What this MCCB carries — and what it doesn't
The Siemens SENTRON 3VA1120-4EF32-0HC0 is a 3-pole molded case circuit breaker rated for a continuous current Iu of 20 A, with a TM240 thermal-magnetic release. Its interrupting capacity hits 121 kA at 240 V, 75.6 kA at 415 V, and 52.5 kA at 440 V — figures that cover most industrial distribution panels and motor branch circuits. At 690 V it still holds 11.9 kA, so it handles the high-voltage end of a 690 VAC line without cascading upstream. The 800 V rated insulation voltage (Ui) means the internal clearances and creepage are sized for 690 V systems with margin. This is a line-protection version — no phase-failure detection, no ground-fault monitoring, no communication module. It is a straightforward thermal-magnetic breaker with a shunt trip (STL) for remote opening and two HQ auxiliary switches for status feedback. The front face carries IP40 protection, so it is fine inside a closed panel but not for washdown zones.
Thermal derating and panel fit
The 20 A rating holds flat from 40 °C to 50 °C. 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. If the panel ambient runs above 50 °C, the continuous load must be reduced accordingly — the TM240 release is calibrated for the 40 °C reference, not the 70 °C operating maximum. The 15000-cycle latching endurance is typical for this class; expect it to outlast the panel's service life in normal switching duty. Dimensions are 76.2 mm wide, 130 mm tall, and 70 mm deep. That 70 mm depth is the body only — add clearance for the shunt trip wiring and the auxiliary switch harness. The width matches the standard 3VA 3-pole footprint, so it drops into the same DIN-rail or screw-mount cutout as the rest of the SENTRON 3VA family.