What this MCCB carries and where it fits
The Siemens SENTRON 3VA1120-3EF32-0HH0 is a 3-pole molded case circuit breaker rated for 20 A continuous current (Iu) with a TM240 thermal-magnetic overcurrent release. It breaks 75.6 kA at 240 V, 52.5 kA at 415 V, 32 kA at 440 V, and 10.5 kA at 690 V — numbers that tell you the SCCR headroom you've got for the fault-current study on your distribution board. The 800 V rated insulation voltage (Ui) means it's comfortable on 480 V and 600 V class systems without derating the dielectric gap. This is a line-protection breaker (not a motor-protection or ground-fault version), so it's the right call for feeder circuits, panel mains, and branch protection where you need a thermal-magnetic curve and no communication or phase-failure logic inside the case.
Temperature derating — the real-world current you can count on
The 20 A rating holds flat from 40 °C to 50 °C. At 55 °C it drops to 19.2 A, at 60 °C to 18.8 A, at 65 °C to 18.4 A, and at 70 °C to 18 A. If your panel sits near a kiln or a hot drive cabinet, size the load at the ambient you actually see — not the 40 °C number on the nameplate. Operating temperature range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. The storage limit is for handling, not running — the breaker can sit in a cold warehouse or a hot shipping container without damage.
Panel footprint and auxiliary contacts
The breaker measures 76.2 mm wide, 130 mm high, and 70 mm deep — a standard 3-pole MCCB footprint that drops into SENTRON mounting bases and busbar systems without adapters. It ships with 2 auxiliary switches plus 1 trip alarm switch (HQ type), and a shunt trip release (STL) is integrated — the release's order code is 3VA9688-0BL30. That means you get remote trip capability and status feedback without adding an external module.