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12. Starting the pump for the first time
When the pump has been connected correctly, the
pump should be started with the discharge valve
closed approximately one third.
Due to the soft start feature, the pump takes approxi-
mately 2 seconds to develop full pressure.
12.1 Motor cooling and other considerations
• Make sure the well is capable of yielding a mini-
mum quantity of water corresponding to the pump
capacity.
• Do not start the pump until it is completely sub-
merged in the liquid.
• As the valve is being opened, the drawdown should
be checked to ensure that the pump always re-
mains submerged.
• To ensure the necessary cooling of the motor, the
pump should never be set so low that it gives no
water.
If the flow rate suddenly falls, the reason might be
that the pump is pumping more water than the
well can yield. The pump must immediately be
stopped and the fault corrected.
12.2 Impurities in the water
If there are impurities in the water, the valve should
be opened gradually as the water becomes clearer.
The pump should not be stopped until the water is
clean, otherwise the pump parts and the check valve
may become clogged.
When the water is clean, the valve should be fully
opened.
12.3 Minimum flow rate
To ensure the necessary cooling of the motor, the
pump flow rate should never be set to a value lower
than 0.2 gpm.
If the flow rate suddenly falls, the reason might be
that the pump is pumping more water than the well
can yield. The pump must immediately be stopped
and the fault corrected.
Note: The pump's dry-running protection is effective
only within the recommended duty range of the
pump.
Note: Do not let the pump run against a closed dis-
charge valve for more than 5 minutes. When the dis-
charge valve is closed, there is no cooling flow and
there is a risk of overheating in motor and pump.
12.4 Built-in protection
The motor incorporates an electronic unit which pro-
tects the motor in various situations.
• In case of overload, the built-in overload protection
will stop the pump for 5 minutes. After that period,
the pump will attempt to restart.
• If the pump has been stopped as a result of dry run-
ning, it will start automatically after 5 minutes.
• If the pump is restarted and the well has not recov-
ered, the pump will stop after 30 seconds.
10
12.5 Resetting the pump
Switch off the electricity supply for 1 minute.
The motor is protected against the following condi-
tions:
• dry running
• voltage surges (up to 6000 V)
In areas with high lightning intensity, external
lightning protection is required.
• overvoltage
• undervoltage
• overload
• overtemperature.
12.6 MS 3 motors
Note: All MS 3 motors are factory-set to detect dry-
running conditions.
Check that the combination of pump and motor corre-
sponds to the data on page 39.
12.7 MSE 3 motors
Note: All MSE 3 motors are factory-set to detect dry-
running conditions. However, if the maximum pump
speed setting is changed, the dry running stop value
must also be changed. Please refer to either the
CU 301 or CU 300 I&O for instructions on this proce-
dure.
12.8 Maintenance and service
The pumps are normally maintenance-free.
Deposits and wear may occur. For that purpose, ser-
vice kits and service tools are available from
Grundfos.
The Grundfos Service Manual is available on request.
The pumps can be serviced at a Grundfos service cen-
ter.
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