What it is and where it fits
The Siemens SIRIUS 3RV2031-4DB15 is a motor protection circuit breaker with Trip Class 20, protecting motors from overload and phase failure. It mounts via screw and snap-on onto 35 mm standard mounting rail per DIN EN 60715, and its 55 mm width means it occupies a single modular slot in a panel — important when you're packing breakers into a tight enclosure. At 149 mm deep and 140 mm high, it fits enclosures with those internal dimensions.
Key ratings and what they mean for the job
Rated operational voltage covers 20 to 690 V AC, handling common line voltages without a separate voltage tap. Breaking capacity at 400 V is 30 kA — that's the fault current it can safely interrupt at the most common industrial distribution voltage, giving you headroom above typical 10 kA panel SCCR requirements. Phase failure detection is built in, meaning it will trip on loss of one phase — critical for protecting three-phase motors from single-phasing damage. The screw-type terminals accept 2x (0.5 to 1.5 mm²) solid or stranded, or 2x (0.75 to 2.5 mm²) — enough for motor leads up to about 2.5 mm² without needing a ferrule.
Mounting and wiring notes
Mounting position is any — no derating for horizontal or vertical orientation, which simplifies panel layout. Clearance: 50 mm above and below, 10 mm to the side — so in a row of breakers you need 10 mm between units for cooling. Operating temperature range is -20 to +60 °C, storage/transport -50 to +80 °C — fine for most indoor industrial environments, but if the panel sits in an unheated warehouse, the -20 °C floor is the limit.