Version 2.02 15.05.2007 Function of VS 3000
28
3.27.3 Control algorithm
Controller cycle time is 1 second. The control algorithm depends on the type of control.
In the wet vapor range the temperature is clearly governed by the refrigerant and pressure:
t = f (p, refrigerant).
The VS 3000 Pack Controller calculates temperatures from the pressures measured as a function of the
refrigerant used. Exclusively temperature measurements are used for control. In this manual therefore,
temperatures (t
0
,t
c
) stand for pressure (p
0
,p
c
).
3.27.4 Control algorithm with step controller
High pressure as detected by an A/D converter is compared with the setpoint. The following relationship applies:
Control error = Actual value (t
0_Act
) − setpoint (t
0_Setp
)
When the control error is positive and pressure is rising, the step switch moves one step up, meaning that one
additional condenser capacity stage is enabled. When the control error is negative and pressure is falling, the
step switch moves down one stage, meaning that one condenser capacity stage is disabled.
Condenser capacity stages are also disabled when all compressors are off and disabling is activated by the
parameter Fan off w/comp (Menu 3-3-1).
Neutral zone (NZ)
t
Time
ZNR. 51203 65 130 E0
c
High pressure
c Setp
- 1/2 NZ
c Setp
+ 1/2 NZ
Step
up
No step Step
down
No step
c Setp
VS 3000 control algorithm HP step controller
t
t
t
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