The Siemens SENTRON 3VM1120-4ED22-0AA0 is a 2-pole molded case circuit breaker (MCCB) from the 3VM series, rated 20 A continuously at 40 °C with an S switching capacity class — meaning it handles high fault currents without needing an upstream fuse for coordination. The TM210 thermal-magnetic release provides LI protection (long-time and instantaneous), with an adjustable instantaneous pickup up to 320 A. At 240 V it interrupts 121 kA; at 415 V it still clears 76 kA, so it's sized for high-available-fault panels where a standard MCB would weld shut.
Ratings and what they mean for fit
The 20 A rating holds flat from 40 °C through 55 °C — no derating needed in a warm enclosure — and only drops to 19 A at 60 °C and above. That's unusual; most MCCBs start stepping down at 40 °C. The 121 kA interrupting rating at 240 V means it can be installed on the line side of a panel fed from a transformer with high fault current without needing a current-limiting fuse ahead of it. The 2-pole configuration with no neutral conductor upgrade option tells you this is a line-protection breaker for single-phase or DC circuits, not a 3-phase main. The TM210 release is a fixed thermal-magnetic design — no electronic trip unit, no communication function, no ground-fault monitoring. The LI protection curve means it has long-time (thermal) delay for overloads and instantaneous magnetic trip for short circuits. The adjustable instantaneous pickup (li max 320 A) lets you dial in coordination with downstream feeders without swapping the breaker.
Panel integration
Dimensions are 70 mm deep, 50.8 mm wide, 130 mm tall — a 2-inch wide footprint that fits a standard 2-pole MCCB slot in most Siemens SENTRON distribution panels. IP40 on the front means it's protected against tools and wires >1 mm, but not against water ingress; mount it inside a rated enclosure if the panel sees washdown or outdoor exposure. The 8 W maximum power loss at rated load matters for thermal budgeting in a sealed enclosure — that's about what a small relay panel dissipates per breaker.