What this MCCB is and what it protects
The Siemens SENTRON 3VA2125-5HM36-0AA0 is a 3-pole molded case circuit breaker (MCCB) rated for 25 A continuous current, designed for line protection in distribution panels. Its 121 kA breaking capacity at 415 V means it can safely interrupt fault currents up to that level without upstream cascading — critical for high-fault installations like industrial mains or transformer secondaries where SCCR coordination matters. The 800 V rated insulation voltage gives headroom for 690 V systems, though the 3.7 kA breaking capacity at 690 V is the limiting factor at that voltage class.
Breaking capacity across voltages — where it fits
Breaking capacity drops sharply above 500 V: 187 kA at 240 V, 121 kA at 415 V and 440 V, 75.6 kA at 500 V, and 3.7 kA at 690 V. That 690 V figure is low enough that for 690 V applications you'd typically step up to a higher-rated frame. The 25 A continuous rating holds flat from 40 °C through 70 °C ambient (–) — no derating needed in warm enclosures, which simplifies panel design in non-climate-controlled locations.
Panel fit — dimensions and mounting
The 3VA2125-5HM36-0AA0 measures 86 mm deep, 105 mm wide, and 181 mm high — a standard 3-pole MCCB footprint that fits most DIN-rail or panel-mount enclosures. The 105 mm width is the critical dimension for multi-pole spacing in a distribution board; verify the busbar or lug kit pitch matches before committing the BOM line.