ABB CI851K01 (3BSE018101R1) – Redundant Communication Interface for AC 800M Controllers

If you’re running an AC 800M automation system and need reliable, fail-safe communication between controllers in a redundant setup, the ABB CI851K01 is typically where you’ll want to start. It’s not flashy, but it does its job well—handling peer-to-peer data exchange with predictable timing and solid integration into ABB’s Control Builder environment.

One thing I appreciate is how seamlessly it supports redundancy. In many cases, when one controller fails, switchover happens without dropping critical process data. That kind of reliability matters in continuous operations like power plants or chemical processing lines.

Key Features

• Redundant Controller Link: Enables high-availability systems by maintaining synchronized operation between primary and backup AC 800M CPUs.
• Optical Fiber Communication: Uses fiber-optic cables (typically ST connectors) to link controllers up to 2 km apart with noise immunity—ideal for electrically noisy environments.
• Hot-Swappable: Can be replaced or serviced without powering down the system, minimizing downtime during maintenance.
• Integrated Diagnostics: LED indicators provide real-time status feedback on link activity, synchronization, and fault conditions—helpful for troubleshooting in the field.
• Compatible with Control Builder M: Fully configurable via ABB’s engineering toolset, making integration straightforward if you’re already in that ecosystem.

Technical Specifications

Parameter	Specification
Brand / Model	ABB / CI851K01 (3BSE018101R1)
HS Code	8535210000
Power Requirements	Supplied via backplane from controller segment (no external power needed)
Dimensions & Weight	Standard 19″ rack module (1 module width), ~200g
Operating Temperature	0°C to +60°C (with derating above 45°C)
Signal Input/Output Types	Fiber-optic duplex (ST connector), dedicated for CI851-to-CI851 communication only
Communication Interfaces	Point-to-point optical link, proprietary protocol over fiber
Installation Method	DIN rail mounted, connects directly to AC 800M controller segment via backplane

Application Fields

This module shows up most often in industries where unplanned outages carry heavy costs. From my experience, it’s commonly found in thermal and hydroelectric power stations, oil & gas compression facilities, and large-scale water treatment plants—all relying on redundant CPU configurations to maintain uptime.

It seems particularly well-suited for distributed control setups where controllers are located in separate rooms or even buildings, thanks to the long-range capability of fiber links.

Advantages & Value

While there are other ways to achieve redundancy, using genuine ABB hardware like the CI851K01 usually reduces integration risk. You avoid compatibility headaches, firmware mismatches, or unsupported configurations that could void warranties.

Procurement teams tend to favor this part because it’s standardized across many ABB reference designs. Spare stocking becomes simpler, and engineers spend less time debugging communication faults. Over time, that translates into lower total cost of ownership—even if the initial price isn’t the lowest on the market.

Installation & Maintenance

Mounting is straightforward—it slides onto the standard DIN rail and locks into the controller segment. Just make sure the cabinet meets IP20 standards, has adequate ventilation, and follows ABB’s grounding guidelines. Poor grounding can lead to intermittent fiber link drops, which might look like hardware failure at first glance.

For maintenance, keep the fiber connectors clean. Dust caps should stay on when disconnected. Technicians occasionally overlook this, and a single speck of dirt can cause signal loss. Firmware updates are handled through Control Builder M during planned outages—nothing runs automatically here, which some find reassuring from a security standpoint.

Quality & Certifications

The CI851K01 carries CE, UL, and CSA certifications, and complies with IEC 61131-2 industrial standards for programmable controllers. It’s also RoHS compliant, so no issues with hazardous substances.

Each unit comes with a 365-day warranty—we’ve seen very few returns, honestly. Most failures we do see turn out to be fiber cable issues or configuration errors rather than actual board defects.

Order Placement & Guarantees

• Warranty: 365 days from date of shipment
• Delivery Time: 1 week for in-stock units; no more than one month for backordered items
• Payment: 50% advance payment required, balance due before shipment
• Shipping: FedEx, UPS, or DHL express delivery—tracking provided

You might notice that we don’t offer open account terms, but given the niche nature of this hardware and global shipping logistics, prepayment helps us move quickly without delays.