Description
3. Key Technical Specifications
| Parameter | Value |
|---|---|
| Function | Redundant MTU for CI840 |
| ModuleBus | Dual electrical ModuleBus connections |
| Communication | Two PROFIBUS DP interfaces |
| Service Ports | Dual RJ45 service tool connections |
| Address Setting | Dual rotary switches (0-99) |
| Power Supply | Dedicated power connections |
| Mounting | DIN rail |
| Keying | Mechanical keying for correct module insertion |
4. Product Introduction
The ABB TU846 is a module termination unit designed for redundant CI840 fieldbus communication interfaces in the S800 I/O system. It provides connections for power, dual ModuleBuses, and PROFIBUS links to support high-availability I/O clusters.
In redundant architectures, this MTU ensures continuous operation if one communication path fails. It is commonly used in critical process areas where downtime must be minimized.
- TU846
- TU846
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| One CI840 not detected | Address switch mismatch | High | Verify both rotary switches | Set matching station addresses |
| No ModuleBus link | Cable or power issue | High | Check ModuleBus LEDs and continuity | Verify daisy-chain and power distribution |
| PROFIBUS errors | Termination or cable fault | High | Measure bus termination resistors | Confirm 220 ohm terminators at ends |
| Service port failure | Wrong cable or config | Medium | Test with standard Ethernet cable | Use proper service tool connection |
| Redundancy switchover fail | Configuration mismatch | Medium | Review controller diagnostics | Check redundancy settings in control builder |
Communication and addressing issues are the most common. Always confirm physical connections and switch settings first.
6. Frequently Asked Questions (FAQ)
What is the TU846 used for? It is the termination unit that hosts two CI840 modules for redundant PROFIBUS DP communication to S800 I/O clusters. It also distributes dual ModuleBus.
Is this new original stock? Yes, New Original / New Surplus. Units are inspected for connector integrity and mechanical function.
Can it support single CI840 operation? It is optimized for redundant (1+1) setups. For single CI840, consider the TU847.
How do I set the station address? Use the two rotary switches on the MTU to set the cluster address (0-99). Both switches should match for redundancy.
Does it include PROFIBUS connectors? Yes, it provides DSUB9 connectors for the two PROFIBUS interfaces plus service ports.
What power does it require? Separate 24 V DC power connections for the communication interfaces. Follow the S800 power distribution guidelines.
Do you provide redundancy configuration support? Yes. We can share typical wiring diagrams and guidance for setting up redundant pairs with the TU846 in your controller environment.
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