What it is and what it does
The Siemens SENTRON 3VA1112-6EF36-0KC0 is a 3-pole molded case circuit breaker (MCCB) rated for 125 A continuous current, with a TM240 thermal-magnetic overcurrent release. Its interrupting capacity hits 220 kA at 240 V and 154 kA at 415 V — that's the short-circuit rating that decides whether it holds or blows upstream on a high-fault panel. Rated insulation voltage is 800 V, and the breaker carries two HQ auxiliary switches for status feedback to a PLC or annunciator. No undervoltage release, no ground-fault monitoring, no communication module — this is a straight line-protection MCCB with a shunt trip (STL) auxiliary release built in.
Breaking capacity — what the numbers mean for your panel
The 220 kA at 240 V is the headline number, but the real-world figure for a 400 V-class distribution board is the 154 kA at 415 V. That's still very high — this breaker is sized for transformer-secondaries or large motor-control-center buswork where fault current runs heavy. At 690 V it drops to 17 kA, so if you're on a 690 V line, verify the available fault current before committing.
Thermal derating — don't lose headroom
The 125 A rating holds steady up to 50 °C ambient. Above that it steps down: 120 A at 55 °C, 117.5 A at 60 °C, 115 A at 65 °C, 112.5 A at 70 °C. If this breaker sits in a hot enclosure next to drives or transformers, use the 70 °C column — you lose 12.5 A off the nameplate. Panel builders should account for that in the fill factor.
Panel fit and mounting
The 3VA1112-6EF36-0KC0 measures 76.2 mm wide, 130 mm tall, and 70 mm deep. That 70 mm depth is the dimension that matters for gland-plate clearance and whether it fits behind a shallow enclosure door. Front face is IP40 rated — fine for a dry indoor panel, not for washdown.