The Siemens SENTRON 3VA1120-3EF32-0HA0 is a 3-pole molded case circuit breaker rated for 20 A continuous current, with a TM240 thermal-magnetic overcurrent release and an integrated shunt trip (STL) for remote tripping. It's built for line protection — the standard job of a distribution MCCB in a panel — and carries interrupting ratings that climb to 75.6 kA at 240 V, 52.5 kA at 415 V, and still 10.5 kA at 690 V. That kind of headroom means it clears high-fault bolted faults without cascading upstream, which is the main reason you spec a SENTRON over a miniature breaker.
What the ratings mean for fit
The 20 A rating holds flat from 40 °C to 50 °C — no derating needed in a warm enclosure. At 55 °C it drops to 19.2 A, and at 70 °C it's 18 A. If your panel ambient runs hot, that's the curve to check against your load. The 800 V rated insulation voltage (Ui) means it's safe on 480 V and 600 V systems, and the IP40 front keeps dust out of the breaker face. No trip indicator, no auxiliary contacts, no undervoltage release — this is a bare-bones line-protection breaker with the shunt trip as the only accessory. If you need status feedback, you'll add the external auxiliary trip (order code 3VA9688-0BL30).
Panel integration and dimensions
The breaker measures 70 mm deep, 76.2 mm wide, and 130 mm tall — a standard SENTRON 3VA footprint that fits the DIN-rail or screw-mount pattern in most distribution boards. The 3-pole body takes up three module widths on the rail. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C, so it's fine for unheated warehouses. The shunt trip (STL) is wired separately; no communication function or phase failure detection is built in, so keep that in mind for remote monitoring setups.