1756-RM2 Redundancy Controller Module Allen-Bradley ControlLogix

Engineering Overview & System Architecture

The **1756-RM2** is an advanced enhanced redundancy module engineered for the **ControlLogix** platform by **Allen-Bradley** (Rockwell Automation). Designed to eliminate single points of failure in critical industrial environments, the **1756-RM2** pairs two independent chassis to achieve seamless controller failover and high-speed memory synchronization.

Core Technical Specifications

Operational Modes & System Compatibility

• Supported Controllers: Fully compatible with ControlLogix 5560 and 5570 series controllers (optimized for Logix 5570 L7x processors).
• Communication Accommodations: Supports up to seven enhanced ControlNet and EtherNet/IP communication modules per chassis.
• Interlink Cabling Options: Connects via dedicated fiber optic patch cables including 1756-RMC1 (1m), 1756-RMC3 (3m), and 1756-RMC10 (10m).
• Chassis Footprint: Occupies exactly a single slot in any standard ControlLogix rack without blocking adjacent system cards.

Installation Guidelines & Commissioning Convenience

• Install identical controller models with matching firmware revisions in both primary and secondary redundant chassis pairs.
• Mount the **1756-RM2** module into any available slot within each ControlLogix chassis.
• Route local I/O, intelligent instruments, and specialty partner cards to third-tier or higher remote I/O racks to maintain redundancy integrity.
• Connect matching LC-type single-mode fiber cables between the redundancy modules to establish high-speed cross-loading links.
• Configure synchronization parameters using RSLinx software tool utilities before initializing primary-to-secondary switchover tests.

Diagnostic Capabilities & Industrial Applications

• Interference-Free Diagnostics: Built-in health monitoring provides real-time status reporting without degrading backplane processing scans.
• Thermal Performance: Maintains structural stability with a maximum thermal dissipation rate of 21 BTU/hr under full operating loads.
• Target Applications: Deployed in mission-critical oil and gas pipelines, continuous chemical distillation units, power generation boiler controls, and water purification facilities.

Global PLC Spare HUB's Insight

Engineers deploying high-availability architectures with the **1756-RM2** often experience synchronization faults if mismatched firmware revisions are flashed onto the redundant 5570 controllers. During a recent offshore platform migration, our engineering team resolved persistent cross-load timeout errors by enforcing strict binary revision parity across both primary and secondary processor nodes before linking the fiber channels.

Logistics, Packaging & Warranty Terms

• Package Inclusion: 1x **1756-RM2** ControlLogix Enhanced Redundancy Module.
• Fulfillment Schedule: Fast 24 to 48-hour order processing and dispatch.
• Global Couriers: Secure worldwide delivery handled via FedEx, UPS, and DHL.
• Warranty Assurance: Fully protected by a comprehensive 12-month operational warranty.

Frequently Asked Questions (FAQ) & Buying Guide

Q: What is the maximum distance supported between two redundant chassis using this module?

A: The module supports fiber optic link distances of up to 10 kilometers, though placing the redundant chassis pair in close physical proximity is recommended for optimal latency.

Q: Can I install standard I/O modules directly inside the primary and secondary redundant chassis?

A: No, local I/O modules, intelligent cards, and encompass partner modules cannot reside in the primary or secondary redundant chassis pair; they must be offloaded to third-order or higher remote racks.

Q: What happens to the process scan time during an active controller switchover?

A: While the processing chassis remains fully synchronized, the system scan time may experience a minor transient delay of up to 10 milliseconds during the switchover event.

Q: How does mixing module series affect the maximum data synchronization speed?

A: Pairing identical **1756-RM2** modules achieves the maximum 1000 Mbps speed, whereas combining mixed Series A and Series B units throttles synchronization down to 100 Mbps.

Q: Buying Guide: When should I choose the 1756-RMC10 cable over shorter options?

A: Select the 10-meter 1756-RMC10 cable if your redundant control cabinets are installed in separate physical enclosures or require routing flexibility across extended panel raceways.

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