Bypass; Measuring Instruments; Electrical Connection; Frequency Converter Operation - Grundfos MTB Installations- Und Bedienungsanleitung

7.5.1 Pipeline mounting
Pumps fitted with motors up to and including 7.5 kW
are suitable for direct mounting in pipes. See fig.11.
Fig. 11 Pump mounted in suspended pipelines
This type of installation does not allow
the use of anti-vibration mountings. To
Note
ensure quiet operation, suspend the
pipes from suitable pipe hangers.

7.6 Bypass

Warning
The pump is not allowed to run against
a closed discharge valve as this will
cause an increase in temperature/
formation of steam in the pump which
may cause damage to the pump.
If there is any risk that the pump may be running
against a closed discharge valve, connect a bypass/
drain to the discharge pipe to ensure a minimum
liquid flow through the pump.The drain can for
instance be connected to a tank.

7.7 Measuring instruments

To ensure monitoring of operation, we recommend
that a pressure gauge is installed on the discharge
side. See fig. 12.
M
M: Pressure gauge connection
E: Drain plug
E
Fig. 12 Position of pressure gauge connection
The measuring range of the gauge should be 20%
above the maximum pump discharge pressure.

7.8 Electrical connection

The electrical connection should be carried out by an
authorized electrician in accordance with local regu-
lations.
Warning
Before removing the terminal box cover
and before any removal/dismantling of
the pump, make sure that the electricity
supply has been switched off.
The motor must be connected to an
external mains switch.
To comply with European standard
EN 809, a motor-protective circuit
breaker must be installed to ensure that
the motor switches off during normal
Note
operation or in case of emergency.
The need for installation of an
emergency stop device must be
considered by the installer.
The operating voltage and frequency are marked on
the motor nameplate. Make sure that the motor is
suitable for the electricity supply on which it will be
used.
All three-phase Grundfos MG and Siemens motors
of 3 kW and up incorporate a thermistor, TP 211. See
the instructions in the motor terminal box.
The electrical connection should be carried out as
shown in the diagram inside the terminal box cover.

7.9 Frequency converter operation

All three-phase Grundfos motors can be connected
to a frequency converter.
We recommend that you protect MG
and Siemens motors against voltage
Caution
peaks higher than 850 V.
Depending on the type, the frequency converter may
cause increased acoustic noise from the motor. Fur-
thermore, it may cause the motor to be exposed to
detrimental voltage peaks.
The above disturbances, i.e. both increased acoustic
noise and detrimental voltage peaks, can be elimi-
nated by fitting an LC filter between the frequency
converter and the motor.
For further information, please contact the frequency
converter supplier or Grundfos.
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