What this MCCB is and what it does
The Siemens SENTRON 3VA1112-4EF36-0AE0 is a 3-pole molded case circuit breaker (MCCB) designed for line protection — meaning it sits on the feeder side of a panel, not downstream at a motor or branch circuit. Its TM240 thermal-magnetic release gives a fixed thermal pickup at 125 A (continuous rating at 40 °C) and a magnetic trip threshold at 240 A. That 125 A holds flat through 50 °C, then derates to 114 A at 70 °C, so the thermal curve stays predictable in a warm enclosure. Interrupting capacity is the headline number here: 121 kA at 240 V, 75.6 kA at 415 V, 52.5 kA at 440 V, and 11.9 kA at 500 V and 690 V. That 121 kA at 240 V means it can safely clear a fault on a high-capacity 240 VAC distribution bus without the arc flashing upstream — a spec that matters when you are coordinating with a transformer secondary or a generator main. Rated insulation voltage is 800 V, so the internal clearances and creepage are sized for 690 VAC systems. The 3VA series uses a rotary handle mechanism common across the SENTRON family, so panel cutouts and bus-bar layouts transfer between frame sizes.
Physical fit and panel integration
Footprint: 76.2 mm wide (3 inches), 130 mm tall (5.12 inches), 70 mm deep (2.76 inches). That 70 mm depth is the body only — add handle throw and wiring space. The 3-pole width matches standard 3-inch MCCB slots in most distribution panelboards. No auxiliary or communication modules are factory-fitted on this variant; the design carries provision for up to 4 auxiliary switches HQ (high-qualified) if you add them later. No undervoltage release, no shunt trip, no ground-fault monitoring, no trip indicator, and no voltage trigger are included on this order code. If you need any of those, you are looking at a different suffix or an add-on accessory. The basic switch supplied is 3VA11124EF360AA0 — that is the internal mechanism this order code ships with.
Thermal and environmental limits
Operating temperature range: -25 °C to 70 °C. Storage range: -40 °C to 80 °C. Maximum power loss at rated current is 28.1 W — that is the heat the breaker dumps into the enclosure, so factor it into your panel thermal budget. The 125 A rating holds at 40 °C, 45 °C, and 50 °C without derating; at 55 °C it drops to 122 A, at 60 °C to 120 A, at 65 °C to 117 A, and at 70 °C to 114 A.