Grundfos CRE Series Installation And Operating Instructions Manual page 24

How to set the PI controller
For most applications, the factory setting of the controller
constants K and T will ensure optimum pump operation.
p i
However, in some applications an adjustment of the controller
may be needed.
Proceed as follows:
1. Increase the gain (K ) until the motor becomes unstable.
p
Instability can be seen by observing if the measured value
starts to fluctuate. Furthermore, instability is audible as the
motor starts hunting up and down. Some systems, such as
temperature controls, are slow-reacting, meaning that it may
be several minutes before the motor becomes unstable.
2. Set the gain (K ) to half of the value which made the motor
p
unstable. This is the correct setting of the gain.
3. Reduce the integral time (T ) until the motor becomes
i
unstable.
4. Set the integral time (T ) to twice the value which made the
i
motor unstable. This is the correct setting of the integral time.
General rules of thumb
• If the controller is too slow-reacting, increase K
• If the controller is hunting or unstable, dampen the system by
reducing K or increasing T .
p i
Signal relay 1 and 2
The signal relays can be configured to be activated by one of the
following incidents:
• Ready
• Operation
• Alarm
• Warning
• Limit 2 exceeded
• Limit 1 exceeded
• Running
• Ext. fan control
• Not active.
The number of available displays depends on the pump type. See
below.
Function (terminal)
Signal relay 1 (NC, C1, NO)
Signal relay 2 (NC, C2, NO)
24
.
p
CRE, CRIE,
CME CRNE, CRKE,
SPKE, MTRE
● ●
● ●
Buttons on pump
The buttons on the pump can be set to the following:
• Active
• Not active.
Number
A number between 1 and 64 can be allocated to the pump. In the
case of bus communication, a number must be allocated to each
pump.