Control Mode - Grundfos Control Mpc Montage- Und Betriebsanleitung

8.4.3 Control mode (2.1.2)

Control mode
Description
There are two control modes, namely closed and open loop.
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 figures below.
System controlled by built-in PI controller (closed loop)
Y
A
Regulation curve for closed loop
24
Pos.
X
Y
A
Setting via the operating panel
• Operation > Further settings > Control mode > Closed loop.
Set the setpoint. See sections Operation (2) and Alternative
setpoints (2.1.3).
Open loop
In open-loop control mode, 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 mode 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 MPC system. In
such cases MPC is like an actuator.
System with external controller (open loop)
Regulation curve for open loop
Pos.
X
Y
Y
100
75
50
25
X
5
Regulation curve for MPC-E system in open loop
Description
Time [sec]
P [bar]
Setpoint
Y
0
5
Description
Input [%] from external controller
3
Flow rate [m /h]
50 70.7 86.6
X
F
1
2
3
4
X
100