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NRS 1-51 - USA - Installation & Operating Manual -
850695-00
The NRS 1-51 level switch is designed for different boiler water conductivities and for the con-
nection of a single level electrode.
When the water exceeds the high water level, the level electrode is immersed and an alarm is
triggered in the level switch. This switchpoint is determined by the length of the electrode exten-
sion (level electrode NRG 1...-51).
When the off delay has elapsed, the two output contacts of the level switch open the control
circuit, e.g., for the feedwater supply. If the feedwater cut-off is interlocked in an external control
circuit, this interlock can only be deactivated once more when the level electrode is exposed. In
addition, the signal contact for external signaling devices closes without a delay.
An alarm is also triggered if faults occur in the level electrode and/or the electrical connection.
If the level electrode is installed in a level pot outside the boiler, make sure the connection pipes
are sufficiently large.
The manufacturer recommends connection pipes of ≥ 1.57 in (40 mm) for steam and ≥ 3.94 in
(100 mm) for water. If smaller connection pipes or fittings are used, these shall not be smaller
than 1-inch NPS. The level pot must have a suitable flushing device at its lowest point. This
device flushes the connection pipes to the boiler.
No shut-off valves of any type shall be placed in the piping between the boiler and the high water
cut-off.
An automatic self-test monitors the safety functions in the level switch. In the event of a fault, the
control circuit opens without a delay and may switch the heating off, for example.
Alarm and fault indications are displayed by LEDs, and a signal output is also actuated without a
delay.
An alarm can be simulated by pressing a button.
Function
