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ABB BC810 3BSE031154R1: CEX-Bus Redundancy in AC800M Systems

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ABB BC810 3BSE031154R1: CEX-Bus Redundancy in AC800M Systems

For plants running ABB AC800M controllers with critical field communication, a single CEX-Bus segment is often the hidden single point of failure. The BC810 3BSE031154R1 interconnection unit is the hardware that lets you split that bus into redundant paths. This article explains how the BC810 works, what a redundant CEX-Bus installation actually requires, and what to check before you buy spare units.

What the ABB BC810 3BSE031154R1 Does

The BC810 is a CEX-Bus interconnection unit, not a process I/O module or fieldbus master. It provides the physical path needed to duplicate the CEX-Bus between the AC800M controller and CEX-Bus communication interface modules, such as redundant PROFIBUS DP masters or redundant Ethernet scanners.

In a standard non-redundant setup, one CEX-Bus cable connects the CPU rack to the communication modules. If that cable, connector, or bus driver fails, communication to the field stops. With two BC810 units configured in a pair, the controller can maintain two independent CEX-Bus channels. One channel acts as active, the other as standby. A failure on the active channel triggers switchover to the standby channel without requiring a controller restart.

Redundancy with BC810 is at the CEX-Bus physical layer. It removes the bus cable and interconnection unit as single points of failure. It does not replace redundant controllers, redundant field power supplies, or redundant process signals. Those still need separate design measures.

How CEX-Bus Redundancy Works in AC800M

The AC800M controller communicates with CEX-Bus modules through a serial bus. When redundancy is required, two BC810 units are mounted near the controller and connected so that each CEX-Bus communication module has two possible paths back to the CPU.

The engineering tool, Control Builder M, must be configured to recognise the redundant communication pair. Hardware installation alone is not enough. If a second BC810 is installed without correct configuration, the system may report a CEX-Bus fault or the standby path will not take over.

Key installation points:

Mount two BC810 units on the DIN rail close to the AC800M processor.
Use the specified ABB CEX-Bus cables. Do not substitute general-purpose cables.
Confirm that the communication interface modules support redundant mode.
Terminate both physical ends of each CEX-Bus segment with the correct ABB termination.
Download the revised hardware configuration from Control Builder M.
Perform a failover test during a scheduled low-load window, not during production.

BC810 vs BC810K01: What to Buy

Item	Typical contents	Best for
BC810 3BSE031154R1	Single CEX-Bus interconnection unit	Replacing one failed unit, spare stock
BC810K01 kit	Two pre-matched BC810 units	New redundant CEX-Bus installation

For a new redundant segment, the BC810K01 kit reduces the risk of ordering mismatched units. For maintenance, a single BC810 can restore a failed channel, but verify revision compatibility with the existing unit already in the rack.

TP857 and TB850 Termination in Redundant CEX-Bus Faults

Many CEX-Bus faults on redundant AC800M networks are not caused by the BC810 itself. They come from missing or incorrect termination.

TP857 and TB850 are ABB CEX-Bus termination accessories. The correct type depends on segment length, cabinet layout, and whether the bus is opened for maintenance. Use the termination specified in the project CEX-Bus drawing. A missing terminator at the first or last node can cause intermittent bus errors, poor signal quality, and false switchover events.

Before replacing a BC810, check:

Both ends of each CEX-Bus segment have the specified termination.
Cable shields are connected according to ABB grounding rules.
No cable is stretched, kinked, or routed near high-frequency drives.
The active and standby BC810 units both show normal LED indication.

Common Faults and Checks

Symptom	Possible cause	Check
CEX-Bus fault after adding a second BC810	Redundant pair not configured in Control Builder M	Verify both units declared and communication modules assigned
Intermittent CEX-Bus error	Missing or wrong TP857/TB850 termination	Check terminator at first and last physical node
Redundant pair does not switch over	Second channel cable not connected or BC810 failure	Swap with known-good spare and retest
BC810 LED shows no CEX-Bus activity	Cable detached or controller side issue	Inspect connectors and controller CEX-Bus link

Sourcing ABB BC810 3BSE031154R1 Spare Parts

For critical AC800M systems, the practical spare strategy is to keep at least one complete BC810 pair per redundant CEX-Bus segment if downtime cost is high. Plants with multiple AC800M nodes often plan 10–15% spare coverage or one BC810 unit per channel as a minimum.

When buying, verify:

Part number label shows BC810 and 3BSE031154R1.
ABB packaging and logo are present.
Revision letter matches the installed unit where possible.
The supplier can provide test records or original certification if required.

Joyoung International Trading Co., Limited supplies genuine ABB AC800M communication and CEX-Bus components. We keep ABB BC810, BC810K01, TP857, TB850, and related AC800M spare parts in stock for fast delivery. See ABB control system spares for current availability.

FAQ

Does the BC810 work with all AC800M controllers?
The BC810 is designed for AC800M controllers with CEX-Bus support, including PM851, PM856, PM860, PM861, PM864, PM865, PM866, PM867, and PM891. Always check the ABB compatibility list for your specific CPU firmware version.

Can I use only one BC810?
One BC810 can be used where a CEX-Bus segment needs physical extension or branching. Redundant operation requires two BC810 units configured as a pair. One unit alone does not create redundancy.

What is the difference between TP857 and TB850?
Both are CEX-Bus termination accessories, but the correct choice depends on the segment layout and maintenance strategy. TP857 is a termination plug for direct termination at a CEX-Bus node. TB850 is a DIN-rail termination unit used where the bus must be opened or where multiple segments meet. Follow the ABB project drawing instead of substituting one for the other.

How do I test BC810 redundancy after installation?
Plan the test during low production load. With the system in run mode, disconnect one CEX-Bus cable or force one channel to fail, then verify that the standby channel takes over without process communication loss. Restore the connection and confirm normal operation returns.