4NRS 1-50 For TWO Electrodes - Installation Instructions - 818953-08
Important Notes
Usage for the intended purpose
The level switch NRS 1-50 is used in conjunction with level electrodes NRG 1...-.. to limit the water
level in steam boilers and (pressurised) hot-water plants.
Water level limiters switch off the heating when the water level falls below the set minimum level
(low water).
Depending on the specified directives or standards, the level switch NRS 1-50 is intended to be used in
combination with the following level electrodes:
Level electrode NRG 1...-..
Functional safety acces-
sory to IEC 61508 SIL 3
NRG 16-50 NRG 17-50 NRG 19-50 NRG 111-50
Functional safety acces-
sory to VdTÜV Bulletin 100
NRG 16-50
NRG 16-11
NRG 17-50
NRG 17-11
NRG 19-50
NRG 19-11
NRG 111-50
NRG 111-11
NRG 16-36
Marine applications
e. g. DNV LR Directives
NRG 16-50S NRG 16-11S NRG 16-38S NRG 16-39S
Function
The level switch NRS 1-50 is designed for different electrical conductivities of the boiler water and for
connecting one or two level electrodes.
See section Schematic representations of arrangements.
When the water level falls below the low level the level electrodes are exposed and a low level alarm is
triggered in the level switch. This switchpoint is determined by the length of the electrode rod
(level electrode NRG 1...-50, NRG 1...-11, NRG 16-36).
After the de-energizing delay has elapsed, the two output contacts of the level switch will open the
safety circuit for the heating. The switching-off of the heating is interlocked in the external safety
circuit and can only be deactivated when the level electrode enters the water again.
In addition, two signal outputs for external signalling devices close instantaneously.
An alarm will also be raised if a malfunction occurs in the level electrode and/or the electrical
connection.
If the level electrode is installed in an isolatable level pot outside the boiler, make sure that the
connecting lines are rinsed regularly. During the rinsing process the water level cannot be measured
in the level pot for 5 minutes. The level switch therefore bypasses the level electrode and monitors the
rinsing and bypass time (standby input, controlled by the logic unit SRL 6-50).
If the connecting lines for steam ≥ 40 mm and water ≥ 100 mm, the installation is considered to be
internal. In this case the rinsing processes do not have to be monitored.
An automatic self-testing routine monitors the safety functions in the level switch and the level
electrodes. In the event of a malfunction the safety circuit opens instantaneously and switches the
heating off.
Alarm and errror messages are indicated by LEDs and a signal output for each level electrode is
energized without delay.
An alarm can be simulated by pressing the test button.
