Flowserve NRS 1-50 For TWO Electrodes User Manual download pdf (Page 4)

Application

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...-..

PED Pressure

Equipment Directive

97/23/EC +

Functional Safety IEC

61508 SIL 3

NRG 16-50 NRG 17-50 NRG 19-50 NRG 111-50 NRG 16-36

VdTÜV Bulletin

“Wasserstand 100”

(= Water Level 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

GL/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 on page 16.

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.

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.

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Flowserve NRS 1-50 For TWO Electrodes User Manual Page 4

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