Frequency Converter Operation; Starting Up The Product; Operating Modes - Grundfos DPK Montage- Und Betriebsanleitung

3.4 Frequency converter operation

Before installing a frequency converter, calculate the
lowest allowable frequency in the installation in order
to avoid zero flow.
3.4.1 Requirements
• The thermal protection of the motor must be
connected.
• Do not reduce the motor speed to less than 30 %
of rated speed.
• Keep the flow velocity above 1 m/sec.
• Let the pump run at rated speed at least once a
day in order to prevent sedimentation in the pipe
system.
• Do not exceed the frequency indicated on the
nameplate. In this case there is a risk of motor
overload.
• Keep the power cable as short as possible.
The peak voltage will increase with the length of
the power cable. See data sheet for the
frequency converter used.
• Use input and output filters on the frequency
converter. See data sheet for the frequency
converter used.
3.4.2 Possible consequences
When operating the pump via a frequency converter,
please be aware of these possible consequences:
• The locked-rotor torque will be lower. How much
lower will depend on the frequency converter
type. See the installation and operating
instructions for the frequency converter used for
information on the locked-rotor torque available.
• The working condition of bearings and shaft seal
may be affected. The possible effect will depend
on the application. The actual effect cannot be
predicted.
• The acoustic noise level may increase. See the
installation and operating instructions for the
frequency converter used for advice as to how to
reduce the acoustic noise.

4. Starting up the product

You can start up the product using either direct-on-
line (DOL) starting or star-delta (Y/D) starting. The
selection of the starting method depends on several
considerations regarding usage and mains supply
conditions.
DANGER
Electric shock
Death or serious personal injury
- Before installation and the first startup
of the product, check the power cable
for visible defects and measure the
cable resistance to avoid short circuits.
DANGER
Electric shock
Death or serious personal injury
- Make sure that the power supply cannot
be accidentally switched on.
CAUTION
Sharp element
Minor or moderate personal injury
- Wear protective clothing (gloves) when
working on the pump or touching the
impeller.
Before starting the product:
- Make sure that the fuses have been
removed.
- Make sure that all protective equipment
has been connected correctly.

4.1 Operating modes

WARNING
Electric shock
Death or serious personal injury
- The pump must be stopped by signal
from the level sensors depending on the
S1 or S3 operation modes.
- The pump must be stopped when the
liquid level falls below the top cover
(S1) when operated continuously in S1
mode.
- The pump must be stopped when the
liquid level falls below the mid stator
housing (S3) when operated
intermittently in S3 mode.
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