48
40
30
20
10
2 4 6 8 10 12 14 16
[bar]
[bar]
40
30
20
10
2 4 6 8 10 12 14
[bar]
[bar]
EN/06.2019/G57 © STULZ GmbH – all rights reserved
C7000 INSTRUCTIONS fOR a/C UNITS
The control with a fixed condensation pressure setpoint leads in combination with speed controlled compres-
sors to the necessity to adjust high setpoints.
As for speed controlled compressors of the ANB series a minimum pressure ratio of 1:1.8 between suction
and pressure side is specified, the condensation pressure setpoint must be set to rather a big value (red line),
to avoid that the compressor is pushed out of its operating zone by the compressor control at a high evapora-
tion temperature. A lower setpoint (blue line) in the example below would result in the fact that the compressor
control detects an error as soon as the evaporation pressure rises above 11 bar.
So with a maximum evaporation pressure of 16,8 bar, a condensation pressure setpoint of 30 bar must be set,
see red line in the ANB52 operating zone.
Compressor ANB52 operating zone
Evaporation pressure
Condensation pressure
condensation pressure setpoint
lower condensation pressure setpoint
dynamic condensation pressure
setpoint
The green line represents the curve for a dynamic condensation pressure setpoint which follows the lower
limit of the operating zone.
Compressor ZP120KCE operating zone
Evaporation pressure
Condensation pressure
condensation pressure setpoint
dynamic condensation pressure setpoint
Compared to that, the operating zone of an on/off compressor is somewhat less problematic. Here you could
also adjust a fix condensation pressure setpoint. Yet the dynamic condensation pressure control benefits also
here.
Dynamic condensation pressure control
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