What this MCCB is and what it does
The Siemens 3VA1112-6MH32-0AB0 is a SENTRON molded case circuit breaker (MCCB) built specifically for starter protection — meaning it's designed to sit ahead of a motor starter and handle the high inrush and overload profile of motor loads without nuisance tripping. Rated 125 A continuous at 40 °C (derates to 114 A at 70 °C), it carries a 3-pole configuration and a TM120M thermal-magnetic release that combines a thermal bimetal for overload protection with a magnetic coil for short-circuit response. The interrupting capacity is a heavy 220 kA at 240 V, stepping down to 154 kA at 415 V, 75.6 kA at 440 V, and 7.5 kA at both 500 V and 690 V — so it can handle high-fault scenarios common in industrial distribution. Rated insulation voltage is 800 V, and maximum power loss sits at 28.1 W, which matters for thermal management inside a sealed enclosure.
What the ratings mean for fit
The 125 A rating at 40 °C is the continuous current the breaker can carry without tripping — but if your panel ambient runs hotter (say 60 °C in a crowded enclosure), you need to derate to 120 A, and at 70 °C to 114 A. The TM120M release is a fixed thermal-magnetic trip unit: the thermal element handles overloads (slow response to sustained overcurrent), and the magnetic element handles short-circuits (instantaneous). No electronic adjustment or communication function here — this is a straightforward, field-reliable design. The 220 kA at 240 V interrupting rating means this breaker can safely clear a fault current up to 220,000 A without welding contacts or rupturing the case — critical for high-capacity transformer secondaries or large motor branch circuits. Two HP auxiliary switches are built in, giving you status feedback for PLC inputs or alarm circuits without needing an external accessory.
Panel integration and mounting
Footprint is 70 mm deep, 76.2 mm wide, 130 mm tall — standard MCCB form factor that fits most DIN-rail or panel-mount enclosures without requiring a custom gland plate. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C, so it's fine for unheated warehouses or outdoor cabinets as long as the enclosure keeps condensation off the terminals.