Grundfos CRE Series Installation And Operating Instructions Manual page 19

Heating
System/application
systems
Q
0.5
t
L [ft]
t
L [ft]
L [ft]
t
0.5
Heating systems are systems in which an increase in pump
performance will result in a rise in temperature at the sensor.
Cooling systems are systems in which an increase in pump
performance will result in a drop in temperature at the sensor.
L) Distance in [ft] between pump and sensor
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
K
p
Cooling
T
i
system
0.5 0.5
–0.5 10 + 1.52L
0.5 10 + 1.52L
–0.5 30 + 1.52L
+2.5 100
.
p
DBP-1 - GRUNDFOS PUMP CRE - 99392005
10.3.3 External setpoint
The input for external setpoint signal can be set to different signal
types.
Select one of the following types:
• 0-10 V
• 0-20 mA
• 4-20 mA
• Not active.
If Not active is selected, the setpoint set by means of the R100 or
on the control panel will apply.
If one of the signal types is selected, the actual setpoint is
influenced by the signal connected to the external setpoint input.
See section 14. External setpoint signal on page 27.
10.3.4 Signal relay
Pumps of 0.5 - 10 Hp have one signal relay. The factory setting of
the relay will be Fault.
Pumps of 15 - 30 Hp have two signal relays. Signal relay 1 is
factory set to Alarm and signal relay 2 to Warning.
In one of the displays below, select in which one of three or six
operating situations the signal relay should be activated.
0.5 - 10 hp
• Ready
• Fault
• Operation
• Pump running (only three-phase pumps, 1 - 10 Hp)
• Warning (only three-phase pumps, 1 - 10 Hp).
15 - 30 Hp
• Ready
• Alarm
• Operation
• Pump running
• Warning
• Relubricate.
Fault and Alarm cover faults resulting in Alarm.
Warning covers faults resulting in Warning.
Relubricate covers only that one individual event.
For distinction between alarm and warning, see
section 10.1.3 Fault indications on page 16.
For further information, see section 17. Indicator lights and signal
relay on page 28.
15 - 30 Hp
• Ready
• Alarm
• Operation
• Pump running
• Warning
• Relubricate.
19