Allen-Bradley 1756-RM ControlLogix Redundancy Enhanced Module | Replacement, Equivalent & Selection Guide
The Allen-Bradley 1756-RM (Rockwell Automation) is the ControlLogix Redundancy Enhanced Module — the core hardware component that enables hot-standby redundancy in ControlLogix chassis-based control systems. It synchronizes controller state, I/O data, and communication status between primary and secondary chassis, ensuring zero-downtime switchover in mission-critical industrial applications.
Buyers searching for a 1756-RM replacement, a ControlLogix redundancy module equivalent, or a substitute for an end-of-life unit will find this guide covers everything needed to make a confident, spec-accurate sourcing decision — including direct drop-in options, functional equivalents, and cross-brand alternatives.
Technical Specifications
- Catalog Number: 1756-RM
- Series: Allen-Bradley ControlLogix (1756 platform)
- Module Type: Redundancy Enhanced Module
- Chassis Compatibility: 1756 ControlLogix chassis (any slot)
- Redundancy Architecture: Hot-standby (primary/secondary chassis pair)
- Fiber Optic Link: Dual redundant fiber cable (1756-RMxx cable required) — key for replacement decisions
- Synchronization: Controller, I/O, and communication module state
- Switchover Time: <10 ms (typical)
- Firmware: Must match between primary and secondary — critical compatibility parameter
- Power Consumption: 3.5 W (backplane)
- Operating Temperature: 0 °C to 60 °C
- Certifications: CE, UL, cUL, ATEX (zone 2)
- Weight: ~400 g
- Dimensions: Standard 1756 single-slot form factor
Compatible Replacement & Equivalent Models
1. Direct Drop-in Replacements
These are identical or revision-compatible units that install without configuration changes, provided firmware versions are matched:
- 1756-RM/A, /B, /C — Earlier series revisions; verify firmware compatibility with your existing controller before substituting.
- 1756-RM2 — Enhanced successor with improved synchronization speed; backward-compatible in most ControlLogix redundancy configurations (confirm with Rockwell release notes).
2. Functional Equivalents
Same function, different catalog or generation — may require minor configuration or cable changes:
- 1756-RM2/A — Next-generation redundancy module with dual-port fiber; functionally equivalent, requires 1756-RM2 fiber cables.
- 1756-RMXT — Extended-temperature variant for harsh environments (−25 °C to 70 °C); same logic, different thermal rating.
3. Cross-Brand Alternatives
For system migrations or cost-driven substitutions — requires engineering evaluation and re-programming:
- Siemens S7-400H Redundancy CPU (6ES7 400-series) — Comparable hot-standby architecture; not pin-compatible, requires full system redesign.
- Schneider Electric Modicon M580 HSBY — Hot-standby redundancy for Modicon platform; cross-brand migration project required.
- GE Automation RX3i CPE400 Redundancy — Alternative for greenfield projects; not a drop-in substitute.
Note: Cross-brand alternatives are engineering projects, not plug-and-play replacements. Contact Konmask for migration feasibility assessment.
Why Choose the Original 1756-RM Model
- Precision-Matched Firmware: Factory-matched firmware ensures deterministic <10 ms switchover — third-party substitutes cannot guarantee this.
- Rockwell Certifications: CE, UL, cUL, and ATEX zone 2 certifications are tied to the original catalog number; substitutes may void system certification.
- Seamless ControlLogix Compatibility: Designed exclusively for the 1756 backplane — no adapter, no workaround, no risk.
- Rockwell Technical Support: Original units retain full Rockwell Automation TAC support and firmware update eligibility.
- Warranty Coverage: Genuine units carry manufacturer warranty; refurbished or equivalent units may not.
- Audit & Compliance Ready: Original catalog numbers simplify SIL, IEC 61511, and plant safety audits.
Typical Applications
- Oil & Gas: Pipeline SCADA systems requiring continuous uptime and SIL-rated redundancy.
