Grundfos SP Series Installation And Operating Instructions Manual page 9

A typical single-phase wiring diagram using a
Grundfos control box is shown in fig 9.
Fig. 9 Single-phase wiring diagram for
Grundfos control boxes
Fig. 10 Three-phase wiring diagram for
Grundfos and Franklin motors
Three-phase motors
Three-phase motors must be used with the
proper size and type of motor starter to ensure
the motor is protected against damage from low
voltage, phase failure, current unbalance and
overload current.
A properly sized starter with ambient-
compensated extra quick-trip overloads must be
used to give the best possible motor winding
protection.
Each of the three motor legs must be
protected with overloads. The thermal
overloads must trip in less than 10 seconds at
locked rotor (starting) current. A three-phase
motor wiring diagram is shown in fig. 10.
Pumps should NEVER be started to
check rotation unless the pump is
totally submerged. Severe damage
Caution
may be caused to the pump and
motor if they are run dry.
3.5.3 High voltage surge arresters
A high voltage surge arrester should be used to
protect the motor against lightning and switching
surges.
Lightning voltage surges in power lines are
caused when lightning strikes somewhere in the
area.
Switching surges are caused by the opening and
closing of switches on the main high-voltage
distribution power lines.
The correct voltage-rated surge arrester should
be installed on the supply (line) side of the control
box; see fig. 11 and fig. 12. The arrester must be
grounded in accordance with the National
Electrical Code and local codes and regulations.
Single phase
power supply
Lightning
arrester
Fig. 11 Single-phase hookup
Three phase power supply
Ground
Lightning
arrester
T1 T2
To SP motor
Fig. 12 Three-phase hookup
The warranty on all three-phase
submersible motors is VOID if:
1. The motor is operated with single-
phase power through a phase
converter.
2. Three-leg ambient compensated
extra quick-trip overload protectors
Note
are not used.
3. Three-phase current unbalance
is not checked and recorded;
see section 4. Startup on p. 11.
4. High voltage surge arresters are
not installed.
3.5.4 Control box/panel grounding
Warning
The control box or panel shall be
permanently grounded in
accordance with the National
Electrical Code and local codes or
regulations.
Ground
True
grounding
point
Pump
panel
Install lightning
protectors before
fuses or circuit
breaker
T3
True
grounding
point
9