ABB TU890 3BSC690075R1 S800 I/O Module Termination Unit

The ABB TU890, also cataloged as the 3BSC690075R1 Module Termination Unit, operates as a dedicated hardware component for field signal termination and ModuleBus distribution within S800 I/O systems.

Hardware Specifications

Backplane ModuleBus and Deterministic Signal Distribution

The passive backplane structure on the unit manages backplane bus communication velocity and address allocation across connected S800 intrinsically safe modules. Position signals embedded in the MTU interface propagate hardware auto-addressing directly into the ModuleBus structure without requiring software assignment. The backplane design ensures isolation between power distribution pathways and deterministic signal transmission lines, maintaining noise immunity for high-density intrinsically safe field wiring terminations.

Frequently Asked Questions

Q: Does the unit support hot swapping of connected S800 I/O modules?

A: Yes. The passive MTU interface allows live removal and insertion of compatible intrinsically safe I/O modules without interrupting ModuleBus communication to adjacent units on the rail.

Q: How is incorrect module insertion prevented during field replacement?

A: Mechanical keying features on the unit interface match specific I/O module key positions, physically blocking the installation of incompatible or non-intrinsically safe module types.

Q: What is the maximum allowed conductor size for process signal wiring?

A: The process connections accept solid wire up to 4 mm2 or stranded wire up to 2.5 mm2 (24 to 12 AWG).

Field Installation Guidelines

1. Mount the unit horizontally on a standard 35 mm DIN rail using the integrated spring-loaded latching mechanism. Ensure the rail is grounded to panel chassis earth.
2. Verify mechanical keying positions match the designated I/O module type prior to mounting the active electronics onto the MTU base.
3. Strip process and power supply wiring according to manufacturer terminal guidelines. Fasten process terminal screws to a torque specification of 0.5 to 0.6 Nm.
4. Maintain separation between intrinsically safe field wiring, power lines, and non-intrinsically safe cabling in compliance with EN/IEC 60079-14 installation standards.