What it is and what it does
The Siemens 3VA1112-4EF32-0AB0 is a SENTRON molded case circuit breaker (MCCB) for line protection, with three poles and a TM240 thermal-magnetic release. It's rated 125 A continuous at 40 °C — that's the full-load current it carries without tripping under normal conditions. The interrupting ratings climb from 121 kA at 240 V down to 11.9 kA at 690 V, so it's sized for high-fault commercial and industrial distribution panels where large upstream transformers or parallel feeds push available fault current above 100 kA.
Real current capacity — the derating curve matters
The 125 A rating holds flat from 40 °C to 50 °C. Above that, it derates: 122 A at 55 °C, 120 A at 60 °C, 117 A at 65 °C, and 114 A at 70 °C. If the panel ambient runs at 60 °C, you're losing 5 A of headroom — factor that into the load schedule. The TM240 release is a thermal-magnetic trip unit with a 240 A frame; the adjustable thermal pickup lets you fine-tune the long-time delay for the connected load.
Physical fit and panel integration
The breaker measures 130 mm tall, 76.2 mm wide, and 70 mm deep — a standard 3-pole MCCB footprint. It mounts directly onto a DIN rail or panel-mount base plate. The 70 mm depth is the same as the 3VA1110-5ED36-0AC0 sibling, so a panel laid out for that earlier variant accepts this one without altering the gland plate or busbar spacing. Power dissipation at full load is 28.1 W; make sure the enclosure's thermal rise stays within the -25 °C to 70 °C operating range.