Applicable Systems
Okken
Symptoms
The Modbus communication to the Acti9 Smartlink circuit monitor is lost. The PLC diagnostic buffer shows a module fault and the last energy values are frozen. The circuit protection remains active.
Possible Causes
- Modbus cable disconnected or damaged at the Smartlink terminal block
- Incorrect baud rate or parity setting between Smartlink and PLC
- Duplicate Modbus address on the network
- EMI coupling into the RS-485 cable from adjacent power cables
Troubleshooting Steps
- Step 1: Check the RS-485 A/B wiring and verify 120 Ohm termination at both bus ends
Signal integrity restored; no framing errors on the bus monitor - Step 2: Verify the Smartlink baud rate, parity, and station address match the PLC configuration
All parameters match exactly (typical: 19200, even, address 1-247) - Step 3: Ping the network address map to confirm no duplicate addresses
All devices respond with unique addresses and no collisions - Step 4: Reroute the Modbus cable >300 mm from power cables and verify shield grounding at one end
Communication re-establishes and remains stable under load
How to Reset
Acknowledge the communication fault in the PLC after restoring the physical link. The Acti9 protection functions operate independently of the bus.
Common Replacement Parts
- A9XMSB11: Schneider Acti9 Smartlink circuit monitor (Compatible with Acti9 iC60 and iDPN breakers)
Frequently Asked Questions
- Q: Does Smartlink still measure energy during a comm failure?
Yes. The Smartlink continues to measure and store data locally. Only remote access to real-time data is interrupted.
- Q: What is the maximum Modbus cable length?
Up to 1200 m at 9600 baud with proper termination and shielding. Higher baud rates require shorter runs.
Source: Schneider Electric PrismaSeT Technical Guide, GDE0001
Category: Electrical