20
NRS 1-51 - USA - Installation & Operating Manual -
850695-00
Electrical connection
Danger
■
A safety power supply unit (SELV / PELV / CLASS2) must be used to supply
the NRS 1-51 level switch with 24 V DC. This must provide a level of isolation
against dangerous contact voltages that at least meets the requirements for dou-
ble or reinforced insulation in accordance with UL 60730-1 (protective electrical
isolation).
Attention
■
Provide the NRS 1-51 level switch with an external 0.5A fuse.
■
Connect the shields to terminal 5 and to the central grounding point
(CGP)
in the
control cabinet.
■
Provide the control circuit with a slow blow T1A fuse to protect the switching
contacts.
■
Switching off inductive loads produces surges that can have a major adverse
effect on open and closed-loop control systems. Connected inductive loads must
therefore have interference suppression (RC combination) as specified by the
manufacturer.
■
Connect terminals 24 and 26 with a wire jumper.
■
Route the connecting cables to the level electrodes and the logic unit separately
from power lines.
■
Do not use unused terminals as support terminals
■
If, despite the necessary measures being taken, one of the signaling outputs
is activated when a relay closes (terminals 23, 24 and 26, 27), there may be a
dangerous second fault. Check the equipment and replace if necessary.
An external signaling device, maximum load 100 mA, is allocated to each monitoring channel in
the level switch. For connection, please use a control cable, e.g., 2 x AWG20 (0.5 mm
2
). In the
event of alarm and fault indications, the signal output (terminals 20, 21 / 29, 30) closes without a
delay.
Connecting the signal output
