Frequency Converter Operation; Start-Up; Priming - Grundfos TP Serie Instrucciones De Instalación Y Funcionamiento

The motors of twin-head pumps are to be connected
separately.
Do not start the pump until it has been
Caution
filled with liquid and vented.

6.1 Frequency converter operation

Motors types MEZ 63, MG 71 and MG 80
for supply voltages up to and including
440 V (see motor nameplate) must be
Caution
protected against voltage peaks higher
than 650 V between the supply
terminals.
Grundfos motors:
All three-phase Grundfos motors from frame size 90
and up can be connected to a frequency converter.
The connection of a frequency converter will often
have the effect that the motor insulation system is
loaded more and that the motor will be more noisy
than during normal operation. In addition, large
motors are loaded by bearing currents caused by the
frequency converter.
In the case of frequency converter operation, the
following should be considered:
• In 2-, 4- and 6-pole motors of 75 kW and up,
one of the motor bearings should be electrically
isolated to prevent damaging currents from
passing through the motor bearings.
• In the case of noise-critical applications, the motor
noise can be reduced by fitting a dU/dt filter
between the motor and the frequency converter.
In particularly noise-critical applications, it is
recommended to fit a sinusoidal filter.
• The length of the cable between motor and
frequency converter affects the motor load.
It should therefore be checked that the cable
length meets the specifications laid down by the
frequency converter supplier.
• For supply voltages between 500 and 690 V,
either a dU/dt filter should be fitted to reduce
voltage peaks or a motor with reinforced insulation
should be used.
• For supply voltages of 690 V, a motor with
reinforced insulation should be used and a dU/dt
filter should be fitted.
6.1.1 Other motor makes than Grundfos
Contact Grundfos or the motor manufacturer.

7. Start-up

Do not start the pump until it has been
filled with liquid and vented. To ensure
Caution
correct venting, the vent screw should
point upwards.

7.1 Priming

Closed systems or open systems where the
liquid level is above the pump inlet:
1. Close the discharge isolating valve and loosen
the air vent screw in the motor stool. See fig. 12.
Warning
Pay attention to the direction of the
vent hole and take care to ensure that
the escaping water does not cause
injury to persons or damage to the
motor or other components.
In hot-water installations, special
attention should be paid to the risk of
injury caused by scalding hot water.
2. Slowly open the isolating valve in the suction
pipe until a steady stream of liquid runs out of the
vent hole.
3. Tighten the air vent screw and completely open
the isolating valve(s).
Open systems where the liquid level is below
the pump inlet:
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 open the
isolating valve in the suction pipe.
2. Loosen the air vent screw. See fig. 12.
3. Remove the plug from one of the pump flanges,
depending on the pump location.
4. Pour liquid through the priming port until the
suction pipe and the pump are filled with liquid.
5. Replace the plug and tighten securely.
6. Tighten the air vent screw.
The suction pipe can to some extent be filled with
liquid and vented before it is connected to the pump.
A priming device can also be installed before the
pump.
Air vent screw
Fig. 12 Position of air vent screw
15