Allen-Bradley 1756-RM/B ControlLogix Redundancy Module | Replacement, Equivalent & Selection Guide
The Allen-Bradley 1756-RM/B is a ControlLogix platform redundancy module designed to synchronize primary and secondary controller chassis, ensuring continuous process operation with automatic failover. This page provides full technical specifications, compatible replacement options, and a structured selection guide to help engineers and procurement teams make confident sourcing decisions.
Technical Specifications
- Manufacturer: Allen-Bradley (Rockwell Automation)
- Part Number: 1756-RM/B
- Series: B
- Platform: ControlLogix
- Function: Redundancy Module – synchronizes primary and secondary chassis
- Communication: Dedicated fiber-optic redundancy cable (1756-RMC / 1756-RMCT)
- Backplane Current Draw: 1.0 A @ 5 VDC; 3.0 mA @ 24 VDC
- Power Dissipation: 5.15 W (max)
- Operating Temperature: 0 °C to 60 °C (32 °F to 140 °F)
- Storage Temperature: –40 °C to 85 °C
- Relative Humidity: 5% to 95% non-condensing
- Dimensions (H × W × D): 94.0 × 94.5 × 69.0 mm (3.70 × 3.72 × 2.72 in)
- Weight: Approx. 0.5 kg
- Certifications: UL, CE, CSA, ATEX (Zone 2)
- Firmware: Compatible with RSLogix 5000 / Studio 5000 Logix Designer
Compatible Replacement & Equivalent Models
The following models are commonly evaluated as direct or functional replacements for the 1756-RM/B. Always verify firmware revision and chassis compatibility before substitution.
- 1756-RM2/A – Next-generation ControlLogix redundancy module (Series A); enhanced synchronization speed; drop-in chassis replacement with firmware upgrade required
- 1756-RM2XT – Extended-temperature variant for harsh environments (–25 °C to 70 °C); functionally equivalent to 1756-RM2/A
- 1756-RM/A – Earlier series; functionally identical but limited to older firmware revisions; suitable for legacy system maintenance
- 1756-RMXT/B – Extended-temperature version of the 1756-RM/B; same electrical specs, wider thermal range
- Third-party equivalents: Some integrators use Siemens S7-400H or Schneider Modicon M580 Hot Standby as platform-level alternatives in greenfield projects — note these require full system redesign and are not drop-in replacements
Why Choose the Original 1756-RM/B
- Proven field reliability in continuous process industries with millions of operating hours globally
- Seamless integration with existing ControlLogix 1756 chassis, power supplies, and I/O modules
- Rockwell-certified firmware ensures deterministic failover with sub-100 ms switchover time
- Full technical support from Rockwell Automation and authorized distributors
- Regulatory compliance for safety-critical and hazardous-area installations (ATEX Zone 2)
- Long-term parts availability through Konmask.com’s verified supply chain
Typical Applications
- Oil & gas upstream/downstream process control (DCS migration and hybrid architectures)
- Power generation and utilities (turbine control, substation automation)
- Chemical and petrochemical batch/continuous processes
- Water and wastewater treatment SCADA systems
- Automotive and discrete manufacturing lines requiring zero-downtime operation
- Mining and minerals processing with remote, unmanned control stations
System Compatibility
- Chassis: 1756-A4, 1756-A7, 1756-A10, 1756-A13, 1756-A17 (and XT variants)
- Controllers: 1756-L6x series (L61, L62, L63, L64, L65); 1756-L7x series with firmware ≥ 19.x
- Redundancy Cable: 1756-RMC (standard) / 1756-RMCT (extended length)
- Software: RSLogix 5000 v16+; Studio 5000 Logix Designer v21+
- Not compatible with: 1756-L8x (ControlLogix 5580) controllers — use 1756-RM2/A instead
Selection Guide
Use the decision matrix below to identify the correct redundancy module for your application:
- Existing 1756-L6x system, standard temperature: → 1756-RM/B (this module) ✓
- Existing 1756-L6x system, harsh/extended temperature: → 1756-RMXT/B
- Upgrading to 1756-L7x controllers: → 1756-RM/B (firmware ≥ 19.x) or 1756-RM2/A
- New installation with 1756-L8x (5580) controllers: → 1756-RM2/A (mandatory)
- Hazardous area (ATEX Zone 2), standard temp: → 1756-RM/B with appropriate enclosure
- Hazardous area, extended temp: → 1756-RM2XT
- Budget-constrained legacy maintenance: → Refurbished 1756-RM/A (verify firmware support)
Quality Assurance & Sourcing
- Source: Authorized and verified secondary-market supply chain; all units traceable to original manufacturer lot codes
- Inspection: Each module undergoes visual inspection, label verification, and functional power-on testing prior to shipment
- Packaging: Anti-static ESD packaging with original or equivalent protective foam insert
- Warranty: 90-day replacement warranty against DOA (Dead on Arrival) defects
- Documentation: Certificate of conformance and test report available upon request
- Lead Time: In-stock units ship within 1–3 business days; contact us for volume orders
How to Order
- Online: Add to cart directly on this page — secure checkout with bank transfer, PayPal, and major credit cards accepted
- RFQ / Bulk: Email support@konmask.com with quantity, required delivery date, and destination country
- Phone / WhatsApp: +0086 19859288691 (Mon–Fri, 09:00–18:00 CST)
- Lead Time: Standard 1–3 business days; expedited same-day dispatch available for in-stock items
- Export: We ship worldwide; DDP/DAP Incoterms available; HS Code: 8537.10
Replacement & Compatibility FAQ
Q: Can I replace a 1756-RM/A with a 1756-RM/B without changing firmware?
A: Yes, the Series B is backward-compatible with Series A firmware in most configurations. However, upgrading firmware to the latest supported revision is strongly recommended for stability.
Q: Is the 1756-RM/B compatible with the 1756-L8x (ControlLogix 5580) platform?
A: No. The 5580 platform requires the 1756-RM2/A. The 1756-RM/B is not supported on L8x controllers.
Q: What cable is required to connect two redundant chassis?
A: The 1756-RMC (standard length) or 1756-RMCT (extended length) fiber-optic cable is required. Standard Ethernet or serial cables cannot be substituted.
Q: Can I use one 1756-RM/B module for redundancy, or do I need two?
A: One module is required per chassis — you need one in the primary chassis and one in the secondary chassis (two modules total per redundant pair).
Q: Do you provide a test report or certificate of conformance?
A: Yes. Request documentation at the time of order via email or in the order notes field at checkout.
Q: What is the difference between 1756-RM/B and 1756-RM2/A?
A: The RM2/A is the successor model with faster synchronization, support for L7x and L8x controllers, and enhanced diagnostics. The RM/B is the correct choice for existing L6x-based systems.
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