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.
Melt function
This function will prevent the air flow in the evaporator from being reduced 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.
Control of two compressors (only with custom set-up)
Two compressor steps can be controlled cyclic or sequentially. At cyclic control, two compressors must be of the
same size, while in sequential control compressor step 1 can be larger than step 2.
Figure 19: Control of two compressors.
Cyclic control
When the controller demands refrigeration, it will first cut in the compressor with the shortest operating time. After
the time delay, the second compressor will be cut in.
When the temperature has dropped to ”the middle of the differential”, the compressor with the longest operation
time will be cut out.
The running compressor will continue until the temperature has reached the cut-out value. Then it will cut out.
When the temperature again reaches the middle of the differential, a compressor will again be started.
If one compressor cannot maintain the temperature within the differential, the second compressor will also be
started.
If one of the compressors has run on its own for two hours, the compressors will be changed over so that
operational time is balanced.
The two compressors must be of a type that can start up against a high pressure.
The compressor's settings for ”Min. On time” and ”Min. Off time” will always have top priority during normal
regulation. But if one of the override functions is activated, like e.g. defrost, door open function, case shutdown,
forced closing, the ”Min. On time” will be disregarded.
© Danfoss | Climate Solutions | 2022.08
BC365212986197en-000201 | 17
AK-CC55 Compact