57 / 97
83000102.Ko
Approval by cold water pressure monitoring on evaporator.
A primary pump is released if:
It is selected in the system configuration of the software,
No motor protection switch faults are queued,
No flow monitoring faults are queued,
No minimum or maximum pump pressure faults are queued.
A condenser fan is released if:
No motor protection switch faults are queued,
No fault is queued at the digital fault input (e.g. control unit group fault).
From the standby state, the chiller can be switched on or off via a software switch in the display. In Automatic
mode the floating contact for the remote control must be closed.
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.
8.7.4.
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.
Figure 21: Cooling and heating sequence
Y
controller
Temperature
100 %
- 100 %
Heating =
electric
Y- cooling
Compressor 1 off
Set - heating
Hy-heating
Set - cooling
P-Band
cooling
Compressor
2 off
Compressor 3 off
Compressor 4 off
Compressor 4 on
Compressor 3 on
Compressor
2 on
Compressor 1 on
75 %
50 %
25 %
- 75 %
- 50 %
- 25 %
