GESTRA Boiler Level Control — Trusted Worldwide
GESTRA (part of the Flowserve group) has been manufacturing boiler water level control equipment for over a century. Their NRG electrode probe and NRS controller systems are the industry benchmark for steam boiler level management in Europe and globally — combining proven conductivity sensing with robust, fail-safe electronic control.
PureSys India supplies GESTRA NRS and NRG level control systems. Visit our GESTRA brand page or boiler equipment section.
Understanding the GESTRA System: NRG + NRS
GESTRA’s level control system is a two-part arrangement:
- NRG series = Electrodes (sensors) — installed in the boiler shell or external chamber; detect water level by electrical conductivity
- NRS series = Controllers (electronics) — analyse signals from NRG electrodes and provide pump control outputs, alarm relays, and safety shutdowns
NRG Electrode Series — The Sensing Element
NRG 16 Series — Conductive Electrodes (Most Common)
The NRG 16 series are the standard conductive electrodes for industrial steam boilers. They operate on the principle that boiler water completes an electrical circuit when it contacts the electrode tip.
- NRG 16-4 / 16-36 / 16-52: Multi-tip electrodes providing several switchpoints (e.g., low water alarm, pump ON, pump OFF, high water alarm) from a single electrode installation. The electrode rod is cut to length to set switchpoints.
- NRG 16-50: Specially designed for use with NRS 1-50 safety limiters — provides high-integrity low-water protection
- Pressure ratings: PN 40 to PN 160 depending on model
- Installation: Direct-mounted in boiler shell or in external level pot with isolation valve
- Protection tube: Required when direct-mounted in boiler to shield from turbulent water and provide accurate level sensing
NRG 17 / 19 Series — High-Integrity Safety Electrodes
The NRG 17-50 and NRG 19-50 are high-integrity electrodes designed specifically for failsafe low-water limiter duty:
- Type-approved to VdTÜV Bulletin “Wasserstand 100” (Water Level 100) — the German standard for boiler level safety systems
- Used with NRS 1-50 safety limiters for automatic boiler shutdown on low water
- Independent installation from the control electrode — mandatory separate low-water protection
NRG 26 Series — Capacitance Electrodes for Continuous Monitoring
The NRG 26-21 and NRG 26-40 are capacitance-based electrodes that provide a continuous analogue level signal (4–20 mA output via the NRS 2-40 controller):
- Continuous level measurement — not just discrete switching points
- Suitable for modulating feedwater control applications
- Adjustable switchpoints via the NRS 2 controller (no rod cutting required)
- Can be used in low-conductivity water where conductive electrodes are unsuitable
NRS Controller Series — The Brain of the System
NRS 1 Series — Level Switches / Safety Limiters
The NRS 1 series controllers work with NRG 16 and NRG 17/19 conductive electrodes to provide switching and safety functions:
- NRS 1-40: Self-monitoring low-water level limiter — automatically shuts down the boiler burner if water falls below the minimum safe level. Self-monitoring circuitry continuously checks electrode and wiring integrity.
- NRS 1-50: Water level limiter used with NRG 16-50, NRG 17-50, or NRG 19-50 electrodes. Provides failsafe boiler shutdown on low water — type-approved to VdTÜV standards. Standard equipment for attended and unattended boiler operation in Europe.
- NRS 1-6: Multi-function level controller providing pump ON/OFF control plus high and low level alarms from a single NRG electrode — suitable for general boiler water level management.
NRS 2 Series — Advanced Controllers with Analogue Output
The NRS 2 series work with NRG 26 capacitance electrodes for continuous level monitoring and modulating control:
- NRS 2-40: Controller for use with NRG 26-40 capacitance electrode. Provides multiple adjustable switchpoints, pump control outputs, 4–20 mA level transmitter output for SCADA/BMS, and high/low alarms.
- NRS 2-4: Electronic amplifier for use with NRG 29/NRG 211 capacitive electrodes in demanding applications requiring precise continuous level measurement.
GESTRA Level Control System Configurations
| Application | Electrode | Controller | Function |
|---|---|---|---|
| Low water safety limiter (attended) | NRG 16-50 | NRS 1-50 | Burner shutdown on low water |
| Low water safety limiter (unattended) | NRG 17-50 or 19-50 | NRS 1-50 | High-integrity failsafe shutdown |
| General level control + alarms | NRG 16-4 or 16-36 | NRS 1-6 | Pump control + 2 alarms |
| Continuous modulating control | NRG 26-40 | NRS 2-40 | 4-20mA output + adjustable setpoints |
| Low-conductivity / DM water | NRG 26-21 | NRS 2-40 | Capacitance-based level control |
Installation Notes
- NRG electrodes must be installed with a protection tube when direct-mounted in the boiler shell — to shield from turbulent boiler water and steam bubbles that could cause false readings
- External level pots provide a calmer environment and allow electrode maintenance without taking the boiler offline
- Shielded cables are required between electrodes and controllers to prevent electromagnetic interference
- Separate independent installation of safety (low-water) and control electrodes is mandatory under most boiler standards
- NRS 1-50 systems require periodic functional testing (typically monthly) — a test switch is built into the controller
Compliance
GESTRA NRS 1-50 and NRG 17/19 systems are type-approved to VdTÜV Bulletin “Wasserstand 100” — meeting the German TRD (Technical Rules for Steam Boilers) requirements. Equivalent compliance with EN 12953 and EN 12952 boiler standards. Accepted by IBR-certified inspectors across India.
PureSys India — GESTRA Level Control Supply
We supply GESTRA NRS controllers, NRG electrodes, level pots, and complete level control panel assemblies for Indian boiler installations. Our engineers can design a complete level control system to IBR compliance requirements.
Contact PureSys India or explore our boiler equipment range and GESTRA brand page.