What this MCCB carries — and what it doesn't
The Siemens SENTRON 3VA1120-4EF36-0KC0 is a 3-pole molded case circuit breaker rated for 20 A continuous current (Iu) with a TM240 thermal-magnetic overcurrent release. It's built for line protection — the fixed version without a trip indicator, undervoltage release, phase failure detection, or ground fault monitoring. What it does have: a shunt trip (STL) auxiliary release and two HQ auxiliary switches integrated, plus a voltage trigger function. The interrupting ratings climb to 121 kA at 240 V and 75.6 kA at 415 V, dropping to 52.5 kA at 440 V and 11.9 kA at 690 V — so the SCCR headroom at typical distribution voltages is substantial.
Thermal derating and panel fit
The 20 A rating holds flat from 40 °C through 50 °C ambient. Above that it derates: 19.2 A at 55 °C, 18.8 A at 60 °C, 18.4 A at 65 °C, and 18 A at 70 °C. Operating ambient range is -25 °C to 70 °C; storage range is -40 °C to 80 °C. Front protection is IP40 — fine for a clean panel interior, not for washdown zones. Dimensions: 130 mm high, 76.2 mm wide, 70 mm deep. That 76.2 mm width (roughly 3 inches) is a standard MCCB footprint for 3-pole frames in this class — it fits existing SENTRON panel cutouts and busbar layouts without rework.