Description
📝 Product Overview
The Gestra NRS 1-50 is a high-performance, digital level switch designed for use in conjunction with Gestra level electrodes (such as the NRG 16-50) to function as a high-reliability water level limiter. Engineered primarily for steam boilers, hot-water plants, and pressure vessels, this unit operates on the conductive measuring principle to provide dual-channel safety protection against low water (LW) or high water (HW) critical conditions, complying with strict SIL 3 safety standards.
⚙️ Technical Specifications
- 📐 Dimensions: 100 mm x 73 mm x 118 mm (Standard DIN-rail module)
- ⚖️ Weight: 0.55 kg
- 🌍 Country of Origin: Germany
🏭 Applications
- Steam boiler high/low water level safety limiting
- Pressurized hot-water generation plants
- Industrial condensate tank monitoring
- Process industry liquid level safety interlock loops (SIL 3)
🛠️ Usage Instructions
- Ensure that the electrode resistance configuration matches the specific conductivity of your boiler water line before commissioning.
- Use the front-panel “Test” and “Reset” buttons to manually execute mandatory safety loop function checks during routine boiler inspections.
- Clean the associated level probe tips periodically to remove scale buildup, which can cause false insulating profiles.
- Do not bypass the internal safety relay outputs during normal boiler operating hours.
🔧 Mechanical Installation Requirements
- Fixing Method: Snaps directly onto a standard 35 mm DIN rail (DIN EN 50022) or can be screw-mounted onto a control panel backplate using an adapter.
- Space Clearance: Leave at least 20 mm of clear horizontal space between the NRS 1-50 and adjacent thermal-generating equipment inside the cabinet.
- Heat Dissipation: Ensure the control cabinet is well-ventilated; the ambient air temperature immediately surrounding the housing must not exceed 55°C.
🔌 Electrical Wiring Guide
- Terminal Definitions: * Terminals 1, 2: 24V AC/DC or 115V/230V AC Supply Power (model dependent)
- Terminals 3, 4: Signaling input from the conductive level electrode
- Terminals 5, 6, 7: Safety Output Relay 1 (Volt-free, NC/COM/NO)
- Terminals 8, 9, 10: Safety Output Relay 2 (Volt-free, NC/COM/NO)
- Terminal PE: Functional earth reference point
- Wire Gauge: Implement 0.75 mm² to 1.5 mm² (18 to 16 AWG) flexible, multi-strand copper wire for control signals, and up to 2.5 mm² (14 AWG) for power supply networks.
- Grounding Norms: The screen of the electrode connection cable must be securely bonded to the local panel earth rail, and the boiler shell must be tied to a low-resistance structural earth point to ensure an accurate conductive circuit return path.
📡 Communication Configuration
- IP Address: Not applicable. This unit operates as a discrete safety relay component and does not feature an onboard Ethernet controller stack.
- Station ID: Not applicable. Device grouping or loop mapping is configured physically via point-to-point hardwiring rather than software addressing nodes.
- Baud Rate: Not applicable. Internal signal evaluation features a fixed response delay (typically 1 to 3 seconds) to prevent false tripping caused by wave movement inside the boiler drum.
❓ Frequently Asked Questions (Q&A)
- Q: Why is the “Fault” LED illuminated even though the boiler water level is correct?
- A: This usually points to an open or short circuit in the wiring loop running to the level electrode, or excessive scale contamination on the electrode insulation sleeve.
- Q: Does the NRS 1-50 automatically clear its alarm state when water returns to safe levels?
- A: No, as a certified safety level limiter, it features a non-volatile lock-out mechanism. Once tripped, it requires a manual press of the local or remote “Reset” button after normal operating levels are restored.
- Q: Can I use a standard unshielded cable to connect the electrode to the level switch?
- A: No, it is highly recommended to use a shielded cable for the electrode run to protect the low-voltage, high-impedance conductive signal path from electromagnetic interference caused by nearby motor cables.
