Description
Honeywell 8939-HN | Multimode Fiber Optic Extender | Series 8 Remote I/O
Key Technical Specifications
| Parameter | Specification |
|---|---|
| Manufacturer | Honeywell |
| Model | 8939-HN |
| Product Type | Multimode Fiber Optic Extender IOTA |
| System | Honeywell Series 8 I/O |
| Application | S8 I/O Extension |
| Electrical Interfaces | 2 × combo cable interfaces |
| Fiber Type | Multimode |
| Typical Fiber | 62.5/125 µm |
| Supply Voltage | 24 VDC |
| Typical Power Consumption | 3 W |
| Electrical Isolation | 2,500 VDC |
| Operating Temperature | -20 to +60°C |
| Storage Temperature | -40 to +85°C |
| Relative Humidity | 5–95%, non-condensing |
| Approximate Weight | 0.1 kg |
Available hardware references identify 8939-HN as a Multi-Mode Fiber Optic Extender IOTA for Honeywell Series 8 I/O extension, with two combo cable interfaces. Published technical listings also specify 24 VDC power, approximately 3 W typical consumption, 62.5/125 µm multimode fiber, and 2,500 VDC isolation.
Product Introduction
The Honeywell 8939-HN is a multimode fiber-optic extender IOTA used in Honeywell Series 8 I/O architectures. Its purpose is to extend the I/O communication path between the control-system side and remote Series 8 I/O equipment, allowing I/O installations to be positioned farther from the primary controller cabinet.
This is a communication-interface device, not an analog or digital I/O channel module. That distinction matters during troubleshooting: a loss of communication affecting an entire remote I/O section should lead engineers to inspect the 8939-HN, associated combo cables, fiber path, connectors, power supply, and remote I/O hardware before replacing individual I/O modules.
8939-HN
Application Scenarios & Field Pitfalls — Engineer’s Perspective
Engineering Pain Point
Fiber-extender faults can produce a broad remote-I/O communication failure while the individual I/O modules remain healthy. A failed 8939-HN, degraded fiber connector, incorrect multimode fiber, or loss of 24 VDC power can therefore look like a complete remote I/O rack failure.
Typical Applications
- Honeywell Experion PKS Series 8 I/O systems
- Remote Series 8 I/O cabinet installations
- Longer-distance I/O communication within process plants
- Distributed I/O arrangements where copper cabling is impractical
- Legacy Honeywell control-system communication infrastructure
Technical Pitfalls to Avoid
- Do not classify 8939-HN as an I/O channel module.
It is a fiber-optic extender IOTA. It does not provide the 4–20 mA, discrete, thermocouple, or RTD channels associated with Honeywell I/O modules. - Verify the fiber type before replacement.
The published hardware information identifies the unit with multimode fiber, including 62.5/125 µm fiber specifications. Do not substitute single-mode optical hardware simply because the connector appears physically compatible. - Inspect both combo interfaces and the complete fiber path.
The 8939-HN uses two combo cable interfaces. When communication drops across a remote I/O section, inspect both ends of the cable assembly, optical connectors, patch points, fiber cleanliness, and link continuity before condemning the extender. - Check 24 VDC at the module under load.
Published specifications identify a 24 VDC supply and approximately 3 W typical consumption. A weak supply or poor terminal connection can create intermittent communication symptoms that resemble an optical hardware failure. - Do not rely on unrelated 8939-HN listings.
Some third-party pages describe the part as a generic Foundation Fieldbus or PROFIBUS-PA fiber extender and publish long-distance figures that are not established by the Honeywell Series 8 identification. For an existing Honeywell cabinet, the installed system drawing and Honeywell hardware documentation should take precedence.
Related Products
- Honeywell 8937-HN — Related Honeywell fiber-optic extender hardware; verify the exact Series 8 architecture before substitution.
- Honeywell Series 8 I/O — Distributed I/O platform using the fiber-extension architecture.
- Honeywell 8-channel/16-channel Series 8 analog input modules — Actual process-signal acquisition modules connected through the I/O architecture.
- Honeywell Series 8 digital input modules — Discrete field-input modules on the remote I/O side.
- Honeywell Series 8 digital output modules — Discrete output modules used with remote I/O.
- Honeywell Series 8 I/O chassis — Mechanical and electrical platform hosting the applicable I/O hardware.
- Honeywell Experion PKS — Control-system environment in which Series 8 I/O is commonly deployed.
Procurement Check
Before approving a Honeywell 8939-HN replacement, verify:
- Exact model: 8939-HN
- Honeywell Series 8 I/O architecture
- Existing I/O extender arrangement
- Multimode fiber requirement
- Installed fiber core type and cable specification
- Two combo cable connections
- 24 VDC supply
- Power quality at the extender
- Optical connector condition
- Fiber attenuation and continuity
- Remote I/O cabinet arrangement
- Hardware revision
- Existing system configuration
- Nameplate information
Recommended procurement description:
Honeywell 8939-HN Multimode Fiber Optic Extender IOTA, Series 8 I/O Extension Interface, 24 VDC, Two Combo Cable Interfaces, for Honeywell Experion PKS Remote I/O Architecture.
The important distinction is simple: 8939-HN is a communication/fiber-extension component, not a process I/O module. For field replacement, match the Series 8 architecture, fiber type, combo-cable arrangement, power supply, and hardware revision rather than selecting a replacement solely by physical size or connector appearance.
