Overview

The ABB TU841 Termination Unit (Part No. 3BSE020848R1) is a passive module designed to connect TB840/TB840A Optical ModuleBus Modems to ABB’s S800 I/O system. Unlike active PLC modules, the TU841 does not perform logic or processing; instead, it ensures secure electrical termination, power supply connections, and cluster address configuration.

It is specifically intended for non‑redundant I/O setups, while the TU840 is used for redundant I/O. The TU841 is widely deployed in ABB 800xA and AC 800M automation platforms, where reliability and ease of installation are critical.

Technical Data

Typical Applications

• Process industries: Connecting optical modems to non‑redundant I/O in chemical and pharmaceutical plants.

• Power generation: Supporting turbine and boiler control systems with secure communication.

• Water treatment facilities: Providing reliable modem termination for pumps and mixers.

• Manufacturing automation: Ensuring stable communication in production lines.

• Infrastructure systems: Applied in building automation and utility monitoring networks.

For example, engineers often use the TU841 when non‑redundant communication is sufficient, saving cost and complexity compared to redundant setups.

FAQ

Q1: Is the TU841 a PLC module?
A1: No, it is a termination unit (MTU), not a PLC processor.

Q2: What is the difference between TU840 and TU841?
A2:

• TU840: Connects TB840/TB840A to redundant I/O.

• TU841: Connects TB840/TB840A to non‑redundant I/O.

Q3: How are cluster addresses set?
A3: A rotary switch allows settings from 1 to 7.

Q4: What accessories are included?
A4: It comes with a power supply connector and a TB807 ModuleBus terminator.

Q5: How is the TU841 installed?
A5: It is DIN‑rail mounted with a mechanical latch for quick installation.