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Technical Information
5
Functions and parameters
More information as minimum, maximum and default values could be found in the Modbus documentation.
Example:
Modbus address
Parameter
Functional description
5.1
Parameter list description
1
Day temperature setpoint
This parameter defines the temperature set point for the cabinet during day operation mode. Depending on
the compressor type this parameter has a different meaning.
Fixed speed compressor: The temperature control is done by a dead band controller. This parameter defines
the cut off temperature for the compressor. The cut on temperature is this parameter plus the day temperature
difference (
57 Day temperature difference
) In case of a sensor failure, the dead band controller runs in cycle
mode.
Thermostat
off
Thermostat
on
Set point
Difference
Control Temperature
Figure 13 Fixed speed control
Variable speed compressor: The temperature control is done by a PI controller. This parameter defines the
temperature set point, which is the middle of the P band. The cut off temperature (compressor off) is this
parameter minus ½ of the day temperature difference (
57 Day temperature difference
). In case of a sensor
failure the PI controller runs with 50% speed. For variable speed applications it is recommended to use a
wider band (~5K) to prevent cut offs after defrost. The cut off band (½ of the temperature difference) is not
influencing the accuracy of PI temperature control. It is only relevant in case the losses of the cabinet are
lower than the cooling capacity at minimum speed. In this case a freezing of the goods is prevented.
0%
Set point
+1/2 Difference
-1/2 Difference
100%
Speed
Figure 14 Variable speed control
2
Mean value (daytime operation)
Selection of measuring sensors for controlling the air temperature. Air inlet or air outlet during daytime
operation.
Control temperature = air inlet + ([air outlet - air inlet] x Mean value / 100)