The Siemens 3VA4120-4ED14-3AA0 is a 1-pole molded-case circuit breaker from the 3VA4 UL Frame 125 family, rated 20 A continuous with a fixed overload setting (Ir = 20 A) and a short-circuit pickup of 15 × In (300 A). The FTFM (Fixed Thermal, Fixed Magnetic) design means both Ir and Ii are permanently set — no field-adjustable dials, no calibration drift. For a BOM line, this simplifies specification: what you order is what protects the circuit, every shot the same. The 3VA4 UL Frame 125 accepts plug-in accessories (auxiliary contacts, shunt trip, undervoltage release) that share the same mounting footprint across the frame size. If the panel design already uses 3VA4 breakers, this unit drops into the same DIN-rail adapter or screw-mount base without re-drilling the backplate.
Export control is straightforward: AL: N / ECCN: EAR99 — no special licensing required for most destinations. RoHS compliant since May 2019;
In a 277/480 V panel, this covers most branch circuits fed from a transformer up to about 150 kVA — enough for lighting panels, small motor control centers, and HVAC equipment. The fixed 15 × In short-circuit pickup (300 A for this 20 A unit) means the magnetic trip will not nuisance-trip on motor inrush or capacitor charging currents that stay below that multiple. For a circuit feeding a 20 A resistive load or a small motor with a nameplate FLA under 16 A, this pickup provides adequate protection without false trips.