AK-CC 550A Manual RS8FS402 © Danfoss 2016-03 7
Coordinated defrost
There are two ways in which coordinated defrost can be arranged.
Either with wire connections between the controllers or via data
communication
Wire connections
The digital input DI2 is connected between the current controllers.
When one controller starts a defrost all the other controllers will
follow suit and likewise start a defrost. After the defrost the indi-
vidual controllers will move into waiting position. When all are in
waiting position there will be a change-over to refrigeration.
Coordination via data communication
Here the system unit handles the coordination.
The controllers are gathered in defrosting groups and the system
unit ensures that defrosting is started in the group according to a
weekly schedule.
When a controller has completed defrosting, it sends a message
to the system unit and then goes into a waiting position. When
every controller in the group is in a waiting position, refrigeration
is again permitted in all the individual controllers.
System manager
Defrost on demand
1 Based on refrigeration time
When the aggregate refrigeration time has passed a xed time,
a defrost will be started. (The function is not activated if the
adaptive defrosting has been set to 2, 3 or 4.)
Adaptive defrosting:
This function assesses the need for defrosting on the basis of the
airow through the appliance. It may even start a defrost and may
even cancel a scheduled defrost.
The following functions can be selected:
0 O
1 Monitoring
A value is calculated for the evaporator air ow here.
An alarm will be triggered in the case of icing up or ash gas.
2 Adaptive day (can replace one defrost per day).
This setting can be used if the appliance does not have a blind or
lid during the day, and blinds or lids are used at night.
A value is calculated for the day evaporator air ow.
The evaporator is monitored during the day only, and the next
scheduled defrost is carried out if required.
If the function does not require a defrost at the time of the
scheduled defrost during the day, the defrost will not be carried
out.
All scheduled and DI defrosts are carried out during the night.
3 Adaptive day and night (can replace defrosting both day and
night).
This setting can be used if the appliance has a door or a sliding
door, or it is completely uncovered both day and night.
The setting is also recommended for rooms.
A value is calculated for the evaporator air ow.
The evaporator is monitored, and the next scheduled defrost will
be carried out as required.
If the function does not require a defrost at the time of the
scheduled defrost, the defrost will not be carried out.
4 Full adaptive (can start an extra defrost).
This setting can be used if the appliance has a door or a sliding
door, or it is completely uncovered both day and night. The
setting is also recommended for rooms.
A value is calculated for the evaporator air ow.
The evaporator is monitored, and a defrost will be carried out as
required regardless of schedules.
All scheduled defrosts will also be carried out.
Adaptive defrosting requires the following connections:
- Expansion valve type AKV
- Temperature signal from both S3 and S4
- Temperature signal from the condensing pressure Pc which is
distributed via the network from a system manager. The value
should show the pressure in front of AKV valve. On plants where
each part is not representative is the signal from system man-
ager not be used. Here, the controller uses a constant.
NOTE. The S3 and S4 sensors must be placed in the air ow/chan-
nel immediately before/after the evaporator.
Note
The function "Adaptive defrost” should only be activated when the
evaporator runs under normal operational conditions.
Min. time between defrosts
There is a 2 hours minimum time between defrosts.
This avoids that planned defrosts in accordance with the weekly
schedule or DI signal are carried out immediately after a defrost
on demand has been carried out. The time applies from when
a defrost on demand has been completed to when a planned
defrost is again permitted. The defrost on demand will not start
defrosting with a shorter interval than the 2 hours either.
Melting function
This function will stop the air ow in the evaporator from being re-
duced by frost created by uninterrupted operation for a long time.
The function is activated if the thermostat temperature has
remained in the range between -5°C and +10°C for a longer
period than the set melting interval. The refrigeration will then be
stopped during the set melting period. The frost will be melted
so that the air ow and hence the evaporator’s capacity will be
greatly improved.
Real-time clock
The controller has a built-in real-time clock which can be used to
start defrosts. This clock has a power reserve of four hours.
If the controller is equipped with data communication, the clock
will automatically be updated from the system unit.
Max. 10
To Next Page
Loading...
