Cause : External fault via digital input comes when an issues related to external devices or conditions. This is a general fault code that can be caused by a variety of issues outside of the drive itself.

F526 External fault in ABB DCS800 drive indicates that the drive has received an external fault signal from connected equipment or monitoring devices, which can halt operation as a protective measure. 

Here’s how to troubleshoot and resolve this fault:

1. Identify the External Fault Source:

• Review the external inputs wired to the drive that could be sending a fault signal. Common sources include external sensors, relays, or protective devices.
• Check the wiring diagram to understand which input terminals are used for external fault signaling and locate connected devices.

2. Check External Wiring and Connections:

• Inspect the wiring for all external devices connected to the drive’s fault input. Look for loose or damaged cables, corrosion, or poor contacts.
• Verify that all connections are secure and that there are no open circuits or short circuits in the wiring leading to the external fault input.

3. Examine Fault Signal Sources:

• Inspect any protective devices like overload relays, temperature sensors, or pressure switches that may trigger the fault. Ensure they are not in a fault state.
• If the external devices include sensors (such as temperature or pressure), measure their values to ensure they are within normal operating limits.

4. Review Drive Configuration and Parameter Settings:

• Check the drive’s configuration settings for the external fault input. Ensure that the parameter settings match the requirements for your application.
• Some applications may have specific requirements for delay or debounce settings on fault inputs, which can be adjusted in the drive’s parameters to avoid false triggers.