What does error 0x20C3 mean on a Felicity ESS?

0x20C3 means: Battery cluster SBCU external bus voltage sampling fault. Invalid external bus voltage sampling.

Is error 0x20C3 a fault or a warning?

0x20C3 is a fault code: the ESS unit enters protection and stops normal operation until it is cleared.

0x20C3

Battery cluster SBCU external bus voltage sampling fault

Critical — the ESS unit shuts down and latches a protection fault. Don't keep restarting it — the cause needs checking first.

Energy storage systemCritical

Battery cluster SBCU external bus voltage sampling fault

Cause: Invalid external bus voltage sampling.

Send faults externally, limit power and request to lower high voltage; if command not received within 5s, cut off the main circuit relay.

Source: FLS-ES232LC-S.pdf

What does error 0x20C3 mean on a Felicity ESS?: 0x20C3 means: Battery cluster SBCU external bus voltage sampling fault. Invalid external bus voltage sampling.
Is error 0x20C3 a fault or a warning?: 0x20C3 is a fault code: the ESS unit enters protection and stops normal operation until it is cleared.
How do I clear or fix error 0x20C3?: Send faults externally, limit power and request to lower high voltage; if command not received within 5s, cut off the main circuit relay.

Compiled from official Felicity user manuals. Always consult your device manual and a qualified technician before performing repairs.