XT Controllers for NLV-CN Compressors
Page 34 / 35
4.7.
Emergency
Cooling Function
The purpose of this function is to ensure a reasonable level of refrigeration in case of an error in the
reference temperature sensor.
For low temperature applications, it is better to run at a high compressor capacity while high temperature
applications prefer a reduced capacity to prevent freezing of the chilled goods.
Functional description:
If the sensor required by the application input setup is in a sensor error state, an emergency cling function
takes over and presets the requested compressor capacity to “Emergency cooling capacity during S1/
S2 error” (n21). The emergency cling function takes over the normal capacity control while all remaining
functions will run unaffected.
When normal compressor capacity control resumes, the PI controller will be “released” from the
emergency cling level and the requested compressor capacity will adapt to the actual needed capacity.
Restrictions:
The function is overruled by the main switch off, service mode, case clean mode, loading of cabinet,
drain function cut out or the defrost mode which do not contribute to the calculation of the requested
compressor capacity.
Dependencies:
If a weighting of S1 and S2 is to be used for the input to the temperature reference, the emergency cooling
function will only be enabled when both sensors are detected to be defective. If only 1 sensor is defective,
the calculation of the cabinet temperature will be based upon the remaining sensor.
Parameter Function Code
Multiple
Apps
Min. Max.
Default
Setting
Unit
Emergency cooling capacity during S1/S2 error n21 x 0 100 60 %
4.8.
Evaporator
Fan Control
The evaporator fan can be controlled separately during normal operation, defrost, nighttime operation,
and by opening the door opening.
To avoid circulation of warm air in the cabinet, the fan can be stopped when the evaporator temperature is
too high.
To reduce noise and power consumption, the controller supports AC fans with 2-wire speed control.
Speed control can be done either by compressor speed or nighttime operation.
To configure the speed control, both parameters for fan control and relays must be set.
Parameter Function Code
Mul-
tiple
Apps
Min. Max.
Default
Setting
Unit Details
Evaporator fan mode:
0=Off
1=Enabled
2=Enabled and fan stop check on T
defr
F01 x 0 2 1 -
If fan mode is 2, the
T
defr
temperature
is checked accord-
ing to F04. When
exceeding this value,
the fan stops. The
fan starts again if
the temperature
at T
defr
gets below
F04–2 K.
Evaporator fan stop on open door
0 = No
1 = Yes
F03 x 0 1 1 -
If set, the fan stops
when the door is
opened.
Evaporator fan stop temperature (T
defr
) F04 X -50 50 10 °C
If the evaporator
temperature is
higher than F04, the
evaporator fan is
stopped.
Evaporator fan speed operation:
0 = No speed control
1 = Low speed at compressor cut out
2 = Fan stop during nighttime operation
3 = Low speed during nighttime operation
4 = Low speed at low compressor speed
5 = (4) + fan stop at compressor stop
F05 X 0 5 0 -
Compressor speed for low Evap
fan speed
F06 x 0 4500 0 rpm
If the compressor
speed is below F06,
the fan is set to low
speed.
When the speed of
the compressor has
increased by 200
rpm over F06, the
fan returns to high
speed.
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