GESTRA NRS 1-50

ONE/TWO Electrodes Level Switch

GESTRA NRS 1-50 Level Switch

GESTRA NRS 1-50 ONE/TWO Electrodes Level Switch
The GESTRA NRS 1-50 is a high-performance level switch controller designed to monitor and control water levels in steam boilers and pressurized vessels. Working in conjunction with one or two electrodes, it acts as a safety cut-out device to prevent low water conditions, thereby protecting boiler systems from potential damage or hazards.

Whether for industrial steam systems, HVAC boilers, or process steam applications, the NRS 1-50 ensures fail-safe operation, full compliance with EN standards, and reliable automation.

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 directives listed below the level switch NRS 1-50 can be used in combination with the following level electrodes:

Directive Level electrode type
Functional safety accessory to

IEC 61508 SIL 3

NRG 16-50, NRG 17-50

NRG 19-50, NRG 111-50

Functional safety accessory to VdTÜV Bulletin 100 NRG 16-50, NRG 17-50

NRG 19-50, NRG 111-50, NRG 16-36

NRG 16-11, NRG 17-11

NRG 19-11, 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

The level switch NRS 1-50 is designed for different electrical conductivities of the boiler water and for connecting one or two level electrodes.
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 tip.
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 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 a 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 electrode. 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 an alarm can be simulated by pressing the test button

Supply voltage

24 VDC +/– 20 %, 0.3 A

100 – 240 VAC + 10/– 15 %, 47 – 63 Hz, 0.2 A (optional)

External fuse

M 0.5 A (semi-delay) Power consumption 7 VA

Sensitvity of response

(Electrical conductivity of water at 25 °C)

> 0.5 … < 1000 μS/cm or > 10 … < 10000 μS/cm

Electrical connection of level electrode

To connect the level electrodes please use:

  • For level switch NRS 1-50 with response sensitivity 10 μS: Screened multi-core control cable, conductor size 0.5 mm2, e.g. LiYCY 4 x 0.5 mm2, max. length 100 m.
  • For level switch NRS 1-50 with response sensitivity 5 μS: Double-screened multi-core low-capacitance data cable, min. conductor size 0.5 mm2, Li2YCY PiMF 2 x 2 x 0.5 mm2, max. length 30 m.

Stand-by input

2 volt-free inputs, 24 V DC, for monitoring the purging and bypass time. Max. bypass time: 5 minutes.

Wiring: control cable 2 x 0.5 mm2.

Safety circuit

2 volt-free make contacts,
6 A 250 V AC / 30 V DC cos ϕ = 1.
Delay of response: 3 seconds, 15 sec. for marine applications.
Provide inductive loads with RC combinations according to manufacturer‘s specification to ensure interference suppression.

Signal output

2 volt-free outputs for instantaneous external signalling, 24 V DC, max. 100 mA (semiconductor output).

Wiring: control cable 2 x 0.5 mm2.

Indicators and adjustors

  • buttons for test and diagnosis, 4 red/green LEDs for indicating the operating mode and alarm.
  • red LEDs for fault diagnosis, 2 two-pole code switches for setting the number of electrodes.

Housing

Housing material: base: polycarbonte, black; front: poly- carbonate, grey. Terminal strips separately detachable Fixing of housing: Mounting clip on supporting rail TH 35, EN 60715.

The GESTRA NRS 1-50 Water Level Limiter is one of the most trusted and advanced level monitoring and safety devices used in modern industrial steam and boiler systems. Engineered for maximum operational safety, precise water level detection, and seamless compatibility, this level switch ensures reliable protection for critical equipment across a wide range of applications.

If you are looking for a certified, high-performance water level limiter for one or two electrode configurations, the GESTRA NRS 1-50 is the gold standard.

The GESTRA NRS 1-50 is an electronic evaluation unit designed for water level limiting and control in conjunction with GESTRA level electrodes. It monitors the water level in steam boilers and other pressurized systems, triggering a safe shutdown when the level reaches a critical point.

This makes the NRS 1-50 a crucial safety component for operations that demand absolute reliability and strict compliance with international safety standards.

Compatible with ONE or TWO Electrodes

Supports both single and dual electrode systems for maximum application flexibility.

High-Sensitivity Water Level Detection

Ensures highly accurate monitoring of MIN/MAX water levels in steam boilers.

Certified Safety Functionality

Complies with leading global safety standards for boiler operations.

Fast Shutdown Response

Instant activation of alarms and protective shutdowns during unsafe conditions.

LED Status Indicators

Clear visual indicators for operating status, switching conditions, and fault alarms.

Long Service Life

Manufactured with industrial-grade components for extended system reliability.

The GESTRA NRS 1-50 stands out because it provides far more than simple water level switching—it ensures engineered safety, operational continuity, and protection for high-value machinery.

Unmatched Accuracy and Sensitivity

Designed to detect even slight deviations in water level with pinpoint precision.

Ideal for High-Pressure and High-Temperature Systems

Engineered specifically for demanding boiler and steam operations.

Reduced Downtime & Maintenance Cost

A trusted device backed by proven GESTRA engineering.

Perfect Integration with GESTRA Boiler Automation Systems

Works seamlessly with GESTRA electrodes and control panels.

The GESTRA NRS 1-50 Water Level Limiter is widely used in:

  • Steam boilers

  • High-pressure boiler plants

  • Thermal process systems

  • Chemical and petrochemical plants

  • Power generation plants

  • Industrial steam and condensate systems

  • Heating and hot-water installations

Its precision and reliability make it essential for industries prioritizing safety and optimal performance.

  • Advanced electronic evaluation circuitry

  • Immediate response to critical water level changes

  • Immunity to electrical noise and electromagnetic interference

  • Robust design suited for 24/7 industrial operation

  • Stable and consistent performance under extreme conditions

  • Suitable for both compact and large-scale boiler systems

We provide 100% original GESTRA products, competitive pricing, fast delivery, and technical support.

Whether you need single units, bulk orders, or replacement/upgrade guidance, our team is ready to assist.

👉 Contact us today for the best offer on the GESTRA NRS 1-50 Water Level Limiter!

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