Motor protection circuit breaker, 8 A, CLASS 10 — what the ratings mean for fit
The Siemens 3RV1021-1HA15-ZW95 is a SIRIUS motor-protection circuit breaker rated for 8 A continuous current and 3 kW at 400 V, with a CLASS 10 trip characteristic. CLASS 10 means it disconnects within 10 seconds at 7.2× the thermal setting — fast enough to protect standard induction motors during a locked-rotor event without nuisance tripping on normal start-up. The 100 kA SCCR at 400 V tells you this breaker can safely interrupt a fault current up to that level without upstream devices needing to clear it; that's a strong selectivity position for a panel feeding motor loads. Phase failure detection is built in, so a lost phase on the line side will trip the breaker rather than letting the motor single-phase and overheat.
Panel integration and mounting
Mounts via screw and snap-on onto 35 mm standard rail per DIN EN 50022. The 45 mm width and 97 mm height are standard for the SIRIUS 3RV1 frame — it occupies one 45 mm slot on the rail. Depth is 96 mm, which matters for enclosure depth planning; typical shallow enclosures under 120 mm may need a check. Front face carries IP20, so it's protected against finger contact but not washdown — keep it inside a panel, not on the machine surface. Terminal capacity: solid conductors 2×(0.5…1.5 mm²) and 2×(0.75…2.5 mm²); stranded 2×(1…2.5 mm²) and 2×(2.5…6 mm²). Screw-type terminals on the main circuit. Mounting position any; no derating needed for horizontal or vertical orientation.
Environmental and mechanical limits
Operating temperature range -20 to +60 °C; storage and transport -50 to +80 °C. Shock resistance 25g / 11 ms. Maximum operating altitude 2 000 m. Power dissipation in hot operating state 9.25 W — relevant for thermal budgeting inside a sealed enclosure. Mechanical endurance of main contacts typically 100 000 operations. Maximum switching rate at AC-3 is 15 operations per hour.