Hardware-level DC bus voltage trip. Same root causes as SW Bus Vol Fault but detected by the protection circuit directly. More severe -- full power cycle required.
Common causes
Large DC transient from PV or batterySurge event on DC sideInternal capacitor fault
What to check
STEP 1
Full power cycle: AC breaker OFF, DC isolator OFF, wait 10 min, restore. Check for visible surge damage at connectors or terminals
STEP 2
Check DC-side SPD (surge protection device) is intact and has not operated
Escalate if
Returns after power cycle with no DC overvoltage — internal fault, escalate
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