The Siemens SENTRON 3VA4120-5ED14-1AA0 is a 1-pole molded-case circuit breaker (MCCB) from the 3VA system-protection family, rated for a continuous current Iu of 20 A across an ambient range of 40 °C to 55 °C before it begins to derate — at 70 °C it still carries 18 A. The headline figure buyers care about is the interrupting capacity: 85 kA at 120 V, 35 kA at 277 V, and 18 kA at 347 V. The TM210 overcurrent release is a fixed thermal-magnetic trip with a magnetic short-circuit pickup adjustable from 300 A minimum to 300 A maximum — that's a fixed instantaneous trip at 15x In.
The 25.4 mm width (1 inch) per pole means a 1-pole unit takes a single 25.4 mm module — standard for SENTRON 3VA panels. Depth is 75.1 mm, height 129.4 mm. If you need remote trip indication or shunt-trip capability, you'd add the appropriate SENTRON accessory modules separately. The power loss is 2.8 W maximum at rated current, so thermal buildup in a dense panel is manageable but worth checking if you're packing multiple units side by side.
UL file MEAM per the evidence — the breaker carries UL 489 listing, so it's accepted for US and Canadian panelboard and switchboard installations. The IEC 81346-2 reference code Q (switching device) applies. No RoHS/REACH statement is in the evidence, but as a current Siemens SENTRON product it would meet standard EU compliance — confirm with your Siemens rep if documentation is needed for your quality system.