Product Manual

CU331SP variable frequency drive
SQ, SQE, CU 331, and SP
10
39
Operating modes
These operating modes can be selected with the
CU331SP:
• Normal
•Stop
•Min.
•Max.
The operating modes can be set without changing the
setpoint setting.
Normal
The pump operates in constant pressure mode.
Stop
The pump has been stopped by user.
Min. curve
The pump is running at a set minimum speed value.
See fig. 24.
For instance, this operating mode can be used during
periods with a very small flow requirement.
Max. curve
The pump is running at a set maximum speed value.
Fig. 24 Min. and max. curves
Control mode
The CU331SP has been developed specifically to
operate submersible pumps in Constant Pressure
mode. This Closed-Loop control mode uses an analog
pressure transducer to provide pressure feedback to
the drive.
Constant pressure with stop function
The outlet pressure is kept constant at high flow rate
(Q > Qmin). On/off operation at low flow rate. See fig.
25.
Fig. 25 Constant pressure with stop function
The pump is controlled according to a constant
pressure measured after the pump. This means that
the pump offers a constant pressure in the Q-range of
Q
min
to Q
max
, represented by the horizontal line in the
QH diagram.
Setting the setpoint by means of the
OPERATION menu
The setpoint can be set or changed during operation
using the setpoint display in the "OPERATION" menu
shown below. It is not necessary to run the start guide
to change the setpoint.
Low flow and stop functions
The pump will check the flow regularly by reducing the
speed for a short time. If there is no or only a small
change in pressure, this means that there is low flow.
The speed will be increased until the stop pressure
(actual setpoint + 0.5 x ΔH) is reached and the pump
will stop after a few moments. The pump will restart at
the latest when the pressure has fallen to the start
pressure (actual setpoint - 0.5 x ΔH).
TM03 8813 2507
Max.
Min.
TM03 8477 2507 TM03 8807 3307
H
set
Q
min
Q
max
CU331SP