ABB TU846 Module Termination Unit for Redundant CI840/CI840A Systems

Product Introduction

In critical industrial processes where uninterrupted communication is non-negotiable, the ABB TU846 Module Termination Unit (3BSE022460R1) provides the robust foundation for redundant field communication interfaces. Designed specifically for redundant configurations of the CI840/CI840A and redundant I/O modules, this passive termination unit ensures system reliability even in the most demanding environments. The TU846 supports two electrical ModuleBuses, two CI840/CI840A modules, and dual rotary switches for station address settings (0 to 99), making it an essential component for high-availability automation architectures.

Technical Specifications Breakdown

The TU846 operates on a 24 V d.c. power input with a range of 19.2 to 30 V, ensuring stable performance under fluctuating power conditions. It distributes ModuleBus current up to 5 V at 1.5 A and 24 V at 1.5 A, supporting connected modules efficiently. Communication relies on PROFIBUS DP-V1 protocol via DSUB9 connectors, with RJ45 service ports for diagnostics. The unit accepts wire sizes from 0.25 to 2.5 mm² (24–14 AWG) with a recommended torque of 0.5–0.6 Nm and stripping length of 6–7.5 mm. Rated insulation voltage is 50 V, with a dielectric test voltage of 500 V a.c., ensuring electrical safety in industrial settings.

Industry Applications

Process industries such as oil and gas, chemical processing, and power generation benefit directly from the TU846's redundancy capabilities. For example, in a refinery control system where a single communication failure could halt production, the TU846 enables seamless failover between two CI840/CI840A modules, maintaining PROFIBUS DP-V1 communication without interruption. This redundancy reduces unplanned downtime and enhances overall equipment effectiveness (OEE), aligning with cost-benefit and ROI goals by minimizing production losses.

Installation & Setup Guidance

Mount the TU846 vertically or horizontally on a standard DIN rail using its integrated latching device for locking and grounding. Ensure sufficient space to the left of the unit for removal, as it cannot be replaced with power applied. Connect power supply to the designated terminals, then attach two electrical ModuleBuses and up to two CI840/CI840A modules. Set the station address using the two rotary switches (0 to 99). Use the four mechanical keys—each with six positions—to configure the MTU for the correct module types, preventing insertion of incompatible modules. The maximum ModuleBus length from the TU846 to the ModuleBus terminator is 2.5 meters.

Maintenance & Reliability

Routine inspection of the TU846 should focus on verifying secure DIN rail mounting and tightness of screw terminals (torque 0.5–0.6 Nm). The unit operates reliably in temperatures from 0 to +55 °C (approvals issued for +5 to +55 °C) and can be stored from -40 to +70 °C. Relative humidity tolerance of 5 to 95% non-condensing ensures performance in humid environments. With IP20 ingress protection, the TU846 is suited for clean indoor industrial enclosures. Its passive design means no active components to wear out, contributing to long service life and reduced maintenance costs—a key factor in maximizing ROI.

Compatibility & Integration

The TU846 integrates seamlessly with ABB's CI840 and CI840A field communication interfaces, supporting PROFIBUS DP-V1 master networks. It works with redundant I/O modules and can be paired with the TB842 ModuleBus Optical Port via TB846 for fiber optic extensions. The unit is compatible with both vertical and horizontal mounting orientations, offering flexibility in cabinet design. For single I/O configurations, use the TU847 instead. Always verify compatibility with your existing ABB system before ordering.

Selection Guide & Purchasing Advice

Before purchasing the TU846, confirm your system requires redundant CI840/CI840A and I/O modules. Check that your power supply delivers 24 V d.c. within the 19.2–30 V range and that your PROFIBUS network uses DSUB9 connectors. The TU846 is available now at BluePLC Industrial, a trusted supplier of industrial automation parts. Contact our team to verify current lifecycle status and availability, ensuring you receive genuine ABB components for your critical applications.