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When the system is switched on the primary pumps are switched on with a 3.5 s delay. After a
further 3.5 s the fan control is released.
When the primary pump is switched on a timing element starts for each pump, which activates
the monitoring of the minimum and maximum cold water pressure at the pump outlet. When the
pump is switched on a timing element also starts for release of the compressor's temperature
control. The compressor's temperature control is released when the time of a pump has expired.
This time is also used for activation of the flow monitoring.
The pressure and flow monitoring takes place with two timing elements:
• Delay at start; the pressure or the flow monitoring does not trigger an alarm.
• Delay during operation; in order to ignore short-term fluctuations in pressure or flow, the
alarm is delayed.
When the system is switched off the temperature control is locked immediately and therefore the
compressor is switched off. The pump continues running to prevent uncontrolled continued
evaporation.
8.7.3. Cold water flow temperature control
In the normal case the sensor in the tank (system with tank, with pump) is used to control the
cold water feed temperature. If this sensor fails, the control switches internally to the sensor in
the cold water return and the target value (setpoint value) is increased by a defined value.
A purely proportional controller is used, which generates an output signal from -100 % to +
100 %. The switching on and switching off points of the cooling levels are set within this range. If
the setpoint is changed the switching ratio between the compressors is retained, it is shifted
overall. If the proportional range is changed the switching ratio is also retained. The range is
extended or reduced.
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