- Power Generation: Turbine and boiler control systems where unplanned shutdowns carry safety and financial risk.
- Water Treatment: Municipal water and wastewater plants with 24/7 regulatory uptime requirements.
- Automotive Manufacturing: Body-in-white and paint shop lines where controller failure halts entire production.
- Chemical Processing: Batch and continuous process control in ATEX-classified hazardous areas.
- Pharmaceutical: FDA-regulated production lines requiring validated, redundant control architecture.
System Compatibility
- 1756-L6x / L7x / L8x Controllers — ControlLogix CPUs; must be redundancy-capable firmware revision.
- 1756-RMxx Fiber Cable — Dedicated redundancy link cable between primary and secondary chassis (required accessory).
- 1756-A7 / A10 / A13 / A17 Chassis — Standard ControlLogix chassis; 1756-RM occupies one slot in each chassis.
- 1756-PA72 / PB72 Power Supplies — Recommended power supplies for redundant chassis configurations.
- 1756-EN2T / EN2TR EtherNet/IP Modules — Communication modules synchronized by the 1756-RM during switchover.
- Studio 5000 Logix Designer — Engineering software for redundancy configuration and diagnostics.
Selection Guide
Answer these three questions before ordering to confirm the 1756-RM is the right fit — or contact Konmask for a free selection review:
- Is your existing system a ControlLogix 1756 platform? The 1756-RM is exclusively designed for the 1756 backplane. If you are running CompactLogix or GuardLogix, a different redundancy solution applies.
- Do you need a direct replacement or a functional equivalent? If replacing a failed unit in an existing redundant pair, firmware revision matching is mandatory. If building a new system, the 1756-RM2 may offer advantages.
- What is your operating environment? Standard environments (0–60 °C) → 1756-RM. Extended temperature or hazardous locations → 1756-RMXT. Unsure? Contact Konmask with your site conditions.
Quality Assurance & Sourcing
Konmask sources the 1756-RM through authorized distribution channels and verified secondary-market suppliers with full traceability. Every unit undergoes a 4-step inspection before shipment:
- Visual Inspection: Housing, label, connector pins, and firmware sticker checked against OEM specifications.
- Functional Test: Module powered and communication verified on a live 1756 test chassis.
- Firmware Verification: Firmware version confirmed and documented.
- Documentation Package: Test report, photos, and traceability record provided on request.
Available documentation: Certificate of Conformance, test report, product photos, and customs HS code declaration.
How to Order
- Submit Your Inquiry: Email support@konmask.com or call +0086 19859288691 with your required quantity, firmware version (if known), and delivery timeline.
- Receive Quotation: Konmask will confirm availability, pricing, and lead time — typically within 24 hours.
- Confirm & Ship: Upon order confirmation, units are inspected, documented, and dispatched with full tracking.
Replacement & Compatibility FAQ
Q: Can I use a 1756-RM2 as a direct replacement for the 1756-RM?
A: In most cases, yes — the 1756-RM2 is the functional equivalent and successor to the 1756-RM. However, it requires different fiber cables (1756-RM2 series) and a firmware update on the paired controllers. It is not a plug-and-play substitute without these changes. Contact Konmask to confirm compatibility with your specific system revision.
Q: Is the 1756-RM compatible with both L6x and L7x ControlLogix controllers?
A: Yes. The 1756-RM is compatible with ControlLogix L6x and L7x series controllers running redundancy-capable firmware. For L8x (5580) controllers, Rockwell recommends the 1756-RM2. Always verify firmware revision compatibility before substituting modules.
Q: What is the equivalent of the 1756-RM for a Siemens or Schneider system?
A: There is no direct drop-in equivalent across brands — redundancy modules are platform-specific. The Siemens S7-400H and Schneider Modicon M580 HSBY offer comparable hot-standby redundancy architectures, but migrating to these platforms requires full system re-engineering. Konmask can advise on cross-brand migration feasibility.
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