What it is and what it does
The Siemens 3VA1120-6EF32-0AG0 is a SENTRON molded case circuit breaker (MCCB) designed for line protection — the primary job is guarding feeder or branch circuits against overloads and short circuits. Three poles, rated 20 A continuous at 40 °C, with a TM240 thermal-magnetic release that combines a bimetal element for sustained overloads and a magnetic coil for instantaneous fault clearing. The interrupting ratings tell the real story: 220 kA at 240 V, 154 kA at 415 V, and still 121 kA at 440 V — numbers that put this in the high-interrupting-capacity class, sized for large transformer secondaries or high-fault industrial distribution panels. At 690 V it still holds 17 kA, which is respectable for a 20 A frame.
Ratings that matter for fit
The 20 A rating holds flat from 40 °C through 55 °C — no derating needed in a warm panel. At 60 °C it drops to 19 A, and at 70 °C it's still 19 A. That's a tight thermal curve; most MCCBs start sliding at 50 °C. The insulation voltage is rated 800 V, so it's comfortable in 480/277 V or 600 V systems with margin. Power loss maxes at 12 W, which matters for enclosure heat load if you're stacking several breakers. The auxiliary switch configuration is 1 auxiliary switch + 1 trip alarm switch HP — that's the standard for remote status and alarm feedback to a PLC or annunciator.
Panel fit
Dimensions: 130 mm tall, 76.2 mm wide, 70 mm deep — a standard 3-pole MCCB footprint that fits most DIN-rail or panel-mount enclosures without surprises. The 70 mm depth means it clears shallow backpanels where some breakers with protruding arc chambers won't. The trip indicator is present, so a quick visual check confirms the breaker has tripped without needing to reset it to find out.