is not as important. In
refrigeration/frost rooms, this setting can ensure major savings
as defrosts take place only when necessary. Scheduled defrosts
will always be carried out. That is to say, a basic schedule can
be input and the adaptive function will then start extra defrosts
itself where necessary..
Minimum time between defrosts
It is possible to enter a minimum time between defrosts. In this
way it can be avoided that planned defrosts according to the
weekly schedule be carried out immediately after the termination
of a adaptive defrost. The time span is from the termination of a
adaptive defrost and until a planned defrost is again allowed.
