Grundfos NB Series, Installation And Operating Instructions Manual

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8. Electrical connection
The electrical connection must be carried out by a qualified elec-
trician in accordance with local regulations.
The operating voltage and frequency are marked on the name-
plate. Make sure that the motor is suitable for the electricity sup-
ply on which it will be used.
The electrical connection should be carried out as shown in the
wiring diagram inside the terminal box cover.
8.1 Motor protection
Three-phase motors must be connected to a motor-protective cir-
cuit breaker.
All three-phase Grundfos MG and MMG motors of 3 kW and up
incorporate a thermistor. See the instructions in the motor termi-
nal box.
Carry out the electrical connection as shown in the diagram
inside the terminal box cover.
8.2 Frequency converter operation
All three-phase motors can be connected to a frequency con-
verter.
Frequency converter operation will often expose the motor insula-
tion system to a heavier load and cause the motor to be more
noisy than usual due to eddy currents caused by voltage peaks.
Large motor driven via a frequency converter will be loaded by
bearing currents.
Check these operating conditions if the pump is driven via a fre-
quency converter:
9. Start-up
Note: Do not start the pump until it has been filled with liquid and
vented.
9.1 General information
9.2 Priming
Closed systems or open systems where the liquid level is
above the pump inlet
1. Close the discharge isolating valve and slowly open the isolat-
ing valve in the suction pipe. Both the pump and the suction
pipe should be completely filled with liquid.
2. Slacken the priming plug in order to vent the pump. Once liq-
uid runs out, tighten the priming plug.
Suction operation with non-return valve
The suction pipe and the pump must be filled with liquid and
vented before the pump is started.
1. Close the discharge isolating valve and slowly open the isolat-
ing valve in the suction pipe.
2. Remove the priming plug (M).
3. Pour liquid through the hole until the suction pipe and the
pump are completely filled with liquid.
4. Fit the priming plug (M).
The suction pipe may be filled and vented via the priming plug.
See fig. 16. Alternatively a priming device with funnel can be
installed before the pump.
Open systems where the liquid level is below the pump inlet
1. If an isolating valve is fitted on the suction side of the pump,
the valve must be fully open.
2. Close the discharge isolating valve and tighten the priming
and drain plugs.
3. Connect a manual venting pump instead of a priming device
(funnel).
4. A slide valve should be installed between the venting pump
and the centrifugal pump in order to protect the venting pump
against excessive pressure.
5. Once the slide valve at the manual venting pump has been
opened, vent the suction pipe using short, rapid pump strokes
until the liquid runs out on the discharge side.
6. Close the valve at the venting pump.
Fig. 16 Drain and priming plug
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 pump must be connected to an external mains
switch.
Whenever powered equipment is being used in
explosive surroundings, the rules and regulations
generally or specifically imposed by the relevant
responsible authorities or trade organisations must
be observed.
Before starting any repair work on motors incorporat-
ing a thermal switch or thermistors, it must be
ensured that the motor cannot restart automatically
after cooling.
Operating
conditions
Action
2-, 4- and 6-pole
motors, frame
size 280 and up
Check that one of the motor bearings is
electrically isolated. Contact Grundfos.
Noise critical ap-
plications
Fit a dU/dt filter between the motor and the
frequency converter (reduces the voltage
peaks and thus the noise).
Particularly noise
critical applica-
tions
Fit a sinusoidal filter.
Cable length
Fit a cable that meets the specifications laid
down by the frequency converter supplier.
(The length of the cable between motor and
frequency converter affects the motor load.)
Supply voltage up
to 500 V Check that the motor is suitable for fre-
quency converter operation.
Supply voltage
between 500 V
and 690 V
Fit a dU/dt filter between the motor and fre-
quency converter (reduces the voltage
peaks and thus the noise),
or check that the
motor has reinforced insulation.
Supply voltage of
690 V and higher Fit a dU/dt filter and check that the motor
has reinforced insulation.
When pumping drinking water, the pump should be
flushed through with clean water before start-up in
order to remove any foreign matters such as preserv-
atives, test liquid or grease.
Pay attention to the orientation of the priming hole to
ensure that the escaping water does not cause per-
sonal injury or damage to the motor or other compo-
nents.
In hot-water installations, special attention should be
paid to the risk of personal injury caused by scalding
hot water.
E: Drain plug
M: Priming plug
T
M
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