11
NRS 1-50 For TWO electrodes - USA - Installation & Operating Manual -
850694-00
Function
The NRS 1-50 level switch is designed for boiler water conductivities of >=10 µS and for the
connection of two or one level electrode(s).
If the water falls below the minimum level, the level electrodes are exposed and an alarm is
triggered in the level switch. This switchpoint is determined by the length of the electrode
extension (level electrode NRG 1...-50).
When the off delay has elapsed, the two output contacts of the level switch open the safety circuit
for heating. The heating cut-off is interlocked in the external safety circuit and this interlock can
only be deactivated again when the level electrode is immersed once more. The NRS 1-50 level
switch must be used in combination with an external manual reset when used as a protective
device per ASME CSD-1
In addition, two signal contacts for external signaling devices close without a delay. An alarm is
also triggered if faults occur in a 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 de-
vice flushes the connection pipes to the boiler and enables the function of the water level limiter
to be tested. No shut-off valves of any type shall be placed in the piping between the boiler and
the low water cutoff.
An automatic self-test monitors the safety functions in the level switch and the level electrodes. In
the event of a fault, the safety circuit opens without a delay and switches the heating off.
Alarm and fault indications are displayed by LEDs, and furthermore a signal output is actuated
without delay for each level electrode. An alarm can be simulated by pressing a button.
