Systems For Parallel Operation With 3 Float Switches; Electrical Connection - Grundfos LCD 108 Installations- Und Bedienungsanleitung

Fig. 4
Figure 5 shows the terminals listed under positions 2 and 3.
Fig. 5
Key to the symbols in figures
Pos. Description
1 Module CU 212.
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
relays (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 the connection of pump 1 and 2.
9 Pg cable entries.
10 Earth bar ( PE).
Input for the PTC resistance/thermal switch of the motor
11
(T11-T21, T12-T22).
3 and 5:
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 for parallel operation with 3 float
switches
Description (see also page 142
The pumps are controlled by the liquid level in the pit.
• When the float switch, pos. 1, registers liquid, the first pump is
started.
• When the float switch, pos. 2, registers liquid, the next pump is
started.
• When the float switch, pos. 1, does not register any liquid, the
"stop delay" is initiated (can be set). After expiration of the
stop delay, both pumps are stopped.
• The pumps operate alternately.
The top float switch, pos. 3, 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 LCD 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.

4.1 Electrical connection

Parallel operation with 3 float switches, pages
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. 1 on page 142.
The figures show all electrical connections required to connect
the LCD 108 for direct-on-line starting, parallel operation with
3 float switches.
Fig. 2 on page 143.
The figure shows all electrical connections required to connect
the LCD 108 for star-delta starting, parallel operation with 3 float
switches.
Warning
The LCD 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.
or 143):
142 or 143.
7