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Start and stop levels
The difference in level between start and stop can be
adjusted by changing the free cable length.
Long free cable = large difference in level.
Short free cable = small difference in level.
Observe the two following points.
•
To prevent air intake and vibrations, install the
stop level switch in such a way that the pump is
stopped before the liquid level is lowered below
the upper edge of the clamp on the pump.
•
Install the start level switch in such a way that the
pump is started at the required level. However,
the pump must always be started before the
liquid level reaches the bottom inlet pipe to the
pit.
The CU 100 control box must not be used
for Ex applications.
Fig. 8
Start and stop levels
8.3 Pump controllers
The following LC and LCD pump controllers are
available:
LC controllers are for one-pump-installations and
LCD controllers are for two-pump-installations.
•
•
•
In the following description, "level switches" can be
air bells, float switches or electrodes, depending on
the pump controller selected.
Controllers for single-phase pumps incorporate
capacitors.
The LC controller has two or three level switches:
One for start and the other for stop of pump. The
third level switch, which is optional, is for high-level
alarm.
The LCD controller has three or four level switches:
One for common stop and two for start of the pumps.
The fourth level switch, which is optional, is for high-
level alarm.
When installing the level switches, observe the
following points:
•
•
Alarm
Start
•
Stop
Additional
stop
For further information, see the installation and
operating instructions for the pump controller
selected.
LC 107 and LCD 107 with air bells
LC 108 and LCD 108 with float switches
LC 110 and LCD 110 with electrodes.
To prevent air intake and vibrations, install the
stop level switch in such a way that the pump is
stopped before the liquid level is lowered below
the middle of the stator housing.
Install the start level switch in such a way that the
pump is started at the required level. However,
the pump must always be started before the
liquid level reaches the bottom inlet pipe to the
pit.
If installed, always install the high-level alarm
switch about 10 cm above the start level switch.
However, the alarm must always be given before
the liquid level reaches the inlet pipe to the pit.
The pump must not run dry.
Install an additional level switch to ensure
that the pump is stopped in case the stop
level switch is not operating.
The pump must be stopped when the
liquid level reaches the upper edge of the
clamp on the pump.
Float switches used in potentially
explosive environments must be approved
for this application. They must be
connected to the Grundfos DC, DCD or
LC, LCD 108 pump controller via an
intrinsically safe barrier to ensure a safe
circuit.
13
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