Systems With 2 Float Switches; Electrical Connection - Grundfos LC 108 Montage- Und Betriebsanleitung

Figure 4 shows the terminals listed under positions 2 and 3.
Fig. 4
Key to the symbols in figs 3 and 4:
Pos. Description
1 Module CU 211.
Terminal block for level inputs
2
(11-12, 21-22, 31-32, 41-42).
Terminal block with:
• output for external alarm device for high-level alarm
3 (H-NC, H-COM, H-NO) (only certain variants),
• output for external alarm device for common alarm
(G-NC, G-COM, G-NO).
Contacts for star-delta starting and motor protection
4
relay (contacts, thermal relay fitted and timing relay).
5 Terminal block for electricity supply.
Fuse holders for control circuit fuses (2 or 3 depending
6
on voltage variant).
7 Isolating transformer.
8 Terminal block for connection of pump.
9 Pg cable entries.
10 Earth bar ( ).
PE
Input for the PTC resistance/thermal switch of the motor
11
(T11-T21).
If the distance between the controller and pit
exceeds 20 metres, it is not advisable to use
electrodes as problems with the signal values
Note
sent back to the controller may arise.
In such cases, it is recommended to use float
switches.
Cables of up to 100 metres can be connected
Note
between the controller and the float switches.

4. Systems with 2 float switches

Description (see also page 187 or 188):
The pump is controlled by the liquid level in the pit.
• The pump is started when the float switch, pos. 1, registers
liquid.
• When the float switch, pos. 1, no longer registers liquid, the
stop delay (can be set) is activated. After expiration of the stop
delay, the pump is stopped.
• The upper float switch, pos. 2, activates the high-level alarm.
Warning
Before starting any work on pumps used to pump
liquids which could be constituted as being
hazardous to health, thorough cleaning/venting
of pumps, pits, etc. must be carried out
according to local regulations.
Before making any connections in the LC 108 or
work on pumps, pits, etc., it must be ensured that
the electricity supply has been switched off and
that it cannot be accidentally switched on.
8

4.1 Electrical connection

2 float switches, pages 187 and 188.
Warning
Before starting work on the system, switch off
the supply voltage and lock the mains switch in
position 0.
Any external voltage connected to the system
must be switched off before work is started.
Fig. A1 on page 187.
The figures show all electrical connections required to connect
the LC 108 for direct-on-line starting, 2 float switches.
Fig. A2 on page 188.
The figure shows all electrical connections required to connect
the LC 108 for star-delta starting, 2 float switches.
Warning
The LC 108 must be connected in accordance
with the rules and standards in force for the
application in question.
The operating voltage and frequency are marked on the controller
nameplate. Make sure that the controller is suitable for the
electricity supply on which it will be used.
All cables/wires must be fitted through the Pg cable entries and
gaskets (IP65).
Maximum back-up fuse is stated on the controller nameplate.
If required according to local regulations, an external mains
switch must be installed.
If the PTC resistance/thermal switch of the motor
Caution
is connected, the factory-fitted short-circuit
jumper must be removed (terminals T11-T21).
Single-phase motors must be connected to an external operating
capacitor and in certain cases also to a starting capacitor.
Further details can be found in the installation and operating
instructions for the pump in question.
Warning
Float switches or electrodes placed in an
explosion hazard area must be connected via an
EEx barrier, e.g. Grundfos number 96440300.
The EEx barrier must not be installed in the
explosion hazard area.
Equipment used in explosion hazard areas must
in each individual case have been approved for
this particular application. Furthermore, the
cables into the explosion hazard area must be
laid in accordance with local regulations.
Float switches of the same type as Grundfos
product number 96003332 or 96003695, i.e. float
switches with gold-plated contacts suitable for
Note
low voltages and currents (40 V/100 mA), must be
used. All EEx-approved float switches are also
suitable.
The float switches must be connected as NO contacts, i.e. brown
and black leads, when float switches, Grundfos product number
96003332 or 96003695, are used.
Key to the symbols in fig. A1 on page 187 and fig. A2 on
page 188:
Pos. Description
1 Float switch for start/stop of pump.
2 Float switch for high-level alarm.
Terminal
number
11-12
31-32