5. Protection and control functions
5.1 Motor protection devices
The motors have three thermal protectors connected
in series and one moisture switch. Ex pumps have
two moisture switches connected in series. Protectors
and switches are connected in two separate circuits.
The thermal protectors are reversible and the
moisture switches are irreversible. The thermal
protection circuit (conductors 1 and 3) and the
moisture protection circuit (conductors 2 and 3) have
separate outputs to enable separate alarms if the
motor is overheated or affected by moisture.
All other sensor connections are either led out of the
motor (sensor version D) by conductors 4 to 9, or
connected to the sensor board (sensor version B) and
led out of the motor by conductors 4 and 5.
5.2 Pump controller
The liquid level can be controlled by Grundfos LC 231
and LC 241 level controllers. The pumps are
protected by thermal switches connected to the LC
controller or a CU 100 control unit.
5.2.1 LC level controllers
LC 231 and LC 241 controllers are for single- and
dual-pump installations. The following LC level
controllers are available:
• LC 231: single pumps up to 12 A or dual pumps
up to 9.6 A (9 A and 7.6 A in US version). Starting
method is Direct On-Line only. For both analog
pressure transmitters and digital float switches.
• LC 241: single and dual pumps up to 72 A.
Starting methods are Direct On-Line, Star Delta
and Soft Starter for both analog pressure
transmitters and digital float switches.
In the following description, "level switches" can be
float switches or pressure sensors. Controllers for
single-phase pumps incorporate capacitors. When
using digital float switches, the LC controller can be
connected up to five float switches:
One for common stop, and one for start each pump.
Optionally, a digital float switch can be used for dry-
run protection, and one for high-level alarm. If an
analog pressure transmitter is used for level
measurement, all levels can be set directly in the
controller itself or by Grundfos GO Remote.
When installing the level switches, observe the
following:
• To prevent air intake and vibrations, install the
stop level switch, so the pump is stopped before
the liquid level is lowered to the middle of the
motor housing.
• Install the start level switch, so the pump is started
at the required level. The pump must always be
started before the liquid level reaches the bottom
of the inlet pipe.
• 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.
For further settings, see the installation and operating
instructions for the selected level controller.
The pump must not run dry.
Install an additional level switch to ensure
the pump is stopped in case the stop level
switch is not operating.
The pump must be stopped when the liq-
uid level reaches the upper edge of the
clamp.
Float switches used in potentially explo-
sive environments must be approved for
this application. They must be connected
to the Grundfos LC 231 or LC 241 level
controller by an intrinsically safe barrier to
ensure a safe circuit. In potentially explo-
sive environments, the anti-seizing func-
tion must be disabled on pump controllers.
Do not install the pump controller in a po-
tentially explosive atmosphere.
Level switches must comply with IEC/EC
50495, Annex D.
24
English (GB)
To Next Page
Loading...
Need help?
General
