Allen-Bradley 1791-24B8 Block I/O Module | Replacement, Equivalent & Selection Guide
The Allen-Bradley (AB) 1791-24B8 is a 24 VDC Block I/O Module from Rockwell Automation’s 1791 Series, designed for distributed I/O applications in industrial automation environments. This page provides full technical specifications, compatible replacement options, system compatibility details, and a structured selection guide to help engineers and procurement teams make informed sourcing decisions.
Technical Specifications
- Manufacturer: Allen-Bradley / Rockwell Automation
- Part Number: 1791-24B8
- Series: 1791 Block I/O
- Supply Voltage: 24 VDC
- I/O Type: Discrete Block I/O (combined input/output)
- Digital Inputs: 8 points (24 VDC sink/source)
- Digital Outputs: 8 points (24 VDC)
- Communication Interface: Remote I/O (RIO) / DH-485 compatible
- Enclosure Rating: IP67 (sealed, suitable for harsh environments)
- Operating Temperature: 0°C to 55°C (32°F to 131°F)
- Mounting: Panel or machine-mount, M12 connectors
- Weight: Approx. 780 g
- Status Indicators: LED per I/O point
- Certifications: UL, CE
Compatible Replacement & Equivalent Models
The following models are commonly evaluated as functional replacements or equivalents for the 1791-24B8. Always verify electrical and communication compatibility before substitution.
- 1791-24B8 (OEM Original) — Direct replacement; preferred for warranty and support continuity.
- 1791D-8B8P — DeviceNet variant of the 1791 Block I/O family; requires DeviceNet network infrastructure.
- 1791ES-IB8XOBV4 — Safety-rated Block I/O; suitable for SIL 2 / PLd applications requiring functional safety.
- 1734-IB8 (POINT I/O) — Modular alternative; offers greater flexibility but requires 1734 adapter and backplane.
- 1756-IB16 (ControlLogix) — Chassis-based alternative for ControlLogix systems; not a direct drop-in replacement.
- Third-party equivalents (Turck, Balluff, Murrelektronik) — IP67 block I/O modules with RIO or EtherNet/IP interfaces; confirm pinout and protocol compatibility.
Note: Konmask.com supplies genuine OEM Allen-Bradley modules. Third-party equivalents listed above are for reference only.
Why Choose the Original Model
- Guaranteed compatibility with existing Rockwell Automation PLC programs and RSLogix configurations — no re-engineering required.
- Full Rockwell TechConnect support and firmware update eligibility.
- Proven field reliability in automotive, food & beverage, and material handling applications.
- IP67 sealed housing eliminates the need for additional enclosures in wet or dusty environments.
- Simplified wiring via M12 connectors reduces installation time and error risk.
Typical Applications
- Distributed I/O nodes on conveyor and assembly lines
- Machine-level I/O in automotive body-in-white and stamping operations
- Packaging machinery with distributed sensor/actuator networks
- Food & beverage lines requiring washdown-rated I/O (IP67)
- Material handling systems with remote I/O drops
- Retrofit and expansion of legacy PLC-5 and SLC 500 Remote I/O networks
System Compatibility
- PLC-5 Series — Native Remote I/O (RIO) compatibility; direct integration.
- SLC 500 Series — Compatible via 1747-SN Remote I/O Scanner.
- ControlLogix / CompactLogix — Compatible via 1756-DHRIO or 1756-RIO bridge modules.
- RSLogix 5 / RSLogix 500 / Studio 5000 — Supported for configuration and diagnostics.
- FactoryTalk View — I/O status visible via standard RIO data mapping.
Not natively compatible with EtherNet/IP or DeviceNet without a protocol gateway.
Selection Guide
Use the criteria below to confirm the 1791-24B8 is the correct module for your application, or to identify a suitable alternative:
- Network protocol: If your system uses Remote I/O (RIO) → 1791-24B8 is correct. If DeviceNet → consider 1791D series. If EtherNet/IP → consider 1732E or 1734 POINT I/O with EtherNet/IP adapter.
- I/O count: 8 inputs + 8 outputs. If more points are needed, consider daisy-chaining multiple 1791 modules or upgrading to 1734 POINT I/O.
- Environmental rating: IP67 is standard. If IP69K (high-pressure washdown) is required, evaluate Turck or Murrelektronik alternatives.
- Safety requirements: Standard (non-safety). For SIL 2 / PLd, select 1791ES series.
- Voltage: 24 VDC. For 120 VAC applications, select 1791-A8B8 or equivalent AC-rated module.
- Form factor: Block (machine-mount). For DIN-rail modular, select 1734 POINT I/O.
Quality Assurance & Sourcing
- Genuine OEM parts sourced through authorized distribution channels.
- Each unit undergoes incoming inspection including visual, label, and date-code verification.
- Traceability documentation available upon request (CoC, test reports).
- Inventory maintained for immediate dispatch; lead time typically 1–3 business days.
- Surplus and refurbished units clearly labeled and priced separately — no mixing with new stock.
How to Order
- Online: Add to cart directly from this page. Bulk pricing available — contact us for a quote.
- Email: support@konmask.com — include part number, quantity, and required delivery date.
- Phone/WhatsApp: +0086 19859288691
- Lead time: In-stock orders ship within 1–3 business days. Out-of-stock items: 5–15 business days depending on sourcing.
- Payment: T/T (wire transfer), PayPal, and major credit cards accepted.
- Export: International shipping available. Export documentation (commercial invoice, packing list, CO) provided.
Replacement & Compatibility FAQ
Q: Can the 1791-24B8 replace a 1791-16B8?
A: No direct drop-in — the 1791-16B8 has 16 inputs vs. 8 on the 1791-24B8. I/O mapping in your PLC program must be revised.
Q: Is the 1791-24B8 compatible with ControlLogix?
A: Yes, via a 1756-DHRIO or 1756-RIO bridge. It is not natively EtherNet/IP capable.
Q: Can I use a third-party block I/O module as a replacement?
A: Functionally possible if the module supports RIO protocol and matches the I/O count and voltage. However, Rockwell does not officially support third-party modules, and PLC program changes may be required.
Q: What is the difference between 1791-24B8 and 1791D-8B8P?
A: The 1791D series uses DeviceNet instead of Remote I/O. They are not interchangeable without a network infrastructure change.
Q: Do you supply refurbished units?
A: Yes, clearly labeled and tested. Contact us for availability and pricing.
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