Flowserve NRS 1-7 - Manual (Page 5)

5
Explanatory Notes
– continued –
Function
The level switch NRS 1-7 is a two-channel unit provided with an automatic self-checking circuitry
in accordance with DIN VDE 0116 prEN 50156 (directives for protection circuits). The self-checking
is effected periodically. The test includes the checking of the cable between electrode and level
switch and of the self-checking circuitry (redundancy). The output relays are not influenced by the
internal tests.
In addition to this self-checking routine, the level switch can also be tested manually by pushing
the button “Test 1”, simulating a defect in the electrode. The test switch “Test 2/Inspection” is
provided for checking the function of the checking circuitry.
As the circuit of the relay contacts of the level switch is normally closed, alarm will also be
signalled in the event of a mains failure.
The level switch can signal the following three operating conditions:
■ Normal operation (correct level)
■ Alarm (low level)
■ Alarm (malfunction in level switch or electrode)
The green LED indicates power supply. The low level or malfunction alarm is indicated by two red
LEDs. The failure of one channel (loss of redundancy) is signalled by the illumination of a single red
LED.
The combination of electrode NRG 16-11, NRG 16-11S, NRG 17-11, NRG 19-11, NRG 111-11 and
level switch NRS 1-7 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 16-11
Level electrode NRG 16-11, PN 40
NRG 16-11S
Level electrode NRG 16-11S, PN 40, for marine applications
NRG 17-11
Level electrode NRG 17-11, PN 63
NRG 19-11
Level electrode NRG 19-11, PN 160
NRG 111-11
Level electrode NRG 111-11, PN 320
Design
NRS 1-7
Plug-in unit in plastic case for installation in control cabinets. The terminals in the case are
accessible after loosening two screws and unplugging the unit from its base.
To avoid confusion with other plug-in units of the GESTRA range, inserts are fitted in the bases so
that only the correct unit may be plugged into each base.
The plug-in unit may be snapped onto a 35 mm supporting rail or screwed into position on a
mounting panel.