What causes a Serial Link Fault (SLF) on an ATS22 Soft Starter, and how can it be resolved?

An SLF (Serial Link Fault) on an ATS22 (Altistart 22) Soft Starter indicates a loss of communication between the starter and the Modbus network.

To resolve the issue, check the following:

• Verify that the Modbus network is correctly connected to the soft starter.
• Confirm the network is active, operating normally, and passing communication traffic.
• Ensure the Modbus address configured on the starter matches the network settings.

If Modbus communication is not being used:

• Check parameter CtrL in the COP menu.
  • Set CtrL = LCL for local control via terminals (factory default).
  • Set CtrL = DBS for Modbus control.

• Note that access to the COP menu is only available if parameter LAC in the CONF menu is set to ON.

If this article does not answer your question, check out our FAQ database that has answers to more commonly asked questions:

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