The Schneider Electric A9Z66491 is a 4-pole residual current circuit breaker (RCCB) from the Acti9 iID range, rated 100 A with 500 mA earth-leakage sensitivity. The Type B-SI (Super Immunised) classification means it handles loads with variable-speed drives, photovoltaic inverters, and lift controllers without nuisance tripping from high-frequency leakage or DC components.
The 500 mA sensitivity is deliberately high — this is not a personnel-protection device (that would be 30 mA); it is sized for equipment protection and fire prevention on circuits where nuisance tripping from normal leakage would be unacceptable. Type B-SI covers AC, pulsating DC, and smooth DC fault currents, which matters when the downstream load includes 3-phase drives, UPS systems, or PV inverters that generate DC residual currents.
Clip-on DIN rail mount, 72 mm wide (4-pole width at 18 mm per pole). IP20 finger-safe, IP40 inside the modular enclosure. Green LED shows voltage present; a mechanical trip indicator flags the faulted pole. Padlocking provision for lockout/tagout.