Figure 11: Coordinated defrost options
System manager
Max 10.
Danfoss
84B8268
Either with wire connections between the controllers or via data communication:
Wire connections
The digital input DI2 must be congured for coordinated defrost and wiring must be connected between the
relevant controllers. When one controller starts a defrost, all the other controllers will follow suit and likewise start a
defrost. After the defrost, the individual 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 manager handles the coordination.
The controllers are gathered in defrosting groups and the system manager 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 manager 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.
Adaptive defrosting
The Danfoss adaptive defrost algorithm detects the amount of ice build-up and cancels a scheduled defrost if it is
not needed, or it can be set up to only perform defrost if the evaporator air ow is getting interrupted by frost or ice.
The overall concept is based on comparison of the energy uptake on the refrigerant ow side with the energy
emission on the air ow side. When the evaporator is clean, an energy balance is assumed, while a growing
imbalance can be identied when ice formation is build up on the evaporator surface ending up with blocked
airow.
4 dierent adaptive defrost modes
0 O
1. Monitoring
Can be set up in parallel to other defrost methods and generate an alarm in case of blocked air ow / ice-up of the
evaporator. If ash gas issues are detected on the refrigerant ow side, a ash gas alarm is generated.
2. Adaptive skip day:
Allows the controller to cancel (skip) defrosts scheduled within day time. Defrosts scheduled at night operation will
be carried through and not skipped. Only defrosts that are set up via a schedule in the frontend using master
control functions or set up via the internal defrost schedule in the controller can be skipped.
3. Adaptive skip day and night:
With this set-up, the controller can allow to cancel (skip) defrosts scheduled both within day time and within night
time. For both adaptive skip day and night max. 3 consecutive defrosts can be skipped, whereafter the 4th
scheduled defrost will be performed even if only little ice should be present.
AK-CC55 Single Coil and Single Coil UI
© Danfoss | Climate Solutions | 2021.02 BC364229688105en-000101 | 14
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