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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.
Defrost based on refrigeration time
When the aggregate refrigeration time has passed a fixed time,
a defrost will be started.
Min. time between defrosts
There is a 2 hours minimum time between defrosts.
This avoids that planned defrosts in accordance with the weekly
schedule are carried out immediately after a defrost on demand
has been carried out. The time applies from when a Defrost based
on refrigeration time has been completed to when a planned
defrost is again permitted. Defrost based on refrigeration time will
not start defrosting with a shorter interval than the 2 hours either.
Melting function
This function will stop the air flow 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 flow and hence the evaporator's capacity will be
greatly improved.
AK-CT 450A
User Guide RS8GR602 © Danfoss 2016-10
System manager
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 more than 24
hours.
If the controller is equipped with data communication, the clock
will automatically be updated from the system unit.
Max. 10 pcs.
7
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