Pepperl+Fuchs Z787.H Safe Zener Barrier | Positive Polarity Series

Global PLC Spare HUB Insight

The Z787.H by Pepperl+Fuchs stands as a robust defense mechanism for hazardous zone instrumentation. As a high-power Zener barrier, it features a lower internal serial resistance than standard models, allowing for higher voltage delivery to field-side devices without sacrificing intrinsic safety. Its integrated diode return mechanism is particularly clever; it effectively nullifies current flow into the hazardous area, simplifying complex safety calculations to a zero-current assumption. We recommend the Z787.H for process-critical loops where maintaining high signal integrity over long distances is as vital as the safety certification itself.

Technical Performance Profile

• Manufacturer: Pepperl+Fuchs
• Model: Z787.H
• Module Type: High-Power Zener Barrier (2-Channel)
• Polarity: DC Version, Positive
• Working Voltage: 26.5 V (at 10 µA)
• Series Resistance: Max. 250 Ω (Min. 235 Ω)
• Fuse Rating: 80 mA
• Mounting: 35 mm DIN Rail (EN 60715)
• Protection: IP20 (Modular terminal housing)
• Dimensions: 12.5 mm x 115 mm x 116 mm

Safety & Diagnostic Capabilities

• Intrinsic Safety Assurance: Acts as a fail-safe gate, preventing high-energy surges from entering explosive atmospheres.
• Diode Return Logic: Incorporates specialized diodes to prevent reverse current, streamlining safety compliance documentation.
• High-Power Efficiency: Optimized internal resistance minimizes voltage drops, making it ideal for devices that require stable operating voltage in the field.
• Automated Fault Response: In the event of a critical over-voltage fault, the internal circuitry conducts and safely triggers the 80 mA fuse, isolating the loop instantly.

Typical Applications & Suitability

• Process Automation: Perfect for reading signals from transmitters and sensors located in ATEX/IECEx rated zones.
• Petrochemical Plants: Used extensively for monitoring valve positions and pressure readings where high-power signals are necessary.
• Explosive Environments: Certified for Gas, Dust, and Mining ([Ex ia Ga] IIC, [Ex ia Da] IIIC, [Ex ia Ma] I).
• System Retrofits: Its slim, modular design makes it suitable for upgrading existing control cabinets with limited rail space.

Logistics & Guarantee

• Global Shipping: Fast transit via FedEx, UPS, or DHL.
• Dispatch Speed: Standard processing in 24 to 48 hours.
• Performance Warranty: 12-month full coverage against manufacturing defects.
• Package Contents: 1x Z787.H Zener Barrier and technical compliance documentation.

Professional FAQ

Question: How does the "diode return" feature simplify my safety loop calculations?

Answer: It eliminates the need to account for current flowing back from the safe area into the hazardous area during safety calculations, setting that specific parameter to zero.

Question: Can I use the Z787.H in a circuit that requires negative polarity?

Answer: No, the Z787.H is strictly a positive polarity barrier; you must select a model designed for negative polarity if your application requires it.

Question: What is the benefit of the "high power" design?

Answer: It offers a lower series resistance compared to standard barriers, which ensures more of your loop voltage actually reaches the field device, preventing signal attenuation.

Question: What should I check if the fuse blows on one channel?

Answer: A blown fuse indicates that the breakdown voltage of the internal Zener diodes was exceeded, typically caused by a short circuit or high-voltage fault in the safe-area wiring.

Question: Is it possible to mount these barriers directly onto existing DIN rails?

Answer: Yes, the Z787.H is designed for snap-on mounting to standard 35 mm DIN rails, ensuring quick integration into existing industrial cabinets.

Procurement Advisory

• Polarity Check: Always confirm that the anode of your Zener diode loop is indeed grounded, as this barrier is specifically engineered for positive polarity systems.
• Space Planning: With a slim 12.5 mm width, you can significantly increase channel density in your panels compared to wider barrier types.
• Safety Compliance: Always refer to your specific loop certificate and Control Drawing (e.g., 116-0118 for FM) before finalizing your wiring design.

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