What this MCCB is and what it does
The Siemens 3VA2125-8HM46-0AA0 is a SENTRON molded case circuit breaker rated for 25 A continuous current on a 4-pole frame. It is designed for line protection with an 800 V rated insulation voltage. The ground-fault monitoring uses summation current formation on L+N conductors, so it detects residual current by comparing line and neutral — common in TN or TT systems where you want earth-fault detection without a separate RCD module. No undervoltage release, no communication function, no trip indicator — this is a straight thermal-magnetic breaker with ground-fault sensing built into the same housing.
Breaking capacity and where it fits
At 240 V it interrupts 440 kA; at 415/440 V that drops to 330 kA; at 690 V it's still 52.5 kA. Those are very high interrupting ratings for a 25 A frame — it's sized for high-fault installations like large transformer secondaries or industrial switchboards where available fault current exceeds 100 kA. The 4-pole format suits three-phase systems with a switched neutral, common in European and Asian distribution panels. Dimensions are 86 mm deep, 140 mm wide, 181 mm tall — a standard MCCB footprint that fits Siemens 3VA mounting accessories and busbar systems. Panel builders will find it occupies roughly the same DIN-rail or screw-mount space as other 160 A frame breakers, despite being a 25 A unit.
Thermal performance and derating
The 25 A continuous rating holds across the full ambient range from 40 °C to 70 °C (–) — no derating needed up to 70 °C. That's unusual for a thermal-magnetic breaker and means it can be packed into a warm enclosure without oversizing. Operating temperature range is -25 °C to +70 °C; storage from -40 °C to +80 °C. Maximum power loss is 0.5 W — negligible for enclosure heat budget.