ABB TU839 3BSE046966R1 Extended Module Termination Unit

Configured for field signal termination and sensor power distribution in ABB S800 I/O platforms, the ABB TU839 (TU839 3BSE046966R1 Extended Module Termination Unit) provides direct physical/electrical execution. Supporting up to 8 individually isolated I/O channels rated at 250 V and 1 A per channel, this unit serves as the physical interface for DI820, DI821, and DI825 digital input modules. The termination unit incorporates two individually isolated sensor power distribution groups equipped with 200 mA fuses while distributing ModuleBus power and shifting positional address signals to adjacent MTUs.

Hardware Specifications

Backplane Bus Communication Velocity and Mechanical Keying

The TU839 routes deterministic ModuleBus communication lines directly across the S800 I/O backplane, preventing signal degradation between adjacent termination units. Integrated position-shifting circuitry automatically passes positional address signals down the DIN rail, establishing precise physical I/O channel mapping without requiring manual DIP switch configurations. Two mechanical keying wheels offer 36 unique physical combinations to lock out incompatible modules, protecting the 200 mA sensor power circuits and field input channels from improper hardware insertion.

Frequently Asked Questions

Q: What protection level do the two integrated sensor power distribution groups provide?

A: The TU839 contains two individually isolated process power groups, each fitted with a 200 mA fuse. This design limits short-circuit current across external field sensors and prevents a single sensor fault from shutting down the entire 8-channel module base.

Q: How does the ModuleBus addressing shift work when adding additional TU839 units?

A: The internal backplane circuit shifts the incoming position signal by one slot as it passes through the MTU. The outgoing signal informs the next MTU on the DIN rail of its relative position, automating address assignment for the main controller.

Q: Can field wiring remain connected when releasing the TU839 from the DIN rail?

A: Yes. Releasing the bottom spring-loaded mechanical latch via a flathead screwdriver unfastens the unit from the standard 35 mm DIN rail, allowing access without disconnecting individual terminal block conductors.

Field Installation Guidelines

1. DIN Rail Alignment: Mount the TU839 onto a standard 35 mm DIN rail (EN 50022). Press firmly until the mechanical latch snaps into place to guarantee physical stability and continuous earth grounding.
2. Mechanical Keying Setup: Set the dual 6-position mechanical keying wheels to match the specific configuration requirements of the target digital input module (DI820, DI821, or DI825) prior to module insertion.
3. Signal and Power Termination: Strip field conductors to the standard length, insert wires (0.2 to 2.5 mm squared / 24 to 14 AWG) into the screw terminal positions, and tighten terminal screws to a torque of 0.5 Nm.
4. Sensor Group Wiring: Connect field sensor power to the dedicated 2-group terminal points, ensuring external current demands stay within the 200 mA rating per fused group.
5. Backplane Joining: Align and press adjacent S800 termination units closely together on the DIN rail to establish reliable ModuleBus connector contact and continuous bus communications.