ABB TU845 3BSE021447R1 S800 I/O Module Termination Unit

Configured for passive field wiring termination and ModuleBus address generation in ABB 800xA and Symphony Plus systems, the ABB 3BSE021447R1 (TU845 Module Termination Unit) provides direct physical/electrical execution. The unit accepts redundant input/output cards including the AI845, AI880, AI880A, and DP840 modules across 8 independent channels. Operating at a nominal rating of 50 VDC (up to 250 V maximum dielectric limits), it routes signal connections and process power directly to the backplane via 40 dedicated terminal connections without requiring active processing electronics.

Hardware Specifications

Deterministic ModuleBus Connectivity & Backplane Velocity

The TU845 interface architecture leverages dual-channel physical slots to maintain backplane bus communication velocity across S800 I/O racks. Mechanical keying pins prevent incorrect module insertion, ensuring that physical module replacement does not corrupt backplane addressing or interrupt adjacent channel signals on the deterministic bus. The integrated ModuleBus routing automatically assigns positional addresses to inserted I/O cards while maintaining galvanic channel isolation up to 2000 VAC against field-side transients.

Frequently Asked Questions

Q: How does vertical mounting affect the thermal rating of the TU845 termination unit?

A: Vertical orientation restricts ambient air convection through the module chassis, lowering the maximum continuous operating temperature rating from +55 deg C down to +40 deg C.

Q: Can the TU845 unit remain wired during an active I/O module replacement?

A: Yes, because the TU845 acts as a passive mounting base, field wiring terminates directly to the unit block, permitting hot-swapping of connected I/O cards like the AI880 without disturbing terminal wiring or adjacent ModuleBus connections.

Q: What torque limits apply to the field terminal connections?

A: Tighten field terminal screws strictly between 0.5 Nm and 0.6 Nm to prevent mechanical damage to the internal bus bars while maintaining gas-tight contact on 24 to 12 AWG conductors.

Field Installation Guidelines

Mount the unit on standard 35 mm DIN rails inside an IP54-rated protective enclosure to meet environmental isolation requirements. Ensure grounding springs establish solid metallic contact with the DIN rail to guarantee signal shielding against electromagnetic noise. Strip all field conductors precisely 7 mm before insertion into the terminal block, and secure clamp screws to 0.5-0.6 Nm. When configuring redundant I/O module pairs, verify mechanical keying codes match the destination module hardware to prevent physical pin damage.