What this MCCB is and what it protects
The Siemens 3VA2025-5KQ42-0AA0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — meaning it sits at the feeder or sub-feeder to protect cables and busbars from overload and short circuit, not a specific motor or load. Rated 25 A continuous across the full ambient range from -25 °C to 70 °C, so no derating curve to chase in a warm panel. Four poles handle three-phase plus neutral, or you can land it as a 3-pole with a switched neutral. The 121 kA breaking capacity at 415 V gives serious SCCR headroom for high-fault industrial services — think transformer secondaries or large motor control centers where available fault current runs high.
Breaking capacity across voltages — what the numbers mean for coordination
The interrupting ratings step down with voltage as expected: 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 3 kA at 690 V. That 3 kA at 690 V is the weak point — if your system runs at 690 V with high fault current, this breaker needs upstream current-limiting fuses or a higher-rated MCCB. At 415 V, the 121 kA figure covers most industrial services in North America and Europe without a second thought. Rated insulation voltage is 800 V, so the internal clearances and creepage are sized for 690 V systems even if the breaking capacity at that voltage is limited.
Ground-fault monitoring and communication — panel integration notes
This variant includes ground-fault monitoring via summation current formation on L + N conductors — it measures the vector sum of phase and neutral currents to detect leakage to earth. No separate GF relay needed if the trip unit supports it. Communication function is present, so it can talk to a higher-level system for power monitoring or remote tripping; check the trip unit variant for protocol support (PROFIBUS, PROFINET, Modbus). Dimensions are 181 mm high, 140 mm wide, 86 mm deep — fits standard SENTRON 4-pole MCCB panel cutouts. Power loss is 0.84 W maximum, negligible for enclosure thermal calculations.