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2.6
Control method
Description / Overview
The fans and the control valve of the water circuit are actuated by a closed loop and open
loop control unit. A closed loop control circuit controls the flow of water through the
air/water heat exchanger as a function of the air outlet temperature of the cooling
module.
The cooling module has four temperature sensors; two in the air outlet at the top and at
the bottom as well as two temperature sensors in the air inlet at the top and at the
bottom. In addition, an external temperature sensor (option) can be connected. The
output signal of these sensors is used as the reference value for the control system. The
reference sensor can be selected in the settings menu.
In order to compensate for temperature stratifications, the air outlet temperature is
measured by two temperature sensor on different levels. The average value of these
temperature sensors is the control variable for the opening characteristics of the control
valve.
Under normal operating conditions, the fans run at constant speed.
In order to ensure sufficient air circulation in the cabinet, the factory setting is 80% of the
nominal speed. The operator can set this value within a range of 30% to 100% via the
settings menu.
If the set temperature is exceeded by 4°C (factory setting), the system will switch to
maximum cooling power, i.e. the control valve will open by 100% and the fan speed will be
increased to 100% of the nominal speed.
If the actual value falls below the set temperature by 3°C, the normal mode will be
resumed.
Note
The control characteristic is defined at the factory. However, it can be changed and
adapted by the service department of Schroff or by a licensed service partner.
VARISTAR Cooling unit SHX 30
15
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