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4.3 Liquid temperatures/cooling
Figure
3
shows an SQ/SQE pump installed in a
borehole. The pump is operating.
Figure
3
illustrates the following:
•
borehole diameter
•
pump diameter
•
temperature of pumped liquid
•
flow past the motor to the pump suction strainer.
Liquid
temperature
Fig. 3
To ensure sufficient cooling of the motor, it is
important to observe the maximum liquid
temperature of 35 °C under all conditions.
The borehole diameter must be at least
Caution
76 mm (approx. 3").
The motor should always be installed above the well
screen. If a flow sleeve is used, the pump may be
installed freely in the borehole.
Do not let the pump run against a closed
discharge pipe for more than 5 minutes.
When the discharge pipe is closed, there
Caution
is no cooling flow and there is a risk of
overtemperature in motor and pump.
If the actual temperature of the pumped liquid
exceeds the specified value or the operating
conditions otherwise fall outside the specified
conditions, the pump may stop. Please contact
Grundfos.
8
5. Electrical connection
5.1 General
The electrical connection should be carried out by an
authorised electrician in accordance with local
regulations.
Borehole
diameter
Pump
diameter
The supply voltage, rated maximum current and
power factor (PF) appear from the motor nameplate.
The required voltage for Grundfos submersible
motors, measured at the motor terminals, is - 10 %/
+ 6 % of the nominal voltage during continuous
operation (including variation in the supply voltage
and losses in cables).
If the pump is connected to an electric installation
where an earth-leakage circuit breaker (ELCB) is
used as an additional protection, this circuit breaker
must trip out when earth fault currents with DC
content (pulsating DC) occur.
The earth leakage circuit breaker must be marked
with the following symbol:
Supply voltage
1 x 200-240 V - 10 %/+ 6 %, 50/60 Hz, PE.
The current consumption can only be measured by
means of a true RMS instrument. If other instruments
are used, the value measured will differ from the
actual value.
On SQ/SQE pumps, a leakage current of 2.5 mA at
230 V, 50 Hz, can typically be measured. The
leakage current is proportional to the supply voltage.
The SQE and SQE-NE pumps can be connected to a
control box, type CU 300 or CU 301.
Caution
Warning
Before starting work on the pump, make
sure that the power supply has been
switched off and that it cannot be
accidentally switched on.
The pump must be earthed.
The pump must be connected to an
external mains switch with a minimum
contact gap of 3 mm in all poles.
If the motor cable is damaged, it must be
replaced by Grundfos, an authorised
Grundfos service workshop or similarly
qualified persons to avoid a hazard.
.
The pump must never be connected to a
capacitor or to another type of control box
than CU 300 or CU 301.
The pump must never be connected to an
external frequency converter.
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