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3. Introduction
This manual introduces all aspects of your Grundfos CU331SP
constant pressure variable frequency drive. Always keep this
manual close to the CU331SP.
3.1 General description
The CU331SP is an external variable frequency drive especially
designed for submersible pumps.
Thanks to the start-up guide in the CU331SP, the installer can
quickly set parameters and put the CU331SP into operation.
Connected to a sensor, the CU331SP will quickly adapt the pump
speed to the actual demand.
3.2 Applications
The CU331SP was developed for use with Grundfos 2, 3, and 5
Hp 4" SP pumps.
The CU331SP provides for constant pressure operation of your
pump across its performance range.
4. Safety and warnings
4.1 Warning
Warning
Any installation, maintenance and inspection
must be carried out by trained personnel.
Warning
Touching the electrical parts may be fatal, even
after the CU331SP has been switched off.
Before making any work on the CU331SP, the
mains supply and other input voltages must be
switched off at least for 7 minutes.
4.2 Safety regulations
•
The On/Off button of the control panel does not disconnect the
CU331SP from the power supply and must therefore not be
used as a safety switch.
•
The CU331SP must be grounded correctly and protected
against indirect contact according to national regulations.
•
The leakage current to ground exceeds 3.5 mA.
•
Enclosure class TYPE 12 must not be installed outdoors
without additional protection against water and the sun.
•
Always observe national and local regulations as to cable
cross-section, short-circuit protection and over current
protection.
4.3 Installation requirements
The general safety necessitates special considerations as to
these aspects:
•
fuses and switches for over current and short-circuit protection
•
selection of cables (mains current, motor, load distribution and
relay)
•
net configuration (IT, TN, grounding)
•
safety on connecting inputs and outputs (PELV).
4.3.1 Aggressive environment
The CU331SP should not be installed in an
environment where the air contains liquids,
Caution
particles or gases which may affect and damage
the electronic components.
The CU331SP contains a large number of mechanical and
electronic components. They are all vulnerable to environmental
effects.
4.4 Reduced performance under certain conditions
The CU331SP will reduce its performance under these
conditions:
•
low air pressure (at high altitude)
•
long motor cables.
The required measures are described in the next two sections.
4.4.1 Reduction at low air pressure
Warning
At altitudes above 6600 ft (2000 m), PELV cannot
be met.
PELV = Protective Extra Low Voltage.
At low air pressure, the cooling capacity of air is reduced, and the
CU331SP automatically reduces the performance to prevent
overload.
It may be necessary to select a CU331SP with a higher
performance.
4.4.2 Reduction in connection with long motor cables
The maximum cable length for the CU331SP is 1000 ft (300 m)
for unscreened and 500 ft (150 m) for screened cables. In case of
longer cables, contact Grundfos.
The CU331SP is designed for a motor cable with a maximum
cross-section as stated in section
section.
5. Identification
5.1 Nameplate
The CU331SP can be identified by means of the nameplate. An
example is shown below.
Fig. 1
Example of nameplate
Text
Description
CU-331 (product name)
T/C:
202P1M2... (internal code)
Prod.no:
Product number: 12345678
Serial number: 123456G234
S/N:
The last three digits indicate the production date:
23 is the week, and 4 is the year 2004.
2.0 hp
Typical shaft power on the motor
Supply voltage, frequency and maximum input
IN:
current
Motor voltage, frequency and maximum output
OUT:
current. The maximum output frequency usually
depends on the pump type.
CHASSIS/
Enclosure class
IP20
Tamb.
Maximum ambient temperature
15.6 Fuses and cable cross-
3
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