20
NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual -
850694-00
A signal output for connecting further external signaling devices, maximum load 100 mA, is allo-
cated 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 outputs
(terminals 20, 21 and 29, 30) close without a delay.
Connecting the signal output
Electrical connection
Danger
■
A safety power supply unit (SELV / PELV / CLASS2) must be used to supply the
NRS 1-50 level switch with 24 V DC. This must provide a level of isolation against
dangerous contact voltages that at least meets the requirements for double or
reinforced insulation in accordance with UL 60730-1 (protective electrical
isolation).
Attention
■
Provide the NRS 1-50 level switch with an external 0.5A fuse.
■
Connect the shields to terminals 5 and 13 and to the central grounding point
(CGP)
in the control cabinet.
■
Provide the safety 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.
