Description
💧 Product Overview
The GESTRA NRS 1-50 is a water level limiter and level switch designed for monitoring low-water conditions in steam boilers and hot-water installations. It works together with compatible GESTRA NRG level electrodes to detect when the water level falls below the defined minimum level.
When a low-water condition is detected, the NRS 1-50 generates an alarm and can open the safety circuit to shut off the heating system after the configured response delay. The unit also provides signal outputs for external alarm indication.
The NRS 1-50 is available in configurations for one or two electrodes. The exact electrode arrangement should therefore be confirmed before ordering or replacement.
⚙️ Main Features
- 🔹 GESTRA NRS 1-50 water level limiter
- 🔹 Low-water level monitoring and protection
- 🔹 Designed for steam boiler and hot-water installations
- 🔹 Compatible with GESTRA NRG series level electrodes
- 🔹 24 V DC supply option
- 🔹 Optional 100–240 V AC supply version
- 🔹 Two electrode configuration available
- 🔹 Adjustable response sensitivity depending on version
- 🔹 Safety circuit with relay contacts
- 🔹 External alarm signal outputs
- 🔹 Diagnostic and test functions
- 🔹 Suitable for industrial boiler automation and marine applications
📊 Technical Datasheet
| Parameter | Specification |
|---|---|
| Brand | GESTRA |
| Model | NRS 1-50 |
| Product Type | Water Level Limiter / Level Switch |
| Main Application | Low-Water Level Protection |
| Compatible Electrodes | NRG 1…-50 / NRG 1…-11 / NRG 16-36, depending on configuration |
| Supply Voltage | 24 V DC ±20% or 100–240 V AC, depending on version |
| Power Consumption | Approx. 7 VA |
| Response Sensitivity | >0.5 to <1000 μS/cm or >10 to <10000 μS/cm, depending on version |
| Safety Circuit | 2 potential-free make contacts, 6 A at 250 V AC / 30 V DC |
| Dimensions | Approx. 100 × 74 × 120 mm |
| Weight | Approx. 0.5 kg |
The published specifications show a 24 V DC version as well as a 100–240 V AC version. The exact supply and sensitivity must be verified against the nameplate of the individual NRS 1-50 before replacement.
🏭 Application
The NRS 1-50 is primarily used as a safety-related water level limiter in:
- 🔥 Steam boiler systems
- 💧 Hot-water installations
- 🏭 Industrial boiler houses
- ⚓ Marine boiler systems
- 🚢 Shipboard steam and auxiliary systems
- ⚙️ Heating and process installations
- 🔧 Boiler control and protection systems
Its primary function is to prevent continued heating when the water level falls below the defined low-water limit.
🔌 System Integration
The NRS 1-50 works together with compatible level electrodes. Depending on the version, the controller can be configured for one or two electrodes.
For a two-electrode configuration, the GESTRA documentation specifies compatible NRG electrode types and provides dedicated electrode connections. The unit also has signal outputs for external alarm indication and a safety-circuit interface.
Before replacement:
- Confirm the complete NRS 1-50 model.
- Check whether the existing system uses one or two electrodes.
- Verify the installed NRG electrode type.
- Confirm the supply voltage from the nameplate.
- Record the existing terminal wiring.
- Check the external safety circuit and alarm connections.
- Verify the configured response sensitivity.
- Perform a functional test after installation.
🛠️ Installation & Maintenance
The NRS 1-50 is a safety-related component, so installation and testing should be performed by qualified personnel familiar with boiler-control systems.
Recommended maintenance includes:
- Inspect terminal connections regularly.
- Check for loose or oxidized wiring.
- Verify the supply voltage.
- Inspect connected level electrodes.
- Check the safety circuit for correct operation.
- Test the alarm outputs.
- Verify the diagnostic indicators.
- Keep the control cabinet dry and free from excessive contamination.
- Perform functional testing according to the applicable boiler maintenance procedure.
The published technical data specifies IP40 protection for the housing and IP20 for the terminal strip.
🔍 Troubleshooting
Low-water alarm occurs unexpectedly
Check the connected level electrodes, electrode wiring, water conductivity, and actual boiler water level before replacing the NRS 1-50.
The safety circuit does not operate correctly
Verify the external safety circuit, relay contacts, wiring, and fuse arrangement. The NRS 1-50 safety interlock itself must be implemented correctly in the external safety circuit where required.
Level electrode fault is indicated
Inspect the electrode, connecting cable, terminals, and grounding arrangement. A wiring fault can also cause an alarm condition.
The module has no power
Check the supply voltage, external fuse, terminal connections, and the exact electrical version of the NRS 1-50.
The replacement unit does not match the original wiring
Check whether the original system uses the one-electrode or two-electrode configuration. Different configurations require different wiring arrangements.
❓ Common Questions & Answers
Q: What is the GESTRA NRS 1-50?
A: It is a water level limiter and level switch used for low-water protection in steam boilers and hot-water installations.
Q: What electrodes can be used with the NRS 1-50?
A: Depending on the configuration, compatible GESTRA electrodes include NRG 1…-50, NRG 1…-11 and NRG 16-36.
Q: Does the NRS 1-50 use 24 V DC?
A: Yes. A 24 V DC version is specified. There is also a 100–240 V AC version, so the exact version must be confirmed before installation.
Q: What happens when the water level becomes too low?
A: The level switch generates an alarm and, when correctly integrated into the external safety circuit, can cause the heating system to be shut down.
Q: Is NRS 1-50 available for one and two electrodes?
A: Yes. GESTRA documentation covers both one-electrode and two-electrode configurations.
Q: What is the approximate weight?
A: The published technical data gives approximately 0.5 kg.
Q: Can the NRS 1-50 be used in marine boiler systems?
A: GESTRA documentation includes marine-use information for the NRS 1-50, including a longer response delay specified for marine use.
🔧 Recommended GESTRA Models
- GESTRA NRS 1-50 Water Level Switch
- GESTRA NRS 1-51 High-Level Alarm Switch
- GESTRA NRS 1-52 Level Switch
- GESTRA NRS 1-53 Level Switch
- GESTRA NRS 1-56 Level Switch
- GESTRA NRG 16-50 Level Electrode
- GESTRA NRG 17-50 Level Electrode
- GESTRA NRG 19-50 Level Electrode
- GESTRA NRG 111-50 Level Electrode
- GESTRA SRL 6-50 Logic Unit
📌 Replacement Note
For replacement purchasing, identify the unit as GESTRA NRS 1-50 Water Level Switch / Water Level Limiter and verify the complete electrical version, electrode configuration, response sensitivity, and nameplate information.
Because the NRS 1-50 is used in safety-related boiler water-level protection, compatibility should be confirmed before installation rather than treating every NRS 1-50 variant as electrically interchangeable.
