Electrical Connection; Motor Protection; Cable Entry And Screwed Connection, Mg Motor; Torque For Terminal Cover Of Mg Motors - Grundfos NB Installation And Operating Instructions Manual

6. Electrical connection

The electrical connection must be carried out by a
qualified electrician in accordance with local
regulations.
DANGER
Electric shock
Death or serious personal injury
‐
Before removing the terminal box
cover and before removing or
dismantling the pump, make sure that
the power supply has been switched
off and that it cannot be accidentally
switched on again.
‐
The pump must be connected to an
external main switch close to the pump
and to a motor-protective circuit
breaker. Make sure that you can lock
the main switch in OFF position
(isolated). Type and requirements as
specified in EN 60204-1, 5.3.2.
The operating voltage and frequency are stated on
the nameplate. Make sure that the motor is suitable
for the power supply of the installation site.
The electrical connection must be carried out as
shown in the wiring diagram inside the terminal box
cover.
DANGER
Explosive environment
Death or serious personal injury
‐
Whenever powered equipment is used
in explosive surroundings, the rules
and regulations generally or
specifically imposed by the relevant
responsible authorities or trade
organisations must be observed.

6.1 Motor protection

DANGER
Electric shock
Death or serious personal injury
‐
The motor must be protected against
overload by an external motor-
protective circuit breaker with IEC trip
class 10 or 20.
‐
Grundfos recommends using trip class
20.
‐
The current setting of the motor-
protective circuit breaker must be
adjusted to the nominal current stated
on the motor nameplate.
30
DANGER
Automatic startup
Death or serious personal injury
‐
Before starting any repair work on
motors incorporating a thermal switch
or thermistors, make sure that the
motor cannot restart automatically after
cooling.
Three-phase motors must be connected to a motor-
protective circuit breaker.
All three-phase Grundfos MG and MMG motors of 3
kW and up incorporate a thermistor. See the
instructions in the motor terminal box.
The electrical connection must be carried out as
shown in the wiring diagram on the back side of the
terminal box cover.
6.2 Cable entry and screwed connection,
MG motor
All motors are supplied without screwed cable entries.
The table below shows the numbers and sizes of
cable entry holes of the terminal box of Grundfos MG
motors according to the standard EN 50262.
Frame Number x
Model
size dimensions
MG 71
B, C 2 x M20 x 1.5
and 80
MG 90
B, C, D 4 x M20
and 100
MG 112 C, D, F,
4 x M25
and 132 H
4 x M40
MG 160
F, H
and 180
2 x M20

6.3 Torque for terminal cover of MG motors

For pumps with below MG motors, torque
specification should be followed to avoid breaking the
terminal cover.
Thread size
Type
(mm)
MG 71/80 d 5.0
MG 90/100 d 5.0
MG 112/132 d 5.0
MG 160/180 d 6.0
Description
The holes have
precast threads
and are closed
with knock-out
cable entries.
The holes are
closed with
knock-out cable
entries.
Tightening torque
(Nm)
1.8 - 2.2
3-4
3-4
4-6