What it is and where it fits
The Siemens SIRIUS 3RV2021-4DA10-ZW96 is a motor protection circuit breaker with CLASS 10 trip characteristic. It mounts via screw and snap-on onto 35 mm DIN rail per DIN EN 60715, so it drops straight into a standard panel enclosure — no adapter plate needed. Dimensions are 97 mm deep, 45 mm wide, and 97 mm high, with 50 mm clearance required above and below, 30 mm to the side, and zero clearance forward or backward — tight enough for dense layouts.
Breaking capacity and selectivity
Rated breaking capacity at 400 V is 25 kA, at 240 V it reaches 100 kA, and at 690 V it holds 2 kA — the 400 V figure is the one that governs most industrial motor branch circuits, and 25 kA is sufficient for typical plant-floor SCCR requirements without upstream fusing. Phase failure detection is built in, so the breaker trips on loss of any phase — a common cause of single-phasing motor burnouts. The gL/gG fuse backup ratings at 400 V are 63 A, at 500 V and 690 V are 50 A — useful when coordinating with upstream fuses for selectivity.
Termination and environment
Main contacts use M4 screw terminals, accepting 2×(1…2.5 mm²) or 2×(2.5…10 mm²) solid or stranded — covers most motor feeder sizes up to 10 mm². Operating temperature range is -20 to +60 °C, storage and transport -50 to +80 °C — fine for unheated plant floors and warehouse storage. Mounting position is any, so it works horizontally or vertically without derating.