What this MCCB carries
The Siemens 3VA1120-4EF32-0JC0 is a 3-pole SENTRON molded case circuit breaker rated for 20 A continuous current across the 40 °C to 55 °C band, derating to 19 A at 60–70 °C. Breaking capacity hits 121 kA at 240 V AC, then drops through 75.6 kA at 415 V, 52.5 kA at 440 V, and settles at 11.9 kA from 500 V to 690 V — so the fault-current headroom you get depends heavily on your system voltage. Insulation voltage is rated 800 V.
Fit and panel integration
Dimensions are 130 mm high, 76.2 mm wide, 70 mm deep — a standard 3-pole MCCB footprint that drops into SENTRON distribution blocks and panel-mount cutouts without re-drilling. The 70 mm depth is the can-body dimension; account for the shunt trip (STL) and auxiliary switch HQ modules on the side when planning wireway clearance.
What the ratings mean for your BOM line
The 20 A frame is sized for feeder or branch circuits pulling up to that load continuously at 40 °C ambient. If your panel sees 60 °C internally, you lose 1 A — still a 19 A continuous rating. The 121 kA SCCR at 240 V is what you'd use for a 240 V distribution board; at 415 V the 75.6 kA still covers most industrial transformer secondary faults. The 11.9 kA at 690 V is the floor — adequate for 690 V drives or motor control centers with limited fault current.