Product Overview
The ABB TU848 Module Termination Unit (MTU) is a passive interface module designed for redundant configuration of Optical ModuleBus Modem TB840 and TB840A. It provides dual power supply connections—one for each modem—and dual electrical ModuleBus connections, enabling seamless integration into redundant I/O architectures. The TU848 also features a rotary switch for cluster address setting (1 to 7) and mechanical keying to prevent incorrect module insertion.
This termination unit is engineered for demanding industrial environments, supporting vertical or horizontal mounting on a DIN rail. Its latching device ensures secure locking and grounding, while the compact form factor (124 mm width, 186.5 mm height, 47 mm depth) fits easily into existing control panels.
Key Features & Benefits
-
Dual Power Supply Connection – Ensures uninterrupted operation even if one power source fails.
-
Redundant ModuleBus – Maintains communication integrity in redundant I/O systems.
-
Rotary Switch for Cluster Address – Allows quick configuration of 1 to 7 addresses.
-
Mechanical Keying – Prevents insertion of wrong module types, reducing installation errors.
-
DIN Rail Mounting – Simplifies installation and provides reliable grounding.
-
Latching Device – Secures the unit and ensures proper grounding.
Technical Specifications
| Parameter |
Value |
| Article Number |
3BSE042558R1 |
| Communication Protocol |
Modulebus |
| Line Redundancy |
Yes |
| Module Redundancy |
Yes |
| Hot Swap |
No |
| Type |
Redundant TB840/TB840A, Redundant I/O, Dual Power |
| Power Input |
24 V d.c (19.2 – 30 V) |
| Mounting |
Vertical or Horizontal |
| ModuleBus Current Distribution |
Maximum 5 V 1.5 A, 24 V 1.5 A |
| Mechanical Keys |
36 different combinations |
| Acceptable Wire Sizes |
Solid: 0.2 – 2.5 mm²; Stranded: 0.2 – 2.5 mm², 24 – 12 AWG |
| Recommended Torque |
0.5 Nm |
| Rated Insulation Voltage |
50 V |
| Dielectric Test Voltage |
500 V a.c |
| Power Dissipation |
2.5 W |
| Operating Temperature |
0 to +55 °C (+32 to +131 °F), approvals issued for +5 to +55 °C |
| Storage Temperature |
-40 to +70 °C (-40 to +158 °F) |
| Relative Humidity |
5 to 95 %, non-condensing |
| Max Ambient Temperature |
55 °C (131 °F); 40 °C (104 °F) for vertical mounting |
| Ingress Protection |
IP20 according to IEC 60529 |
| Equipment Class |
Class I according to IEC 60536 (earth protected) |
| Dimensions (W×H×D) |
124 mm × 186.5 mm × 47 mm (4.88 in × 7.34 in × 1.85 in) |
| Weight |
0.45 kg (0.99 lbs) |
Industry Applications
The ABB TU848 is ideal for process industries such as oil and gas, power generation, and chemical manufacturing where system reliability is critical. Its redundant design ensures continuous operation in critical control loops, minimizing downtime. In a typical DCS application, the TU848 connects redundant TB840/TB840A modems to redundant I/O, providing a fault-tolerant communication backbone. This makes it particularly suitable for safety-critical environments where a single point of failure is unacceptable.
Installation & Setup
Mount the TU848 vertically or horizontally on a standard DIN rail. Use the latching device to lock the unit in place and ensure proper grounding. Set the cluster address using the rotary switch (1 to 7) before wiring. Connect dual power supplies and dual ModuleBus cables as per the wiring diagram. Mechanical keys are pre-configured; you can change them with a screwdriver to match your module type. Use recommended torque of 0.5 Nm for terminal screws and wire sizes from 0.2 to 2.5 mm² (24–12 AWG). Always verify polarity and voltage (24 V d.c, 19.2–30 V range) before powering up.
Maintenance & Reliability
Routine inspection of the TU848 is straightforward. Periodically check for loose connections and verify that the latching device remains secure. Keep the unit clean and free of dust to maintain IP20 protection. Operating within the specified temperature range ensures long service life. The passive design (no moving parts) minimizes wear, and the redundant power and ModuleBus connections enhance overall system reliability, reducing unplanned maintenance costs.
Compatibility & Integration
The TU848 works exclusively with ABB TB840 and TB840A Optical ModuleBus Modems. It supports redundant ModuleBus communication and is designed for use with redundant I/O configurations. The unit communicates via the Modulebus protocol and is compatible with ABB DCS systems that employ these modems. Verify that your system firmware supports the TU848 before integration.
Buying Guide
Before purchasing the ABB TU848, confirm your system requires redundant I/O and dual power. Check that your TB840/TB840A modems are compatible. The TU848 is a passive unit; it does not require separate power. Ensure your panel has adequate space for the 124×186.5×47 mm dimensions. For peace of mind, purchase from PLC Source PRO, a trusted supplier of industrial automation parts, offering genuine ABB products and reliable support.