ABB TU846 Module Termination Unit (MTU)

1. Introduction

The ABB TU846 is a Module Termination Unit (MTU) used as an interface between AC 800M I/O modules and field wiring. It provides the mechanical and electrical connection points required to install, operate, and maintain I/O modules efficiently. Designed for use with S800 I/O systems, the TU846 offers simplified installation, modular flexibility, and high reliability—making it a fundamental component in ABB’s distributed control systems (DCS).

2. Technical Specifications

3. Structure and Design

The TU846 MTU serves as a connection hub between field devices and the I/O module. It is composed of:

Baseplate Connector: Provides a plug-in interface for the I/O module.

Field Terminal Blocks: Screw-type terminals for direct field wiring.

Power Bus Contacts: Deliver 24 V DC power to the connected module.

ModuleBus Connector: Enables communication between I/O units within the S800 system.

Mechanical Latch: Ensures secure attachment and easy replacement of modules.

Its modular and compact design allows it to be installed side by side with other MTUs, minimizing space requirements while maintaining high wiring density.

4. Key Features and Advantages

Provides electrical and mechanical interface for S800 I/O modules

Supports both signal and power distribution in one unit

Screw-type terminals for reliable and vibration-resistant wiring

Easy installation and hot-swappable design for quick maintenance

Integrated ModuleBus connector for seamless data communication

Compact and modular form factor for high-density control panels

Designed for harsh industrial environments with robust construction

Full compatibility with ABB AC 800M and 800xA automation platforms

5. Application Fields

The ABB TU846 is widely implemented in:

Process automation systems (oil, gas, and petrochemical industries)

Power generation and substation control

Water treatment and environmental monitoring systems

Manufacturing, pulp, and paper industries

Mining, metals, and materials processing

Transportation and infrastructure automation

6. Installation and Maintenance

Mounting: Fix the TU846 securely on a DIN rail or mounting plate inside the control cabinet.

Connection: Wire field signals to terminal blocks and connect the I/O module onto the MTU’s backplane connector.

Power Supply: Distribute 24 V DC through the system’s power rail; ensure proper grounding.

Communication: Verify ModuleBus connectors are correctly linked to adjacent units.

Inspection: Check terminal screws periodically to ensure secure connections.

Replacement: Modules can be removed or replaced without disconnecting field wiring, minimizing downtime.

7. Reliability and Performance

The TU846 ensures stable electrical connections, mechanical strength, and low maintenance effort. Its modular design enables rapid configuration changes and expansions, while ABB’s proven quality ensures long-term reliability in mission-critical industrial environments. Together with S800 I/O and AC 800M controllers, the TU846 contributes to a flexible, scalable, and efficient automation infrastructure.