Code reference · NEC 705.28(A); 240.6(A); 705.12; 706 disconnect/marking
10 kW AC-coupled ESS at 240 V: circuit sizing (NEC 705.28)
A 10 kW AC-coupled battery inverter at 240 V outputs 41.67 A continuous. Its output circuit is sized at 125% of continuous output: 52.08 A minimum conductor ampacity (NEC 705.28(A)), protected by a 60 A standard breaker (240.6(A)) on at least 6 AWG copper. If it backfeeds a load-side busbar, the 705.12 interconnection limits apply on top of this.
Article 706 requires a readily accessible disconnecting means for the ESS, within sight or lockable-open, marked with nominal voltage and available short-circuit current. That marking is not busywork: large LiFePO4 banks can deliver fault currents that exceed the interrupt (AIC) rating of bargain fuses — the OCPD's AIC must exceed the computed available fault current at its terminals.
Practical trap: AC coupling doesn't remove DC-side sizing — the battery-to-inverter circuit still needs its own 125% treatment at battery voltage, and both circuits appear separately in a permit package.
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More references: 3 kW inverter on 48 V batteries: circuit sizing (NEC 706) · 5 kW inverter on 48 V batteries: circuit sizing (NEC 706) · 5 kW AC-coupled ESS at 240 V: circuit sizing (NEC 705.28) · NEC Table 310.16 ampacity, explained · The NEC 705.12 120% rule, actually explained · What wire size for a 100 A sub panel? · all 97 references