English (GB)
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8. Motor protection
The booster module must be connected to an effective
motor-protective circuit breaker which must protect the motor
against damage from voltage drop, phase failure, overload and a
locked rotor.
In power supply systems where undervoltage and variations in
phase symmetry may occur, a phase failure relay should also be
fitted. See section
15. Checking of motor and cable
The control circuit must always be made in such a way that all
modules are stopped if one module fails.
8.1 Setting of motor-protective circuit breaker
For cold motors, the tripping time for the motor-protective circuit
breaker must be less than 10 seconds (Class 10) at 5 times the
rated full-load current (I
1/1
/I
SFA
) of the module. See the module
nameplate.
In order to ensure the optimum protection of the submersible
motor, the motor-protective circuit breaker should be set in
accordance with the following guidelines:
1. Set the motor-protective circuit breaker to the rated full-load
current (I
1/1
/I
SFA
) of the module.
2. Start the module, and let it run for half an hour at normal
performance. See section
9. Before starting the booster
3. Slowly grade down the scale indicator until the motor trip point
is reached.
4. Increase the overload setting by 5 %.
The highest permissible setting is the rated full-load current (I
1/1
/
I
SFA
) of the module.
For modules wound for star-delta starting, the motor-protective
circuit breaker should be set as described above, but the
maximum setting should be as follows:
Motor-protective circuit breaker setting = rated full-load current x
0.58.
The highest permissible startup time for star-delta starting is 2
seconds.
9. Before starting the booster module(s)
The booster module(s) must be filled with water before startup.
Procedure:
1. Slacken the vent valve of the booster module, if any.
2. Ensure an inlet pressure on the booster module.
3. Completely open the isolating valve.
4. Wait 3 to 5 minutes to ensure optimum venting.
5. Tighten and clean the vent valve.
Checking the direction of rotation
Procedure:
1. Close the isolating valve on the discharge side of module 1
(figures
) to approx. 1/3 of maximum flow.
2. Start module 1, and record discharge pressure and flow
readings.
3. Stop the module, and interchange two of the phases to the
module.
4. Restart the module, and re-record discharge pressure and
flow readings.
5. Stop the module.
6. Compare the results taken under points 2 and 4. The
connection which gave the larger pressure and flow is the
correct direction of rotation.
The check of the direction of rotation should last for the shortest
possible time.
If the booster system has several modules, starting and rotation
checks must be made in the order 1-2-3-4 until all modules are
running. When module 2 is checked, module 1 must be running.
When module 3 is checked, modules 1 and 2 must be running,
etc.
If modules in series are also connected in parallel (fig.
), the
direction of rotation of each section connected in series should be
checked.
After having checked the direction of rotation, stop the modules in
the order 4-3-2-1.
The booster system is now ready for operation.
10. Operation
Start
The booster modules must be started in the order 1-2-3-4 at
intervals of 1 to 2 seconds. See section
connected in series and in parallel
. If other intervals are required,
contact Grundfos.
Module 1 is always the first module on the suction side. During
startup, we recommend to close the isolating valve 3/4 and open
it slowly (2 to 3 seconds).
In systems involving the risk of water hammer in connection with
start/stop, the necessary measures must be taken to minimise
this risk, e.g. by installing a diaphragm tank.
Operation
During operation, the inlet pressure must be checked in
accordance with section
The total discharge pressure and flow of modules connected in
series should never be changed by stopping one or more of the
modules. If other pressures or flows are required, the following
procedures are applicable:
• Bypass of module(s): Install a bypass between two modules.
See fig.
Stop the module(s) which is/are not required, and close the
isolating valves on either side of the module. See section
10.1.2 Flushing of the booster module
The module(s) to be bypassed is/are always the last
module(s) in the flow direction.
• Fit a reducing valve to the discharge pipe.
The values stated in section
must
be observed.
• Modules with three-phase motors: Install a frequency
converter for speed control of the last booster module in the
flow direction. See section
7.1 Frequency converter operation
.
Stop
The modules must be stopped in reverse order, i.e. 4-3-2-1, at
intervals of 1 to 2 seconds. See section
connected in series and in parallel
If the booster system is taken out of operation for a long period,
the modules should be flushed through with clean freshwater.
See section
10.1.2 Flushing of the booster module
. The modules
are then left with freshwater until they are to be used again.
Note
If this requirement is not met, the motor warranty will
be invalidated.
Warning
The booster modules are not allowed to run against a
closed discharge valve for more than 5 seconds as
this will cause an increase in temperature/formation
of steam in the module which may cause damage to
the pump and motor.
If there is any risk of the modules running against a
closed discharge valve, a minimum liquid flow
through the module should be ensured by connecting
a bypass or a drain to the discharge side of the
module. The drain can for instance be connected to a
tank.
