What this breaker carries and what it means for the panel
The Siemens 3VA1120-3EF36-0BH0 is an IEC frame 160 molded-case circuit breaker with breaking capacity class N — 25 kA at 415 V. That rating tells you it can safely interrupt a fault current up to 25 kA without welding its contacts or venting arc gas into the enclosure, which is the minimum for most 400 V distribution boards feeding motor control centers or lighting panels. The TM240 trip unit gives you thermal-magnetic protection: overload adjustable from 14 A to 20 A (In=20 A) and a short-circuit magnetic pickup set at 8 to 16 times In. For a 20 A feeder, that means the magnetic trip fires between 160 A and 320 A — fast enough to clear a bolted fault before the upstream device sees it, but high enough to avoid nuisance trips from motor inrush on a lightly loaded line. It ships with an undervoltage release (UVR) coil rated 24 V DC. If the control voltage drops below the dropout threshold, the UVR opens the breaker instantly — standard practice for emergency-stop circuits or loss-of-mains protection on conveyors and machine tools.
Auxiliary contacts and alarm switch — what they add
Two HQ auxiliary switches and one HQ trip alarm switch are factory-fitted. The aux switches signal the breaker's open/closed position to a PLC or status lamp; the trip alarm switch changes state only when the breaker trips on fault, not on manual opening — useful for remote fault annunciation without wiring separate shunt-trip monitoring.
Integration notes — DIN rail and wiring
The 3VA1 frame mounts on a standard DIN rail (EN 60715). Clamp terminals accept copper conductors — no lugs needed for the rated current range. Leave at least 25 mm clearance above and below for arc-vent space and tool access when terminating the UVR and aux-switch wires.