5
Explanantory Notes
– continued –
Function
The level switch NRS 1-8 is a two-channel unit provided with an automatic self-checking circuitry in
accordance with DIN VDE 0116, prEN 50156. The self-checking is effected periodically. During the
test the cable between electrode and level switch and the self-checking circuitry (redundancy) are
checked.
The output relays are not influenced by the internal tests.
The level switch can also be tested manually by pushing the button “TEST 1” to simulate a mal-
function in the level electrode.
The toggle switch “TEST 2 / INSPECTION” is designed for testing the function of the self-checking
routine by simulating a malfunction. The contact relays are of the normally closed type and will
automatically signal alarm condition in the event of a malfunction. The level switch can signal the
following three operating conditions:
n
Normal operation (correct water level in boiler)
n
Alarm (level in boiler too high)
n
Alarm (malfunction in level switch or level electrode)
A green LED indicates power supply. Two red LEDs signal an alarm in the event of high water level or
system malfunction.
The failure of one channel (loss of redundancy) is signalled by one red LED.
The equipment combination of electrode NRG 16-12, NRG 17-12 or NRG 19-12 and level switch
NRS 1-8 provides fail-safe protection against a first fault, i. e. the system will still continue to provide
the safety function even after the occurrence of a first fault.
System components
NRG 16-12
Level electrode
NRG 16-12
, PN 40
NRG 17-12
Level electrode
NRG 17-12
, PN 63
NRG 19-12
Level electrode
NRG 19-12
, PN 160
Design
NRS 1-8
Plug-in unit in plastic case for installation in control cabinets. Remove cover to access the terminals
in the housing base. Thanks to the code plug the equipment cannot be connected inadvertently to
wrong GESTRA equipment. The equipment may be snapped onto a 35 mm supporting rail or screwed
into position on a mounting panel.
