What this MCCB is and what the ratings mean
The Siemens 3VA1112-3EF32-0JC0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — the primary feeder or distribution circuit, not a motor or generator. It carries a continuous current rating of 125 A at 40 °C, and the thermal derating curve is explicit: still 125 A at 50 °C, then 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. That means in a 50 °C panel you get full rated current; above that you lose about 2–3 A per 5 °C step. The interrupting ratings are where this breaker earns its place: 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 11.9 kA at both 500 V and 690 V. Those are the SCCR values the breaker can safely clear without welding or rupturing — critical for a high-fault panel. The 800 V rated insulation voltage tells you the internal creepage and clearance are built for 690 V systems. This is a 3-pole unit with no undervoltage release and no ground-fault monitoring. It ships with a shunt trip (STL) for remote tripping and two HQ auxiliary switches for status feedback to a PLC or annunciator. No communication module, no trip indicator flag — you get the auxiliary contacts for position indication, but no local mechanical flag. The supplied basic switch is order code 3VA11123EF320AA0.
Where it fits in the panel
The 3VA1112-3EF32-0JC0 measures 130 mm high, 76.2 mm wide, and 70 mm deep — a standard SENTRON 3VA footprint that mounts on a DIN rail or screws into a panel base. The 76.2 mm width (3 inches) is the 3-pole form factor; it occupies three 18 mm module spaces on the rail. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. Maximum power dissipation is 28.1 W — that's the heat you need to vent inside the enclosure, not a trivial number in a sealed cabinet.