SIRIUS 3RV2021-4BA25-ZW96 — Motor Protection Circuit Breaker
The Siemens SIRIUS 3RV2021-4BA25-ZW96 is a motor protection circuit breaker designed to protect induction motors against overload, short-circuit, and phase failure. It carries a Trip Class 10 characteristic, so it trips within 10 seconds at 7.2× rated current — standard for protecting standard 4-pole motors during start-up. Phase failure detection is built in, meaning a lost phase on the supply side triggers a trip before the motor overheats on single-phase current. Rated breaking capacity hits 25 kA at 400 V AC, enough to clear a bolted fault on most industrial distribution boards without cascading upstream breakers. At 690 V it still interrupts 2 kA. The 45 mm wide housing snaps onto a 35 mm DIN rail per EN 60715 — standard panel footprint, no adapter needed.
Mounting and Wiring
Mounts in any position — vertical, horizontal, or flat — on 35 mm DIN rail (EN 60715) or via screws. The 45 mm width and 97 mm depth fit a standard 8-module enclosure row; allow 50 mm clearance above and below for cable entry and heat dissipation. Side clearance is 30 mm. Main circuit terminals are spring-loaded, accepting 2 × (0.5 … 2.5 mm²) solid or stranded wire. No screw torque to worry about — strip to the correct length, push in. Auxiliary contacts share the same terminal type where fitted.
Breaking Capacity and Coordination
Short-circuit breaking capacity at 400 V is 25 kA. At 240 V it reaches 100 kA, at 500 V it drops to 5 kA, and at 690 V it is 2 kA. For a 480 V system the continuous current rating is 20 A; at 600 V it is also 20 A. The gL/gG fuse backup ratings at 400 V are 63 A, at 500 V and 690 V are 50 A — relevant when coordinating with upstream fuses for Type 2 coordination.