Description; Function; System Components; Design - Gestra NRS 1-9 Betriebsanleitung

Explanatory Notes

Description

Self-monitoring water level controller & limiter with automatic self-testing routine designed for use
in conjunction with level electrode NRG 6-6. This equipment combination controls the water level,
detects the max. allowable water level (high level alarm) and the min. allowable water level (low level
alarm). Application in compliance with the German regulations for use in steam and hot-water plants
according to TRD 60 and TRD 604, sheets  and .

Function

The switching controller NRS -9 features a two channel circuit and is provided with a self-monitoring
and routine testing function in accordance with DIN 576/VDE 06. The two channels are designed
to monitor the operation of each other (redundancy). The periodic self-checking logic unit checks the
integrity of the cable between the electrode and the switching controller, and the two channel circuits
for malfunction.
Unless it finds a fault, this internal test does not interfere with the output contacts of the controller and
therefore the boiler operation is not interrupted.
A manual test push button is also provided. When the push button "TEST " is pressed, it simulates a
fault in the electrode. There is also a toggle switch "TEST /Inspection" for checking the function of the
self-checking circuitry. The output contact relays of the switching controller are of the normally closed
type and will therefore signal alarm condition in the event of mains failure.
The switching controller can signal the following four operating conditions:
Normal operation (feedwater control)
n
Alarm (high water level)
n
Alarm (low water level)
n
Alarm (fault in switching controller or level electrode)
n
A green LED indicates power ON. Low water level alarm or malfunction of the low water level limiter
system is indicated by the two red LEDs. The failure of one channel (loss of redundancy) is signalled by
the lighting up of one red LED. The other green LED indicates feedwater pump is running. High water
level alarm is signalled by another red LED.
The use of SMART combination electrode NRG 6-6 in conjunction with switching controller NRS -9
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36
Level electrode NRG 1636, PN 40

Design

NRS 19
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 5 mm supporting rail or screwed into position
on a mounting panel.
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