The Siemens SIRIUS 3RV1321-4AH10-ZX95 is a three-pole circuit breaker designed for starter combinations — the integrated overload and short-circuit protection block that sits ahead of a contactor in a motor feeder. Rated 16 A continuous, it switches a 7.5 kW motor at 400 V AC-3 duty, which is the standard induction-motor load class. Breaking capacity runs 25 kA at 400 V, 6 kA at 500 V, and 2 kA at 690 V; the 25 kA figure at the common 400 V distribution level means it can interrupt a bolted fault on a typical industrial panel bus without upstream fuses needing to clear first.
Zero clearance required at the sides or rear, which simplifies rail packing in a crowded enclosure. Any mounting position is permitted, so vertical or horizontal rail orientation is fine.
Main circuit terminals are screw-type, accepting 2x (1 to 2.5 mm²) or 2x (2.5 to 6 mm²) solid or stranded conductors, with the same range for finely stranded wire with ferrules. AWG equivalents are 2x (14 to 10). The auxiliary switch is present (yes), but no auxiliary contacts are pre-fitted — the unit has zero factory-installed aux contacts, so any add-on block is ordered separately.