What it is and what it does
The Siemens 3RV2021-1HA20-0BA0 is a SIRIUS motor protection circuit breaker in size S0, designed for motor protection with phase failure detection and a Class 10 trip characteristic. Rated at 8 A in AC-3 duty at 400 V, it switches motor loads up to that current, with a maximum breaking capacity of 100 kA at 400 V AC — sufficient for high-fault-current industrial panels. Mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, in any position, making it a drop-in fit for standard European-style enclosures.
Key ratings and what they mean for fit
The 100 kA breaking capacity at 400 V (AC) means it safely interrupts faults up to that level without cascading upstream — critical for SCCR compliance in a panel. Class 10 trip ensures the breaker opens within 10 seconds at a locked-rotor current, matching standard IEC motor starting profiles for pumps, fans, and compressors. Phase failure detection is built in, so a lost phase on the line side trips the breaker — no separate phase monitor relay needed. Spring-loaded terminals on the main circuit accept 2x 1–10 mm² solid or stranded wire, sized for motor branch circuits up to the 8 A rating.
Integration and mounting
Size S0 footprint: 45 mm wide, 97 mm deep, 119 mm tall. Requires 50 mm clearance above and below, 30 mm to the side, and zero clearance forward or backward. Snap-on onto 35 mm DIN rail per DIN EN 60715; screw fixing also supported for vibration-prone installations.