Z728 zener barrier ratings, grounding and hazardous-area loop checks
Pepperl+Fuchs Z728 is a one-channel positive-polarity zener barrier intended to limit energy transferred from the safe area into an intrinsically safe circuit. Unlike a galvanically isolated module, a zener barrier depends on the correct installation and earthing arrangement. The shared montage is only a category image; confirm the physical label and circuit before purchasing Z728.
Key technical data
| Technical item | Verified value / selection note |
|---|---|
| Exact type | Z728 |
| Barrier form | Single-channel positive-polarity DC zener barrier |
| Working voltage | 26.5 V at 10 µA in the product summary |
| Nominal resistance | 300 Ω |
| Series resistance | Maximum 327 Ω |
| Fuse rating | 50 mA |
| Connection | Hazardous-area terminals 1 and 2; safe-area terminals 7 and 8 |
| Mounting | 35 mm DIN rail; verify required intrinsic-safety earth |
How the barrier protects the loop
In normal use Z728 passes the permitted signal through its series resistance. Under a defined overvoltage fault, its zener elements conduct and the protective fuse can open. This behavior does not remove the need for a compliant earth and a documented intrinsic-safety system calculation. Keep the exact polarity and terminal assignment visible on the wiring drawing.
Electrical selection
Match Z728 to the connected device's allowable voltage, current, power, capacitance and inductance limits using the current approval documents. The 300 Ω nominal resistance also affects available voltage at the field device. Do not substitute a high-power or fused variant based on the Z728 prefix alone; resistance and fuse values differ.
Grounding and installation
Follow the manufacturer's mounting and earthing instructions and site hazardous-area rules when fitting Z728 on a DIN rail. Keep safe-area and hazardous-area wiring segregated, check conductor identification and inspect terminal tightness. A failed barrier or blown fuse should prompt a cause investigation before replacing the device.
Verification and sourcing
Before return to service, confirm continuity, loop operation, protective earth, signal level and the installation's approved documentation. For Z728 enquiries, provide the full label, zone/division, connected field device, circuit parameters, rail arrangement and required certificate set. Document any proposed alternative for engineering approval.
Related model references
Z728.F and Z728.H are related designations, not default replacements; fuse arrangement and resistance may differ.
- Z728.F
- Z728.H
Manufacturer documentation
For Z728, check the latest Pepperl+Fuchs datasheet and the complete label against the installed device before final selection or commissioning.
Additional visually similar Pepperl+Fuchs model designations
These complete codes are collected for model search and identification because their printed designations look similar. They may represent different products, electrical interfaces, mechanical sizes or approvals. They are not declared interchangeable with Z728. Verify each complete designation against the manufacturer record and the installed equipment before ordering.
- Z715
- Z722 71784
- Z728 71788
- Z764
- Z765
- Z778
- Z779
- Z779.F
- Z779.H
- Z779.H 71976
- Z787
- Z787.F
- Z787.H.F
- Z787.H.F 072179
- Z788
- Z896
- Z896 71809
- Z928 71857
- Z954
- Z960
- Z961
- Z961.H
- Z964
- Z966
