Operating Modes; Control Modes; Uncontrolled Operation (Open Loop) - Grundfos CUE Series Installation And Operating Instructions Manual

Figures 42 and 43 show installations with and without filter and
where to use screened and unscreened cable.
Unscreened cable
CUE
Fig. 42 Example of installation without filter
Unscreened cable
CUE
Fig. 43 Example of installation with filter. The cable between
the CUE and filter must be short.
CUE and filter close to well
Screened
Unscreened
cable
cable
CUE
Fig. 44 Submersible pump without connection box. Variable
frequency drive and filter installed close to the well.
Screened
cable
Unscreened
cable
CUE Filter
* Both ends of the screened cable between filter and
connection box must be connected to ground.
Fig. 45 Submersible pump with connection box and screened
cable. Variable frequency drive and filter installed
close to the well.

7. Operating modes

The following operating modes are set on the control panel in
menu OPERATION, display 1.2. See section 10.5.2.
Operating mode Description
The pump is running in the control mode
Normal
selected.
The pump has been stopped (green indicator
Stop
light is flashing).
Min. The pump is running at minimum speed.
Max. The pump is running at maximum speed.
Max.
Min. and max. curves.
The pump speed is kept at a given
set value for minimum and maximum
Min.
speed, respectively.
18
Screened motor cable
M
Screened motor
cable
Filter M
Unscreened
drop cable
Filter
M
Screened Unscreened
cable drop cable
M
Connection
box*
Example: Max. curve operation can for instance be used in
connection with venting the pump during installation.
Example: Min. curve operation can for instance be used in
periods with a very small flow requirement.

8. Control modes

The control mode is set on the control panel in menu
INSTALLATION, display 3.1. See section 10.7.1.
There are two basic control modes:
•

Uncontrolled operation (open loop)

• Controlled operation (closed loop) with a sensor connected.
See sections 8.1 and 8.2.
8.1 Uncontrolled operation (open loop)
Constant curve.
The speed is kept at a set value in
the range between the min. and max.
curve.
The setpoint is set in %
corresponding to the required speed.
Example: Operation on constant curve can for instance be used
for pumps with no sensor connected.
Example: Typically used in connection with an overall control
system such as the MPC or another external controller.