ABB TU848 S800 I/O Module Termination Unit

The ABB TU848 3BSE042558R1, also cataloged as the TU848 Module Termination Unit, operates as a dedicated hardware component for dual-power distribution and ModuleBus signal routing within ABB S800 I/O systems.

Hardware Specifications

Backplane Bus Communication Velocity and Redundant Network Execution

The TU848 interfaces directly with the Optical ModuleBus infrastructure, hosting redundant TB840 or TB840A modems to maintain unbroken backplane communication paths. Internal bus execution routes dual power feeds and parallel electrical ModuleBus traces to connected high-integrity I/O modules, including the DI880, DO880, AI880, and AO880 series. Rotary switches located on the termination assembly assign cluster addresses from 1 to 7 without requiring external configuration utilities. Dual 6-position mechanical keying locks configure up to 36 physical key combinations using a standard screwdriver, physically preventing mismatched module insertion into the backplane slots.

Frequently Asked Questions

Q: How does the TU848 enforce physical slot keying for compatible modules?

A: Two integrated 6-position mechanical keying dials set up to 36 unique mechanical profiles on the termination base, which align exclusively with keying notches on designated I/O modules to prevent incorrect card insertion.

Q: What are the primary backplane current distribution limits on the TU848?

A: The internal ModuleBus power rails support a maximum current distribution rating of 1.5 A at 5 VDC and 1.5 A at 24 VDC to power hosted modem modules and field interfaces.

Q: Why does vertical DIN-rail mounting decrease the maximum operating temperature limit?

A: Mounting the MTU vertically alters internal natural convection airflow over the termination block and connected I/O cards, necessitating an upper ambient temperature reduction from +55 deg C down to +40 deg C to manage thermal dissipation.

Field Installation Guidelines

Mount the unit directly onto standard DIN rails in either horizontal or vertical orientation inside a protective enclosure meeting IP54 or higher standards. Route dual 24 VDC primary power feeds to the independent power supply terminals, ensuring line redundancy across the backplane. Strip field wires to 7 mm and secure solid or stranded conductors (24 to 12 AWG) into the terminal blocks, tightening terminal screws to a torque rating between 0.5 Nm and 0.6 Nm. Maintain proper earth grounding along the rail assembly to ensure full 2000 VAC dielectric isolation and shield immunity against transient voltage surges.