ABB TU838 3BSE008572R1 S800 I/O Extended Module Termination Unit

Product Overview

The ABB TU838 (3BSE008572R1) is an S800 I/O Extended Module Termination Unit designed for ABB distributed control systems. It provides the electrical and mechanical interface between field wiring and S800 I/O modules within System 800xA architectures.

This MTU distributes process power, routes ModuleBus signals, and supports up to 16-channel I/O configurations. It is widely used in process automation environments where stable signal termination and modular expansion are required.

The TU838 supports fused transducer power outputs, redundant L+ / L- supply paths, and mechanical coding to prevent incorrect module installation.

Key Features

• 16-channel S800 I/O termination unit

• Compatible with ABB System 800xA and Advant OCS

• Integrated fused transducer power distribution

• Mechanical keying system prevents incorrect module insertion

• DIN rail mounting with integrated grounding latch

• Redundant L+ / L- process power support

• Automatic ModuleBus sequential addressing

• Designed for industrial process automation systems

Technical Specifications

System Function and Architecture

The TU838 operates as a passive termination and distribution module within S800 I/O systems. It does not process signals but provides structured routing between field devices and I/O modules.

ModuleBus communication uses sequential slot detection, allowing automatic addressing without software configuration. Each MTU passes position signals to the next unit in the DIN rail chain.

The unit also distributes process power through fused output groups, protecting connected field instruments from overload conditions.

Installation and Wiring Guidelines

Proper installation is required for stable system performance.

Mount the unit on a 35 mm DIN rail in a horizontal position. Ensure the DIN rail is properly grounded using low-impedance bonding to the cabinet earth system.

Maintain a wire stripping length of 7 mm and tighten terminal screws to 0.5–0.6 Nm. Use proper separation between signal wiring and AC power lines to reduce electromagnetic interference.

Field wiring is divided into 16 signal channels with grouped fused transducer outputs. Some configurations allow shared fuse groups depending on module design.

Mechanical Keying System

The TU838 includes a dual mechanical keying system with six selectable positions per key, enabling 36 configuration combinations.

This prevents incorrect insertion of S800 I/O modules such as AI810, DI810, or DO814. The system ensures mechanical compatibility and protects internal circuits from incorrect field voltage exposure.

EMC and Grounding Requirements

Stable operation requires proper grounding and EMC design.

The DIN rail acts as a functional earth connection through the integrated latching mechanism. The cabinet must be connected to a low-impedance grounding system using copper braid.

Signal cables should be separated from power cables to minimize noise coupling. Avoid long parallel routing between high-voltage and low-voltage lines.

Applications

The ABB TU838 is used in:

• Industrial process automation systems

• Oil and gas control systems

• Power generation plants

• ABB System 800xA DCS architectures

• Large-scale factory automation

• Safety-critical instrumentation networks

Ordering Information

• Product ID: 3BSE008572R1

• ABB Type: TU838

• System: S800 I/O

• Minimum Order Quantity: 1 piece

FAQ

What is the function of TU838 in S800 I/O systems?
It provides signal termination, power distribution, and ModuleBus routing between field wiring and I/O modules.

Does TU838 require software configuration?
No. Module addressing is handled automatically through sequential ModuleBus signaling.

Can the fuses be replaced?
Yes. Fuses are field replaceable and can be upgraded depending on application requirements.

What happens if grounding is incorrect?
Improper grounding may lead to EMC interference, unstable signals, or system communication errors.