What it is and what it does
The Siemens SENTRON 3VM1120-3EE32-0AA0 is a 3-pole molded case circuit breaker (MCCB) rated for line protection, with a maximum current of 320 A and a TM220 thermal-magnetic overcurrent release. At 240 V it interrupts up to 76 kA; at 415 V that drops to 53 kA, at 440 V to 32 kA, and at 500 V to 12 kA — so for a 400 V distribution panel the 53 kA figure is the one that governs SCCR coordination downstream. Continuous current rating is 20 A from 40 °C through 55 °C, then derates to 19 A at 60 °C through 70 °C — no derating needed for most panel ambient conditions, but worth checking if the breaker sits near a heat source or in a sealed enclosure above 55 °C. Dimensions are 70 mm deep, 76.2 mm wide, 130 mm tall — a standard MCCB footprint that fits most DIN-rail or panel-mount enclosures without gland-plate surprises. IP40 on the front means it is protected against tools and wires >1 mm, but not against water ingress; keep it inside a rated enclosure.
Sourcing and lifecycle
Rated insulation voltage is 800 V, so it is suitable for 400 V and 480 V distribution systems with headroom. No undervoltage release, no ground-fault monitoring, no communication function — a straight line-protection MCCB, no frills.
Panel integration notes
Mounts on DIN rail or directly to a backplate via the standard MCCB cutout. The 76.2 mm width (3 in) matches the common 3-pole MCCB slot; plan for 70 mm depth clearance behind the panel door, including wiring bend radius. Power loss is 12 W maximum at rated load — negligible for thermal budgeting in most enclosures, but worth noting if the panel is densely packed with multiple breakers.