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7. Protection and control functions
The liquid level can be controlled via the Grundfos
LC, LCD 107, LC, LCD 108, LC, LCD 110 level
controllers, and the pumps can be protected via
thermal switches or the Grundfos CU 100 control
unit.
7.1 LC and LCD level controllers
LC controllers are for one-pump installations and
LCD controllers are for two-pump installations.
The following LC and LCD level controllers are
available:
•
LC 107 and LCD 107 with air bells
•
LC 108 and LCD 108 with float switches
•
LC 110 and LCD 110 with electrodes.
In the following description, "level switches" can be
air bells, float switches or electrodes, depending on
the level controller selected.
7.1.1 LC, LCD
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 the 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:
•
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.
For further information, see the installation and
operating instructions for the level controller
selected.
7.2 Thermal switches
All pumps have two sets of thermal switches
incorporated in the stator windings.
The thermal switch in circuit 1 (T1-T3) will break the
circuit at a winding temperature of approx. 150 °C.
This thermal switch must always be connected.
The thermal switch in circuit 2 (T1-T2) will break the
circuit at the following approximate winding
temperatures:
170 °C for three-phase pumps
160 °C for single-phase pumps.
The maximum operating current of the thermal
switches is 0.5 A at 500 VAC and cos
φ
0.6. The
thermal switches must be able to break a coil in the
supply circuit.
When the thermal switches in standard pumps close
the circuit after cooling, the pump will be restarted
automatically by the controller.
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 107, LC, LCD 108 or LC, LCD
110 level controller via an intrinsically safe
barrier to ensure a safe circuit.
After thermal cutout, explosion-proof
pumps must be restarted manually. The
thermal switch in circuit 2 must be
connected for manual restarting of these
pumps.
DANGER
Explosive environment
Death or serious personal injury
- Do not install the separate motor-
protective circuit breaker or control unit
in potentially explosive environments.
