Configured for intrinsic safety field signal routing and process power distribution in S800 I/O architectures, the ABB TU891 (3BSC840157R1 Module Termination Unit) provides direct physical/electrical execution.

Part Identification & Version Layout

• Base Model: TU891
• Ordering Catalog Part Number: 3BSC840157R1
• Hardware Variant: Compact Module Termination Unit (MTU) with Terminal Block Connection
• Target Application: Intrinsic Safety (Ex i) Signal Distribution

Hardware Technical Specifications

System Integration & Bus Architecture

• Backplane Bus Communication Velocity: Distributes the ModuleBus to the mounted I/O module while propagating address shift signals down the rack tier to subsequent termination units.
• I/O Density Scaling: Accommodates compact 8-channel deployments utilizing 27 gray terminal blocks designed explicitly for hazardous area signal segregation.
• Firmware Flash Compatibility: Acts as a passive physical connection medium with no internal firmware execution requirements.
• Network Determinism: Preserves deterministic bus timing across distributed nodes when paired with certified intrinsic safety modules such as AI890, AI893, AI895, AO890, AO895, DI890, and DO890.

Associated Delivery Scope

• 1 x TU891 3BSC840157R1 Module Termination Unit
• Standard industrial packaging housing (Electronic I/O modules supplied separately)

Mechanical and Electrical Deployment Directives

• DIN-Rail and Slot Mounting: Secure the compact unit horizontally onto standard DIN-rail assemblies, ensuring the grounding latch engages cleanly.
• Mechanical Keying Verification: Utilize the factory-installed mechanical keys, which feature opposite polarization compared to standard units, to ensure only approved IS modules can be inserted.
• Signal Wiring Terminations: Route field wiring to the 27 gray terminals, keeping intrinsically safe conductors strictly separated from non-IS control loops to maintain compliance.
• Grounding Continuity: Verify that the DIN-rail latching mechanism establishes proper chassis reference for system shielding integrity.

Engineering Inquiry & Troubleshooting

• What is the primary operational purpose of the TU891 unit?

  It serves as a compact module termination unit designed specifically for intrinsic safety (Ex i) applications in S800 I/O systems.

• Which specific I/O modules are compatible with this termination unit?

  It supports certified IS modules including AI890, AI893, AI895, AO890, AO895, DI890, and DO890.

• How many total channels and terminal connections does the unit feature?

  The MTU provides 8 input/output channels supported by 27 gray terminal blocks.

• What are the electrical voltage and current limitations?

  The unit is rated for a maximum voltage of 50 V (optimized for 24 V systems) with a current ceiling of 2 A per channel.

• How does the unit prevent incorrect module insertion?

  It incorporates specialized mechanical keys of a reverse gender configuration that mate exclusively with compatible IS modules.

• What role does the unit play in ModuleBus communication?

  It distributes the internal ModuleBus and shifts outgoing position signals to correctly address subsequent MTU nodes.

• What are the net weight and shipping envelope dimensions?

  The unit weighs 0.2 kg with shipping package dimensions of 7.6 x 7.6 x 20.3 cm.

• Does the hardware require an external power supply connection?

  No, it functions as a passive physical distribution base powered via system bus architecture.