Control Mode (2.1.2) - Grundfos CONTROL MPC Installation And Operating Instructions Manual

11.5.3 Control mode (2.1.2)

Fig. 17 Control mode
Description
There are two control modes, namely closed and open loop.
Examples:
Closed loop
The typical control mode is closed loop where the built-in
PI controller ensures that the system reaches and maintains the
selected setpoint. The performance is based on the setpoint set
for closed loop. See figs 18 and 19.
Fig. 18 Booster system controlled by built-in PI controller
(closed loop)
P [bar]
Setpoint
Fig. 19 Regulation curve for closed loop
Setting via control panel
1. Mark the Operation menu with
2. Mark Further settings with
3. Mark Control mode with
4. Select Closed loop with
5. Set the setpoint. See sections 11.5.4 Setpoints (2.1.3) and
11.5.1 Operation (2).
Time [sec]
.
or , and press .
or , and press .
or , and press .
Open loop
In open-loop control, the pumps run at a fixed speed.
The pump speed is calculated from the performance set by the
user (0-100 %). The pump performance in percentage is
proportional with the flow rate.
Open-loop control is usually used when the system is controlled
by an external controller which controls the performance via an
external signal. The external controller could for instance be a
building management system connected to the Control MPC.
In such cases the Control MPC is like an actuator.
See figs 20 and 21.
Fig. 20 Booster system with external controller (open loop)
3
Flow rate [m /h]
0
5
Fig. 21 Regulation curve for open loop
3
Flow rate [m /h]
100
75
50
25
5 50 70.7
Fig. 22 Regulation curve for Control MPC-E in open loop
Input [%] from
external controller
Flow rate
Pump 1
Pump 2
Pump 3
Pump 4
Input [%] from
86.6 100
external controller
19